real benefits of belt drive

[Deep Powder Guy]

For years I've thought about removing the CVT of snowmobile all together including the need of a chain/belt drive. The direct drive system links the PTO directly to the tracks driver via an internal automatic transmission. This would also require a radical change in motor configuration which would be beneficial to the balance and weight distribution of the over all snowmobile...This radical design brings a whole new meaning to less rotating mass.

I'm 100% certain OEM engineers have designed this already however CVT parts are a million dollar annual business to the OEM's parts department and the radical new design would eliminate those huge annual profits.

Imagine the performance gain of a snowmobile without inefficient CVT belt and springs ?

DPG

 

[elkhunt]

The other plus to belts is less HP lost due to heat generation. A sled with a chain case, even a well maintained one. Will boil off the oil in a good day of riding (why they only run genuine Dino oil in the iron dog sleds, the synthics don't survive the heat generation and boil off in short order). While belt tooth profile and proper design play a large role in the amount of heat generated in a belt drive, a properly designed and tensioned system will never get much over 150 degrees F. 100 plus degrees cooler than a chain case in similar conditions.

QUOTE]

I must say that I find it hard to believe that the chain case is generating 250+ degrees of heat, which is hotter than my transmission or rear diff temp on my pickup. Guess I should clamp my hot-dogger on it!

I must respectfully disagree with your assertion that Dino oil is superior to synthetic oil in any way (except price), especially heat. It is not hard to find synthetic oil that will withstand 400 deg much harder to find Dino oil that will.
http://www.mne.psu.edu/chang/me462/syn_vs_min.pdf
The above link is a bit of dry reading but very informative

 

[snengineer]

For years I've thought about removing the CVT of snowmobile all together including the need of a chain/belt drive. The direct drive system links the PTO directly to the tracks driver via an internal automatic transmission. This would also require a radical change in motor configuration which would be beneficial to the balance and weight distribution of the over all snowmobile...This radical design brings a whole new meaning to less rotating mass.

I'm 100% certain OEM engineers have designed this already however CVT parts are a million dollar annual business to the OEM's parts department and the radical new design would eliminate those huge annual profits.

Imagine the performance gain of a snowmobile without inefficient CVT belt and springs ?

DPG

CVT, its time to move on, it works ok but technology is such that CVT has run its course as far as capability goes.

Been thinking the same thing, with a slight twist.

-Direct Drive/Drive Shaft to the rear axle on the suspension (would work with a split track setup)
-Electric motor powered by small engine generator (eliminated need for any sort of transmission)
-lighter structural materials

These changes allow for so many sled specific variations (specially for mtn sleds) it is really exciting.

These are just the rough concepts, when rubber hits the road the professionals can make it work and work well. As far as weight goes, your losing much more then your gaining with this sort of drive line. The track thing needs work cause a split track hasn't been proven to work well as of yet.

For all you electric motor critics out there.....read up on the latest technology its pretty awesome.

Someone have the kajones to release it....Arctic Cat is looking to save face, might be worth the risk

 

[LoudHandle]

The other plus to belts is less HP lost due to heat generation. A sled with a chain case, even a well maintained one. Will boil off the oil in a good day of riding (why they only run genuine Dino oil in the iron dog sleds, the synthics don't survive the heat generation and boil off in short order). While belt tooth profile and proper design play a large role in the amount of heat generated in a belt drive, a properly designed and tensioned system will never get much over 150 degrees F. 100 plus degrees cooler than a chain case in similar conditions.

QUOTE]

I must say that I find it hard to believe that the chain case is generating 250+ degrees of heat, which is hotter than my transmission or rear diff temp on my pickup. Guess I should clamp my hot-dogger on it!

I must respectfully disagree with your assertion that Dino oil is superior to synthetic oil in any way (except price), especially heat. It is not hard to find synthetic oil that will withstand 400 deg much harder to find Dino oil that will.
http://www.mne.psu.edu/chang/me462/syn_vs_min.pdf
The above link is a bit of dry reading but very informative

As stated, the iron dog racers will not run the synthetic chaincase oils because they end up cooking it off. The Dino chaincase oils do not cook off. Believe whatever you want. Just stating the facts.

 

[LPIdaho]

I must say that I find it hard to believe that the chain case is generating 250+ degrees of heat, which is hotter than my transmission or rear diff temp on my pickup. Guess I should clamp my hot-dogger on it!

