OT: hydraulic help needed!

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GhoulweJ

Trad climber

El Dorado Hills, CA

Feb 8, 2013 - 08:39pm PT

Ok cool.

I run a wholesale tractor parts company with locations around the world.

I've listened to hundreds of stories like this resulting in buying a part anyway.

I would pay $300 for the part. Seems cheap enough.

That tractor has low resale value BECAUSE of the high price of parts for it so I do understand wanting to avoid expense.

I just put more value on my time than that. Just a pesrsonal choice.

Good on ya for determination, but these tractors can drive u MAD!!!

Oh how I know (said while shaking my head at myself).

Good luck bro

adatesman

climber

philadelphia, pa

Topic Author's Reply - Feb 8, 2013 - 10:04pm PT

Part of the problem, GhoulweJ, is that they only made this line for 2 years (4 if you include the mostly-similar 300B series), so they simply didn't make all that many of them in a relative sense and used parts are scarce (and therefore spendy). Fortunately everything on it is pretty simple and straight forward, so it's a good match for my love of tinkering. Case in point, first thing I did upon getting it home was cut out bad repairs on the lower swivel of the backhoe.

This pic was from partway through the exploratory surgery to see how far up the crack went. In the end all of the plates were cut off and that corner weld removed.

And then it was forced back into proper alignment and fixed properly. Both sides needed to be done, and all told it took ~12 pounds of rod (6011 for the roots, then fill with 7018).

Probably shouldn't be surprising that until the little one came along my daily driver was a '66 Volvo 122 and 'fun car' a '59 Triumph TR3 (which had also been a daily driver for a while). So yeah, this backhoe might drive me mad, but it was bound to happen anyway.... :-)

hillrat

Trad climber

reno, nv

Feb 9, 2013 - 01:27am PT

Kinda concerned this might be going on, but really depends on how big the holes are from one side of the spool lands to the other and whether there's any leakage past the lands back to return. If enough pressure builds up on the end of the spool, it could lock it in place in the applied position.

Edit: this is the valve as you've depicted it. After thinking more on it this morning, I've flipped the illustration, deleted another post where I was working out operation, and added a new one this morning below.

This post is I think what's happening now, thinking the pressure/delivery are crossed, and the delivery to the cylinders I think is wrong as it would be depicted here. Please see the next post, as I think that's what actually should be happening.

hillrat

Trad climber

reno, nv

Feb 9, 2013 - 11:04am PT

Ok. Thought it over a bit. I think maybe the diagram showing hoses etc is backward. Try reassembly with the original relief in the valve body... I don't think it's actually a relief. I think it's a check valve, intended as a check valve to enable steering when the engine is off or the pump fails.

Reassemble, and reverse the pressure/return hoses and what you may end up with is this:

If in fact pressure and return have been reversed this whole time, you'd get many of the symptoms of poor steering you've been fighting, as the pressure on the end of the spool would be locking it in the applied position. that would cause the assembly to be dependent on spool position as of assembly. Further, the way it's built, when the engine is off and there's no flow in the system, the cylinder would act as a pump, and the check valve would allow oil circulation so that the system wouldn't get hydraulically locked. Even further, in this last configuration, you're steering against the pressure acting on the end of the spool which is trying to center it. So the more force you put on the wheel, the further the spool would travel and the faster your steering would work. This makes more sense to me now. I hope.

Damn if that wouldn't be a trip if all this time the whole problem was crossed lines. For that matter, without full disassembly/assembly you could try crossing the lines first, then if it works, change out the "relief" so it works if the engine stalls.

hillrat

Trad climber

reno, nv

Feb 10, 2013 - 12:10pm PT

Couple more thoughts. If you swap lines so the "relief", which I think is actually a check valve, so that it stops pump pressure from flowing through it, then you shouldn't see any flow back to the reservoir in neutral.

