[Kuraki]

I'm still pondering and researching and scribbling in my spare time with the intent of building a small crawler. I'm kind of a buy-once cry-once measure twice cut once individual (only because of multiple, multiple past mistakes), so I'm trying to make sure that what I build is going to do what I want.

Basically, I'm looking at this ZTR setup: https://www.surpluscenter.com/item.asp?item=13-1489&catname=powerTrans

As a way of driving and controlling the drive sprockets for my track frames. SC specs that it is capable of delivering 115 ft/lb of torque continuous, or 150 intermittent.

So what does that mean (assuming I have the engine power necessary to develop that at the speed I want to apply it)?

115 ft/lb of torque, driving a 12" sprocket. Sprocket circumference is 37.7" or 3.14'. Torque arm length is 6" or 0.5'.

115 ft/lb / 0.5 = 230 pounds of linear force x 2 (pump/motors) = 460 lbs of linear force forward?

150 RPM * 3.14 feet = 471 ft/min * 60 = 28,260 ft/hr / 5280 = 5.35 MPH?

5 MPH I'm happy with as a top speed for a crawler that would for the most part be used to move snow. But 460 lb of continuous linear force sounds light to me? Even at intermittent 150 ft/lbs of torque, linear force comes out to only 600 lbs? That sounds a little better, and would be closer to the point of the tracks spinning on the ground rather than pushing the snow in front of it.

My thinking is that if the crawler + me = >600lbs it would never lose traction before it ran out of power. Would that be accurate? If I want to effectively push snow, do I need to look for a bigger pump/motor combo with higher torque output?

 

[TUDOR]

Mmm, 12" diameter sprocket has a circumference of 37.7", but the lever arm is from axle center to track contact with the ground, not the perimeter of the sprocket. Your applied torque will be slightly less than calculated and your speed slightly higher.

I'm not sure of the traction availability of growsers over tires and chains, but my 2400 lb MF1655 can deliver almost 800 ft-lb of torque to the rear wheels and it will break traction whenever I put too much power to it. With 4 times the weight and about 1/4 the ground contact, I'm not sure where equality would be between the 2 machines. Top speed of the 1655 is 4.5 mph in LO.

I'm suspecting that you'll be a little light in the traction department, and maybe in the power department as well.

Are your hydro units supporting weight or only transmitting power? The weight of the sprockets and tracks does not count when calculating the load on those units.

 

[Hydronerd]

Those transmissions are far too light, IMHO. Ztr's have casters at the front, they turn easy, going straight is the challenge. Crawlers, like skid steers take alot of power just to turn. I use to drive a skid steer and could go forward and back in idle, but it would stall when you tried to spin, you needed at least 50% throttle to spin, without a load. Crawlers are all about traction, I would size the hydraulics to the engine size. What size engine will you use. You probably need only 10 to 15HP. Will it be a very small machine? 600 lbs seems light. A lot of GT's weigh that much without tracks.