I would like opinions on wether I totally screwed this axial piston motor. I put it (disassembled and in cardboard boxes) into the back of my pickup in the rain for about 45 minutes. 8 hours later I unpacked the parts and found that several key components had, you guessed it, rusted. There is rust on the surface of the cylinder barrel where it mates to the valve plate. It is deep enough to feel with your finger nail. Also a couple of pistons got some spots where they ride in the shaft (looks like brass guide). One of the piston rings got some spots the size of a pin head on the ring. This is a 33 year old volvo-parker voac bent axis F11-78 motor (obsolete) and parts are impossible or harder to come by. I will try and add some photos of the damage. Question: can these rust spots be dressed out or am I totally screwed?

Ok, I guess I can't post the photos. I tried to create a photo album but...

I think this will allow viewing of the photos. I posted them to a google album. I hope this works.

http://picasaweb.google.com/drbuzz777/NewAlbum10408618PM#

quote:

33 year old volvo-parker voac bent axis F11-78 motor

everybody in this forum are not familiar with a 33 year old volvo-parker voac bent axis F11-78 motor. Would be interesting to know what equipment is utilizing this motor.....It's a very common motor originally from Volvo Hydraulics.....I'm sure there is hope out there for you...VOAC is owned by Parker now...use their contact on this site and link them to your pix ...They'll give you the best advice...
Parker Hydraulic

try a local rebuild shop and see if the valve plate/block surfaces can be lapped. they can tell from seeing the parts

k

The dressing out how was it done? Lapped? Why was this unit taken apart to start with?
Sand paper as a lap will never work with this unit. I would do as Kevin has posted and try to find a local shop that may be able to lap these for you. The parts should be ok for that old of a unit providing that the rings and block is ok.
I know i have had customers that there pump sat in the back of the runners truck for more than a few hours and have worked things out.

Kevin, there is no local shop that will work on it.

The story of this motor is..
It is part of the hydrostatic transmission in my boat. I wrapped a crab pot line around the prop a couple of times. Each time the pump would destroke and after I cleared the line, everything was fine. On one occasion we were anchoring the boat and wrapped a line again. With the boat adrift in a small bay and many other boats around, I instructed my wife who was driving, to "just put it in gear and hold it there". WRONG. The prime mover quit (from about 1000 rpm). AFter that I thought I detected some extra noise and vibration. Just recently I noticed that I could not get full rpm out of the system without the pump destroking. I have been trying to trouble shoot the system for quite some time. I live in a rather isolated area with one qualified hydraulics repair guy, but he is booked for 6 months and has told me in the past that he doesn't want to get involved. The pump is, I believe, a marinized sauer/sundstrand type 18. (pics here)
http://picasaweb.google.com/drbuzz777/PumpAlbum10608100PM#

see this discussion for more...
http://forums.hydraulicspneumatics.com/eve/forums/a/tpc...1063911/m/9381030992
or
http://forums.hydraulicspneumatics.com/eve/forums?a=tpc...551015392#1551015392

I had this motor into an "authorized" Parker shop who said they could find nothing wrong with it (this shop is 3 hours away.) After inspecting the shaft myself, I could see where a bearing had spun on the shaft. Question is why? The shop then told me that parts are not available from Parker. I picked up the motor in pieces on Friday and that's when it got wet
Update:
After talking with my good friend Ric, who has many years of training and experience working on heavy equipment, I put the cylinder block on a piece of crocus cloth on glass with oil as a lubricant. I polished the surface being careful to keep it flat. I carefully cleaned the pistons and one ring the same way, cleaning in the opposite direction of movement. I took it to a machine shop today and the machinist said I did a great job and that it should work just fine. You can see the pics at the google link above. While at the machine shop I had the machinist look at the bearings. They don't look that bad except that one of them spun. After looking at the bearing the machinist said he thought maybe foreign body got in the bearing. I do know that the seal was bad and this motor was sitting in 33 years of crud with salt water in the bottom. Part of the housing that retains the seal was corroded away. I didn't inspect the seal but I am confident that there was little left. So either crud got into the motor via a bad seal, or there is damage in the pump and it's making metal. Yikes!
I plan to replace the bearings (aftermarket) and put it back together myself.
I have to decide if I am going to tear into the pump, or put this motor back in service and test the system by running it. If the pump destrokes, I'll know it wasn't the motor. If it doesn't, I still won't know that its making metal until something else goes wrong.

