Pulling force of a BX23S

JWR · Dec 8, 2017

bcp said:
Remember that drawbar pull is not the same as how much weight it will pull when the weight is on wheels or skids.

Here is a good start:

From:
Tractor drawbar pull - AnandTech Forums

"From a review I was able to find, a Kubota BX23 tractor was able to pull 750LBs in 2WD, 1420 in 4WD, 1760 in 2WD w/ 600LBs of ballast, 1920 in 4WD with 600LBs of ballast, and it has an operating weight of 1520."

Bruce

Any car/truck/tractor wheeled & powered device can pull no more than it's own weight , I hasten to say with some specific exceptions. As a physics problem the 1:1 weight to pulling force ratio only happens when the coefficient of friction is perfect. As a practical matter the coef of friction is rarely as much as 1.0 so the tractor "can" pull something approaching its' own weight under best of circumstances. I assume through all this discussion that the tractor can, with gearing, pull more than it's own weight aside from traction issues. It should be noted that in some momentary circumstances with Ag tire lugs sticking down into ideal just-right-strength soil the coef of friction in effect goes above 1.0 In other words the cleats of the tire have penetrated the ground and are pulling against the ground along the direction of travel, NOT depending on friction. Like climbing a horizontal ladder.
All that out of the way, the review bcp found is probably a very good source of info. But be skeptical of what you read -- the quoted review says that the BX23 pulled 1920 lbs of force while weighing 1520 lbs !!?? No it did not, not unless it dug into the ground somehow while pulling in order to exceed 1.0 for a coef of friction or was loaded with some weight to make it heavier.
I did not take time to look, but Jerry in post # 7 mentions the Nebraska Test Lab. If anyone has authoritative data on what a tractor will pull it would be the Nebraska Lab. If they do have data, they will spell out exactly what the conditions are.
And finally, the 5:1 block and tackle that Tractor Dell has is irrelevant in terms of what a BX23 (or any other machine) "can pull." If you hook one end of a glorified block and tackle (who cares how many pulleys) to an immovable object (like a tree or other anchor of some sort) then any pulling source of force -- say a man walking along pulling on the rope or chain -- can produce as much pulling force as you choose based on the mechanical advantage he has via the force multiplier of the block and tackle. That is meaningless except that what the OP called a "5 pulley system" may well be an asset that he has and can apply in his circumstance. Has nothing to do with what a BX23 can or cannot produce in pulling force.

bcp · Dec 9, 2017

I read it as the BX pulled 1920 pounds with a weight of 1520 plus 600 pounds ballast. Hard to be sure with that little quote. I couldn't find the quoted review with a quick Google search.

Bruce

SDT · Dec 9, 2017

Jerry/MT said:
If you can find somedata like from the Nebraska Tractor Test Lab on drawbar power, you can calculate the drawbar force. It's simply Fd= HPdb/velocity, where Fd is the drawbar force and HPdb is the drawbar horsepower and Velocity is the velocity at which the drawbar horsepower was determined. As I recall that's in the Nebraska Test results.

Unless things have changed recently, Kubota does not submit machines for NE evaluation.

I've wondered if they will do so now that they are entering the higher HP market???

SDT

BrentB · Dec 9, 2017

Tractor Dell said:
I was wondering if anyone knows what the pulling force of a BX23S (or similar tractor) is at the drawbar?
...
I have looked all around the internet, but can't seem to find anything on this. Thanks!

According to Caterpillar Performance Handbook, the max coefficient of traction of rubber tires is:

0.9 on concrete
0.55 on dry loam
0.45 on wet clay loam
0.4 on wet sand
0.2 on dry sand
0.36 on loose not hard gravel road
0.2 on packed snow
0.12 on ice

Grandad4 · Dec 9, 2017

SDT said:
Unless things have changed recently, Kubota does not submit machines for NE evaluation.

I've wondered if they will do so now that they are entering the higher HP market???

SDT

The Kubota M5, M6 and M7 ag and utility tractors have been tested at the Nebraska lab (2016 and 2017); reports published. Looks like Nebraska lab is not doing much with "compact" tractors. At least no recent Kubota or Deere models tested. Makes some sense because the Nebraska evaluation seems mainly oriented toward ag field work, which is not what CUT's are designed for.

JWR · Dec 9, 2017

BrentB said:
According to Caterpillar Performance Handbook, the max coefficient of traction of rubber tires is:

0.9 on concrete
0.55 on dry loam
0.45 on wet clay loam
0.4 on wet sand
0.2 on dry sand
0.36 on loose not hard gravel road
0.2 on packed snow
0.12 on ice

That is great info. Never saw that in print before. Good find.

Understood that these things are NOT 3 decimal place accuracy and do not need to be, but this gives us a feel for the relative numbers from a serious commercial source. The coef can at least momentarily exceed 1.0 (like I described before with tread cleats getting down deep enough in just the right soil, etc.) The usual debate and interesting exception comes up in drag racing where the large "slicks" are made of super soft rubber compounds allowing the the rubber to get down in "behind" granular surfaces of the pavement. In effect raising the coef of friction above 1.0 for very short periods of time.