By Tom Cole
Several years ago when we were developing our crankcase ventilation system for the Tecumseh Star engine, I got some seat-of -the-pants experience with the value and need of crankshaft balancing. I was accustomed to driving a 3” bore, 3” stroke test engine, which had one of our billet crankshafts in it. The 3x3 crank had been balanced, and ran very smooth considering it was producing about twice as much horsepower as the Star. The Star’s crank/rod/piston setup had not been balanced, and the difference took me by surprise. As I made 8000 rpm, my vision was so blurred from the engine’s vibration that I had to slow down to see the turn. My teeth and ribs felt like they were banging together and after my 15 lap stint at this ¼ mile asphalt oval, I was not interested in driving any more that day. My body was directly reporting to me the increased pain and fatigue that an unbalanced crankshaft can do to an engine and driver.
Clarence Clark is a friend of mine and he is what I would call an engine-building guru. For many years, Clarence’s company rebuilt the engines for the world’s largest fleet of racecars, the United Parcel Service. He has since traveled the country doing seminars for rebuilding supply companies like Goodson and Cobra Products. When I told Clarence about my experience, he went over to his tool box and produced a metal “H” which was made out of five, six inch long 3/8” metal pipes and two 3/8” pipe “T’s”. He handed me this contraption and told me to gently hold the cross pipe in one hand like an axle and spin it. Everything was fairly in balance and it spun easily making five or six revolutions. He then removed one of the four, six-inch uprights from the “H” and said “now it’s out of balance, spin it again.” I did and it only made one revolution! When I tried to spin it real hard, it only made two revolutions. This was an example of the need of both Force and Couple or “Dual Plane” balancing of a crankshaft. He told me one of the most interesting things about an out-of-balance crank or cam is that this tendency to stop (or inertia) increases with RPM so it requires more and more horsepower to obtain the same RPM as a balanced setup! It is hard to believe that we spend so much time and money on carburetors, valves, porting, flow and displacement and many of us ignore or are unaware of such a power robbing aspect of an engine.
Force and Couple balancing are technical terms used that really just mean top-to-bottom and side-to-side balance and are commonly referred to as “Dual Plane Balancing.” They are easily illustrated with a little history in tire balancing. Many years ago, when car tires were balanced, the rim and tire assembly was mounted on a shaft and then placed on a frame with the shaft resting in a ball bearing V fixture. The tire assembly would then rotate around until the heavy part came to rest at 6 o’clock. A wheel weight was then placed at 12 o’clock on one side of the tire. You kept adjusting this weight until the tire would not move regardless of how you repositioned it in the V fixture. This process is called, Static, or Force balancing and it is the method that is used on most kart and Jr. Dragster wheels today. Later, an improvement was made in this process by splitting the weight and putting half on the inside of the rim and half on the outside. This was the first form of Couple balancing in the tire industry. As years went by the advent of much wider tires came into being, so the need for more accurate Couple balancing increased because the part of the tire that was out of balance was often further from the centerline of the tire. And since one side of the tire could weigh more than the other, it became necessary to be more precise than to just split the weight in half to achieve optimum balance. We now have electronic tire balancers that spin the tire and wheel and calculate the amount of weight needed to Force balance. Then it calculates what amount goes on the inside of the rim and what goes on the outside. This is Dual Plane balancing of a tire.
The crankshaft of an engine has counterweights to dynamically offset the effect that the movement of the reciprocating mass has on the rotating mass of the crankshaft. The reciprocating mass is a percentage of the total mass of the top half of the connecting rod, the piston, wristpin, rings and circlips. The percentage used comes from a chart, which is calculated from expected RPM and stroke length. The rotating mass is the total mass of the bottom half of the connecting rod, the rod bolts, washers and bearings. To balance a single cylinder crankshaft, a bob weight is attached to the journal of the crankshaft that represents 100 % of the rotating mass and the percentage of the reciprocating mass from the chart. This assembly is then placed on the ball bearing V’s of our Stewart-Warner crankshaft-balancing machine and spun up to the expected operating RPM setting. The balancer can read the change in weight on both sides of the crankshaft and precisely tell the operator the amount of weight that needs to be added or removed from the left or right counterweights to achieve optimum dual plane balancing.
Balancing a crankshaft in itself does not produce more horsepower; it improves output potential by eliminating or greatly reducing a non-productive use of horsepower. It also helps prolong the life of an engine by reducing damaging vibration. In any situation where some grinding of the crankshaft or modification of the piston is permitted, it is a largely untapped source of performance gain.
Wednesday, October 29, 2003
Thursday, May 8, 2003
Setting Ignition Timing
By Tom Cole
Almost every day someone calls or emails us asking how to set the ignition timing on their engine. It is an important topic because as little as one degree can be the difference between an engine that runs up front and an engine that sputters and pops its way to last place. In this article, I am going to describe what I believe to be the most accurate and reliable method to set the timing on a Briggs and Stratton™ Engine. If you are using an ARC adjustable hub flywheel, begin by setting the hub index mark in the middle of the degree marks on the aluminum body. This will give you the maximum amount of adjustability after you set the timing based on the cam manufacturer’s specifications. The adjustable hub gives you an “at the track” advantage, because it allows you to easily advance or retard the ignition timing to tune for variable conditions.
The first thing you must do to set the timing is to identify the exact position of the flywheel’s magnet in relation to the coil when ignition occurs. To do this right, you need a plain old induction timing light and a car battery. Some folks will tell you about aligning the trailing edge of the magnet with the center of the little button just in front of the left leg of the coil, and for the most part, they are correct. But there is no such button on the Animal coil and factors such as coil gap make this method only a close approximation.
Below is the technique I use to find the exact trigger point using a timing light:
You are now ready to set the timing. Truthfully, it is more accurate to set the timing by fixing the piston at a measured distance before it reaches its highest point on the compression stroke. But, although everyone knows the “in the hole” distance for a pure stock setup, (30deg is .2115”) it is difficult to calculate the distance needed by different length rods since the distance traveled by the piston per degree of rotation varies with rod length and/or stroke. You can calculate it, but it just really isn’t worth the effort.
So, since the cam manufacturers generally provide you with a recommended ignition timing expressed in degrees before top dead center (BTDC) of the compression stroke, it is going to be best to set your timing using a degree wheel. (This is a good time to degree your cam too) On to the dreaded degree wheel…
Almost every day someone calls or emails us asking how to set the ignition timing on their engine. It is an important topic because as little as one degree can be the difference between an engine that runs up front and an engine that sputters and pops its way to last place. In this article, I am going to describe what I believe to be the most accurate and reliable method to set the timing on a Briggs and Stratton™ Engine. If you are using an ARC adjustable hub flywheel, begin by setting the hub index mark in the middle of the degree marks on the aluminum body. This will give you the maximum amount of adjustability after you set the timing based on the cam manufacturer’s specifications. The adjustable hub gives you an “at the track” advantage, because it allows you to easily advance or retard the ignition timing to tune for variable conditions.
The first thing you must do to set the timing is to identify the exact position of the flywheel’s magnet in relation to the coil when ignition occurs. To do this right, you need a plain old induction timing light and a car battery. Some folks will tell you about aligning the trailing edge of the magnet with the center of the little button just in front of the left leg of the coil, and for the most part, they are correct. But there is no such button on the Animal coil and factors such as coil gap make this method only a close approximation.
Below is the technique I use to find the exact trigger point using a timing light:
- Install only the crank, its bearings and its timing gear in the engine block and put on the side cover.
- Install the sheet metal guard that goes behind the flywheel.
- Install the flywheel with a standard key on the crank and snug it up with the starter nut. (No need to torque it, you are going to take it back off)
- Install the coil with the proper gap. (It will not be removed so tighten it up)
- Attach a spark plug to the plug wire and tape it to the block so as to ground it and create a spark.
- With the magnet at 12 o’clock under the coil put a white line on the outside rim of the flywheel at about 3 o’clock. This line needs to be plainly visible when looking at the block from the front.
- Attach the timing light to the battery and clamp the induction lead on the plug wire. Be careful that all wires are away from the flywheel.
- With the timing light pointing at the front of the block, turn the crankshaft clockwise with a drill or starter and you will see the timing strobe light up the white line. You need to spin it faster and more consistently than possible with a pull starter because a magneto has a retarding effect at higher rpm, and you want to compensate.
- While the strobe is flashing and the flywheel is spinning, make a white mark on the sheet metal guard or block that aligns with the white mark shown by the timing light on the flywheel. You can now place the magnet exactly where the spark is triggered when and if you ever remove the flywheel. BUT, if you move the coil or the metal guard, you have to start all over again.
- Remove the flywheel, side cover and crank, and install the piston, rod, crank, cam, etc (leaving off the cylinder head) getting to the point where you are ready to install the flywheel and set the timing.