Also, and I wish I'd thought of this before, if you can see flow in the tank, then you can check the cylinder seals that way. Bottom out the steering either right or left, and hold it there continuing to put in steering effort. You should see no flow coming through to the tank. If you do, then you need to reseal the piston.

adatesman

climber

philadelphia, pa

Topic Author's Reply - Feb 10, 2013 - 11:51pm PT

Hillrat, you really are a treasure. Thanks so much. No matter how this ends up, got we've got a little something tasty in mind to compensate for the trouble you've gone to. Kindly drop me your snail mail address when you get a chance.... BTW, this is Helen, otherwise known as thelittleone, who is very much looking forward to having her own "digger" that she's "going to drive and Daddy's going to fix". She's not even 3 yet, and I already can't wait to teach her to weld. :-)

As for your posts over the weekend, well.... Much as I agree it makes no sense for there being a check valve that never closes, it also makes no sense for a parts diagram to show an incorrect hose connection and not get updated sometime over the intervening 60 years. Which is to say it doesn't surprise me in the least that this might be the case, given what I've seen on the similar-vintage cars I've had over the years. That said, once I get back over there I'm going to hold off on swapping the hoses because I suspect the bushing I made for the far end of the spool wasn't long enough and allowed pressure to build at the end once the bushing slipped past the end. There is a ~1/4" deep bore in the end of the cylinder for the bushing which had been taken up by an o-ring, but I instead made a bushing that fit properly and looked like the one depicted in the parts diagram. In hindsight given the passages under the lobes on the spool I can see that bushing being forced off an getting jammed at the end, so want to pull it apart and see what happened.

Basically another example of why it's a bad idea to have your tools split between 2 workplaces... all of my wrenches are with the backhoe, which means the one I need when working on the pump at home isn't there, or when I'm over there the measurement tools for this sort of thing are at home.... Which leads to "just machine it to half a thumbnail long", which may or may not work. :-(

Anyway, will be back on this as soon as I can, and frankly I'm liking the hoses-are-reversed answer. But I also liked the "make a new valve with a spring" answer... :-)

adatesman

climber

philadelphia, pa

Topic Author's Reply - Feb 12, 2013 - 01:16pm PT

HOLY CRAP!!!!!!! IT WORKS!!!!!!!!!

Hillrat- looks like you were right! The parts diagram shows the hoses reversed! The only thing I did today was remove the spring from the valve I made (0.100" orifice, left the ball in place) and swapped the input and exhaust lines. Pressure stays low with the spool centered and jumps to 600-800psi when moved to either side. And even better, it's possible to turn the wheels while parked on concrete!

Woo-frickin-HOO!!!!!

I'm kinda curious whether it would also work with the hoses hooked up as shown in the diagram, but no way I'm messing with it further.

THANKS SO MUCH EVERYONE!!! And Hillrat in particular!!!

-Aric.

FRUMY

Trad climber

SHERMAN OAKS,CA

Feb 12, 2013 - 01:21pm PT

Hillrat -- you are a treasure.

Glad to see both of you stuck with it till it worked.

WBraun

climber

Feb 12, 2013 - 01:26pm PT

Victory !!!!

Awesome !!!!

And another special thanks to hillrat ........

adatesman

climber

philadelphia, pa

Topic Author's Reply - Feb 12, 2013 - 01:32pm PT

Oh, and Hillrat- please pm me your snail mail address.... I really would like to send a proper thank you. :-)

bajaandy

climber

Escondido, CA

Feb 12, 2013 - 01:36pm PT

Ah! The sweet taste of VICTORY! (Although in this case it tastes a bit like hydraulic fluid, I bet.) Glad you got it working.

hillrat

Trad climber

reno, nv

Feb 12, 2013 - 01:38pm PT

Hey- sweet! Not the first time the book has been a little off. Good luck with your project. No special thanks needed, it was a fun little mystery. All the same, I,ll pm you.

My little germ-catcher-
Someday soon she,ll start talking. Then the real fun begins. Lookin forward to when she can walk and talk and tell me things, like yours is doing. Changes yer life, eh?