DRIVE CLUTCH BALANCING DIFFERENCES

burndown said:

Your thought process is sound. The reason that you can't include the belt into the balancing equation of the clutches is that the belt is static to the clutches, i.e. a different part of the belt touches different sections of the clutch on each rotation of the belt-so taking that into consideration isn't possible, whereas a tire on a wheel is constantly beaded to that same part of a wheel on a car. Of course, you shouldn't run a belt missing sections or with burned spots in it....

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Exactly my point.....you have major part of the rotating mass that cannot be included in the balance of the clutch, but it is ALWAYS present.
If your tire on your truck DID rotate on the wheel (like the belt on a clutch) would we even bother trying to attain balance? Would it make ANY sense to balance just the wheel (clutch) and then throw a tire (belt) on it that we know will throw it off balance?? To top it off, the belt is only acting on 1/2 of the circumference of the clutch so the force exerted is no where close to equal or constant. just thinking out loud- a little slow at work today :face-icon-small-win

Mountainhorse, I think you and I agree much more than we disagree!:face-icon-small-win
And, not to rag on indydan, because I do believe he is very intelligent and provides good service, but right in his first post he states he sets belt to sheave clearance at zero to .010 MAX, which you and I would both agree is probably not correct.....but, to each his own....

Yep.... I think we do.

His zero to .010" is on a brand new belt that will break-in to be.010 to .020" once run....

So does having your clutches balanced really have a big effect on how a sled performs?

polaris dude said:

So does having your clutches balanced really have a big effect on how a sled performs?

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YES YES AND YES

This thread SHOULD be named "Drive clutches... making them work the way they need to"

An old worn out clutch that is balanced is still an old worn out clutch.

If your clutch is in excellent condition, with good bushings, no grooves in the shieves, with the side clearance set then the balance will make the engine smoother if it is out of balance in the first place.

Most of the factory clutches that I've seen are not balanced very well from the factory. I say this because I have personally seen a night and day difference in smoothness from many new, factory robotic balanced, that were re-shimmed and re balanced. The factory can only take so much time to balance a clutch... plus there are errors sometimes that happen.

Since the Primary is THE power link from the engine to the remainder of the drive-train, I believe that it should be as good as can be and that you should have the clutches set up as good as they can be in order to get the most out of the sled.

I have seen a couple (2) brand new 2009 & 2010 800 Dragons (one in Cali one in Idaho) that the Primary was not functioning properly from the factory. The dealer could not figure out why the sled would not pull RPM's... lots of work and even a factory rep out to check the sled... Installed a new "loaner" clutch off another working sled... problem went away and the sled ripped.

Go figure.

For the investment that we put in these sleds and in using them... I think that it is good money spent to have this stuff verified to be "Spot-On"... All the clutch kits in the world wont do a thing for you if the clutch is not working the way it should.

Heck... I checked out over 30 sleds on my road trip last year... just because I was curious.. only about 8 or 9 of them were even close to being in spec for belt deflection and side clearance, only one of those was within the factory spec of .020"... most of those sleds were sitting new on the showroom floors of the dealers...

MH the clutch I got from you last season that had been balanced by Dan made quite a noticable difference in felt virations on the 9.

Kreg,

I'm glad to hear it!!

Going to throw my 2 cents in here because I think a few things are being missed. I will tell you first off that polaris told me that there was no way the clutch balance was off using Burndowns reasoning. I went ahead and had it balance it what we found was sickening. The balance was so far off from the factory that it would have been better if they had not even tried to balance it.
The clutch two sheaves actually had to be turned and re-indexed so it could even be made to be balanced or you would have been drilling holes directly opposite this great factory balance you think you have.

Bubble Balancers are Crap. You can not possible balance a clutch precisely enough with one. You can not even balance a tire precisely on one. If I saw a shop was balancing a clutch on a bubble balancer I would never ever have that shop work on anything.

I will agree that yes you need the proper duel axis machine to be able to balance these. I have no doubt that Indydan has the equipment to do this and after reading his post I will probably send him my clutch to rebalance because what he is doing is not just balancing it, it sounds to be a completely rebuild with a balance at a price that is unbelievably cheep for this kind of work.


There is a guy in Missoula Mt who was balancing clutches for 100. That did not include all the machine work Dan is adding in. The machine he uses is a Duel axis balancer designed for just what burndown said balancing cranks on drag motors. He has special adapters to be able to do snowmobile clutches. Would I expect to find this machine in a private shop in Missoula, hell no. I can not remember what he said the cost of the machine was but it was over 100,000 and if memory serves me right 300,000 does sound about right.

He also told me another spec that I can not remember but maybe a IndyDan might know about the amount of force exerted by a spinning object that was 1 gram out of balance turning at a certain rotational speed. Wish I could remember the numbers but the amount of force is unreal, all beating on the end of your crank.