You are now ready to set the timing. Truthfully, it is more accurate to set the timing by fixing the piston at a measured distance before it reaches its highest point on the compression stroke. But, although everyone knows the “in the hole” distance for a pure stock setup, (30deg is .2115”) it is difficult to calculate the distance needed by different length rods since the distance traveled by the piston per degree of rotation varies with rod length and/or stroke. You can calculate it, but it just really isn’t worth the effort.
So, since the cam manufacturers generally provide you with a recommended ignition timing expressed in degrees before top dead center (BTDC) of the compression stroke, it is going to be best to set your timing using a degree wheel. (This is a good time to degree your cam too) On to the dreaded degree wheel…
- Using coarse grit sand paper, rough up the tapered part of the crank and then make sure it is clean. If you are un-willing to lick it, it isn’t clean enough!
- Similarly, rough up and clean the inside of the hole in the flywheel hub.
- Set the crank so, according to the degree wheel, you are at the cam manufacturers specified degrees of ignition timing before the piston reaches the highest point of its compression stroke BTDC.
- Put a few drops of Loctite™ on the tapered part of the crank and install the flywheel with the white timing lines aligned. DO NOT USE A KEY! Keys do very little to prevent a flywheel from spinning, and they will hinder your accuracy.
- Carefully tighten down the starter nut. Check and recheck the timing several times as you tighten to be sure that the white timing lines are still aligned and that the degree wheel is still where it is supposed to be. Then tighten the starter nut, A LOT. You are shooting for tight enough to hold it together, but not so tight as to split the flywheel.
- If you have an ARC adjustable hub flywheel, you can fine-tune your ignition timing using a dyno or a stopwatch and a Digatron CHT/Tach at the track.
Friday, April 12, 2002
Is 1° Costing You The Win?
By: Tom Cole
Do you REALLY know if advancing or retarding the ignition timing of your engine 1° will increase horsepower? I think most of us can agree that there is a good chance that we would find some improvement, if we checked. How easy is it to experiment with your motor? As I have said before, I am no expert. I am just a father like many of you who likes to build his son’s racing motors. I love the feeling when a motor I built takes the checkered flag, and I have felt the heat and disappointment from the driver (and the wife) when it is obvious that MY poor performing engine cost us the race.
One fact I have learned is that perfect timing is when your motor runs at the proper temperature, responds the way you want it to respond, and you win races. There are no magic numbers or exact calculations that can tell you where timing needs to be. There are only beginning reference points. Just like the carburetor, timing must be tuned to the conditions and variables specific to each motor, track, driver, and kart. Throw in the altitude and the weather conditions, and you can see that the ability to adjust timing quickly and accurately is something that can set you apart from the crowd.
Because the degree wheel infuriates me, and offset keys are a joke, I set ignition timing by aligning the trailing edge of the flywheel magnet with the middle of the coil trigger button while the top of the piston (before top dead center) is at a measured depth from the top of the cylinder. The depth of the piston in the hole varies with many factors, but your cam manufacturer will usually give you a good starting point. (30° BTDC = .2115” in the hole when popup is 0.000” on a stock engine) Once I have everything aligned, I carefully hand tighten the starter nut. Then I recheck my measurements, torque the starter nut down to somewhere around 1,000,000 in./lbs. (I give it all I’ve got with hand tools) and recheck my measurements again. Also note that I do not use an offset key. I lap the flywheel and crankshaft together and then apply Locktite™ to the taper (not the threads) on the crankshaft before installing the flywheel. Now I reassemble the motor, mount it up to the kart, and give it a test run. This whole process takes about 30 minutes.
Now how many of us are going to take that motor and go through that same process at least three more times to check and see if +or- 1° makes a noticeable difference? The method I use to set the timing has a margin of error of at least +or- 2° because I don’t know the exact firing point of the coil trigger button. I know I need to experiment, but what a pain! And how much stress am I putting on the stock flywheel each time I knock it off and torque it back down. Haven’t they been known to fly apart? And how well is that flimsy stock animal flywheel going to hold up? I have heard of engine builders breaking them when they are first installed!
It wasn’t until I faced all this trouble with that touchy little blue-plate slapper-cam motor that the value of ARC’s billet finned flywheel with its adjustable timing hub really came into view. I can literally be finished getting the motor’s ignition timing right with the ARC flywheel, before I can test the first timing change on a stock or fixed hub flywheel. How much time do you have at a race between practice and the first heat? I am too busy changing oil, cleaning and prepping tires, and making chassis adjustments to tear down a motor.
Do you REALLY know if advancing or retarding the ignition timing of your engine 1° will increase horsepower? I think most of us can agree that there is a good chance that we would find some improvement, if we checked. How easy is it to experiment with your motor? As I have said before, I am no expert. I am just a father like many of you who likes to build his son’s racing motors. I love the feeling when a motor I built takes the checkered flag, and I have felt the heat and disappointment from the driver (and the wife) when it is obvious that MY poor performing engine cost us the race.
One fact I have learned is that perfect timing is when your motor runs at the proper temperature, responds the way you want it to respond, and you win races. There are no magic numbers or exact calculations that can tell you where timing needs to be. There are only beginning reference points. Just like the carburetor, timing must be tuned to the conditions and variables specific to each motor, track, driver, and kart. Throw in the altitude and the weather conditions, and you can see that the ability to adjust timing quickly and accurately is something that can set you apart from the crowd.
Because the degree wheel infuriates me, and offset keys are a joke, I set ignition timing by aligning the trailing edge of the flywheel magnet with the middle of the coil trigger button while the top of the piston (before top dead center) is at a measured depth from the top of the cylinder. The depth of the piston in the hole varies with many factors, but your cam manufacturer will usually give you a good starting point. (30° BTDC = .2115” in the hole when popup is 0.000” on a stock engine) Once I have everything aligned, I carefully hand tighten the starter nut. Then I recheck my measurements, torque the starter nut down to somewhere around 1,000,000 in./lbs. (I give it all I’ve got with hand tools) and recheck my measurements again. Also note that I do not use an offset key. I lap the flywheel and crankshaft together and then apply Locktite™ to the taper (not the threads) on the crankshaft before installing the flywheel. Now I reassemble the motor, mount it up to the kart, and give it a test run. This whole process takes about 30 minutes.
Now how many of us are going to take that motor and go through that same process at least three more times to check and see if +or- 1° makes a noticeable difference? The method I use to set the timing has a margin of error of at least +or- 2° because I don’t know the exact firing point of the coil trigger button. I know I need to experiment, but what a pain! And how much stress am I putting on the stock flywheel each time I knock it off and torque it back down. Haven’t they been known to fly apart? And how well is that flimsy stock animal flywheel going to hold up? I have heard of engine builders breaking them when they are first installed!
It wasn’t until I faced all this trouble with that touchy little blue-plate slapper-cam motor that the value of ARC’s billet finned flywheel with its adjustable timing hub really came into view. I can literally be finished getting the motor’s ignition timing right with the ARC flywheel, before I can test the first timing change on a stock or fixed hub flywheel. How much time do you have at a race between practice and the first heat? I am too busy changing oil, cleaning and prepping tires, and making chassis adjustments to tear down a motor.
Thursday, January 17, 2002
Rolling Resistance
By: Tom Cole Date: January 17, 2002
Every rear wheel drive car or truck on the road or racetrack uses tapered roller bearings in their front hubs. The reasons for this are simple, less friction and combined radial (perpendicular to the axial) and thrust (parallel to the axial) load capacity. So why are kart racers using ball bearings which are designed only for radial loads on their karts? I can understand why Jr. Drag racers don’t care about thrust load. They just go fast in a straight line. But kart racers go fast and turn fast. Usually, the one who gets through the turns the fastest wins. So again, why are so many kart racers using ball bearings? Endplay! Somebody has actually sold people on the idea that karts with tapered roller bearing hubs have so much endplay that you can’t set the toe-in. What a pile! How is it that those NASCAR and F1 boys can set the alignment on their cars? Never mind that endplay tolerance for a wheel with tapered roller bearings is only .002” (that’s half the thickness of a piece of notebook paper). How precise are the widths of the inner and outer races of a .65-cent ball bearing? How precise is the relationship between the inner and outer races? Are they parallel? Are they precisely on the same plane? How precise is the bore of the hub? Is the center sleeve exactly long enough? Well guess what! None of this matters if you use a properly installed tapered roller bearing. The guy beating you doesn’t give a rip how the wheel rolls on the rack. How the wheels roll on the track, in the turn under thrust load and down the straightaway under radial load is what matters in wheel bearings. And he is not going to tell you why he’s beating you.
All ball bearings roll on a “point” of contact between the ball and the races. A tapered roller bearing distributes the load over the length of the roller in a “line” of contact. This greatly reduces the friction coefficient allowing tapered roller bearings of the same diameter as comparable ball bearings to carry a greater load and achieve a much greater fatigue life. Simply put, it will roll easier than a ball bearing. The angle of the races along with the taper of the bearing rods allows a tapered roller bearing hub to roll equally well in the turns or on the straight-aways. Standard ball bearings DO NOT roll as well through a turn as they do down the straightaway, and they do not handle the demands of a kart racer as well as a tapered roller bearing.
