Hydraulic motors

use torque

^^^^^^^^^^^^^^^^^^^^^ There are 16 oz. to the pound, and 12" to the foot, so 1 foot lb would equal 16 x 12 = 192 in oz. So a 600 in oz motor would deliver just over 3 ft lb of torque. But that tells you nothing about the horsepower. To calculate that, you would have to know the RPM. To develop 2 HP, the RPM would have to be 3368. I don't think you can run a hydraulic motor that fast.
Are you really thinking about powering a minibike? Where are you planning to get the power to drive the hydraulic pump that delivers pressure to the hydraulic motor?
In order to understand this, you need to sort out the difference between torque, force and power. But that would require a physics lesson.
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You're asking about physics. so don't act like a physics "lesson" is not the answer.
You have to go to public school if you want to learn "science" without knowing any math or physics.
Women want to sit in a car, turn the key, and go. Men look under the hood and want to know why it goes.
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Amazingly, in 5 sentences you made 5 incorrect (and fairly obnoxious) assertions.
Dats 100%!!! Plus boucou extree credit for the obnoxiousness!
You musta gone to one helluva Catlick skool.
Go, Richard, Go!!!
--
DT



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snipped-for-privacy@gmail.com wrote:

Why would you want to introduce the losses of both a pump and hydraulic motor when the chain is so much more efficent. Are you planning to use a pump that has a swash plate so you can 'gear' down?
Wes
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On Oct 4, 9:51 pm, snipped-for-privacy@gmail.com wrote:

Thanks everyone for your help, except Richard of course, who can go ---- himself. I wanted to make an electric mini bike to get the mail and check on the critters. I saw a friend who made a new endplate for a chevy starter motor and mounted a sproket on the the shaft, which he then chained to the rear wheel. The battery was a normal lead acid car battery and the rig was good for fifteen minutes or so before it needed to be recharged, just about the time I need to do chores. I wanted to use a motor controller, but they are afortune. Even buying mosfets and making one up is expensive. I have hydraulic pumps that could be driven by a starter motor and they are good for about 6 gal per minute at 2000 psi. I checked and saw that hydraulic motors that worked in this range were in the 600 - 1000 inch ounce range. That is what brought about my question. Before some like Richard tells me that the starter motor is not designed for constant usage, I realize that but my friends mini bike shows it up to the task. Using a hydraulic set up it would be possible to govern the speed of the mini bike rather than just off and on the motor. And it could be done cheaper than a $450.00 motor controler. Another idea was to but a centrifugal clutch on an electric motor so that it would disengage when the motor is turned off . Thanks for your thoughts and if any more come up please post them! Rick
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snipped-for-privacy@gmail.com wrote:

Most DC permanent-magnet motors have fairly low torque when there is no current flowing, so in an application like this you could just leave them connected.
I would expect a starter motor would be the same. You'll have some losses, but not that bad.
Just as speed * force = power, and rotary speed * torque = power, flow * pressure = power. You could find the absolute maximum power to the wheel fairly easily by finding the power in a 6GPM, 2000psi flow.
Dunno how efficient a hydraulic motor is, though -- I could see such a device being valued far more for controllability than efficiency. But at least you'd get that max number.
--

Tim Wescott
Wescott Design Services
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Didn't you say you have exra hydraulic pumps lying around? I believe you could use one of the pumps as a motor by pushing fluid through it.
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Hi Leo, That is a good question that I don't have and answer for. I have noticed that most pumps, in the range I am thinking about, have input shafts around 3/8". Motors of this capacity have output shafts that are around 5/8" to 3/4". I am not sure why that is other than perhaps they are designed for "radial load" rather than just a twisting load. I don't think I said that well but I hope you get what I am trying to say! Rick
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Indeed. Google "hydraulic generators".
--
DT



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wrote:

That's about 5220 watts or 7.0 HP.
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On Sun, 5 Oct 2008 14:08:42 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Car starter motors are intermittent duty non-ventilated, and way too much power for the use - a controller of some sort is not optional. And series-wound motors do strange things when you apply full voltage unloaded, they tend to do nice things like spin up to destruction and then go off like a grenade - don't ever have the chain break...
Regular car batteries do not take kindly to deep-cycling, and all wet batteries (deep cycle included) do not like severe vibration.
Go get yourself a kid's electric scooter, they are mass produced and rather cheap and come with a set of gel batteries. Bladez is a premium maker, but there are hundreds of Taiwan Knockoffs that are a lot less yet still suitable for the task.
--<< Bruce >>--
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