Again, the fault was: unable to reach full operating rpm before the hydraulic system reached max recommended operating pressure and destroking.

Thanks to everybody for taking your time to read all this and offer your expertise.

this falls in the 'don't try this at home' that we all advise against, yet do when there is no other option and no parts at hand. I recall your earlier posts.

If the pump is compensating on pressure before reaching full rpm, it means the load is too great. Thus, the odds are fair that the motor and bearing and load is still the issue, hopefully not the pump. However, motor trash gcould have damaged the motor.

It is a calculated risk, but I would put it all together, run the pump and motor freespin for several minutes without any prop load if possible to flush and clean the loops. Then gently get some loads on it.

k

Kevin,
thanks for the response. Yah, I would have gladly paid somebody to help me straighten out my mess. I think there is a great demand for someone who really knows hydraulics and is willing to work, at least in my locale.
Question: is it possible that the output shaft seal was so badly corroded (I didn't see it but the housing was badly corroded in this area) that in the presence of a high torque incident or just incidently, it allowed dirt to enter the motor? I mean if fluid can go out, then stuff can get in no? Or perhaps the high torgue produced a slight flat spot in the bearing. I can see scuff marks on both bearing races that are perpindicular with the direction of rotation. Certainly a bearing which shows signs of spinning on the shaft would produce extra load I think.
What say you?
thanks
buzz

can you install this motor without connecting to the prop shaft load? break in slowly, then freespin it and read the pressures, ideally directly at the pump.

I maybe missing something, but if the system compensates on pressure before reaching full rpm, the load is too high. so we need to determine if the shaft is the load, if the motor is the load, or if there is a piece of junk/bolt/adaptor somewhere in the piping that causes a hydraulic pressure drop. Thus, the closer to the pump port you can get a gauge installed, the better. Or, best yet, in the PC control line if there is such a port.


and DON'T forget to fill the case before startup! I don't know if there is a built in flushing valve, but to be safe, fill the case with clean fluid.

k

Wow, after composing a lengthy reply I lost the whole thing by trying to attach a photo. OK.
Kevin, I have posted some pics and documents at this link:
http://picasaweb.google.com/drbuzz777/PumpAlbum10608100...6_oFQQwb1hzFz2RxPGw#
To answer your questions, Yes I can do as you suggest. I can put it all back together and ease the motor back into service without the prop shaft. The prop is of course disconnnected at this time and it turns easily by hand. The restriction is either in the motor, the pump, or the lines. If I can measure the motor rpm I can calculate the flow. I have service manuals now for the motor and pump. the only problem with the manual for teh pump is that I have a "marinized" version which makes it appear different than the pictures and diagrams. My take on it is that those pics and diagrams in the service manual are fairly generic. Anyhow, assuming my pump to be a Sundstrand pump (marinized), I have aquired said service manual and spoken with the local sundstrand rep who suggests hooking up pressure guages to the charge pump and measuring the pressures. I can only see one port that looks like it could be a pressure port. The pump should also have a relief valve accessible from the outside and so what I can see is either a port for a gauge or the relief valve. One way to find out is take it off, huh?
Question: do you think the bearing is the cause or effect of the problem? Or is it impossible to tell at this point. I have a pressure guage attached to the high pressure port of the pump only at this point. I'm not sure what a PC control line is but I have no external controls to the pump other than mechanical linkage direct to the swashplate. (see diagrams at link above).

the Sauer/sundstrand service manual can be viewed here: http://www.sauer-danfoss.com/Literatur/index.html
under "hydrostatic propel" and "type 18"

On the motor: I am waiting for bearings, I have to locate a seal kit and snap ring, and have the machinist cut a new seal surface and press bearings on. Then I get to assemble the thing.
doesn't look too complicated. Much easier with the service manual.
thanks for any and all help.
buzz

interesting unit. I assumed by marinized it was just epoxy coated or something but this is a totally different packaged unit than I have seen.