Every rear wheel drive car or truck on the road or racetrack uses tapered roller bearings in their front hubs. The reasons for this are simple, less friction and combined radial (perpendicular to the axial) and thrust (parallel to the axial) load capacity. So why are kart racers using ball bearings which are designed only for radial loads on their karts? I can understand why Jr. Drag racers don’t care about thrust load. They just go fast in a straight line. But kart racers go fast and turn fast. Usually, the one who gets through the turns the fastest wins. So again, why are so many kart racers using ball bearings? Endplay! Somebody has actually sold people on the idea that karts with tapered roller bearing hubs have so much endplay that you can’t set the toe-in. What a pile! How is it that those NASCAR and F1 boys can set the alignment on their cars? Never mind that endplay tolerance for a wheel with tapered roller bearings is only .002” (that’s half the thickness of a piece of notebook paper). How precise are the widths of the inner and outer races of a .65-cent ball bearing? How precise is the relationship between the inner and outer races? Are they parallel? Are they precisely on the same plane? How precise is the bore of the hub? Is the center sleeve exactly long enough? Well guess what! None of this matters if you use a properly installed tapered roller bearing. The guy beating you doesn’t give a rip how the wheel rolls on the rack. How the wheels roll on the track, in the turn under thrust load and down the straightaway under radial load is what matters in wheel bearings. And he is not going to tell you why he’s beating you.
All ball bearings roll on a “point” of contact between the ball and the races. A tapered roller bearing distributes the load over the length of the roller in a “line” of contact. This greatly reduces the friction coefficient allowing tapered roller bearings of the same diameter as comparable ball bearings to carry a greater load and achieve a much greater fatigue life. Simply put, it will roll easier than a ball bearing. The angle of the races along with the taper of the bearing rods allows a tapered roller bearing hub to roll equally well in the turns or on the straight-aways. Standard ball bearings DO NOT roll as well through a turn as they do down the straightaway, and they do not handle the demands of a kart racer as well as a tapered roller bearing.
Monday, March 20, 2000
STROKER ROD DESIGN
By: Carl Amundsen Date: March 20, 2000
Evidently a lot of people have read and paid attention to our editorial " Oil Clearance is Not a Myth But a Calculation ". We appreciate all the calls and hope it has helped save some engines.
A constant question that keeps coming up is about the bore size on the stroker rod for the .875 (7/8) journal crankshaft.
Why are the rod bores on some brands of stroker rods as much as .004" out of round, right out of the box?
These rods all have angled or what is termed "splayed rod bolts". This is a necessary design because of the amount of stroke in the crankshaft and the need for clearance at the camshaft and inside the block.
The problem occurs when the parting surfaces at the rod and cap are not 90 degrees to the rod bolts. On the illustration below the right rod bolt enters at 15 degrees and the left rod bolt enters at 7 1/2 degrees. The parting surfaces of the rod and cap are at 75 degrees and 82 1/2 degrees respectively to the rod bolt.
It is easy to see from the illustration that the seat area under the rod bolt and the seat area of the cap will be at an angle to the parting surfaces of the rod assembly. This is where the problem begins.
During the manufacturing process the rod and cap are assembled together and the bolts are tightened to a specific torque value. The final machining of the bore now takes place, and comes out on size and round. The next thing that happens is that the rod bolts are removed and new ones are installed. Here is your problem. Because of the adverse angle at which the bolts enter the seam of the rod, they pull the bore out of round. It will always come out egg shaped, and the more you play with the torque values the worse it gets. This is not a one out of ten problem this will happen 100 times out of 100 times. It can be bad enough to lock the motor up. Bet on it. THE PROBLEM IS IN THE DESIGN.
To add insult to injury, some rods are designed with the rod bolts exposed to the bore. This just reduces the integrity of the bore and weakens the seam area. If that's not enough, you must grind some clearance into the back side of the bearings to accommodate the rod bolts.
THE FOLLOWING IS AN ILLUSTRATION OF THE ARC DESIGNED STROKER ROD, NOTICE THAT THE BOLTS AND THEIR PARTING EDGES ARE PERPENDICULAR TO ONE ANOTHER. THIS DESIGN ELIMINATES THE PROBLEMS CAUSED BY THE ANGLED BOLT TO PARTING EDGE SITUATION. OUR WAY STILL ISN'T PERFECT, BUT IT IS A HUGE STEP IN THE RIGHT DIRECTION.
Evidently a lot of people have read and paid attention to our editorial " Oil Clearance is Not a Myth But a Calculation ". We appreciate all the calls and hope it has helped save some engines.
A constant question that keeps coming up is about the bore size on the stroker rod for the .875 (7/8) journal crankshaft.
Why are the rod bores on some brands of stroker rods as much as .004" out of round, right out of the box?
These rods all have angled or what is termed "splayed rod bolts". This is a necessary design because of the amount of stroke in the crankshaft and the need for clearance at the camshaft and inside the block.
It is easy to see from the illustration that the seat area under the rod bolt and the seat area of the cap will be at an angle to the parting surfaces of the rod assembly. This is where the problem begins.
During the manufacturing process the rod and cap are assembled together and the bolts are tightened to a specific torque value. The final machining of the bore now takes place, and comes out on size and round. The next thing that happens is that the rod bolts are removed and new ones are installed. Here is your problem. Because of the adverse angle at which the bolts enter the seam of the rod, they pull the bore out of round. It will always come out egg shaped, and the more you play with the torque values the worse it gets. This is not a one out of ten problem this will happen 100 times out of 100 times. It can be bad enough to lock the motor up. Bet on it. THE PROBLEM IS IN THE DESIGN.
To add insult to injury, some rods are designed with the rod bolts exposed to the bore. This just reduces the integrity of the bore and weakens the seam area. If that's not enough, you must grind some clearance into the back side of the bearings to accommodate the rod bolts.
THE FOLLOWING IS AN ILLUSTRATION OF THE ARC DESIGNED STROKER ROD, NOTICE THAT THE BOLTS AND THEIR PARTING EDGES ARE PERPENDICULAR TO ONE ANOTHER. THIS DESIGN ELIMINATES THE PROBLEMS CAUSED BY THE ANGLED BOLT TO PARTING EDGE SITUATION. OUR WAY STILL ISN'T PERFECT, BUT IT IS A HUGE STEP IN THE RIGHT DIRECTION.
Tuesday, February 8, 2000
OIL CLEARANCE IS NOT A MYTH IT IS A CALCULATION
By: Carl Amundsen Date:2/8/2000
Over the years I have had many opportunities to discuss oil clearance with engine builders. Some are building for their own use, some are small shops while some are large. In any event when the question is posed "HOW DO YOU KNOW WHAT YOUR OIL CLEARANCE IS?" the responses vary. Some can give a good mathematical response, some don't have a clue. The common denominator here is that everyone knows they have oil clearance.
A common phenomenon that occurs when a motor fails is that no one looks in the mirror for answers. The vast majority of the time it is blamed on an engine part failure. The connecting rod too many times is the favorite fugitive.
A LESSON IN MEASUREMENTS
A very dangerous but commonly used method of measuring is a dial caliper. The average dial caliper is super for measuring the thickness, inside diameter, and outside of an empty toilet paper roll. A SHOCKING STATEMENT , NO DOUBT! If you look through some catalogs you will find a dial caliper for $40.00 that has an advertised accuracy of +/- .008 . That is an error factor of 16 thousandths. Pay $200.00 for a digital caliper with advertised accuracy of +/- .0015, the margin of error is now 3 thousandths. An error factor of 1 thousandths can cost you a motor. Calipers are great tools for some things but not for the task at hand. WE MUST BE ABLE TO READ IN TENTHS OF THOUSANDTHS(.0001)
ON WITH THE LESSON
If you were to take a good 0 to 1 inch micrometer and measure the thickness of a page in the ARC catalog, you will find it to be five thousandths (.005) thick. This is very important to remember as you read on. Now feel the paper with your fingers and imagine somehow splitting one of these pages 50 times. One single sheet would now be 1 tenth of 1 thousandth of an inch thick (.0001). I hope I have your attention, because this is getting down so that you can't even feel the thickness. Just incase I am going to be confusing you with decimals please remember the following:
1.0000 = 1 inch0.1000 = 100 thousandths 0.0100 = 10 thousandths0.0010 = 1 thousandth0.0001 = 1/10 thousandth
It makes no difference who you buy your parts from, nor does it matter what brand they are, ARC included,they need to be checked and double checked. NOBODY IS PERFECT.
For example let's build a stock stroke Briggs racing engine. The following is the measurement specifications on the typical parts to be used:
Stock Briggs crank rod journal size......................... .998 +/- .0015Aftermarket Connecting Rod................................... 1.150 +/- .005Aftermarket Rod Bearing thickness........................ .075 +/- .003
ALL THE PARTS WE ARE USING ARE WITHIN THE MANUFACTURERS TOLERANCES.
