Determining tractor center of gravity.

[PapaPerk]

Hello,

I'm starting my 3 point log skidder attachment project.

Included on the attachment will be a bracket for suitcase weights for loader counterbalance. In an effort to determine max counter weight needed, I need to determine the tractors current center of gravity.

To determine center of gravity I need to measure tractor's front and rear axle weight. To do this cheaply I'm thinking about using a bath scale coupled with a long moment arm. I will have to weigh each wheel... or at least one front and rear wheel. Anyone ever done such a thing? :anyone:

I know the bath scale, moment arm technique works well for measuring trailer tongue weight.

 

[zzvyb6]

Just remember to keep the wheels on the axle being measured at exactly the same height (especially the rears), otherwise load transfer will affect the results (although you just need F/A CG height for this only..... Does your manual contain axle weights (but loaded tires affect this greatly).

 

[melanelly]

What th... Bathroom scale? what size tractor you got. One of those JD peddle jobs?:laughing:

 

[PapaPerk]

What th... Bathroom scale? what size tractor you got. One of those JD peddle jobs?:laughing:

6000 lbs tractor. By using a lever arm u reduce load applied to the scale to around 250. Simple mechanics.

 

[Chain Bender]

Do like I did today. I was pushing some tops and logs trying to clean up behind a bunch of slob loggers that clear cut my neighbors 52 acres. I was looking at my next push instead of where I wsa backing and ran squar up on a 20" diameter stump that was about 1/2 taller than my tractor (B3200). Even the FEL wouldn't lift enough to push the back timres to the ground. wound up taking a chaing saw and cutting a 5-6" diameter pole about5' long. urned the bucked about 3/4 way down and captured the lople and lifted hard and rolled the bucked just enough to slide me off the stump. Thank goodness, cause it was gonna be a long walk home to get a chain and a com-a-long.

Chain Bender

 

[hizoot]

Could someone explain how to set up the moment arm for this? I understand about fulcrums/leverage...but cant envision how to do this without mounting the bathroom scales on the ceiling


thanks!

 

[284 International]

Set a piece of pipe on a hard, flat surface some distance away from the scale. Put a mark on a heavy beam where it rests upon the pipe. Run the beam to the scale, where another short piece of pipe is resting on the scale. Mark that distance and measure the distance between them, and zero the scale.

Now you have a repeatable, known distance with fairly discrete reference marks. Then, jack up the tractor and set up the apparatus underneath, using the same reference marks, and then set the tractor onto the beam, much closer to the pipe on the ground than the scale (Say, by a factor of 10 or 20 times). It would be more accurate to run a 2x4 or something perpendicular to the beam, to keep the tire up, and give a more precise location for the weight of the tractor.

Read the weight on the scale, and multiply by whatever the multiple of distance is between the tractor and the pipe on the ground and the tractor to the scale. So, if the tractor is 1 foot away from the pipe on the ground, and 10 feet away from the scale, and the scale reads 100 lbs, you multiply 100 lbs by 10, and learn that the tractor weighs 1000 lbs on that tire.

I don't understand why the OP needs to know the CG, but it sounds like something interesting to look at his posted photographs when he does it!

 

[Gordon Gould]

Why not just put a block in the center of the scale. Place a sturdy beam that will hold your tractor like a 6X6 on the block with the other end on the floor so you have a ramp. Make a dummy for the other wheel so you go up level. Drive up the ramp until you get a good weight at about 3/4 capacity of the scale. Measure lever arms ( beam lenghts, floor end to scale and floor end to tractor) Wt = (beam lenth/tractor length)X(scale reading)

 

[PapaPerk]

Set a piece of pipe on a hard, flat surface some distance away from the scale. Put a mark on a heavy beam where it rests upon the pipe. Run the beam to the scale, where another short piece of pipe is resting on the scale. Mark that distance and measure the distance between them, and zero the scale.

Now you have a repeatable, known distance with fairly discrete reference marks. Then, jack up the tractor and set up the apparatus underneath, using the same reference marks, and then set the tractor onto the beam, much closer to the pipe on the ground than the scale (Say, by a factor of 10 or 20 times). It would be more accurate to run a 2x4 or something perpendicular to the beam, to keep the tire up, and give a more precise location for the weight of the tractor.

Read the weight on the scale, and multiply by whatever the multiple of distance is between the tractor and the pipe on the ground and the tractor to the scale. So, if the tractor is 1 foot away from the pipe on the ground, and 10 feet away from the scale, and the scale reads 100 lbs, you multiply 100 lbs by 10, and learn that the tractor weighs 1000 lbs on that tire.

I don't understand why the OP needs to know the CG, but it sounds like something interesting to look at his posted photographs when he does it!

Exactly! That's how u do it. I just have to make sure to keep the tractor level on all four corners while doing it! Lol!

The reason I want the CG is to calculate how much ballast I need on the back of the tractor. I've made an excel spreadsheet that calculates tire axle loading based on loader loads and rear ballast load. I'm trying to reduce stress on front axle when picking up heavy logs.

I'll be sure to take photos and share when I do the weight measurements.

 

[PapaPerk]

Why not just put a block in the center of the scale. Place a sturdy beam that will hold your tractor like a 6X6 on the block with the other end on the floor so you have a ramp. Make a dummy for the other wheel so you go up level. Drive up the ramp until you get a good weight at about 3/4 capacity of the scale. Measure lever arms ( beam lenghts, floor end to scale and floor end to tractor) Wt = (beam lenth/tractor length)X(scale reading)

This is a good idea with some minor changes. The lever arm has to be level and the rear of the tractor also has to be level. But I think this is how I'll do it. Thanks for the input!