In a perfect world yes the clutch would stay perfect. What people are not taking into account for here is that the entire rotating mass of the engine would also have to be perfect with a crank runout of 0.00. Since this is almost never seen on the 900 motor, even the most perfectly balance clutch is still taking abuse from the other internal forces within the engine as well as external forces from the belt. These forces cause things to wear. This is why the clutch needs to be carefully inspected for wear before balancing. You can not balance a worn out clutch. I can see visible wear in my clutch from the spring, I am sure there are other parts that can not be seen without disassembly.

Is it worth it and does it make any difference? Yes and Yes. Before my 900 at idle was like watching a Harley idling. You could visibly see the handlebars shaking. After the balancing it was hard to believe it was even the same sled. There was only a slight shaking at idle which almost completely disappeared at higher RPM's. My only regret is that I didn't know about clutch balancing and have it done sooner, the sled is so much nicer to ride now.

Great info. I have been balanceing Harley fly wheels since the early 80s huge differents.Had my 700 done two years ago.Now I need a clutch for a 07 600 rmk the rollers are shot,the weights set at a angle[ is this correct ]and the outer sheave is cracked this sled has 2000 miles on it.Indy Dan do you sell clutches all set up to specs or do I have to buy a clutch and send it out.

clutch

Dan thanks for the info will be sending my clutch out monday to get balanced and weights checked Josh

I found some info on the force exerted on a spinning crankshaft with a 2 gram imbalance. This is basically what we are dealing with because once the clutch is bolted on it becomes a part of the spinning crank assembly.

Forces In Action
To better understand the mechanics of balancing, let’s look at the theory behind it. As everybody knows, a rotating object generates "centripetal force." Centripetal force is an actual force or load generated perpendicular to the direction of rotation. Tie a rope to a brick and twirl it around and you’ll feel the pull of centripetal force generated by the "unbalanced" weight of the brick. The faster you spin it, the harder it pulls. In fact, the magnitude of the force increases exponentially with speed. Double the speed and you quadruple the force.


The centripetal force created by a crankshaft imbalance will depend upon the amount of imbalance and distance from the axis of rotation (which is expressed in units of grams, ounces or ounce-inches). A crankshaft with only two ounce-inches of imbalance at 2,000 rpm will be subjected to a force of 14.2 lbs. At 4,000 rpm, the force grows to 56.8 lbs.! Double the speed again to 8,000 rpm and the force becomes 227.2 lbs.

This may not sound like much when you consider the torque loads placed upon the crankshaft by the forces of combustion. But centripetal imbalance is not torque twisting the crank. It is a sideways deflection force that tries to bend the crank with every revolution. Depending on the magnitude of the force, the back and forth flexing can eventually pound out the main bearings or induce stress cracks that can cause the crank to snap.


That is with a 2 gram imbalance, 227 lbs of force at 8000 rpm. I believe this is precisely what is happening on the 900 engines that causes the crank breakage.

Here is the site I got that off of, they have a picture of a balancing machine that you need to do this kind of precise balancing on there and more info.

http://www.rpmmachine.com/engine-balancing.shtml

ttt:bump2:

mountainhorse said:

In this world, You get what you pay for most of the time...

RON on the forum here took the time to write up a great mini-article on his process that took him to the balancers shop.

http://www.snowest.com/forum/showthread.php?t=87640

His adventure in going thru his complete clutch to get it to the balance shop parallels your process above.

He spent a lot of time on his Brand new ZERO HOUR clutch just to get it ready to balance.
That was on his brand new 2009 800 RMK!!

It's great to see all of this info posted on the forums for all to read.

Thanks to both you and RON (great pix by the way) a lot more people on the forum here know a lot more about the process.

I can see your main point that the clutch must be in great shape before the process can even be started... RONS was NEW and he still needed to spend a lot of time on getting it right.

Rockin RMK.... Have a look at RONS post with his new Dragons clutch... very good presentation that will answer your question.

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I just installed a clutch on my 06 900 that had a full service done on it at indy specialty, and what a huge improvement my sled runs sooo smoothe. Ski tips don't move at all! They did alot of drillin on it, machined the sheave faces, and im sure alot more that I don't see! WELL WORTH the$ !!!!

danduvall said:

I just installed a clutch on my 06 900 that had a full service done on it at indy specialty, and what a huge improvement my sled runs sooo smoothe. Ski tips don't move at all! They did alot of drillin on it, machined the sheave faces, and im sure alot more that I don't see! WELL WORTH the$ !!!!

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It's pretty amazing isn't it. I argued with polaris for the longest time about the clutch being out of balance. It will be like a whole different machine now and your hands won't be cussing you at the end of a long day of riding.

Im glad I spent the extra$ and got a quality clutch servicing from the boys at I.S. . There's almost no vibe in the bars at idle, and zero vibe at off-idle rpms! Not gunna waste the$ on a isovibe or shockblokr now! Whoop!

I agree with all that has been said, the best money I have spent on the 900, is the clutch work and balancing done by Dan and the boys at Indy Specialties. The vibration is substantially less and worth every penny!!

hey i would like to have my clutch balanced how long would it take to do and when would it work for you to get at it ??