- #1
meld2020
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I am calculating the amount of torque required to give mobility to a 7000 lbs oilfield service vehicle. The vehicle has a rectangular frame with fairly even weight distribution. The radius, from wheel center to edge of tire is 11.5 inches. These tires are treaded with various half-inch tall "cleats" along the tire. for lack of a better word. I'm mentioning this because I do not know how to accurately characterize the coefficient of rolling friction for the Force calculation. For my example, I have used 0.04, which seemed like a fairly coarse road tire:
F = (c)ma = (0.04) (7000 lb) (32ft/s^2) = 280 lbf.
The above would presumably be the force required to roll the unit along the grade of surface described by the coefficient; while it will be on generally flat surfaces, it must be loaded into a dovetail trailer, so an incline, 45 degrees assuming the worst, will be present for a short period of time. Is this the correct equation? This is where I begin having trouble profiling the additional torque required.
F = (280 lbf) (sin 45) = 198 lbf = the gravitational force acting upon the object at 45 degrees?
This value is lower than the original value, so that's where I get a little lost. Must I add the original (280) + 198 + a cushion amount to guarantee good acceleration up the ramps?
Once I figure that out, I am trying to determine how a gear reduction to the (electric) drivetrain would ease up my power requirements. One luxury is that the unit only needs to move 5mph, max. I would prefer it be mechanically limited from a safety perspective (wireless electronics will be controlling the throttle, through a receiver, to the motor controller)
With this speed in mind, is there an expression I can reference to determine the torque required to move this object, of this weight, with this friction loss and pitch requirement, with respect to X gear ratio?
Regards,
Mel
F = (c)ma = (0.04) (7000 lb) (32ft/s^2) = 280 lbf.
The above would presumably be the force required to roll the unit along the grade of surface described by the coefficient; while it will be on generally flat surfaces, it must be loaded into a dovetail trailer, so an incline, 45 degrees assuming the worst, will be present for a short period of time. Is this the correct equation? This is where I begin having trouble profiling the additional torque required.
F = (280 lbf) (sin 45) = 198 lbf = the gravitational force acting upon the object at 45 degrees?
This value is lower than the original value, so that's where I get a little lost. Must I add the original (280) + 198 + a cushion amount to guarantee good acceleration up the ramps?
Once I figure that out, I am trying to determine how a gear reduction to the (electric) drivetrain would ease up my power requirements. One luxury is that the unit only needs to move 5mph, max. I would prefer it be mechanically limited from a safety perspective (wireless electronics will be controlling the throttle, through a receiver, to the motor controller)
With this speed in mind, is there an expression I can reference to determine the torque required to move this object, of this weight, with this friction loss and pitch requirement, with respect to X gear ratio?
Regards,
Mel