Physics .. "Active" tractor weights .. Shifting the C/G ZTR ??

   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ?? #1  

tmajor

Platinum Member
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Oct 9, 2007
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Location
NE PA
Tractor
2010 MF 1529, Woods ZTR MZ1952, National Mower sickle bar circa 1963
Here is a new concept, I'm mentally working on.

I've got 30 pounds of weight under the rear of my ZTR mower. This helps with traction, however, even the 30 pounds doesn't balance out the weight of the front (deck, castor wheels, etc.). If I'm going down an incline, with a roll, the mower won't turn toward the up-hill side of the roll. Reason being, the up-hill rear drive wheel has very little weight on it. The 30 pounds underneath, and the mower deck, throw the center of gravity of the tractor toward the lower side.

My thoughts are: If there were two, identical, movable weights (left and right), tied together with a cable and run over a pulley, they would move oppositely, up and down with gravity. This, in itself would not change the center of gravity, but still, make it fall toward the lower wheel. But ... if they were guided by tubes, which were placed at an angle (left and right), the center of gravity would shift toward the higher wheel and away from the lower wheel, possibly keeping the center of gravity line more under the center of the tractor.

Let me hear your thoughts.
 

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   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ?? #2  
Marketing could call it Active Stability Control. "Ask for ASC".
Sounds like a great idea. I'd think an electrically driven, horizontally mounted linear actuator (ball screw), driving a weight to the left or right would be a start. Keep it low & that would really help. If the actuator could also swing about a vertical pivot, then you could also slew the weight fore-n-aft.

Of course, the first one to malfunction and flip a machine would bring down a hellfire of bad press & lawsuits that would probably finish the company.

Oh well, the beat goes on ...
 
   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ?? #3  
Here is a new concept, I'm mentally working on.

My thoughts are: If there were two, identical, movable weights (left and right), tied together with a cable and run over a pulley, they would move oppositely, up and down with gravity. This, in itself would not change the center of gravity, but still, make it fall toward the lower wheel. But ... if they were guided by tubes, which were placed at an angle (left and right), the center of gravity would shift toward the higher wheel and away from the lower wheel, possibly keeping the center of gravity line more under the center of the tractor.

Let me hear your thoughts.

Playing with any substantial movable weights of a vehicle can be a tricky thing. If the weights can move by themselves, that's usually not a good thing. Ditto if they move from centrifugal force because a sharp turn or abrupt stop might then flip the vehicle.

Your premise is interesting! It's unlikely the weights would move up or down in the tubes by themselves. And if they did, there's no guarantee they'd move the way you want them to. Were you planning on creating an active rather than a passive system? If so, what would move the weights and also assure they moved only in the correct direction?
 
   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ?? #4  
How about two oil tanks, you already have the hydro pumps, pump to the uphill side, think ballest tanks on ships.
 
   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ?? #5  
As drawn I believe the weights will move the opposite direction shown, unless there's some external force acting on them (like you turning a crank or something). Assuming a frictionless tube, the right weight is effectively getting lighter and lighter as the hill steepens, and the left weight is getting heavier and heavier. Take it to the extreme and imagine the right tube pointing horizontally and the left tube pointing vertically. At that point the right weight exerts no force on the rope at all and the left weight exerts a force equal to it's full weight in the down direction.
 
   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ??
  • Thread Starter
#6  
As drawn I believe the weights will move the opposite direction shown, unless there's some external force acting on them

I tend to disagree. There is an external force .. "gravity", which will be applied to both. I'll make a mock up of some kind to see what happens.
 
   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ??
  • Thread Starter
#7  
Marketing could call it Active Stability Control. ...
Of course, the first one to malfunction and flip a machine would bring down a hellfire of bad press & lawsuits that would probably finish the company.

I'm not going to market them!
 
   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ?? #8  
If the weights are of equal mass and if the only force acting on them is gravity, they will just sit wherever they happen to be when you install them.
 
   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ??
  • Thread Starter
#9  
This is going to be fun! :laughing:
 
   / Physics .. "Active" tractor weights .. Shifting the C/G ZTR ?? #10  
I tend to disagree. There is an external force .. "gravity", which will be applied to both. I'll make a mock up of some kind to see what happens.

Saying that they have weight is another way of saying there is gravity acting on them. If there were no gravity they wouldn't weigh anything. A simple mockup would be two forks connected by a string. Put one fork on the kitchen table, the other hanging over the edge, and see which way they move. You could tip the kitchen table and repeat the exercise until the table surface is vertical, in which case the forks will balance each other and not move.
 
 
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