Where's Our Tractors' Center Of Gravity?

[ddl]

Re: Where\'s Our Tractors\' Center Of Gravity?

what you should be more concerned with when dealing with any slope is the change in rotatinal speed. In other words a chanfe in position as the wheel goes into a hole or climbs up a rock. The sudden cahnge will cause a roll over fast then just increasing the slope you are driving on. This cahnge will be so fast if you ar not watching for holes or rocks, you will not have a chance to recover.

Be aware, be safe

Dan L

 

[Anonymous Poster]

Re: Where\'s Our Tractors\' Center Of Gravity?

Hi,

<font color=blue>what you should be more concerned with when dealing with any slope is the change in rotatinal speed. In other words a chanfe in position as the wheel goes into a hole or climbs up a rock. The sudden cahnge will cause a roll over fast then just increasing the slope you are driving on.</font color=blue>

I agree totally that speed is critical to safety when traversing a slope! Slower is better...no doubt about it at all.

BUT I still would like to have an idea about how stable or unstable my tractor may be. Must just be my nature!

A tractor with a wider stance and a lower center of gravity will certainly be more likely to survive that hole or bump that it hits while crossing a slope. If I had two tractors, and knew the center of gravity was higher on one than the other, while the wheel spread was the same, I would certainly be inclined to drive the less stable one slower than the other across a slope.

I guess I have trouble dealing with unknowns! If I desire to buy something, I need to know the price before I agree. I can set the water heater temperature in the house at a point where it is hot enough, but not hot enough to scald someone...if I lift with a chain or cable, I want to know the load rating.

Seems like it may be conservative to figure that the center of gravity would be between the top of the tires and the top of the rear wheel rims. I will have to do a couple simple calculations and see what come out.

All this means nothing really, as I don't think my behavior will change regardless of what things calculate out to be.

I wish I had the capability to weigh the tractor at different angles! But I can�ft even weigh it level! Don�ft have any scales that big. Would be neat to see where the real center of gravity is. If I ever come across those scales, Turfman... /w3tcompact/icons/smile.gif

I guess I keep thinking about how I never really knew how far I could go on my bicycle when I was a kid until I fell off it a couple times. And now that I�fm in my second childhood with a new tractor...I don't want to fall off to learn the limits I can operate in, but still would like to have an idea of what they are.

Bill in Pgh, PA

 

[SethO]

Re: Where\'s Our Tractors\' Center Of Gravity?

The center of gravity (COG) of any object is fixed, and it is very important in determining the stability of the object. That stability however depends a lot on the path of the force that the earth's gravity exerts on the object crudely defined as acting on the COG. In a tractor the COG is somewhere inside the tractor itself, probably in the midpoint from the front to the back, at the level just above the transmission. If a tractor is level and stationary, the force will pass between the width of the tires and the tractor will be fine. As the tractor tilts, the line of the force changes to the point whereby it may pass outside the width of the tire and the tractor will overturn. The lower the COG, the greater the tilt that can be achieved before the tractor tilts.

The weight of the tractor plays no role in this stability, but the height, and the distribution of the components in the tractor do.

I have attached a rough sketch of what I am trying to describe.

 

[SethO]

Re: Where\'s Our Tractors\' Center Of Gravity?

This is the sketch.

 

[Egon]

Re: Where\'s Our Tractors\' Center Of Gravity?

I goofed, Not unusall. The center of gravity of an object remains constant. The metacentric height varies and this is the one that is important.

All this aside Beenthere has said it all.

Egon

 

[frank_f15]

Re: Where\'s Our Tractors\' Center Of Gravity?

i can't give u any technical descriptions of COG. i just know that if i take it slow, and loads low, i don't have a problem. a loaded bucket carried high will cause all kinds of problems, plus too much speed just compounds it. so my moto is LOW & SLOW /w3tcompact/icons/smile.gif

 

[Egon]

Re: Where\'s Our Tractors\' Center Of Gravity?

Empirical data always gives the best results.
As Beenthere says " keep your lunch low"

Egon

 

[Will]

Re: Where\'s Our Tractors\' Center Of Gravity?

I really liked Turman's suggestion for figuring out the center of mass. Here's what I THINK the formula ends up being.

You'll need to weigh your tractor below each axle while it is level. You'll also need to jack the front end up and then weigh the tractor again, but just below the rear axle this time.

L = this is the wheelbase length of your tractor. I'm assuming that when you weigh the tractor you are driving either the front tires or back tires onto a scale. L is the distance between these two weighing points measured on the ground.

H = height that you jack the front end of the tractor up. It should be measured in the same units as L. 1 foot will do.

W = weight of tractor, just add up the front and rear axle weights.

D = difference between the rear axle weight of the tractor before and after you jack up the front end.

The formula for the height h of your center of mass is:

h = (L*D*sqrt(L^2 - H^2))/(W*H)

When I tried to figure out this formula I made the simplifying assumption that the entire weight of the tractor would rotate when the front end was jacked up. This isn't quite right if your rear tires are only partly filled with fluid. Still if I haven't messed up the calculation, this formula should be pretty close even in that case.