You are going to use a medium weight oil and you are shooting for .0025
The Connecting Rod is on the small side................. 1.1495The Rod Bearing is on the big side.......................... .0753The Crankshaft is on the big side.............................. .9985
Let's put this motor together and go racing.
The Connecting Rod is small by .0005...................... 1.1495The Thickness of the Rod Bearingare big by .003(2 bearings) =.1506............................. - .1506Net Rod Bore size with Bearingsinstalled................................................................... . 9989The Crank Rod Journal is big by .0005..................... - .9985The Calculated oil Clearance = ............................... .0004We were shooting for ............................................... .0025
With a little luck this motor will crank up and run, as long as the motor is running at no load and a low RPM it may be OK for a while. The minute you go racing the lack of oil flow between the bearing and the crank journal will cause heat build up. The bearing will seize on the crank journal, break the rod and just make a mess of everything. BAD PARTS RIGHT ? WRONG !
Now let's build another motor and go the opposite way, still trying to achieve an oil clearance of .0025
The Connecting Rod is on the big side........................ 1.1505The Rod Bearing is on the small side.......................... .0747The Crankshaft is on the small side.............................. .9965
The Connecting Rod is big by .0005............................ 1.1505The Thickness of the Rod Bearingare small by .003(2 bearings) =.1494............................. - .1494Net Rod Bore size with Bearingsinstalled...................................................................... 1.0011The Crank Rod Journal is small by .0015..................... - .9965The Calculated oil Clearance = .................................. .0046We were shooting for .................................................. .0025
This motor is going to run, but what is going to happen here is: The bearing is going to get pounded at the top and bottom of the rod bore, because there is an air gap between the two surfaces. The oil is not thick enough to prevent this from happening. This is going to convert the rod bore into the shape of an egg standing on end. The crankshaft will now start to loose it's round shape and wear.
EVERY MINUTE IT RUNS, THESE PARTS WILL INCREASE THE OIL CLEARANCE UNTIL IT EXPLODES. HOW LONG WILL IT LAST? I CAN'T SAY EXACTLY, BUT NOT TO LONG!
The crying shame here is that everyone will point their fingers at the connecting rod, bearings and/or crankshaft as the culprit.
THE MOST OVERLOOKED AREA IN ENGINE BUILDING IS AS FOLLOWS:You have a motor that has run for many months , but you notice you're getting a little blow-by and it could probably use a set of rings. It needs freshening up so we tear it down. Every thing looks great so we touch the bore with a hone and put a new set of rings in. Back to the races. If it ain't broke don't fix it. STOP! Under the most ideal conditions engine parts will change with use. Bearings can look good but will wear, connecting rod bores will change shapes and crank journals will wear and rod bolts will stretch and fatigue. It is just as important now as ever to check the dimensions of the parts. Don't go to sleep.
Some may think there is some deep mystery behind the term oil clearance. The reason is, everyone has a different opinion as to what it should be. As a rule of thumb, it can be anywhere between .0015 and .0035 and be in the ball park. If the clearance is on the low side, use thin oil, heavy oil will not work. If clearance is on the high side , use a heavier oil, thin oil will not work. How can you make a judgment on the oil to use unless you know what your oil clearance is? THERE IS NO MAGIC, YOU CANNOT KNOW WHAT YOUR OIL CLEARANCE IS UNLESS YOU MEASURE THE PARTS THAT AFFECT IT.
DEFINITION OF WHAT OIL CLEARANCE IS:
"The distance between two very smooth moving surfaces that will allow oil to be present at all times, coating both parts with a film of oil so that metal on metal contact never happens. It must be small enough to retain enough oil and large enough to allow a fresh cool supply to move through every microsecond."
If you do not check your parts and build 4 motors and 3 of them seem to have a pretty good life span you are lucky. If one fails out of the gate or shortly thereafter, shame on you. It takes less than 15 minutes to check and measure all the parts in a motor and the benefits are fantastic. It is possible to build an engine that will run until the cows come home, or something like that. There are many engine builders out there that do a fantastic job in this area, but on the other hand there are more that don't.
ASSUME NOTHING, BELIEVE NOTHING AND LAST BUT NOT LEAST, CHECK EVERYTHING.
I hope we have given you an insight to one reason for engine failures. If you need us, give us a call, it's all free. 1-800-521-3560
Over the years I have had many opportunities to discuss oil clearance with engine builders. Some are building for their own use, some are small shops while some are large. In any event when the question is posed "HOW DO YOU KNOW WHAT YOUR OIL CLEARANCE IS?" the responses vary. Some can give a good mathematical response, some don't have a clue. The common denominator here is that everyone knows they have oil clearance.
A common phenomenon that occurs when a motor fails is that no one looks in the mirror for answers. The vast majority of the time it is blamed on an engine part failure. The connecting rod too many times is the favorite fugitive.
A LESSON IN MEASUREMENTS
A very dangerous but commonly used method of measuring is a dial caliper. The average dial caliper is super for measuring the thickness, inside diameter, and outside of an empty toilet paper roll. A SHOCKING STATEMENT , NO DOUBT! If you look through some catalogs you will find a dial caliper for $40.00 that has an advertised accuracy of +/- .008 . That is an error factor of 16 thousandths. Pay $200.00 for a digital caliper with advertised accuracy of +/- .0015, the margin of error is now 3 thousandths. An error factor of 1 thousandths can cost you a motor. Calipers are great tools for some things but not for the task at hand. WE MUST BE ABLE TO READ IN TENTHS OF THOUSANDTHS(.0001)
ON WITH THE LESSON
If you were to take a good 0 to 1 inch micrometer and measure the thickness of a page in the ARC catalog, you will find it to be five thousandths (.005) thick. This is very important to remember as you read on. Now feel the paper with your fingers and imagine somehow splitting one of these pages 50 times. One single sheet would now be 1 tenth of 1 thousandth of an inch thick (.0001). I hope I have your attention, because this is getting down so that you can't even feel the thickness. Just incase I am going to be confusing you with decimals please remember the following:
1.0000 = 1 inch0.1000 = 100 thousandths 0.0100 = 10 thousandths0.0010 = 1 thousandth0.0001 = 1/10 thousandth
It makes no difference who you buy your parts from, nor does it matter what brand they are, ARC included,they need to be checked and double checked. NOBODY IS PERFECT.
For example let's build a stock stroke Briggs racing engine. The following is the measurement specifications on the typical parts to be used:
Stock Briggs crank rod journal size......................... .998 +/- .0015Aftermarket Connecting Rod................................... 1.150 +/- .005Aftermarket Rod Bearing thickness........................ .075 +/- .003
ALL THE PARTS WE ARE USING ARE WITHIN THE MANUFACTURERS TOLERANCES.
You are going to use a medium weight oil and you are shooting for .0025
The Connecting Rod is on the small side................. 1.1495The Rod Bearing is on the big side.......................... .0753The Crankshaft is on the big side.............................. .9985
Let's put this motor together and go racing.
The Connecting Rod is small by .0005...................... 1.1495The Thickness of the Rod Bearingare big by .003(2 bearings) =.1506............................. - .1506Net Rod Bore size with Bearingsinstalled................................................................... . 9989The Crank Rod Journal is big by .0005..................... - .9985The Calculated oil Clearance = ............................... .0004We were shooting for ............................................... .0025
With a little luck this motor will crank up and run, as long as the motor is running at no load and a low RPM it may be OK for a while. The minute you go racing the lack of oil flow between the bearing and the crank journal will cause heat build up. The bearing will seize on the crank journal, break the rod and just make a mess of everything. BAD PARTS RIGHT ? WRONG !
Now let's build another motor and go the opposite way, still trying to achieve an oil clearance of .0025
The Connecting Rod is on the big side........................ 1.1505The Rod Bearing is on the small side.......................... .0747The Crankshaft is on the small side.............................. .9965
The Connecting Rod is big by .0005............................ 1.1505The Thickness of the Rod Bearingare small by .003(2 bearings) =.1494............................. - .1494Net Rod Bore size with Bearingsinstalled...................................................................... 1.0011The Crank Rod Journal is small by .0015..................... - .9965The Calculated oil Clearance = .................................. .0046We were shooting for .................................................. .0025
This motor is going to run, but what is going to happen here is: The bearing is going to get pounded at the top and bottom of the rod bore, because there is an air gap between the two surfaces. The oil is not thick enough to prevent this from happening. This is going to convert the rod bore into the shape of an egg standing on end. The crankshaft will now start to loose it's round shape and wear.
EVERY MINUTE IT RUNS, THESE PARTS WILL INCREASE THE OIL CLEARANCE UNTIL IT EXPLODES. HOW LONG WILL IT LAST? I CAN'T SAY EXACTLY, BUT NOT TO LONG!
The crying shame here is that everyone will point their fingers at the connecting rod, bearings and/or crankshaft as the culprit.
