1stDeuce
Gold Member
This is a cool little project, though it appears you may need quite a bit of ballast on the back of it if you plan to haul a loader full of dirt...
The above recommendations are on point. You have too much pump for the HP of the motor, and too much pump in general if you were targeting 10mph, which is probably too fast for your hilly 1/2 acre property. I would think 5mph plenty fast for running through trees and maneuvering around things...
Actions you need to take: 1st, you need to figure out the pressure needed to the motors to provide the tractive force that you desire for moving the thing around. If it weighs 500lbs, and is going to haul a loader full of dirt, that's ~1000lbs. Driving that up a 30% (20ｰ - pretty steep!) slope would require 340lbs of tractive force. Even though you have two motors sharing the load, so 170lbs each, I would do calculations based on one, because as oldnslo also points out, skid steering will take significantly more torque than going straight... Hmm, actually, you're not only providing tractive force, but also skidding tires as you go. Perhaps use 500lbs as the required tractive force just to be sure it'll be able to turn if you're going up hill.
Knowing the torque required of the motor to provide the tractive force, you can get the pressure needed to generate that torque. If it is greater than the max operating pressure of the motors, you will have to gear down until it is below the operating pressure, or buy larger displacement motors. If it is not above the motor max pressure, you now have a required pressure needed to maneuver the rig.
Using that pressure, calculate the max pump displacement that your motor will run while providing that pressure. That is your maximum pump size.
Now, knowing the pump displacement, you can calculate the speed your unit will go with the engine running 3600rpm's. You can further reduce the pump displacement to slow the thing down, and give it more tractive power, but you can't speed it up without sacrificing power.
I'll take a swag and say that your 6.5hp motor might be able to hit 2mph going straight once you have the pump sized appropriately, and the gearing or motor size corrected if needed. Crunch the numbers and let us know how it works out.
The above recommendations are on point. You have too much pump for the HP of the motor, and too much pump in general if you were targeting 10mph, which is probably too fast for your hilly 1/2 acre property. I would think 5mph plenty fast for running through trees and maneuvering around things...
Actions you need to take: 1st, you need to figure out the pressure needed to the motors to provide the tractive force that you desire for moving the thing around. If it weighs 500lbs, and is going to haul a loader full of dirt, that's ~1000lbs. Driving that up a 30% (20ｰ - pretty steep!) slope would require 340lbs of tractive force. Even though you have two motors sharing the load, so 170lbs each, I would do calculations based on one, because as oldnslo also points out, skid steering will take significantly more torque than going straight... Hmm, actually, you're not only providing tractive force, but also skidding tires as you go. Perhaps use 500lbs as the required tractive force just to be sure it'll be able to turn if you're going up hill.
Knowing the torque required of the motor to provide the tractive force, you can get the pressure needed to generate that torque. If it is greater than the max operating pressure of the motors, you will have to gear down until it is below the operating pressure, or buy larger displacement motors. If it is not above the motor max pressure, you now have a required pressure needed to maneuver the rig.
Using that pressure, calculate the max pump displacement that your motor will run while providing that pressure. That is your maximum pump size.
Now, knowing the pump displacement, you can calculate the speed your unit will go with the engine running 3600rpm's. You can further reduce the pump displacement to slow the thing down, and give it more tractive power, but you can't speed it up without sacrificing power.
I'll take a swag and say that your 6.5hp motor might be able to hit 2mph going straight once you have the pump sized appropriately, and the gearing or motor size corrected if needed. Crunch the numbers and let us know how it works out.
