belt drives the future?

[geo]

"Cause it ain't snowing for me yet, cause some of this is cut and paste from a PM, cause I like "refining your sled" threads (lolol and some merry xmas reading) I thought t start a thread on refining your belt drive if you want.
Benefits are cooler running belt (godda be more HP to track lol) and for me, easier to roll off the truck is important too lol.

We still are the only OEM to give the opportunity to get a belt drive stock. Maybe '13 scared them. Maybe it's too expensive. Maybe it's because some still don't trust them lol but IMO it has been a very nice addition to my sled.
After market still does well here too.

Not much in issues discussed since the introduction of the stronger belt in '14. That's good but I don't have stock because I wanted to gear down.
I picked C3 because it has the lowest rotating mass and they were close by. The gearing I picked gave me two sprockets without belt guides. They are narrow too and the tensioner is the only guide here so I probably had more reason than some to pursue refinement of the belt drive in an OEM sled.


I've been on a quest since the first 100 miles to get rid of the heat in the belt area and in the belt itself. First year (stock) I caught issues and fixed them and each one helped some but after any higher speed stuff (like returning to the truck lol) the open it up and pack the top pulley with snow was needed (for me anyway). Got 1700 miles on the belt so all was good except for the temp for me.

Second year with guideless pulleys I had to reshim things just to keep the belt on but that was handled quickly. Thing is if I ran reverse for a bit I watched the belt walk across the pulley (again C3 pulleys I have, have nothing to stop the belt on the edges) and the more I ran it in reverse the more it tried to climb out of the tensioner-guide. If I loosened the belt enough it would walk right off. No amount of shimming on the pulleys or tensioner would stop this from happening.
I probably would not have noticed this if the pulleys had guides or were wider but by the time the C3 tensioner was doing some belt guiding the belt would be slightly off the bottom pulley in reverse (or forward if I was shimmed wrong) . That bugged me.
And, I still had the heat at higher belt speeds too. Dang, but no failures in the shorter 1000 miles though the belt had funny enough wear that it became the spare for this year. I wanted more.


This year has been a "high speed" year for my few rides lol so temps (for me) should be a problem. Particularly the top pulley that I've jammed snow on so many times lol. It's not. Belts drives don't need to run hot even at high speeds.

I changed pipe and track this year.
First thing I wanted to do was move the Aaen can away from the belt drive. Did this for two reasons. One was to give me access to the silly C3 tensioner bolt spot and second was because I always thought the radiant heat from the can was some of the problem. Stiil don't know lol but I like the temps now.
I moved the top of the can forward 4 in. or so and did what I had to do to make things fit. When I checked things last year on the black C3 tensioner assy temps were over 200'F and top pulley check was 240 plus at the truck. Always. This year I had 140 at the tensioner and 140 at the top pulley at the truck. Low snow but high speeds.
My hand in the field is very happy. No snow needed.

Second thing I did was bolt things up with out the track and figure out the belt walking thing. Had to be something in alignment IMO but I thought I had trued things up last year using the normal C to C, smart level, steel ruler-tape measure stuff I`ve done before. I didn't realize how far off I was stock and that my original alignment method was only good in an arc. It wasn't good enough for my belt drive.
C3 sent me some outside washers and a new top gear to fit them (cause I whined lol) so I bolted stuff up with present shimming and now the belt would stay on the bottom pulley (cause it can`t move on the top) but it still walked side to side going from forward to reverse. Not good enough lol. Still wanted to know why and get rid of this.
I was out 6 thou. top to bottom (top tilted in) and 5 thou front to back (front tilted to the left) with the smaller diameter than stock C3 bottom after my "trueing" of the previous year. Stock holes (on clutch side) gave me 12 thou (top tilted in) and 5 thou. (back tilted to left). Small amount out on the clutch side alignment is very easy to measure using the machined pulley surfaces on the C3 stuff to measure off.