THE MOST OVERLOOKED AREA IN ENGINE BUILDING IS AS FOLLOWS:You have a motor that has run for many months , but you notice you're getting a little blow-by and it could probably use a set of rings. It needs freshening up so we tear it down. Every thing looks great so we touch the bore with a hone and put a new set of rings in. Back to the races. If it ain't broke don't fix it. STOP! Under the most ideal conditions engine parts will change with use. Bearings can look good but will wear, connecting rod bores will change shapes and crank journals will wear and rod bolts will stretch and fatigue. It is just as important now as ever to check the dimensions of the parts. Don't go to sleep.
Some may think there is some deep mystery behind the term oil clearance. The reason is, everyone has a different opinion as to what it should be. As a rule of thumb, it can be anywhere between .0015 and .0035 and be in the ball park. If the clearance is on the low side, use thin oil, heavy oil will not work. If clearance is on the high side , use a heavier oil, thin oil will not work. How can you make a judgment on the oil to use unless you know what your oil clearance is? THERE IS NO MAGIC, YOU CANNOT KNOW WHAT YOUR OIL CLEARANCE IS UNLESS YOU MEASURE THE PARTS THAT AFFECT IT.
DEFINITION OF WHAT OIL CLEARANCE IS:
"The distance between two very smooth moving surfaces that will allow oil to be present at all times, coating both parts with a film of oil so that metal on metal contact never happens. It must be small enough to retain enough oil and large enough to allow a fresh cool supply to move through every microsecond."
If you do not check your parts and build 4 motors and 3 of them seem to have a pretty good life span you are lucky. If one fails out of the gate or shortly thereafter, shame on you. It takes less than 15 minutes to check and measure all the parts in a motor and the benefits are fantastic. It is possible to build an engine that will run until the cows come home, or something like that. There are many engine builders out there that do a fantastic job in this area, but on the other hand there are more that don't.
ASSUME NOTHING, BELIEVE NOTHING AND LAST BUT NOT LEAST, CHECK EVERYTHING.
I hope we have given you an insight to one reason for engine failures. If you need us, give us a call, it's all free. 1-800-521-3560
Tuesday, January 18, 2000
The Jury is Back and the Verdict is In
By: Carl Amundsen Date : January 18, 2000
The Case: To produce the best crankshaft ever.
The Jury: Engine builders, car owners, chassis builders from our customer base.
The Evidence:
The Material to be used
Much to do has been made about what kind of material should, could and would be used to make a crankshaft. Manufactures tout theirs are made of 4140, 4150, 8690, Stressproof, or other high mucky muck number designations. We investigated all of these options, but when the smoke cleared we came back to a material we had been using for 20 years. The material does not have a number designation because it is proprietary to the manufacturer and is patented. The brand of the material shall remain anonymous for our own reasons. The biggest user of this material is the mining industries, where it is used in augers, blades, conveyors or anything that requires a hard wear resistant material. We have used this material for 20 years in impeller blades for steel shot machines. Through its manufacturing process and mineral content it requires no hardening before it is used. It comes in the door with a hardness of 44 to 46 on the Rockwell "C" scale and the more it is used the harder it gets. This is all accomplished without it becoming brittle. The only negative side of this is that it is a nightmare to machine. It took about 6 weeks of trial and error to come up with the right feed rates and spindle speeds. The only tooling material that is compatible is solid carbide. Tool life at best is very expensive.
Design and Engineering
Instead of taking a brand new crankshaft out of the box and starting the process of cutting and grinding. This is not necessary with ARC cranks for most applications of camshafts and lifters etc. You will also find that there is no note in the box instructing you to deburr sharp edges, this has already been done. This was one of the more important items that we addressed in the manufacturing process. At least 15% 0f the machining time is spent removing sharp edges. This is an absolute must , this is also the reason other manufacturers simply leave you a note in the box. A sharp edge is an invitation for a crack to start, and no matter how small it is, it will grow just like cancer. I am sure everyone has seen the old trick of tearing a telephone book in half, same principal. We borrowed technology from NASCAR in designing the (airplane wing ) airfoil style counter weights. NASCAR has proven that it improves windage in the crank case and increases horsepower. The crank pin even has a true 1/8" radius for added strength and durability. Other crankshafts advertise that they are already balanced, NOT. We went through a very pain staking design process to make sure we could and should advertise a balanced crank. You will without a doubt notice the difference. ARC provides two differently balanced models of the +.563 stroker, one is balanced for the smaller bore up to .190 over and the 3 x 3 for the large 3 inch bore. Appearance, cosmetics and detail have always played a major roll in parts produced by ARC. I think we raised the bar on this one. Besides our logo, all ARC crankshafts are engraved with the part number and the date the part was manufactured. Little more can be said until you hold one in your hand, this crank is truly a work of art. Its worth mentioning , if you haven't already noticed, ARC has a habit of not following what the industry thinks or does. If we can't do it better, we just don't do it.
The Testing:
The latter part of August 1999 we made our first live test. You might think this is a crazy way to start testing, but we needed to build a motor that would come apart fairly easy, I mean explode! This was done with a blockzilla block, our new +.563 crank, an old .190 over piston with new rings, a used 4.225 rod with old rod bolts and a used 436 lift camshaft. We knew from the start that the rod bolts and/or the rod should break, they just had to much time on them. If our crankshaft was going to live it would have to withstand this. The tension and anxiety is growing. Over the next four weeks we made over 250 passes down our local 1/8-mile drag strip, seeing RPM's in excess of 9600. Nothing happened. Not being able to break it was becoming very frustrating. The next test we felt sure "The old wore out rod and bolts" would fail, and we would have our desired results. We put the motor on a kart chassis and ran it on the local 1/4 mile asphalt oval. This is the hardest test on any motor because you are constantly in and out of the throttle. We now had shipped a number of crankshafts to select customers with their promise to have them in motors very quickly, and report to us with results.
The results from the field are as follows:
"That's a beautiful part, works great.""Smoothest running motor I have ever seen, what did you do to it ?""I can't believe this , it's great !" "How soon can I get five more?" And so on. Everybody loves it and no one has had any problems.
We were now getting well into October and getting a little curious , what will break it ? We have over 125 laps on the kart and the motor just purrs. The only maintenance we had done was keeping oil in it. It was even suggested that we run it without oil, dumb idea of course but we were desperate for some results. We didn't do that obviously. At this time we turned the motor over to a local drag racer to finish the job. Finally some results. One of our crank shafts had made it through one of our renowned engine builder customers well west of the Mississippi and back to San Antonio , Texas. Charlie Bass Sr. and his son Charlie Bass Jr. are kart racers that race an outlaw class against the highly touted 2-cycles. However they use a Briggs Blockzilla. Over the past year they were using a 563 stroker crank of an origin I will not mention. They had the power they needed to lead and win races but kept breaking crankshafts. NEED I SAY MORE ? YES, I WILL! THEY WHIPPED EVERYONE AND WENT ON TO BECOME POINTS CHAMPION! A footnote to this is he always used ARC rods.
CONGRATULATIONS TO THE BASS FAMILY, WE LOVE YOU !
Texans have always laid claim to being a little different and I wouldn't debate that. Charlie Sr. had a strikingly different approach for checking for burrs and rough edges on our crank. He wiped the crank down with a pair of panty hose, and did not get a run in them. I didn't ask who the panty hose belonged to.
More Comments
"We no longer have to hold the kart down on the rack when we run the motor, it just sits there and purrs." " I can read the temp. gauge and tack now, I can see the flags." Charlie Bass Jr. " Is this smooth or is this smooth "
At their request we have put the Bass' in the unprotected witness program.
Charlie Jr. Leddfutt24@worldnet.att.net
Charlie Sr. DrBriggs94@worldnet.att.net Home phone 210-923-5730
THANKS AGAIN TO THE BASS FAMILY
Now back to our test motor. We were closer than we thought, it only took two more weekends of racing to do it. When we tore it down the rod bolts had broken along with the rod (as we predicted) and chunked the whole mess out of the side of the block. FINALLY RESULTS WE WERE WAITING FOR. WHEN WE BUILT THIS MOTOR WE INTENTIONALLY USED AN OLD ROD WITH OLD BOLTS, THAT SHOULD HAVE BEEN JUNKED. WE KNEW THE ROD WOULD BREAK , WE JUST DIDN'T KNOW WHEN. The crank was still straight, the crank pin was still in perfect shape and the only damage was some scuff marks on the counter weights. We checked the hardness of the crank pin and it had gone up 5 pts. on the Rockwell scale. Magnaflux revealed no stress or cracks. Anyone in his right mind would think surely this is enough, NOT US. What everyone wanted to see now was just what would break it. GET THIS, the stage was set, the crank was placed in a hole in our heavy duty welding bench which is two inches thick. The crankshaft was vertical with one counter weight resting on the table. Our weapon of destruction was a 10 lb. sledge hammer with a 36" handle powered by Randy Amundsen. Smashing down on the exposed counter weight, we wanted to see if the counter weights would touch before breaking the crank pin. To me this seemed cruel, it reminded me of the turkey losing his head Thanks Giving morning. This crank surely didn't have a chance.
