Just another question, if a 174" track weighs 75lbs. and a 151 weighs 50 lbs. Is the engine/motor that is driving it only seeing half of it's weight being pulled, as the other half is sitting stationary on the ground and the machines components are sliding/rolling thru? Just make sure you drive from the backside of the track or topdead ctr and have large dia. wheels 10" or so. It is supposed to be more efficient pushing the top of the track rather than pulling it?
Mike
Well, there is a certain amount of energy required to spin that mass around at a constant speed. That energy comes from the frictional loses in/on the track. Where weight of a track is really the kicker is when trying to accelerate the track. All that extra mass takes a lot more energy to spin. Longer tracks also have the effect of spinning in a larger radius(if you imagine it spinning in a perfect circle it's easier to analyze.) Think about spinning a large disk compared to spinning an axle or something. So bigger tracks have 2 things working against them in terms of energy used to accelerate them.
During constant velocity, the motor is only seeing the sum of all the frictional, heat, drag, etc losses.
During acceleration, it sees all those loses plus the energy it takes to accelerate the mass of the snowmobile and its components.
Rotating mass is pretty tricky. Especially when you try to change its direction. For example, take off a bike wheel, hold it by the axles, spin it, and try to move it around.
It's all based around this: F=ma (force equals mass times acceleration) so if there is no acceleration, there is no force. Rotating mass will have an acceleration directed toward the center of the arc and therefore a centripetal force in that direction as well. The motor does not work against these centripetal forces.
In regards to the larger wheels, this helps by decreasing the resistance in the track. It's easier to bend a track around a 5" radius than compared to a 3" radius. Another thing to consider is porting the track, this helps the track bend easier and makes it lighter. 2 birds with one stone.
Oh, and it's been proven that it's more efficient to drive the track in the opposite manner of what a snowmobile does. Imagine the drive cogs where the rear wheels of a sled are, that's the most efficient. The location of a regular sled isn't as good due to all that track that is basically floating up in the tunnel. The cogs are pulling on that portion. The efficiency is lost in that area because of the elasticity of the track and it basically flopping around up there.