MO. The use of the side plates to stop the belt from walking is the biggest problem for OEM belt drives (and most aftermarket) because now you are covering up something that is losing HP, creating heat and wear, increasing loads on belt that it is not designed for. You never find out how far off your sled may be.
I can run the original "guideless" pulleys and the belt stays on now

All stock aligned sleds are far from perfect. A belt drive needs to be as close to perfect as possible.
If you use the top pulley as a zero point for aligning it is simple to match the bottom ( by shimming) for one dimension. Add 2 more dimensions and issues (heat, failure, etc.) start to show on a belt drive.
Imagine a bottom gear that is out by 1.5 degrees only, on a vertical axis, to the top gear. Add a 1 degree misalignment on the horizontal axis too. A 1" plus wide rigid belt will walk "downhill" constantly. Each tooth is putting the wrong pressure on the belt and maybe only 60% 70% of the "longditudinal" fibres (the strength and they don't stretch) are taking the load until the belt actually "fails" slightly (trying to make full contact with the tooth) on the downhill side.
I think Polaris already knew this and hence break-in requirements (like the aftermarket recommendations after supplying OEM adapting kits) and expected replacement time info.
So build a stronger belt lol. I think different lol.

Assuming your bottom drive shaft is true, changing the "3D" alignment at the pulleys will help "blueprint" your drive shafts too. It can be as simple as and 1/16th in. down and 3/32 forward (or something) on the clutch side and can be done with everything in place on the sled by removing the bearing mounting plate and making the holes slightly bigger in the proper place. Jiggle it around til things are perfect on the other side. Tighten it up and recheck. I threw in a couple of rivets so next time it would be easy to put it back to the exact same spot.
It's actaully easier to do this than with trueing up a chaincase set-up.

Critical tools required are, a 12" straight edge that is true to less than a thou. and set of feeler gauges from 20 to 60 thou. so when you are measuring you know all 4 corners are equal clearance in relation to the top sprocket. Clamp the straight edge to the top sprocket and rotate back and forth to check clearances between bottom pulley edges and straight edge.

I made my own straight edge (couldn't find one and when checking what I thought was my straight edge it turned out it wasn`t lol) by using some grade 8 shop technique. Start with 1/2' key stock and file-sand until your lapping plate (thick piece of glass and some jewelers rouge is good too)shows flat and true. Every good ol' mechanic will have the feeler gauges.


If your into it, you can make your pulley alignment as true as an expensive CMX set-up with any belt system you put on. I think this is how it should be but very difficult for production and for chain-gears this is far less critical. If your pulleys are true you get 100% use of the belts strength. Should lessen the impact of break-in. Should live long. Maybe forever if HP is well within the designed load.
I might of had one of the worst ones off the production line. Its' good now lol. I'm gonna start handing it some full throttle snow x type landings until the snow flies again cause that's what I got to ride presently lol. Never needed the spare in the field yet.

Only belt drive that has impressed me is the CMX. Starting with a true flat plate makes it easy compared to adapting to stock OEM castings etc. But even that still requires the opposite side of the driven and drive shafts to be true to the plate simply because of radial play in a bearing. Maybe they even take care of most of this with double row bearings on that side? They are also the only one that tensions out (per the recommendations of the belt manufacturer), making a bigger more efficient circle and don`t say that more wrap on the top pulley equals longer belt life.

Hope it helps your project. Hope it snows more soon too lol.

 

[BILTIT]

I am not sold on belt drives reliability yet. Two friends just put C3 belt drives on doo etecs (turbo) and they both blew them up with only about 2-300 miles.

I am not saying it's the manufacturer that was the issue but like you say, they need to nail down a way to install a belt drive and it run perfectly aligned with minimal heat to help them survive.

 

[BILTIT]

Maybe the pulleys need a built in fan like alternators?

 

[rmscustom]

Maybe the pulleys need a built in fan like alternators?