LET THE CONTEST BEGIN
After 5 or 6 hits the crank was holding up fairly well. After about 12 hits the crank was bending but still refused to crack. Someone muttered " that crank thinks Randy is a wimp". After more than 25 over the head death blows the crank finally gave up. Before Randy could catch his breath another brand crankshaft was set up ready for the same challenge. Two smashes latter we knew who had the toughest crankshaft on the market. This was ARC's real world extreme testing at it's best and our new crankshafts finest hour.
CASE RESTED.
THE VERDICT
1. Its design and engineering is well thought out. 2. The appearance and cosmetics leaves the competition in dust 3.The balance is superb. 4.The strength is probably beyond necessary. 5.The price is higher but well worth it. 6.Go to market.
SUMMARY
ARC has created a crankshaft with limited sales potential. It is going to last the customer too long and greatly reduce repeat sales. It may create for the first time in history, a USED CRANKSHAFT MARKET.
The Case: To produce the best crankshaft ever.
The Jury: Engine builders, car owners, chassis builders from our customer base.
The Evidence:
The Material to be used
Much to do has been made about what kind of material should, could and would be used to make a crankshaft. Manufactures tout theirs are made of 4140, 4150, 8690, Stressproof, or other high mucky muck number designations. We investigated all of these options, but when the smoke cleared we came back to a material we had been using for 20 years. The material does not have a number designation because it is proprietary to the manufacturer and is patented. The brand of the material shall remain anonymous for our own reasons. The biggest user of this material is the mining industries, where it is used in augers, blades, conveyors or anything that requires a hard wear resistant material. We have used this material for 20 years in impeller blades for steel shot machines. Through its manufacturing process and mineral content it requires no hardening before it is used. It comes in the door with a hardness of 44 to 46 on the Rockwell "C" scale and the more it is used the harder it gets. This is all accomplished without it becoming brittle. The only negative side of this is that it is a nightmare to machine. It took about 6 weeks of trial and error to come up with the right feed rates and spindle speeds. The only tooling material that is compatible is solid carbide. Tool life at best is very expensive.
Design and Engineering
Instead of taking a brand new crankshaft out of the box and starting the process of cutting and grinding. This is not necessary with ARC cranks for most applications of camshafts and lifters etc. You will also find that there is no note in the box instructing you to deburr sharp edges, this has already been done. This was one of the more important items that we addressed in the manufacturing process. At least 15% 0f the machining time is spent removing sharp edges. This is an absolute must , this is also the reason other manufacturers simply leave you a note in the box. A sharp edge is an invitation for a crack to start, and no matter how small it is, it will grow just like cancer. I am sure everyone has seen the old trick of tearing a telephone book in half, same principal. We borrowed technology from NASCAR in designing the (airplane wing ) airfoil style counter weights. NASCAR has proven that it improves windage in the crank case and increases horsepower. The crank pin even has a true 1/8" radius for added strength and durability. Other crankshafts advertise that they are already balanced, NOT. We went through a very pain staking design process to make sure we could and should advertise a balanced crank. You will without a doubt notice the difference. ARC provides two differently balanced models of the +.563 stroker, one is balanced for the smaller bore up to .190 over and the 3 x 3 for the large 3 inch bore. Appearance, cosmetics and detail have always played a major roll in parts produced by ARC. I think we raised the bar on this one. Besides our logo, all ARC crankshafts are engraved with the part number and the date the part was manufactured. Little more can be said until you hold one in your hand, this crank is truly a work of art. Its worth mentioning , if you haven't already noticed, ARC has a habit of not following what the industry thinks or does. If we can't do it better, we just don't do it.
The Testing:
The latter part of August 1999 we made our first live test. You might think this is a crazy way to start testing, but we needed to build a motor that would come apart fairly easy, I mean explode! This was done with a blockzilla block, our new +.563 crank, an old .190 over piston with new rings, a used 4.225 rod with old rod bolts and a used 436 lift camshaft. We knew from the start that the rod bolts and/or the rod should break, they just had to much time on them. If our crankshaft was going to live it would have to withstand this. The tension and anxiety is growing. Over the next four weeks we made over 250 passes down our local 1/8-mile drag strip, seeing RPM's in excess of 9600. Nothing happened. Not being able to break it was becoming very frustrating. The next test we felt sure "The old wore out rod and bolts" would fail, and we would have our desired results. We put the motor on a kart chassis and ran it on the local 1/4 mile asphalt oval. This is the hardest test on any motor because you are constantly in and out of the throttle. We now had shipped a number of crankshafts to select customers with their promise to have them in motors very quickly, and report to us with results.
The results from the field are as follows:
"That's a beautiful part, works great.""Smoothest running motor I have ever seen, what did you do to it ?""I can't believe this , it's great !" "How soon can I get five more?" And so on. Everybody loves it and no one has had any problems.
We were now getting well into October and getting a little curious , what will break it ? We have over 125 laps on the kart and the motor just purrs. The only maintenance we had done was keeping oil in it. It was even suggested that we run it without oil, dumb idea of course but we were desperate for some results. We didn't do that obviously. At this time we turned the motor over to a local drag racer to finish the job. Finally some results. One of our crank shafts had made it through one of our renowned engine builder customers well west of the Mississippi and back to San Antonio , Texas. Charlie Bass Sr. and his son Charlie Bass Jr. are kart racers that race an outlaw class against the highly touted 2-cycles. However they use a Briggs Blockzilla. Over the past year they were using a 563 stroker crank of an origin I will not mention. They had the power they needed to lead and win races but kept breaking crankshafts. NEED I SAY MORE ? YES, I WILL! THEY WHIPPED EVERYONE AND WENT ON TO BECOME POINTS CHAMPION! A footnote to this is he always used ARC rods.
CONGRATULATIONS TO THE BASS FAMILY, WE LOVE YOU !
Texans have always laid claim to being a little different and I wouldn't debate that. Charlie Sr. had a strikingly different approach for checking for burrs and rough edges on our crank. He wiped the crank down with a pair of panty hose, and did not get a run in them. I didn't ask who the panty hose belonged to.
More Comments
"We no longer have to hold the kart down on the rack when we run the motor, it just sits there and purrs." " I can read the temp. gauge and tack now, I can see the flags." Charlie Bass Jr. " Is this smooth or is this smooth "
At their request we have put the Bass' in the unprotected witness program.
Charlie Jr. Leddfutt24@worldnet.att.net
Charlie Sr. DrBriggs94@worldnet.att.net Home phone 210-923-5730
THANKS AGAIN TO THE BASS FAMILY
Now back to our test motor. We were closer than we thought, it only took two more weekends of racing to do it. When we tore it down the rod bolts had broken along with the rod (as we predicted) and chunked the whole mess out of the side of the block. FINALLY RESULTS WE WERE WAITING FOR. WHEN WE BUILT THIS MOTOR WE INTENTIONALLY USED AN OLD ROD WITH OLD BOLTS, THAT SHOULD HAVE BEEN JUNKED. WE KNEW THE ROD WOULD BREAK , WE JUST DIDN'T KNOW WHEN. The crank was still straight, the crank pin was still in perfect shape and the only damage was some scuff marks on the counter weights. We checked the hardness of the crank pin and it had gone up 5 pts. on the Rockwell scale. Magnaflux revealed no stress or cracks. Anyone in his right mind would think surely this is enough, NOT US. What everyone wanted to see now was just what would break it. GET THIS, the stage was set, the crank was placed in a hole in our heavy duty welding bench which is two inches thick. The crankshaft was vertical with one counter weight resting on the table. Our weapon of destruction was a 10 lb. sledge hammer with a 36" handle powered by Randy Amundsen. Smashing down on the exposed counter weight, we wanted to see if the counter weights would touch before breaking the crank pin. To me this seemed cruel, it reminded me of the turkey losing his head Thanks Giving morning. This crank surely didn't have a chance.
LET THE CONTEST BEGIN
After 5 or 6 hits the crank was holding up fairly well. After about 12 hits the crank was bending but still refused to crack. Someone muttered " that crank thinks Randy is a wimp". After more than 25 over the head death blows the crank finally gave up. Before Randy could catch his breath another brand crankshaft was set up ready for the same challenge. Two smashes latter we knew who had the toughest crankshaft on the market. This was ARC's real world extreme testing at it's best and our new crankshafts finest hour.
CASE RESTED.
THE VERDICT
1. Its design and engineering is well thought out. 2. The appearance and cosmetics leaves the competition in dust 3.The balance is superb. 4.The strength is probably beyond necessary. 5.The price is higher but well worth it. 6.Go to market.
SUMMARY
ARC has created a crankshaft with limited sales potential. It is going to last the customer too long and greatly reduce repeat sales. It may create for the first time in history, a USED CRANKSHAFT MARKET.
