Hydraulic motors

600 divided by 12 is 50 , divided by 16 is around 3.3 ft/lbs . A lot depends on how many rpm's , and can it be geared down to a usable rpm/torque number ...

wrote: (clip) I have a feel for foot pounds because I 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.

And Power (hp) = Torque (ft-lb) * RPM / 5252 Art

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.

3.3 ft-lbf (600 in-ozf) at 1800 RPM would be 843 watts or 1.13 HP. This torque would produce 2 HP at 3183 RPM.

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

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!!!

Great comment from Don Foreman on the power/speed continuum! Shows some of the interlinked phases of physics. In another venue, Don could explain how gazillions of watts of power could be transmitted on a wire the size of a hair, voltage and insulation permitting.

Bob Swinney

3.3 ft-lbf (600 in-ozf) at 1800 RPM would be 843 watts or 1.13 HP. This torque would produce 2 HP at 3183 RPM.

the interlinked phases

power could be

I can't tell if you're being snide or not.

At any rate, to transmit lots of power with an itty bitty wire you just need to pull on it at less than it's breaking force, fast enough to so that your (speed)(force) equation equals your desired gazillions of watts.

I really can't figure out what this "voltage" and "insulation" stuff is, though :-).

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

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 sez: "I can't tell if you're being snide or not I really can't figure out what this "voltage" and "insulation" stuff is, though :-)."

Better it should have been said "electrical energy" rather than power. Power doesn't really happen until something spins or heats up at the far end of the energy conduit, whatever that may be. Technically it also should have been "gazillions of kilowatt-hours" All that being said, P = Voltage ^2 / R Thus it is theoretically possible to transmit very large amounts of energy over a very small conductor - think cryogenics and super high voltage. Hmmmnnnn, P = dt/de 'Nother way of saying it.

Bob Swinney

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.

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

figure out what this

doesn't really happen

whatever that may be.

being said, P =

amounts of energy over a

= dt/de 'Nother way

Except that very small wire diameters don't get along well with very high voltages -- most of your power goes away in corona spray. :-)

Enjoy, DoN.

Indeed. Google "hydraulic generators".

That's about 5220 watts or 7.0 HP.

But not the correct way.

P = dE/dt. or dW/dt.

Also, your distinction between energy and power is not valid, in the above.

If "energy happens", then "power happens". If power happens, energy happens. Always.

It's only that without specifying time, you can't specify *how much* of each. But one *always* implies the other.

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.

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