It's just an idea - I have to finish many other projects before I can even think of starting on this one. Basically I want to turn one of my Cub Cadet garden tractors into a mini snow-cat:  Tracked concept II - More complicated, but lowers the ride height and allows me to change the gearing to slow down or speed up the tracks, as needed. (By changing the ratio of the sprockets going from the rear axle to the rear drive sprocket.) An addition to this idea - add a manual transmission behind the hydro to make it have a 3 speed rear end! (As an added bonus, it raises the rear end by 4", which helps with track clearance issues.)  And the tracked Cub with the 3-speed rear end:  Manual rear end from a 128:
Gearing notes, from Garden Tractor Pulling tips: The factory-installed gears that originally came in IH Cub Cadet transaxles are 13 tooth 1st gear, 16, 17 or 19 tooth 2nd gear
and 26 tooth 3rd gear. The "tooth" count are the number of teeth
on each upper gear. The 16 tooth 2nd came out in the early 1960's,
while the 19 tooth replaced it in later years. To find the gear ratio, always divide the number of teeth on the lower gear by the number of teeth on the upper gear. The mating upper and lower gears together have a total of 52 teeth. There are no exceptions. For example: 2nd speed has 19 teeth on the upper gear and 33 teeth on the lower gear to equal 52 teeth total (19 + 33 = 52). And 3rd speed have two 26 tooth gears, resulting in a total of 52 teeth (26 + 26 = 52). And so forth. Factory stock OEM gear ratios are as follows:
Based off this, I got pretty close by counting revolutions: 1st Gear: 7:1 -> 3:1 -> 4.6:1 = 96.6:1 (96:1 by counting) 2nd Gear: 7:1 -> 1.74:1 -> 4.6:1 = 56.028:1 (56:1 by counting) 3rd Gear: 7:1 -> 1:1 -> 4.6:1 = 32.2:1 (32:1 by counting) So at full throttle, in 3rd gear, with full load, the rear axles would be turning at 100 rpm. Assuming I want 20 mph at top speed, I would need to have a rear sprocket with a circumference of: 20 miles / 1 hour * 1 hour / 60 minutes * 5280' / 1 mile = 1,750' / 1 minute 1,750' / 1 minute * 1 minute / 100 revolutions = 17.5' / revolution So I would need a BIG sprocket with a diameter of 66.84" C = 2(pi)r 17.5' = 2 (pi) r 2.785 = r 2.785 * 2 * 12 = 66.84" So with the alternate reduction housing gearing of 3.88:1, the final ratio would be 17.85:1. This means at full throttle, 3rd gear the rear axles would be spinning at 179 rpm, reducing our sprocket size to 37" 28" would get me to 15 mph Hmm, definitely going to have to do some gearing on the final drive in order to get up to speed with a reasonably sized sprocket. (Something around 24" would be great, while still going 20 mph.) Side note, for my future reference - Good info on the carb that's on my Kohler KT17: http://outdoorpowerinfo.com/repairs/kohler_walbro_whg_adjustable_carb.asp Ground Pressure: Hovercraft: 0.7 kPa (0.1 psi) Human on Snowshoes: 3.5 kPa (0.5 psi) Rubber-tracked ATV: 5.165 kPa (0.75 psi) Ground pressure of 14 kPa (2 psi) or less is recommended for fragile ecosystems like marshes. |
