A few motor questions

Rustyiron · Apr 4, 2014

JJ - CJONE Got a TRW/Ross MAB06003 A4. All that I have been able to find out about it is it seems to be obsolete. What could you direct me to on the net to find out it's specs. and if it need it, is it rebuildable? I think that it is a gearotor motor. Once before I found a site that had recommended replacement pumps/motors, I can not find that site now.
Now that I'm here asking dumb questions....

Are all hyd motors reversable?
Does a motor need a special valve? (to just operate it)
If you starve a hyd motor a few gpm under it's rating, will it just slow it down, and will this also reduce torque?
Is a large disp. motor required for low rpm/high torque?
They (in surplus center's fine catalog) seem to measure torque in inch/lbs. This is divided by 12 to get ft./lbs right? I can somewhat relate to ft/lbs.
I see "case drain" on some motors, is this mostly on larger, high gpm/disp. motors?

I'm trying to cobb together a light winch for an attachment I'm building for the back of the tractor to yank logs out of the woods. I don't really have any big hardwood and am looking to pull out smaller 10"-14" stems that I can't get to with my machinery. I have an old (it seem's all my ch!t is old) winch with a simple big gear - little gear that is 40/1 reduction. The tractor has about 17 GPM pump, I'm not sure if that's all available at the rear remote's, and the SS has close to 30gpm. I would like to have it be able to work on either.

J_J · Apr 4, 2014

No, not all hyd motors are reversible.

If you reduce GPM, you slow the motor.

Pressure and CU IN determines the torque.

The motor you choose should be able to handle the GPM's and pressure.

Some manufacturers use case drains.

As long as you supply GPM to a hyd motor it will run. However, a valve with relief is advisable

Most valves for motors use a motor spool valve which can be reversible.

Some pumps have different sections for different GPM's for things like steering, attachments, etc.

wdchyd · Apr 4, 2014

Parker bought TRW/Ross.....some parts are avail

Only need a case drain if the exhaust port sees high pressure (IE: using multiple motors in series)

yes, reversible

J_J · Apr 4, 2014

An axial piston motor with a fixed swashplate is unidirectional (rotate in 1 direction only). To be bi-directional, the swashplate would need to be variable position.

Piston motors will have a case drain line to allow piston leakage to flow to return.

All 4 hyd motors on my Power-trac have case drains, where other Power-Tracs do not.

In looking up the order code for some hyd motos, some of them have a selection for clockwise, counter clockwise, or bi-rotational.

Seems like the port size are the same for bi-rotational, and for uniderictional, the out port is larger than the IN port.

This is a Ross hyd motor, and it is reversible.

16 cu in ROSS MAF32017 HYD MOTOR.

Ports are the same size.

MHarryE · Apr 5, 2014

J_J said:
An axial piston motor with a fixed swashplate is unidirectional (rotate in 1 direction only). To be bi-directional, the swashplate would need to be variable position. Piston motors will have a case drain line to allow piston leakage to flow to return. All 4 hyd motors on my Power-trac have case drains, where other Power-Tracs do not. In looking up the order code for some hyd motos, some of them have a selection for clockwise, counter clockwise, or bi-rotational. Seems like the port size are the same for bi-rotational, and for uniderictional, the out port is larger than the IN port. This is a Ross hyd motor, and it is reversible. 16 cu in ROSS MAF32017 HYD MOTOR. Ports are the same size.

JJ - are you referring to axial piston motors being uni-directional because of a unidirectional flow pump? I have had multiple applications with bi-directional axial piston motors. Caterpillar double drum vibratory compactors for example. We turn the motors one direction for high amplitude and reverse direction of rotation which changes the centroid of the weights to get a different vibration amplitude running in the opposite direction. Axial piston motors because bent axis motors did not have the capability to run motors in series i.e. Have 6000 psi inlet pressure, 3200 outlet pressure ton to the second motor which then has 3200 psi inlet pressure, 400 psi outlet pressure which is the charge pressure. The first motor on the circuit seeing summation 9200 psi is a bearing challenge - we used Bosch Rexroth AA4 motors which are bi-directional and have extremely high load and temperature capabilities.

J_J · Apr 5, 2014

I believe the uni-directional rotation has to do with a fixed swashed plate.

If the swash plate is variable, then it is bi-directional.

I guess the point is that most hyd motors are bi-directional.

wdchyd · Apr 5, 2014

Jj, I've seen many bi-rot piston motors with fixed swash plates

Rustyiron · Apr 5, 2014

Thanks Guy's, answering from a list (like I gave) is not easy in this format. So any site you can think of that would have spec's and substitute replacement suggestions? Building with hydraulics when you are mostly guessing can be expensive. I learned this about 35 years ago building my hyd. log splitter (that I am still using today) , but now we have this internet thing and hopefully my "wrong parts" pile will not be as big on this project.

J_J · Apr 5, 2014

The direction of a hyd motor is nothing to argue about.

Excerpt:

Direction of Rotation – Motors can be uni-directional or bi-directional. Aerospace applications tend to be bi-directional pumps. Obviously, the control valve position must be matched to the appropriate direction of rotation.

I agree that most hyd motors are bi-directional.

Facts are facts, and you should know that you can order a hyd motor that will run in a certain direction, and it should be piped that way. The valve you use will probably be different than a bi-directional motor.

This valve can control the speed of a hyd motor, and is similar to what I use on my Power-Trac to control the speed on the PTO implements.

1/2 NPT HYD FLOW CONTROL VALVE W/RELIEF RDRS150-16

However, the implement hyd motor could very well be bi-directional, and there is no reason that I could not run it in reverse if I pipe it right.

Here is a good run down on hyd motors.

http://www.daerospace.com/HydraulicSystems/MotorDesc.php

Motors, Hydraulic - Description

Can you just look at a hyd motor and tell just what it is, I doubt it. You will probably need the order code to really know.

Just one letter in the order code will determine the rotation.

Rustyiron · Apr 5, 2014

Well today I got the right fittings to "plumb it" to the tractor rear aux. I have 2 motors and both of them spun each direction and the tractor valve even let me "feather" the speed. Didn't end up with a puddle of oil and no crazy hyd noise so that's a good start. One motor has a higher rpm than the other. That surprised me, the bigger, actually bigger around, was faster than the smaller dia. but longer one. Like I said, I'm only learning about motors. What I'm trying to cobb together a small (in capacity) winch that will hopefully have a 4000# pull or so. I guess my best bet without knowing the motor specs is to just assemble it on a suitable pc. of steel and play with the sprocket combinations and put it under load before I attach anything to my "log getter" that I'm building. This is a not so great (early) picture of what I have going on.