Moving Felled Trees

[CobyRupert]

It comes down to the coefficient of friction between the tractor tires and the ground. A big tractor on glare ice can't move itself but a tractor on a good surface and the right tires can pull until it runs out of horsepower to turn the wheels.

And it depends on the stability of the soil and the traction of the tires, direction of the pull (i.e. the load pulling down on the axle) .
Note those old tractors may have pulled, 135% of their weight, but were they comparing to the weight on the sled, or the force in the chain? As others gave noted, you can pull many times your weight if there's little friction between that weight and the ground.
However, I would think that a 1hp 300lb , could exert tons of pulling force if geared low enough and big lugged or steel tires being pulled downward "into" the ground to get traction.

 

[vtsnowedin]

And it depends on the stability of the soil and the traction of the tires, direction of the pull (i.e. the load pulling down on the axle) .
Note those old tractors may have pulled, 135% of their weight, but were they comparing to the weight on the sled, or the force in the chain? As others gave noted, you can pull many times your weight if there's little friction between that weight and the ground.
However, I would think that a 1hp 300lb , could exert tons of pulling force if geared low enough and big lugged or steel tires being pulled downward "into" the ground to get traction.

One horsepower equals 550 foot-pounds per second, meaning you can raise 550 pounds one foot vertically in one second or one pound 550 feet vertically per second. If you had a 10,000 lb load and had frictionless gearing it would take 18.18 seconds to raise it one foot with a one HP engine. When you throw in friction loses it won't even move.

 

[CobyRupert]

One horsepower equals 550 foot-pounds per second, meaning you can raise 550 pounds one foot vertically in one second or one pound 550 feet vertically per second. If you had a 10,000 lb load and had frictionless gearing it would take 18.18 seconds to raise it one foot with a one HP engine. When you throw in friction loses it won't even move.

I follow and agree, right up to the last sentence. (that is you would need gears that convert the 1 hp (at x rpm's) to 1ft/18sec linear speed) Drop down to a lower gear (let's say 1ft/ 30 sec) and you could overcome the frictional losses. Heck, a 1/4hp motor could lift 20000 lbs with the right transmission.

I suspect most tractors can develop a force at the drawbar that exceeds their weight given the right soil conditions/tire lugs and hooked to a chain that pulls the rear axle downward to maximize traction.

 

[vtsnowedin]

I follow and agree, right up to the last sentence. (that is you would need gears that convert the 1 hp (at x rpm's) to 1ft/18sec linear speed) Drop down to a lower gear (let's say 1ft/ 30 sec) and you could overcome the frictional losses. Heck, a 1/4hp motor could lift 20000 lbs with the right transmission.

I suspect most tractors can develop a force at the drawbar that exceeds their weight given the right soil conditions/tire lugs and hooked to a chain that pulls the rear axle downward to maximize traction.

Friction losses in low gears can be as much as 40% so no that would not work.
Here is a useful formula I found on wiki (seems to work). load(lbs) x speed (mph)/375=HP required. So a 10,000lb load at one mph needs 26.67 HP to pull it. Cut the speed in half and you can move it with 14 hp but more likely 16 due to the extra gear-train losses cut the speed in half again and you can probably do it with not 8Hp but 10HP etc.

 

[john_bud]

The load on the chain pulling a tree can easily reach huge numbers if pulling quickly and you run the butt end into a stump. That impact or shock load is what breaks the chain. As others have said, the machine can't steady pull hard enough to break the chain, but the chain (or a strap) can still snap easily. I've seen chain break when someone thought a "running start" would be a smart way to save time.

(it wasn't)

 

[vtsnowedin]

The load on the chain pulling a tree can easily reach huge numbers if pulling quickly and you run the butt end into a stump. That impact or shock load is what breaks the chain. As others have said, the machine can't steady pull hard enough to break the chain, but the chain (or a strap) can still snap easily. I've seen chain break when someone thought a "running start" would be a smart way to save time.

(it wasn't)

Glad to see I'm not the only one.