Rexroth hydraulic motor

Attie

My mate bought a beat chopper with a rexroth hydraulic motor, has seen a few hard winters. The motor was leaking oil from around the shaft we had to rebuild the shaft.
So put in new seal which promptly failed, 2 more seals later I'm here.
I'm trying to help him but can't get my head around the principal but I think there should be no pressure on the seal unless the return pipe is to small but we are working with original pipes.
Only thing is we are putting it on a loading shovel instead of a tractor which would have more oil flow maybe need to up the return pipe.
Thanks for reading any help appreciated Attie.

blue5000

I'm no expert, but I'd say you are on the ball with the return pipe AFAIK it should be larger than the in feed pipe. But what happens if the lad driving it puts it in reverse by pushing the spool lever the wrong way?

patsy_mccabe

Hydraulic motors can be driven in either direction so back pressure should not cause a problem. Are you sure you have the right seal in There? Redwood Hydraulics in Cork are agents for Rexroth . Maybe they can help you.
The shaft may be worn or roughened at the seal area which would cause it to leak too.

Muckit

I would be no expert either but reckon it's like what patsy is saying. Shaft is rough near seal. Hydraulic pressure wouldn't feck the seal. Look at all the pressure on a trailer tipping ram. Usually damaged chrome rod surface (rust, scrape etc) that buggers seal.

Bring it in disassembled to that crowd and they should sort you

Attie

patsy_mccabe wrote: »

Hydraulic motors can be driven in either direction so back pressure should not cause a problem. Are you sure you have the right seal in There? Redwood Hydraulics in Cork are agents for Rexroth . Maybe they can help you.
The shaft may be worn or roughened at the seal area which would cause it to leak too.

Thanks Patsy we have already rebuild the shaft but we are putting in ordinary seals.
Should the seal be a high pressure one ? ?.
Thanks Attie.

White Clover

Any chance ye are running it in reverse and pumping through the big hose and trying to force the oil out through the smaller hose? That may be putting higher pressure on the seal.

Water John

If, from what I'm reading here, you have rebuilt the shaft where the seal is positioned, you won't be able to seal it.
As some one else posted that surface needs a chrome finish, like any ram.

White Clover

Water John wrote: »

If, from what I'm reading here, you have rebuilt the shaft where the seal is positioned, you won't be able to seal it.

We would be assuming it has been built up and machined back to the correct diameter using a lathe?

Water John

We overlapped on my edit, Clover. The tolerance would be extremely small I think, that is why the chrome finish would be smooth enough.
From doing water, our tolerance was .03mm on plastics. Could not be moulded. A special grinding machine to get that low a tolerance.

Attie

White Clover wrote: »

Any chance ye are running it in reverse and pumping through the big hose and trying to force the oil out through the smaller hose? That may be putting higher pressure on the seal.

White clover both hoses are the same size as on shovel.
The seal holds until the pressure is uped by raves.
Thanks Attie

White Clover

Attie wrote: »

White clover both hoses are the same size as on shovel.
The seal holds until the pressure is uped by raves.
Thanks Attie

Can you reduce the oil pressure going through the 3rd service on the loader? I'm assuming it has a diverter valve or an independent 3rd spool.

Attie

Water John wrote: »

We overlapped on my edit, Clover. The tolerance would be extremely small I think, that is why the chrome finish would be smooth enough.
From doing water, our tolerance was .03mm on plastics. Could not be moulded. A special grinding machine to get that low a tolerance.

Water John now I think we are getting down to the finer points as has been suggested before tolerance would be small.
Shall look into this your help is much appreciated.
Happy new year to all thanks Attie.

patsy_mccabe

Who did you get the seals from? Did you get a full set?
Can you get a serial number from the motor? That should help you get the right seal kit.

dh1985

Attie wrote: »

My mate bought a beat chopper with a rexroth hydraulic motor, has seen a few hard winters. The motor was leaking oil from around the shaft we had to rebuild the shaft.
So put in new seal which promptly failed, 2 more seals later I'm here.
I'm trying to help him but can't get my head around the principal but I think there should be no pressure on the seal unless the return pipe is to small but we are working with original pipes.
Only thing is we are putting it on a loading shovel instead of a tractor which would have more oil flow maybe need to up the return pipe.
Thanks for reading any help appreciated Attie.

When the additional seals failed were they chewed up or did they extrude. Is there nylon rings with the seals also or what type seal is it

tomwaterford

Get a better quality/high temperature seal??

Or just buy a new motor...youd have one got,in and with warranty while your at this one

Water John

I was dealing in plastics.
I think your looking for machine tooling using a CNC machine.
Google that for any one near you, to see could they do it.

Attie

With a lot of grief getting these resized to show what I'm at.
I think a new motor might be the best way but getting the mate to spend money is like pulling teeth out of a hen.
Anyway thanks folks for all your help it was good of you all to take time to post I shall keep ye all updated after the holidays as to what took place.

Attie

Nekarsulm

http://www.whitehouseproductsltd.com

Try these guys, if all else fails.

Attie

Update on the Rexroth motor had to get the two plates re faced as they were pitted and letting oil pressure built up in chamber where none should be,then had to put none return valve on drive side of motor someone must have taken it off. Now going good o
Attie
PS thanks for all reply's.