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full hydraulic steering problems, need ideas to try

rjfguitar said:
A 2x10 cylinder is pretty darned small, so I wouldn't see why the stock pump couldn't move enough oil. You might have foaming issues, which could cause your problems, more fluid would help if thats the issue.

You most likely do need more fluid capacity anyway, northern tool & equipment carries a bunch of small hydraulic reservoirs that would be perfect. Once you have added some oil capacity, cooling shouldn't be an issue. The use of an actual cooler shouldn't be required, as the volume of fluid in the tank will likely wick away enough heat. It's not like you are tying to drive a hydraulic motor, steering systems don't generate much heat to begin with.
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2x10 is small? Pretty common the big mud trucks around here. They seem to turn tires without trouble.

I think that a reservoir might be my first attempt. Shouldnt cost too much to try it. Plus, I think it is needed no matter what.

If this was a trail rig, I would probably get a cooler as I have seen some get pretty damn hot. But, I wont be running it continuously for ours on end. Plenty of time to cool between runs.
 
four_by_ken said:
2x10 is small? Pretty common the big mud trucks around here. They seem to turn tires without trouble.

I think that a reservoir might be my first attempt. Shouldnt cost too much to try it. Plus, I think it is needed no matter what.

If this was a trail rig, I would probably get a cooler as I have seen some get pretty damn hot. But, I wont be running it continuously for ours on end. Plenty of time to cool between runs.
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A 2" cylinder is definitely small for full hydro. It will turn tires in lower traction situations (i.e. not rocks) but it is very hard on pumps and in high traction situations won't have the power you need (we use 2" cylinders in hydro assist systems sometimes on top of the stock power steering that is in the ballpark of the assist a 1.5" cylinder adds).

If you're running a single ended cylinder with a stock pump/reservoir I can guarantee that you're sucking the pump dry, it needs quite a bit more capacity to run a single ended system. When you turn one direction it will push fluid out of the reservoir, when you turn the other it will run the pump dry (and/or let air in the system).

#1 you need to add at least another quart of fluid capacity.

Beyond that, who knows if your steering control valve is limiting anything, if you have more details on that it will help.

The reason it's hard on pumps is that the pump has to operate near 100% a lot of the time, if you were using a larger cylinder the pump can operate at a lower psi and generate the same steering force. This is easier on the pump and gives it a better duty cycle.

Shaft size has a big influence on the steering force that is produced but most full hydraulic cylinders are 2.5" and even 3" with really big tires. It's easy for that 3" cylinder to have double the force that the 2" cylinder would.
 
four_by_ken said:
2x10 is small?
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In hydraulics terms, yes. a 2" bore is fairly small. What I was meaning, fairly small also in the amount of oil it would take to run it, which wouldn't be much. I would think the GM pump could do 3gpm? I'm running dual 3x8 cylinders on my Cummins/Peterbilt project with just a small vickers 6gpm pump. Again, I would think that GM pump would have no problem running a 2" bore cylinder.

The other thing, what orbital are you using? It also has to be sized correctly.
 
I don't know the orbital. I got it from a local give that supplies the same one to a lot of other big tire trucks. Orbital isn't the problem.

You guys keep saying the 2" cylinder is small. That's what everyone is running around here. Strange. And these are 50"+ tire trucks.

When it does turn, it turns great. Completely effortless. I am thinking more and more that it's lack of fluid.
 
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four_by_ken said:
I don't know the orbital. I got it from a local give that supplies the same one to a lot of other big tire trucks. Orbital isn't the problem.

You guys keep saying the 2" cylinder is small. That's what everyone is running around here. Strange. And these are 50"+ tire trucks.

When it does turn, it turns great. Completely effortless. I am thinking more and more that it's lack of fluid.
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We aren't saying a 2" cylinder is too small for your application, because it probably isn't, we are just saying, hydraulically speaking, a 2" cylinder is pretty small in general. The GM pump should move enough oil for a 2" cylinder, I don't think your problem is there.

The size of the orbital does matter, because if it is too large, you get hard steering or shuddering because the orbital wants to move more oil than the pump can supply, causing pressures to drop off. A professionally built system uses an orbital matched to the pump's output. The other issue is if the orbital is closed or open center. A lot of them are open center, and I don't believe a GM PS pump is designed to work open center..?? Maybe someone else can chime in on that, as I'm not positive.

If you say that orbital is being used in other trucks, with stock power steering pumps and 2" cylinders, than you are right, that shouldn't be your problem.

I would get more fluid capacity, as you mentioned, and go from there.

http://www.northerntool.com/shop/tools/product_200466862_200466862

here is the tank I am using. This would be better anyway, as it allows you to use a filter if you want.
 
rjfguitar said:
We aren't saying a 2" cylinder is too small for your application, because it probably isn't, we are just saying, hydraulically speaking, a 2" cylinder is pretty small in general. The GM pump should move enough oil for a 2" cylinder, I don't think your problem is there.

The size of the orbital does matter, because if it is too large, you get hard steering or shuddering because the orbital wants to move more oil than the pump can supply, causing pressures to drop off. A professionally built system uses an orbital matched to the pump's output. The other issue is if the orbital is closed or open center. A lot of them are open center, and I don't believe a GM PS pump is designed to work open center..?? Maybe someone else can chime in on that, as I'm not positive.

If you say that orbital is being used in other trucks, with stock power steering pumps and 2" cylinders, than you are right, that shouldn't be your problem.

I would get more fluid capacity, as you mentioned, and go from there.

http://www.northerntool.com/shop/tools/product_200466862_200466862

here is the tank I am using. This would be better anyway, as it allows you to use a filter if you want.
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Did you add it to the high or low pressure side? Where did you mount it?
 
I say a pump because you said you need to rev it a little. We just had that same issue on a friends comp buggy and it turned out to be the pump was bad. It was a PSC pump so a modded stock pump was put in the PSC can and it worked fine.
 
wayne said:
I say a pump because you said you need to rev it a little. We just had that same issue on a friends comp buggy and it turned out to be the pump was bad. It was a PSC pump so a modded stock pump was put in the PSC can and it worked fine.
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I am thinking more an more about when it was happening. I think it was whenever I turned on direction... cant remember which.

If it wasnt so late, I would go start it and try. But, not with open headers at 10pm.
 
Also, he bought the stuff needed to check the pressures, and found really low pressure at idle and just above idle.
 
four_by_ken said:
I am thinking more an more about when it was happening. I think it was whenever I turned on direction... cant remember which.

If it wasnt so late, I would go start it and try. But, not with open headers at 10pm.
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Go ahead and start it. Won't bother me.

It's on the non ram side of the piston. Move volume to push it.
 
OK, looking at my pictures and remember when I was trying to park it and how I had to jockey it around...

It was on the side when the shaft was sticking out that I have the problem. I could not turn that direction very far.
 
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