Every single component of the modern mountain sled has evolved significantly since the bathtub inspired sleds of the 80s., Every part except one that is – the sled’s clutch system. In this we ask ‘why?’ and suggest a logical progression to this vital part.
The CVT clutch system is a bit of a mechanical marvel. Considering the challenge it set out to solve, transferring power to the ground, while keeping the motor at optimum operating RPM and varying shift out depending on load, it does an admirable job. But then again, a Model T is also a mechanical marvel that too did an admirable job for its time – its just a bit of an antique at this point. We don’t use the telegraph to transmit information and we don’t play with rabbit ears on our TV sets anymore. Good inventions get beat out. Its how the world turns. So why are we still using technology from the pre-internet era to transfer power to the snow of our sleds?
Ask 10 seasoned sledders their clutching setup and you’ll likely get 10 different answers. Everyone has their own take on the “art” of clutch setup. Though every company has a chart suggesting best clutching for a specific elevation, track length/type, gear ratio etc, this is still more of a guess and check chart. Not something overly scientific.
Slap a turbo on your sled or heavily modify the motor and you are likely to end up in no-man’s land where data becomes sparse and setups even more varied. Weights, shapes, helix types and springs all enter into the equation where everything will effect everything else. It can become costly figuring out what works for you, playing with each variable usually requires the purchase of a new part. No matter how close you get to perfect, you’ll still be fighting other unknown variables (elevation, motor’s ability to “perform” on a given day etc) which can sometimes leave the rider chasing his own tail.
Reliability, though not bad, leaves something to be desired as well. See: Those riding the new 850s. Jeff riding his turbo sled last year. Belts are expensive and a pain to clean up. Springs break.
Again, is there a better way? Answer is absolutely “yes”. At least in theory. What if we brought computers to do something a mechanical device once did? Sound familiar? How many of you bought a sled with a carburetor on it this year. Fuel injection now controls your motor. I’m suggesting something similar begin to control our power transmission.
What I propose is to utilize stepper motors to control the shift out of a clutch based on a pre-set “map”. This map could be modified or changed from the dashboard of the sled and could allow the rider to set their engagement RPM and general shift profile. Drag racing? Cool, there is a map for that. Mountain riding? Sweet. There is a map for that too. Going down a big hill and need the clutch to stay engaged as much as possible? No problem, just enter “descend” mode.
The system would tie into the sled’s RPM and MAP sensor. This way it would be able to “see” elevation and operating RPM. Belt slip too could be monitored as well as clutch temperature giving optimum clutch operation at all speeds and all elevations.
There would be some mechanical loss, as running a stepper motor isn’t “free energy”. The precision, fuss free operations and overall gains in reliability this could bring forth could very well be worth it.
In theory, the stepper motor would take the place of springs – allowing us to move the clutch inward or outward depending on what the transmission sensors are telling them to do.
Will wee see something like this? Probably not anytime soon. Not because it won’t work, but because it’d be too expensive and because we’re already a super small market. That said, I’d wager we see something like this in the automotive space sooner than later. And that’ll maybe trickle down to sleds by the time the time 2025 rolls around.
Food for thought…
Take a look at a camless motor. Utilizing stepper motors to control something that was previously mechanical. Sound familiar?