Hydraulic wheel motors
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Re: Hydraulic wheel motors
Re: Hydraulic wheel motors -- john-oden	Post Reply	Top of thread	Forum

Posted by: randykimball ® 12/26/2005, 17:46:50 Author Profile eMail author Edit

John, You may want to tell the forum group if it is ok to put a reduction gear at the wheel, and perhaps what reduction is allowed. This will greatly effect the resultant torque. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

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Re: Hydraulic wheel motors
Re: Re: Hydraulic wheel motors -- randykimball	Post Reply	Top of thread	Forum

Posted by: jvan ® 01/04/2006, 12:08:22 Author Profile eMail author Edit

John, You may have a problem, especialy with the gradeability. If we ignore air resistance because of your low speed; tractive effort is the sum of Rolling Resistance and gradeability. I am an old guy used to imperial so here goes. GVW= 14000 kg or 30865 lbs Speed is 10km/h or 6.2 mph Rolling Radius (r) is 1135 mm dia. or 44.68" dia so 22.34" 15 degree grade is 26.8 % grade (STEEP) Road Rolling Resistance= (GVW x R (a factor, 20 lbs for poor concrete))/ 1000 so Road Rolling Resistance = 617 lbs Grade Resistance = .01 x GVW x %grade so Grade Resistance = 8272 lbs. So Total Tractive Effort = 8272 lbs + 617 lbs = 8889 lbs. Tractive Effort= (Torque x 12)/r; solving for Torque Torque = (TE x r)/12 = (8889 X 22.34)/12= 16548 ft/lbs or 4137 ft/lbs per motor for a 4 wheel drive vehicle. Speed (mph) = (RPM x r) /168 (a constant) solving for RPM RPM= MPH x 168 / r = 46 RPM Fluid Motor Torque in in/lbs T= (Pressure x displacement (cubic inches))/ 2 Pi so Displacement = (T x 2Pi) / Pressure Assuming a 3000 PSI system with 2000 psi available at the drive motors. Displacement = 156 cubic inches. Any gear ratio will change this displacement, but the flow will just increase, power is power. Drive flow = (motor RPM x Displacement)/ 231 cubic in. per gallon = 31 GPM per motor. Since one horsepower gets you approx. 1 gpm at 1500 psi, 31 gpm at 3000 psi would be 62 HP or 46 kw per drive motor. The large torque required is due to the high gradeability, to solve your problem you are probably going to have to go to a two speed motor ( higher torque on the grade) or get tricky with a series parallel circuit on the motors, series for high torque, parallel for high speed. I've done these calcs in a hurry, but a good hydraulic designer can probably design a circuit for you that will work, or sacrifice some on the gradeability. If you have any questions, I will be happy to help if I can. John Modified by jvan at Wed, Jan 04, 2006, 16:55:37

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Re: Re: Hydraulic wheel motors
Re: Re: Hydraulic wheel motors -- jvan	Post Reply	Top of thread	Forum

Posted by: Dan wilson ® 08/31/2007, 17:00:23 Author Profile eMail author Edit

jvan, would it be fesible to build the following with hyd wheel motors? A 6 wheel amphibious atv, with 4 of the wheels steering. not a skid steer type. I want, say 3 wheels, or better, 2 wheels to pull the load since it will always be climbing bad, rutted, sandy banks of a creek to get in and out. that will weigh 1200 lbs, loaded. will go 15 mph on flat ground (off road) will go up a steep incline, 30 deg , at any mph, say 2 mph will have 25" dia low press off road tires a 20 hp gasoline motor. 2000 rpm What would be the pump capacity and motors needed for this atv? Does this sound fesible? Maybe I could change motor size or something else to make it more fesible or affordable? What do you think? Thanks, Dan

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