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.) 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 1 ^{st} gear, 16, 17 or 19 tooth 2^{nd} gear
and 26 tooth 3^{rd} gear. The "tooth" count are the number of teeth
on each upper gear. The 16 tooth 2^{nd} came out in the early 1960's,
while the 19 tooth replaced it in later years.To find
the gear ratio, - Direct Drive Reduction Housing is
**7:1**(lower gear has 84 teeth, top gear has 12 teeth... 84 ÷ 12 = 7) - If I can somehow mate the hydro spur directly to the reduction gear, this will change to 84 ÷ 17 = 4.94:1
- If I have to use the hydro reduction gear, the ratio will be 66 ÷ 17 = 3.88:1
- 1
^{st}speed ratio is**3:1**(lower gear has 39 teeth, upper gear has 13 teeth... 39 ÷ 13 = 3:1) -
2
^{nd}speed ratio is either 2.25:1 for a 16 tooth (lower gear has 36 teeth, upper gear has 16 teeth... 36 ÷ 16 = 2.25); 2.06:1 for a 17 tooth (lower gear has 35 teeth, upper gear has 17 teeth...35 ÷ 17 = 2.06) and**1.74:1**for a 19 tooth (lower gear has 33 teeth, upper gear has 19 teeth... 33 ÷ 19 = 1.74) -
3
^{rd}speed ratio is always**1:1**(upper and lower gears have 26 teeth each... 26 ÷ 26 = 1) -
The ring and pinion gears in all IH Cub Cadets have a
**4.6:1**ratio (ring gear has 46 teeth, pinion has 10 teeth... 46 ÷ 10 = 4.6)
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. |