drive system with reverse capability...

[ruffryder]

So what are us poor 4 stroke guys going to do about it? Polaris has a belt drive this year, looks like skidoo might too.

What do you think Yamaha could offer that still allows us to keep reverse?

The lightest thing I could think of would be to get the engine to turn backwards... going to take some complex head / camshaft engineering work though.

Any other options? What is arctic cat doing with their 4 stroke and reverse?

I love reverse, don't want to ever give it up, but the chaincase, reverse, driveshaft, trackshaft, complete drive system on the yamaha could use a lot of lighter weight stuff!!

 

[grossman]

Some sort of electric motor? I don't know. That would probably add more weight then would saved by the belt drive. I'm guessing they simply won't go with the belt drive.

 

[sk-rx1]

I don't think running the motor backwards is an option. Cat I believe has a mechanical system, but it's actuated electrically not with levers. Interesting question.

 

[blueironranger]

Phazer is ready for belt drive, I has a separate reverse mechanism already on the cross shaft.

 

[kinger]

Personally I would like to see no more CVT and go to a transmission that shifts automatically or manually. Soaking up 48% of your engines power through drive train losses is un real. Imagine if your 160 apex is delivering 80hp to the snow now, then go to a 90% efficient drive system and you get 144 hp to the snow, that is better then what my SC apex lays down to the track.

Besides CVT was derived because of the peaky powerband of a 2 stroke engine, not the broad TQ of a 4 stroke like the yammies or doo 1200. Its time to change.

Removing the weight of the CVT clutches, jackshaft, chaincase, and adding the weight of a transmission seems like it would net with weight savings. MPG would be in the 25 mpg+ range.

Pipe dreams! LOL

 

[oldguy2]

Cat tried the auto trans many years ago but it didn't work. Maybe technology today could make it work.

 

[greenthumb]

Personally I would like to see no more CVT and go to a transmission that shifts automatically or manually. Soaking up 48% of your engines power through drive train losses is un real. Imagine if your 160 apex is delivering 80hp to the snow now, then go to a 90% efficient drive system and you get 144 hp to the snow, that is better then what my SC apex lays down to the track.
Removing the weight of the CVT clutches, jackshaft, chaincase, and adding the weight of a transmission seems like it would net with weight savings. MPG would be in the 25 mpg+ range.

Pipe dreams! LOL

X2 I have been thinking the same thing!

Hondas VFR1200 uses a double clutch setup that can be operated manually or automatically. Shifting is essentially instantaneous.
There is a guy in Revelstoke that is using a CBR engine in a home built sled. Haven't seen it in person or know how well it works though.

 

[Vectornut]

Doesn't Honda use the starter to put their motorcycles into a momentary reverse while the motor is running?

 

[grader]

the cvt system is quite effecient as many small cars now use it. the 50 or so percent loss is in the drivetrain, not the clutches. think of cutting the throttle on any sled, 2 or 4 stroke, how far do you coast or freewheel along? its almost as bad as a tracked bulldozer. the sled requires power constantly to move forward or it stops. the cvt drive also keeps the motor in its powerband and adjusts with the load from the track. effeciency can be improved with a belt drive or even a direct drive to eliminate frictional drivetrain losses.

 

[ruffryder]

I guess the big issue is the type of riding that is being done. For trail riding, high speed, and high traction conditions, a manual transmission might be acceptable.

In the mountains where speeds can change very quickly and power requirements can change even faster, I think it might not work so well.

Any momentary loss in power via shifting a transmission could mean you loose momentum and are stuck. It could also upset the chassis and your riding if you weren't ready for it.

Just some thoughts on the mountain aspect of the issue..

 

[blueironranger]

The CVT really doesn't suck too much power and a geared tranny would only put an extra 10hp if that to the ground. I know a CVT grizzly 450 and a Manual Rancher 420 put out roughly 26-27hp at the crank and the rancher only has a 1-2hp advantage at the rear wheel meaning the CVT is only sucking up 1-2hp more than a manual geared tranny. Most of the power loss comes from the track alone, look at how many times the track has to flex on its trip around the skid and back to the drivers.

 

[ruffryder]

I think it has more to do with the drivers to the track junction.. but you are right, it takes hp to turn that heavy stiff track!

 

[Alatalo]

Personally I would like to see no more CVT and go to a transmission that shifts automatically or manually. Soaking up 48% of your engines power through drive train losses is un real. Imagine if your 160 apex is delivering 80hp to the snow now, then go to a 90% efficient drive system and you get 144 hp to the snow, that is better then what my SC apex lays down to the track.

Most of that loss is because of the track, not because of the CVT system. If 80 hp would get lost in the CVT system, it would be on fire within seconds...Some of the old Ski-Doo racing manuals had a graph that showed the efficiency of the CVT system based on some pretty serious measurements. I seem to remember the peak efficiency was reached at 1:1 ratio and relatively low rpm's (under 8000) and it was something like 88-89 % efficient.

Really, the problem is the track. Propelling yourself forward by pulling away the carpet you are standing on is a silly idea in the first place...

 

[blueironranger]

The sad part is that there is really no way to improve the track either. If you make the belt thinner/more flexable then it isn't stiff enough to keep the lugs from folding over. The only thing that would help significantly is to install huge 12 tooth drivers, 10" idlers in the back, and make up the gearing in the chaincase. Although it would cause enough of a gearing change to allow a planetary gear set to be used instead of a chain and sprockets.

 

[BETHEVIPER]

there is another way, check out the rear track drive system out there, better traction, more afficent, and insanely better braking.

There is also a company in finland that makes a computer controlled primary and or secondary clutch that uses servos to shift. I am surprised this has not shown up on a sled yet. you can change everything about it on your puter and it has three different buttons on the bar to change from power, mileage or towing. wouldnt that be great. They claim more power to the ground but I wonder if that is just from having a more perfectly adjusted clutch. its about 2000$ for the kit.