I must respectfully disagree with your assertion that Dino oil is superior to synthetic oil in any way (except price), especially heat. It is not hard to find synthetic oil that will withstand 400 deg much harder to find Dino oil that will.
http://www.mne.psu.edu/chang/me462/syn_vs_min.pdf
The above link is a bit of dry reading but very informative

And that's with 1987 technology. If they are cooking off a synthetic they are using the wrong type of syn oil for the application. Efficiency gains on syn are certainly worth the cost for a racing application.

 

[LoudHandle]

And that's with 1987 technology. If they are cooking off a synthetic they are using the wrong type of syn oil for the application. Efficiency gains on syn are certainly worth the cost for a racing application.

The factory synthetic chaincase oil, granted the conditions are far more severe than the average joe will ever subject a sled to, but never the less it does as I have stated. Try running ~2000 miles in ~24 hours and see for yourself.

 

[elkhunt]

"The factory synthetic chaincase oil, granted the conditions are far more severe than the average joe will ever subject a sled to, but never the less it does as I have stated. Try running ~2000 miles in ~24 hours and see for yourself."

IF you could come close to that time "24 hours" you would be superman running an average of 83 mph!

The last winner did 2031 miles in 37 hours of "on course time" averaging 55 mph BIG difference! He also had 50 layover hours during the race to cool his chain case.

http://www.irondog.org/

 

[rab]

http://www.uwplatt.edu/files/sae/CSC_Documents/05_uw-platteville_design_paper.pdf


http://www.mtukrc.org/download/platteville/platteville_ic_design_paper_2014.pdf


same results in norway university just cant find the link , its on Doo talk somewheres

 

[lancelarue]

Belt drive

Here's an interesting observation:
Never would have thought of this but had some problems and in looking for the culprit was amazed at this fact>,

06' Skidoo rev chassis:
with belt drive installed checking alignment etc. etc. I would grab brake rotor and turn drive train . After many measurements etc. / bracket modifications >>>, took the belt drive off.
Re-installed new 15 wide chain & sprockets. Being totally anal measured everything again and made some new spacers etc. to get perfect. In all the turning to check alignment etc., big shock! Mind you, I had just taken the belt drive off!!!!!!!!
Chain & sprockets turned way easier, I mean not even close.
So I thought ok, I have something screwed up with the belt drive that I didn't see.
Re-installed and tried again. This time I gradually backed off the idler wheel to take tension off the system and also checked alignment AGAIN.
Here's the bad news folks, no comparison with my set up anyway. Chain & sprockets turns WAY easier than cog belt. Doesn't make sense???????????

 

[LoudHandle]

Here's an interesting observation:
Never would have thought of this but had some problems and in looking for the culprit was amazed at this fact>,

06' Skidoo rev chassis:
with belt drive installed checking alignment etc. etc. I would grab brake rotor and turn drive train . After many measurements etc. / bracket modifications >>>, took the belt drive off.
Re-installed new 15 wide chain & sprockets. Being totally anal measured everything again and made some new spacers etc. to get perfect. In all the turning to check alignment etc., big shock! Mind you, I had just taken the belt drive off!!!!!!!!
Chain & sprockets turned way easier, I mean not even close.
So I thought ok, I have something screwed up with the belt drive that I didn't see.
Re-installed and tried again. This time I gradually backed off the idler wheel to take tension off the system and also checked alignment AGAIN.
Here's the bad news folks, no comparison with my set up anyway. Chain & sprockets turns WAY easier than cog belt. Doesn't make sense???????????

While that may well be the case at zero speed. The real benefit of the belt drive is as the RPM increase. With the chain you have the parasitic drag of the oil as well as the pins / plates and sliding contact friction between the plates and the sprockets, which gets exponentially greater as you increase the RPM. The belt actually gets easier to turn as it gets a bit warmer / more limber as RPM increases.

You can also liken it to a loose track. Sure it rolls around the shop easier, but in reality by running a loose track you are loosing both efficiency and traction. If you observe a loose track at speed; it is coming off the drivers and continues to follow them around until the track tension forces the track to change direction. This concavity (the only reason to ever spear a track) hinders your sleds ability to get up on the snow and creates drag. It also hinders traction as the paddle is no longer perpendicular with the snow. So it is not getting the bite it should have / could have with the track tensioned correctly.