Didn't Cat try something like that in 12 but on the other side of the sled? lol

 

[89sandman]

Poo's system seems to be very reliable. There will always be those who abuse their stuff and then whine when it breaks. If your gonna ride it like you stole it then put on your big boy underoos when you break it Poo is just way ahead of the competition in so many different areas.

The cat thing was to help cool the clutches I believe.

 

[LoudHandle]

Maybe the pulleys need a built in fan like alternators?

If they are hot enough to need a fan you are throwing Horsepower and reliability to the wind!

Fix it.

When things are in alignment they will run cool.

A Belt drive is not for everyone, if you are a hammer mechanic? You should stick to the good old chain case.

If you are perfection orientated and like to use finesse instead of Thor's hammer when you're wrenching, belt drive will treat you well. They are not a 30 minute bolt on and ride. Regardless of brand! If you want to get the most out of it, verify alignment and double check everything, as Geo stated.

 

[Ultrasauras]

belt drive

have 700 hard miles on my 2012 with a TKI bely drive and have not had one issue.

 

[geo]

LOL. I read the post I did between cooking stints yesterday. I got lost lol.

In a nut shell. The belt drive system should be considered a rigid set-up. It NEEDS to be as close to perfect as possible in a 3D alignment. It is also very easy to get this correct with a few tools and some thought.
Many think a chain is rigid but it has much more forgiving play with each link a pivot point for re-alignment to the sprockets.

Something else. 6 thou. may not seem like much but you have to picture that 6 thou. inwards at the top also means 6 thou. outwards at the bottom (or front to back) because the pivot for adjustment-movement is in the middle and the pulley is flat on those planes.
The pulley still spins visually true and wobble free because it spins from the center, if you know what I mean.

Stock, my sled had 12 thou. misalignment. Not very much but that means 24 thou. total misalignment each revolution on only one plane. Doing quick average math in my head, at 1 to 1 clutch ratio at 8000 rpm, my bottom pulley is forcing the belt to compensate for alignment approx. 3400 times a min.

To picture the temp difference (and probably efficiency) I have experienced, think of a tire at highway speeds inflated at 40 psi and then at 80 psi. At lower pressure the tire has to flex more each revolution, so more heat is created, more power required to turn, more wear on the tread.

 

[JMCX]

Obviously your method relies on the faces of the pulleys being true to the shaft when the bolt is tight. They hardly have a precision fit on the splines. When you made your adjustment at the PTO side of the drive axle what direction did you move it (towards 3,7,10 o'clock)? I realize this would probably be sled specific.

 

[geo]

You're right JMCX. That presumption is very important and my C3 pulleys are very precisely machined. Interference fit to the splines. I would think any kit would be. OEM has to be within a 1/2 thou or less here to.

This is a general discussion of belt drives and the importance (compared to chains) of the best possible alignment on all planes between the pulleys. It's on the pro forum because we have them stock and some have changed them out for gearing changes.
I also read and see some very early failures after mounting kits on all brands of sleds. It`s not the belt or kit IMO.
In no way do I want this to be a comparison between TKI, C3,CMX or any other kit. Just info to make what you have or what you are building better. If you want.
Most stock stuff is living just fine now. Teething over. If your happy good. This is info about making your belt drive what in should be. Stronger, maintenance free and more efficient than a chain.
It`s also MO from my experience.

Stock pulleys would need more attention to get to do this. If I had stock pulleys still, I would now take the time, from what I have learned in my quest for less heat here to get a true surface on both pulleys to check from.
Like I said before, if I hadn't had this C3 kit (no pulley guides) and I probably would have lived with it because guides on a pulley keep the belt on. And, like I said before I think this is one of the reasons some don`t think too much of the belt drives IMO.
With guides on the pulleys and just slap on a kit, You never get to see the effects of slight mis-alignment. Just your belt does.
I also think this slight misalignment is one of the reason Poo picked the 11mm pitch instead of 9mm.

