Chain at 16000 rpm

[LEE1969GB]

I am putting a rotax 800 engine in my pilot (see subaru transmission) and I am driving from the jack shaft to the diff input shaft with chain and sprockets. I am starting to wonder if the chain will be ok as the engine revs to about 8000 rpm and the cvt drive must at least double that so the jack shaft will be doing about 16000 rpm when flat out.
I am only using a 14 tooth sprocket on the jack shaft and 28 on the diff so that should help but it is still a lot of rpm for a chain. The chain I will be useing is 530 motorcycle chain and I am thinking of geting a good quality light weight chain to help to keep the centrafugal forces down.
I will have a strong guard around the chain as the sprocket is about 2 inches from the back of the seat

[Bugpac]

your actually going down, if that was the case the tires would turn 64000 rpm after the 4:1 diff... i think but dont quote, that cvt is about 2:1, so i would say the jack shaft is turning about 4 k at max...and at 4 k you need to have some good bearings, not pillow blocks or flange bearings, but some good machined fit bearings...just my .02

[renegadespec1]

LEE'
Yor sled clutching goes from about 3.76 to 1 up to about .75 to 1 K-fab could help you out there, so your slowing down off the jack shaft... There was some discussion before you joined I forget the name of the thread Rorty and K fab both posted a boatload of really good onfo on sled motors and clutching and tuning I run polaris motors and drives in my buggies...and heavily modified clutches so I really can't help you out on the ski doo stuff...

[Kludge]

Originally Posted by LEE1969GB\";p=\&quot

... I am starting to wonder if the chain will be ok as the engine revs to about 8000 rpm and the cvt drive must at least double that so the jack shaft will be doing about 16000 rpm when flat out......

Hi LEE1969GB,

The snowmobile CVT's I'm familiar with have at most a 0.95:1 overdrive (IIRC) *8000 engine -> 8420 Jackshaft
They have their maximum reduction at belt engagement between 4:1 and 3:1 depending on the clutch.
Keep the top sprocket small to reduce the centripetal force, but not so small that you wear out the chain quickly (like 15 to 17 tooth for a 50 series chain). I don't know if O-ring chain will be happy at those speeds, a good roller bushing chain would be better.

[Kludge]

Wow renegadespec1, is fast today.

[K-fab]

O-ring chain will be fine. *Just keep it lubed with a dry wax type lubricant. *PJ1, Maxima, etc. sell lubes for o-ring chains.

Superbikes, Moto GP bikes and the likes run upwards of 200 mph. *I don't know the overall diameter of the rear wheel, but I'm going to guess about 21 inches tall. - so one rev of a tire covers 66 inches of ground.

200 mph = 293 ft/sec = 3520 in/sec
3520/66 = 53.33 rev second = rear wheel 3200 rpm

I think the drive ratio is approximately 3.5:1 - so 3200 x 3.5 = 11,200 rpm of the counter shaft sprocket. *If the chain can survive those sort of rpm around the sprockets, what you have should be just fine. *(provided I actually did my math correctly...)

Everyone's correct - the driven (secondary) clutch will only hit 8500 at full upshift. *Not 16K.

Most sled drivetrains prefer an overall drive ratio of between 10:1 (600cc) down to about an 8:1 (1000cc) for the secondary to axle output ratio. *With the 800 Rotax you plan on using, I'd start in the 9:1 range.

So, you want your driven shaft to turn 9 revs for every revolution of your final (axle) output shaft.

Above 10:1 you end up just spinning the wheels, below about 7:1 you're going to burn up belts.

[K-fab]

Someone with a Busa - give me sprocket teeth numbers and the diam of the rear wheel and we'll plug in the numbers at 186 mph (what the Busa's limited to). *That will be nice, real world numbers that will make sense. *I am guestimating big time on the above numbers...

[LEE1969GB]

With 4.1 to 1 DIFF(thats a saw point) and 2 to 1 on the sprockets I have 8.2 to 1 from secondary clutch to wheel but my tyres are only 22 inches high not 25 *as origonals so that should help I think!

[renegadespec1]

Originally Posted by Kludge\";p=\&quot

Wow renegadespec1, is fast today.

Kludge,
I'm high on life, I'll post a couple of pix in the big adventure... [smilie=bs_offtopic.gif] and I'm on fire or is that the belt burning?????

[ultraman]

Lee, I run a polaris 680cc in my ride with reverse chaincase. 1.66 in the chaincase , 14t jackshaft sprkt 48t axle. # 50 5/8 pitch roller chain. with 18" tires in rear i run about 84mph @ 8000 rpm. The chain has held up fine. Don't do any hardcore dunning or racing though