Hydrostat issue...with video

[Ambush]

The engine driving the pump and motor to drive the pump and motor is redundant and costly in efficiency.

Maybe a double pulley and use a flat idler to engage/disengage for easier starting? Looking at your accomplishments, I'd say that would be easy for you.

I'm not convinced that it's the hydro itself causing the lock up. They are about as basic as you can get and a mechanical swash to. If you have spring pressure holding the barrels to the valve plates and they are sealing, and you have the required charge pressure, then not much else to go wrong.

Sometimes, if there is not enough barrel spring pressure, the barrel will suddenly lift off the valve plate then slam back causing a shudder in the system, causing all the hoses to jump violently.

[Ambush]

I'm probably saying things you already know, but a cheap belt from places like Harbor Freight or Tractor Supply is not going to stand up long under that load. You'll need a HP rated industrial belt.

The fellow that owns the shop I worked at is building (another) skid steer loader. It's powered with a 16HP engine that runs a tandem hydrostat that is powering four gerolor motors. Plus a 6 gpm pump and a 1.5 gpm pump mounted on the end. It has a dual pulley set up. He's using an automotive belt tensioner set up from a pick up truck. In your case you could have a lever to remove tension and releasing it would put constant pressure on the belts.

I also don't think the original pulley on the pto is capable of the load your machine is under, the pulley being too narrow, the diameter too small and possibly the clutch itself not up to the task. You need a wider belt Also six inch pulleys will be much better than four inch. Myself, I'd leave the original pto clutch pully out of it. If you want a clutch, then buy a HP rated centrifugal pulley. Expensive, but probably way cheaper in the long run.

Save the pump/motor set up you have now for the next project that you'll dream up just because you have them. I would advise dissembling the pump and motor and checking the housing and side plates for damage. Some housing wear is expected.

[sawdustdad]

I've been using a Gates industrial belt, (AX50-30) and it would stall the motor before it slipped.

I'm beginning to really like your idea of the double belts and a tensioner. I think the hardware for that is readily available and I think I have he space to do that. I have a couple tensioner pulleys on hand that should work.

I don't know what to make of the problem with the hydro. I'm going to replace it. If it were working, the output should spin with the drill. It's not. The other (front axle) hydro does. Other hydros I have used a drill on all work under drill power.

That said, my curiosity has me wanting to know why it doesn't work, as you've said, there are only so many parts and they all seem OK. Blocked oil passage in the cover? Maybe I'll remove the bottom pipe plugs and relief valves and check that out.

As for the drive (pump/motor) to hydro(pump/motor) arrangement I was willing to accept the efficiency losses to achieve durability and reliability--no more belts to fail or change. I even thought about a pair of right angle gear boxes.

I really appreciate all your comments, Ambush. Sometimes it takes another person looking at the issue from a different perspective to solve the problem.

[Ambush]

That's a quality belt. Just not enough belt for the job, I don't think, a C or D being much better. Double pulleys mean you can use less tension and less side load as well. Even at that, myself, I'd incorporate a two bolt flange bearing near the pulley. Save the pump bearings, but more so the shaft. It could suffer quite a bit of deflection and eventually fail.

I was re-reading your test when you first started up with the added pump and motor drive and the sudden loading and unloading. I would be willing to bet that that was your new motor, not the hydro. I've seen it many times on the test bench where a gear motor would lock up before it got its load turning. All the pressure is on one side of the gear set, pushing the slack side into the housing and jamming it up. With enough pressure sometimes it would turn, taking some metal from the housing with it. The gears essential "machine" into the housing. Gear pumps and motors should be broke in under no load, then a series of heavier loads with a no load run in between. Do that up to your working pressure, then change the filter.

If you open your motor, you'll likely see some material gone. Ditto the pump, but maybe not as bad. That material is now in your hydro system.

You've good some great machinery there and obviously the skills to use it. Couple that with your aptitude and attitude and you're going to have a very unique and useful "toy" when you're done. Basically; You Got This!

[sawdustdad]

Just ordered a pair of double belt pulleys and taper lock hubs. I think I'm headed down that path now. Assuming I can get a working hydro.

I cleaned out the hydro fluid from the rear end (actually twice) and did not see any debris but can't rule out the presence of some very fine metal particles. I also changed the hydro filter. If anything from the motor I added went into the gear case, it's gone now.

[Ambush]

Looking forward to seeing you grading!

It would be interesting to cut your rear hydro filter open. I just hacksaw around the outside of the threaded end then lay the element out. Good diagnostic tool.

[sawdustdad]

Originally Posted by Ambush

Looking forward to seeing you grading!

It would be interesting to cut your rear hydro filter open. I just hacksaw around the outside of the threaded end then lay the element out. Good diagnostic tool.

Here it is in action earlier this year.

https://youtu.be/lveiY__nZis

[Ambush]

Very cool! That's an impressive and sophisticated bunch of fab'ing and machining. Very satisfying when a plan gets off the paper and onto the ground.

[Billy-O]

I've been reading some (if not all) of this thread and I've been wondering if you inspected your bearing cages? Either on the input or output shafts. If a cage failed, the bearing could possibly jam. Forgive me if I missed any mentioning of this before.

[Mike McKown]

Originally Posted by Billy-O

I've been reading some (if not all) of this thread and I've been wondering if you inspected your bearing cages? Either on the input or output shafts. If a cage failed, the bearing could possibly jam. Forgive me if I missed any mentioning of this before.

I've been thinking this but............

That means there are two problems.