About the machining on the splines-pulley. It better be pretty good but more importantly the back mounting surface has to be square perpendicularly to the running surface of the pulley. First thing to look for is a wobble in the pulley when torqued up.
If you have any wobble get rid of the pulley or the shaft 'cause something is bent. They are torqued up solid.
If you don't have a wobble in the pulley it should be fairly simple and cheap for a machinist to figure out how to chuck the pulley in a lathe using either the back bearing surface or tooth face to give you an accurate skim on the outer faces for checking.

To answer your question JMCX, and you are right it is sled specific but may be surprised as to why, I needed to move mine towards the 1 oclock 2 oclock position.
If you take the time to look at the age old method of mounting of the lower drive shaft on the clutch side, just loosen the three chassis bolts a bit and you can probably get a 150 to 200 thou diameter circle out of the stock holes.
I had to slot the holes some so mine may have been the worst case scenario. Maybe not lol.
That method of alignment was OK when you circliped a lower gear into place for your chaincase. Still people building something took the time to get it more accurate and knew the benefits of this.
I think it has to be way more accurate for a belt drive. It might become a production alignment procedure if belt drives hit the flats.

Anyhow, enjoy the season boys. This is a FYI thread started on a day off. Good thing is it looks like winter is starting.

 

[Hawkster]

I don't think it's possible to have a secondary belt tracking with very little movement from side to side when working the throttle .

I ride sometimes without the hood and the belt is very easy to watch tracking , when it's a new belt it isn't as likely to walk from side to side . It eventually walks more with age . This one has over 14,0000 on the skid and if I remember correctly it's seen six belts and some of them where just shear abuse .

This set up is adjustable on the shafts , the jack shaft is aluminum and the bottom pulley is a slipper clutch on a hollow drive shaft so if your dumb enough to air out and land wide open it will ratchet instead of nuking the belt . Tension is set by a Gates belt adjuster .

If more people would start comparing the pros and cons with an open mind the consumer will end up with a much better product .

 

[AKrider]

I had no idea so many things could contribute to belt drive wear. Thing is, why do them seem reliable on street bikes where the swingarm is moving one pulley in an arc compared to the other one? Even on a street bike the belt is exposed to dust and road grime. Maybe the belts on a sled are too short and need to be longer to reduce the heat? Not sure how you'd easily do that without making things more complicated and defeating the purpose going away from a chain case in the first place. I'd think if a guy wanted to possibly save some weight, run an exposed 520 size o-ring motorcycle chain with a tensioner. Use off the shelf sprockets for less expense and maybe everything would be lighter than a chain case? That said, I think the exposed chain on my kids 120 is a pain in the ***. I hate lubing it.

 

[Lorduss]

exposed moto chain wont work in this application, heres why.
In the world of Single man dune buggys (a project im building on currently) normaly with streetbike motors in our horsepower range, commonly people start out running a short chain to the back axle, in a configuration much shorter than most street and dirt bikes have, yet still much longer than our chaincase center to center, a problem they run into is excessive heat destroying expensive chains very fast, our oil soaked chaincase keeps our chain cool enough to run in such a short config under high horsepower and long durations, that oil soaking all over that alum tunnel helps keep it cool and disperse heat.
buggys have to find a way to run a longer chain setup, I have thought about going to a gates belt with my buggy for this reason, and then on top of that running a chaincase for finer gearing options and giving up the huge 60-70 tooth rear sprocket.

you would be replacing chains every day of riding, stock chaincase for me.

 

[AKrider]

That's interesting, I didn't know buggies ran chains. I'm wondering if the short length of the sled belt drive and heat build up isn't the Achilles heel to the system. It isn't like Polaris is afraid of putting things out that may or may not be an improvement.

I don't see people being able to get the precise alignment of their pulleys like some have posted. I think about the horsing around I do getting a drive axle in place during a track swap and it isn't exactly work that lends itself to exacting tolerances. Then I think about chassis flex and what happens to alignment when bashing through bumps or hucking huge jumps with crusher landings. I think tolerances on the loose side are better for a snowmachine drive system.