I am confused, so backing up: I think you said before that the unit compensates at 2300 psi? and does not increase speed any further.

Pressure override or pressure compensated means the controller actually interrupts the stroke control and prevents the swash plate from going further, thus limiting the pump flow. This is what I assumed was happening, thus the load on the system (or restriction in the piping) exceeds 2300 psi and the pump was doing exactly what it should.

From the pics and service book pages, it appears this is a direct manual control of swashplate. The lever on top directly moves the swash plate, with no pressure override or stroke controller. Is that the case? Or is there some sort of controller up under the water/oil cooler tube near the engine? Does your hand control/lever/cable move that swashplate lever directly, or does a separate controller pull on it?

If direct manual control, do you mean the system goes across a relief valve at 2300 psi?

The difference is that pressure override/pressure limiter interrupts the 'production' of high pressure fluid flow energy by destroking the pump to less output. Relief valves just dissipate the energy and flow, that was already put into the fluid, to heat across the RV orifice but the engine and pump are still fully loaded.

How and where did you measure the 2300 psi load when the pump maxed out, and what were the operating conditions, the reaction of pump, reaction of pressure gauge(s) and reaction of motor to the various conditions? I don't know the unit at all, so don't know which port would be suction, charge, servo, forward, or reverse pressures.


kcj

Kevin,
I'll try and be as clear as I can.
1. By marinized, I mean they put the pump guts into a "marine" alloy aluminum housing which mounts directly on the back of the prime mover. IT is also an integral reserviour and has oil coolers which circulate "raw" water from outside the boat through a heat exchanger to cool the oil.
2. The unit "compensates" at 2300 rpm (rpm of the prime mover). The pump is direct coupled to the prime mover so that means the pump is also at 2300 rpm
3. The compensation occurs at about 2150 or 2200 psi, maybe as high as 2300psi, I don't remember exactly now. This pressure measurement is at a high pressure port (forward) which connects via hose to the hydraulic motor. When it "compensates" the swashplate (pump) and directly controlled lever, move toward neutral, and teh prime mover unloads a little. The pressure drops back to 2000 psi and prime mover rpm goes up slightly. I can't tell what difference this has on the hyd. motor, but it seems that the motor speed drops off. the speed of the boat drops back a bit as well, indicating that the motor rpm is less.
4. Yes, the lever on top of the pump connects directly to the swashplate. A cable connects this lever to an operator controlled lever in the cockpit. No seperate controller
5. In answer to your question about wether the system goes across a relief valve, I have to say that it is my guess that a relief valve of some sort must be activating. Although from your description, it would be more like a pressure override.
6. I think the motor had enough damage to cause a high pressure to develop. You can see where the bearing spun on the shaft in these pics.
http://picasaweb.google.com/drbuzz777/Motor101608549PM?...#5257918841903039410
Now I have to figure out how to put this back together. the shop that had it didn't mark numbers on the shaft where the pistons go back in. I called them to ask about it. No answer yet. then I have to have the have the shaft reworked at the machine shop. they have to cut a new keyway because of the damage done by the repair shop. If I can salvage this motor, it will be a miracle.
thanks for all the help everyone.
Kevin, I hope I answered your questions.

What happens if the pump control lever is held at 100% on stroke?
Maytag

quote:

Originally posted by maytag:
What happens if the pump control lever is held at 100% on stroke?
Maytag

extra growling! It is obvious the system is not happy. I couldn't tell where the growling was coming from.
B.