Additionally, IMO there is too much flex in the SkiDoo and Cat chassis' to really see a benefit from the belt drive. In order for the belt drive to perform as needed it must stay true in all three planes. There is just too much twist in the Doo and Cat chassis Designs to maintain whatever alignment you set it up with at rest.

FWIW

 

[longtrack156]

CVT, its time to move on, it works ok but technology is such that CVT has run its course as far as capability goes.

Been thinking the same thing, with a slight twist.

-Direct Drive/Drive Shaft to the rear axle on the suspension (would work with a split track setup)
-Electric motor powered by small engine generator (eliminated need for any sort of transmission)
-lighter structural materials

These changes allow for so many sled specific variations (specially for mtn sleds) it is really exciting.

These are just the rough concepts, when rubber hits the road the professionals can make it work and work well. As far as weight goes, your losing much more then your gaining with this sort of drive line. The track thing needs work cause a split track hasn't been proven to work well as of yet.

For all you electric motor critics out there.....read up on the latest technology its pretty awesome.

Someone have the kajones to release it....Arctic Cat is looking to save face, might be worth the risk

Agree whole heartedly.
Smaller governed engine running a generator with lipo battery pack and electric motor on the skid should be lighter and produce way more power to the track.

 

[lancelarue]

Chassis twist

While that may well be the case at zero speed. The real benefit of the belt drive is as the RPM increase. With the chain you have the parasitic drag of the oil as well as the pins / plates and sliding contact friction between the plates and the sprockets, which gets exponentially greater as you increase the RPM. The belt actually gets easier to turn as it gets a bit warmer / more limber as RPM increases.

You can also liken it to a loose track. Sure it rolls around the shop easier, but in reality by running a loose track you are loosing both efficiency and traction. If you observe a loose track at speed; it is coming off the drivers and continues to follow them around until the track tension forces the track to change direction. This concavity (the only reason to ever spear a track) hinders your sleds ability to get up on the snow and creates drag. It also hinders traction as the paddle is no longer perpendicular with the snow. So it is not getting the bite it should have / could have with the track tensioned correctly.

Additionally, IMO there is too much flex in the SkiDoo and Cat chassis' to really see a benefit from the belt drive. In order for the belt drive to perform as needed it must stay true in all three planes. There is just too much twist in the Doo and Cat chassis Designs to maintain whatever alignment you set it up with at rest.

FWIW

Well you sure won't get any argument from me on the Rev chassis flex. In all fairness though, I didn't have any problems until I passed a certain threshold in power output.
Previous engine build had no problem with belt drive in same chassis.
Also never had any chain issues with prior builds.
Without trying to sound like "blowing my own horn", once power reached certain level problems started.
I'm thinking a third bearing in middle of jackshaft is in order now. We'll see.

Also, food for thought,> lots of people running good power have lots of clutch/belt heat so even though they might be putting out horrendous power @ the crank, it's never getting to the drive train with clutches slipping. So no chassis flex. I ran into this with a turbo'd Cat 275hp. Things didn't start really moving around until I got the clutches cooled off & balanced for heat, then holy mackerel! Clutches started coming together, driven rubbing @ inside, jackshaft bowing etc. Crazy!!!!!

 

[lancelarue]

Belt drive

Well, went for another ride, this time back to the original 15 wide chain, sprockets.
To be perfectly honest, I don't know if you could feel the difference on my mod sled from the belt drive. Clutches shifted out every bit as far as with belt drive.

Sure liked the concept.>>>>>>>. Now if I could just convince the sled ?!!!!!

 

[mtncat1]

going from 11' 12' to 13 ' or newer my but tells me that the belt drive is the real deal . kudos to polaris for being the first to bring this tech to the masses , and for pushing the envelope with their light weight mountain chassis. your welcome doo and cat riders ,if not for polaris you sleds would be 80 lbs heavier than polaris instead of just 40lbs.

 

[madmax]

I have two identical 15' Polaris 800's. Only difference is one is beltdrive and one chaincase. Clutched the same, running the same track and engine rpm. Chain drive sled always has run stronger. I understand all the chain vs belt arguments, but don't believe there is any performance gain from a belt drive other than the 'bling and cool factor'. Depending on the sled there is some weight loss.