Tuesday, June 1, 1999
Probable Cause of Most Rod Failures
To help prevent engine failure, here's a few tips:
For the most part, a quality billet connecting rod doesn't just break. There are several things that can really shorten the life of a rod of which bearing clearance is probably the most important and too much is worse than not enough.
Visual inspection (or eye balling) is not good enough. The only way to check a crankshaft, rod or bearing is with micrometers and dial bore gauges. Dial calipers or digital calipers are just not accurate enough. Even with the ones that have .0005" graduations, the accuracy is generally + or - .001" which means outside to inside measurements could have a total error of .004".
The Crankshaft:Just because a crankshaft looks good, doesn't mean it is to size and round.Using a 1" micrometer, measure the rod journal of the crankshaft in 4 places. A crankshaft with more than .0005" wear or out-of-round will probably not last very long in a 9500 rpm race environment.Keep in mind, what you might get by with in a stock engine, will not be as forgiving in a high rpm, high horsepower engine.
Surface finish of the rod journal is also very important especially when a babbit bearing is used. Most of the new Raptor III cranks I've seen and checked are way too rough.
Bearings: One of the most common things we hear is "The bearing looked ok, so I reused it"Again, looks can be very deceiving. Take a 1" ball micrometer or use a ball anvil attachment on your mic to measure the bearing thickness in several places. The ball anvil is necessary because of the curvature of the bearing.The measurement should be .075" and, on a crankshaft that measures .998" on the rod journal, this should give you .0025" clearance.
On a bearing that has been run or has been honed or sanded for clearance, carefully mic each half on the outside edges and in the middle.Remember, a new bearing should measure .075" which should give you .0025 clearance. If the top bearing measures .073" and the lower bearing measures .074", you now have .0055" clearance.
Some engine builders use a ball type hone to clearance bearings and this can cause a major problem. The Babbitt material is very soft and easily removed. What happens is that as the flex ball hone enters and exits the bearing bore, it removes far more material from the edges than from the center producing an hour glass shape. Using a plastigage or measuring the bearing in the center may give you a false and possibly fatal reading.You may think you had .003" clearance (and you did in the center) but, it will be a very narrow contact area and wear rapidly and as this clearance increases, it compounds the problems.This additional clearance pounds the bearings until the rod & piston assembly becomes a 9000 rpm slide hammer. This is when you have a failure.
Special note: Never file or grind the ends of a bearing. If the installed i.d. of the bearing is too large (measured inside diameter of the bearings installed in the rod and torqued too 150 inch/pounds), gently and slowly remove material from the parting edges of both halves with fine emery cloth on a flat surface until you get an installed i.d. of .9995" to 1.0015" for stock .998" cranks and .8765" to .8785" for stroker .875" cranks. It is better to sneak up on this slowly.
These bearings are designed to crush in the bore of the rod which holds them in place and prevents them from spinning. The tangs are primarily for location. If your crank measures less than .997" or .874", it is probably a good idea to replace it. In any case, it is not a good idea to try to compensate for a worn crank journal by reducing the i.d. of the bearing.
Inspect and/or replace the bearings regularly. By examining the bearings, you can set up a schedule of how often to replace them - plus - by measuring and looking for excessive smearing or wear-through of the babbit material, you'll be able to tell if your oil is doing its job.
Rod Bolts: Proper rod bolt torque is VERY important. In order to keep from backing out, it is necessary for a bolt to stretch a specific amount so the threads lock into place. This is a little known or understood requirement for a bolt to do the job it is designed to do. The proper stretch for a bolt is usually achieved by torquing the bolt a calculated amount based on the bolt's design and the characteristics of the application. ARC's rod bolts are custom designed to achieve thread-lock at 170 inch/lbs. This MUST be measured with an accurate inch/lb torque wrench. Failure to properly torque the bolts is a all to common cause of rod failure, second only to the oil clearance issues explained above.
Treat your engine as the piece of precision equipment that it is. The environment in which it operates is extremely harsh and attention to detail along with precise measurements is absolutely necessary.
For the most part, a quality billet connecting rod doesn't just break. There are several things that can really shorten the life of a rod of which bearing clearance is probably the most important and too much is worse than not enough.
Visual inspection (or eye balling) is not good enough. The only way to check a crankshaft, rod or bearing is with micrometers and dial bore gauges. Dial calipers or digital calipers are just not accurate enough. Even with the ones that have .0005" graduations, the accuracy is generally + or - .001" which means outside to inside measurements could have a total error of .004".
The Crankshaft:Just because a crankshaft looks good, doesn't mean it is to size and round.Using a 1" micrometer, measure the rod journal of the crankshaft in 4 places. A crankshaft with more than .0005" wear or out-of-round will probably not last very long in a 9500 rpm race environment.Keep in mind, what you might get by with in a stock engine, will not be as forgiving in a high rpm, high horsepower engine.
Surface finish of the rod journal is also very important especially when a babbit bearing is used. Most of the new Raptor III cranks I've seen and checked are way too rough.
Bearings: One of the most common things we hear is "The bearing looked ok, so I reused it"Again, looks can be very deceiving. Take a 1" ball micrometer or use a ball anvil attachment on your mic to measure the bearing thickness in several places. The ball anvil is necessary because of the curvature of the bearing.The measurement should be .075" and, on a crankshaft that measures .998" on the rod journal, this should give you .0025" clearance.
On a bearing that has been run or has been honed or sanded for clearance, carefully mic each half on the outside edges and in the middle.Remember, a new bearing should measure .075" which should give you .0025 clearance. If the top bearing measures .073" and the lower bearing measures .074", you now have .0055" clearance.
Some engine builders use a ball type hone to clearance bearings and this can cause a major problem. The Babbitt material is very soft and easily removed. What happens is that as the flex ball hone enters and exits the bearing bore, it removes far more material from the edges than from the center producing an hour glass shape. Using a plastigage or measuring the bearing in the center may give you a false and possibly fatal reading.You may think you had .003" clearance (and you did in the center) but, it will be a very narrow contact area and wear rapidly and as this clearance increases, it compounds the problems.This additional clearance pounds the bearings until the rod & piston assembly becomes a 9000 rpm slide hammer. This is when you have a failure.
Special note: Never file or grind the ends of a bearing. If the installed i.d. of the bearing is too large (measured inside diameter of the bearings installed in the rod and torqued too 150 inch/pounds), gently and slowly remove material from the parting edges of both halves with fine emery cloth on a flat surface until you get an installed i.d. of .9995" to 1.0015" for stock .998" cranks and .8765" to .8785" for stroker .875" cranks. It is better to sneak up on this slowly.
These bearings are designed to crush in the bore of the rod which holds them in place and prevents them from spinning. The tangs are primarily for location. If your crank measures less than .997" or .874", it is probably a good idea to replace it. In any case, it is not a good idea to try to compensate for a worn crank journal by reducing the i.d. of the bearing.
Inspect and/or replace the bearings regularly. By examining the bearings, you can set up a schedule of how often to replace them - plus - by measuring and looking for excessive smearing or wear-through of the babbit material, you'll be able to tell if your oil is doing its job.
Rod Bolts: Proper rod bolt torque is VERY important. In order to keep from backing out, it is necessary for a bolt to stretch a specific amount so the threads lock into place. This is a little known or understood requirement for a bolt to do the job it is designed to do. The proper stretch for a bolt is usually achieved by torquing the bolt a calculated amount based on the bolt's design and the characteristics of the application. ARC's rod bolts are custom designed to achieve thread-lock at 170 inch/lbs. This MUST be measured with an accurate inch/lb torque wrench. Failure to properly torque the bolts is a all to common cause of rod failure, second only to the oil clearance issues explained above.
Treat your engine as the piece of precision equipment that it is. The environment in which it operates is extremely harsh and attention to detail along with precise measurements is absolutely necessary.
Thursday, January 7, 1999
The Crankcase Vacuum System (CVS)
By: The ARC R&D Team Date: January 7, 1999
Re: Crankcase pressure management
For as many years as I can remember, crankcase ventilation went like this:
If you were blowing oil and having gasket and seal problems, you just added another line from your motor to the catch can. I have seen as many as 6 lines running from a motor, but the problem was still there.
In case you didn’t know it, we were just adding insult to injury.
Viewed from the crankcase, the single cylinder motor is an excellent air compressor. The more air you take in, the more you have to push out somewhere. Consequently the more air that is being passed through the crankcase, the more oil that will follow the air out.
All small engine manufactures have done a fair job in their crankcase ventilation system, but it only works up to about 3,000 rpm.
NASCAR and the Drag Racing industry have long used a dry sump oiling system that also creates a negative pressure (or partial vacuum) in the crankcase.
A multi-cylinder engine is a little simpler to deal with because one piston going up is canceling the pressure of the other one coming down. The basic thing you are dealing with here is called blow-by.
Without getting into a long technical and complex discussion on the subject, let me just make this statement. The rings on the piston are designed to work at their maximum with pressure from the top and vacuum from the bottom.
Common sense will also tell us that the piston will function much better and develop more horsepower if it is being pushed down in a negative pressure environment. In fact, with vacuum in the crankcase, the piston is actually being sucked down the cylinder wall.
Any positive pressure in the crankcase will allow a certain amount of oil to get passed the rings and contaminate the fuel charge. This can and will reduce horsepower.
Our Crankcase Vacuum System is very complex in design and every hole, groove, passage and vent are critical to its successful operation. Even the length and size of the tubing used in the catch can model for Kart racing are critical.
While the design is very complex, the operation is very simple to explain.
Without the CVS, the tappet room (valve spring area) is continually being flooded with oil and, contrary to popular opinion, this volume of oil is NOT being caused by the length or design of the dipper on the connecting rod - the cam gear is the culprit.
A little side note right here on horsepower. If the tappet room is flooded with oil and the valve guides are a little on the sloppy side, oil can easily be sucked by the valve stem and contaminate the fuel charge.
Our CVS works like this:
As oil and air are being pushed up to the tappet room, the first baffle is atomizing the oil and lubricating the valve stem with a mist. The second baffle is now starting to separate the air from the oil.
The 2 check valve discs are sensing the blow-by of each down stroke of the piston, regardless of how minute the amount, and are opening and closing on each stroke.
When the piston is at the top of the stroke, we will have our maximum vacuum. When it nears the bottom, vacuum gives way to the amount of blow-by pressure from the rings. The best calculations we can come up with is that we have vacuum 95% of the time and little or no pressure 5% of the time.
As the mist of oil and air move through the CVS, we are continuing to separate the two in our maze of holes, grooves and passages.
In the final step of this unique process, we are now using the vacuum in the crankcase to pull the oil, which is heavier, back into the crankcase, and the oil free air is vented.
AND THAT’S JUST HOW SIMPLE IT WORKS !
While the operation is simple, the R&D on this project has been the most intense of any project we have ever undertaken at ARC Racing. The Dyno testing has been extensive, not only by us, but other engine builders as well along with track testing that has been on going for months.
The results: THIS UNIT HAS MADE HORSEPOWER ON EVERY SINGLE TEST.
Re: Crankcase pressure management
For as many years as I can remember, crankcase ventilation went like this:
If you were blowing oil and having gasket and seal problems, you just added another line from your motor to the catch can. I have seen as many as 6 lines running from a motor, but the problem was still there.
In case you didn’t know it, we were just adding insult to injury.
Viewed from the crankcase, the single cylinder motor is an excellent air compressor. The more air you take in, the more you have to push out somewhere. Consequently the more air that is being passed through the crankcase, the more oil that will follow the air out.
All small engine manufactures have done a fair job in their crankcase ventilation system, but it only works up to about 3,000 rpm.
NASCAR and the Drag Racing industry have long used a dry sump oiling system that also creates a negative pressure (or partial vacuum) in the crankcase.
A multi-cylinder engine is a little simpler to deal with because one piston going up is canceling the pressure of the other one coming down. The basic thing you are dealing with here is called blow-by.
Without getting into a long technical and complex discussion on the subject, let me just make this statement. The rings on the piston are designed to work at their maximum with pressure from the top and vacuum from the bottom.
Common sense will also tell us that the piston will function much better and develop more horsepower if it is being pushed down in a negative pressure environment. In fact, with vacuum in the crankcase, the piston is actually being sucked down the cylinder wall.
Any positive pressure in the crankcase will allow a certain amount of oil to get passed the rings and contaminate the fuel charge. This can and will reduce horsepower.
Our Crankcase Vacuum System is very complex in design and every hole, groove, passage and vent are critical to its successful operation. Even the length and size of the tubing used in the catch can model for Kart racing are critical.
While the design is very complex, the operation is very simple to explain.
Without the CVS, the tappet room (valve spring area) is continually being flooded with oil and, contrary to popular opinion, this volume of oil is NOT being caused by the length or design of the dipper on the connecting rod - the cam gear is the culprit.
A little side note right here on horsepower. If the tappet room is flooded with oil and the valve guides are a little on the sloppy side, oil can easily be sucked by the valve stem and contaminate the fuel charge.
Our CVS works like this:
As oil and air are being pushed up to the tappet room, the first baffle is atomizing the oil and lubricating the valve stem with a mist. The second baffle is now starting to separate the air from the oil.
The 2 check valve discs are sensing the blow-by of each down stroke of the piston, regardless of how minute the amount, and are opening and closing on each stroke.
When the piston is at the top of the stroke, we will have our maximum vacuum. When it nears the bottom, vacuum gives way to the amount of blow-by pressure from the rings. The best calculations we can come up with is that we have vacuum 95% of the time and little or no pressure 5% of the time.
As the mist of oil and air move through the CVS, we are continuing to separate the two in our maze of holes, grooves and passages.
In the final step of this unique process, we are now using the vacuum in the crankcase to pull the oil, which is heavier, back into the crankcase, and the oil free air is vented.
AND THAT’S JUST HOW SIMPLE IT WORKS !
While the operation is simple, the R&D on this project has been the most intense of any project we have ever undertaken at ARC Racing. The Dyno testing has been extensive, not only by us, but other engine builders as well along with track testing that has been on going for months.
The results: THIS UNIT HAS MADE HORSEPOWER ON EVERY SINGLE TEST.
Dual Plane Balancing
We receive lots of calls about balancing and one of the first questions is always, "What is DUAL PLANE BALANCING".
If you read the book on it, and you had a background in engineering and physics, you could get a good understanding of it. The two terms that are used in the explanation are Force and Couple balancing. What we are going to attempt to do is reduce all of this down to a non-technical explanation.
Lets go back many years to tire balancing. Your rim and tire assembly was mounted on a shaft and then placed on a frame with the shaft resting in a ball bearing V fixture. The tire assembly would then rotate around until the heavy part came to rest at 6 o’clock. A wheel weight was then placed at 12 o’clock on one side of the tire. You kept adjusting this weight until the tire would not move regardless of how you repositioned it in the V fixture.This process is called, Static or Force balancing.
Then an improvement was made in this process. Instead of putting all the weight on one side of the rim, it would be split with ½ of the weight going to the inside. This was the first form of Couple balancing in the tire industry. Not perfect, but an improvement.As years went by, and the advent of much wider tires came into being, the need for Couple balancing increased.
We know have electronic tire balancers that spin the tire assembly and calculates the amount of weight needed to Force balance. Then it calculates what amount goes on the inside of the rim and what goes on the outside. This is Dual Plane balancing of a tire.
How does Dual Plane Balancing apply to the Briggs Crankshaft ?
A bob weight is attached to the rod journal of the crankshaft that represents 100 % of the rotating weight and a percentage of the reciprocating weight. This assembly is then placed on the ball bearing V’s of the balancer. It is then spun up to the operating RPM. Now the balancer can read both sides of the crankshaft and precisely tell the operator the amount of weight that needs to be added or removed from the left or right counter weight.This completes the Force and Couple (Dual Plane) balancing.
Special Note:If you change the connecting rod and/or piston, wrist pin and rings, the crankshaft may need re-balancing.
If you read the book on it, and you had a background in engineering and physics, you could get a good understanding of it. The two terms that are used in the explanation are Force and Couple balancing. What we are going to attempt to do is reduce all of this down to a non-technical explanation.
Lets go back many years to tire balancing. Your rim and tire assembly was mounted on a shaft and then placed on a frame with the shaft resting in a ball bearing V fixture. The tire assembly would then rotate around until the heavy part came to rest at 6 o’clock. A wheel weight was then placed at 12 o’clock on one side of the tire. You kept adjusting this weight until the tire would not move regardless of how you repositioned it in the V fixture.This process is called, Static or Force balancing.
Then an improvement was made in this process. Instead of putting all the weight on one side of the rim, it would be split with ½ of the weight going to the inside. This was the first form of Couple balancing in the tire industry. Not perfect, but an improvement.As years went by, and the advent of much wider tires came into being, the need for Couple balancing increased.
We know have electronic tire balancers that spin the tire assembly and calculates the amount of weight needed to Force balance. Then it calculates what amount goes on the inside of the rim and what goes on the outside. This is Dual Plane balancing of a tire.
How does Dual Plane Balancing apply to the Briggs Crankshaft ?
A bob weight is attached to the rod journal of the crankshaft that represents 100 % of the rotating weight and a percentage of the reciprocating weight. This assembly is then placed on the ball bearing V’s of the balancer. It is then spun up to the operating RPM. Now the balancer can read both sides of the crankshaft and precisely tell the operator the amount of weight that needs to be added or removed from the left or right counter weight.This completes the Force and Couple (Dual Plane) balancing.
Special Note:If you change the connecting rod and/or piston, wrist pin and rings, the crankshaft may need re-balancing.
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