Servo pump pressure

[opto]

Anybody knows what pressure the servopump produces?

[john8662]

Servo Pump? Do you possibly mean the vacuum pulled by the vacuum pump? If so, the Vacuum pump should pull ~20" Hg of vacuum at idle.

[opto]

What I mean is the power steering pump (and hydroboost). I'm interested in knowing the pressure and flow from the pump.

Since steering components never seem to last for very long, I'm planning on building a custom steering with a hydraulic assisted steering based on a hydraulic cylinder similar to what is on tractors nowadays. In order to do so I will need to either modify my steering gear or get one used with rockram systems. I also need to consider flow and pressure rates when designing.

[NH2112]

Will the rest of the system be capable of withstanding the force of your steering setup? For 6 years I worked on scissorlifts by Skyjack and Marklift, and the Skyjacks could break Dana 60 or Dana 70 front ends if you tried steering with the wheels up against something. For example, a 27' Skyjack scissor has a 2-section fixed-displacement gear pump driven at engine RPM. The small section of the pump provides flow for steering, at a rate of 0.366 c.i./rpm. At a normal 2800rpm this produces 1025 c.i./min of flow, with a system relief of 2800 psi. Pushing against the base end of a hydraulic piston with an area of about 2-3 sq in, you can exert 5600-8400 pounds of force on the steering system. Now this is in a system with fixed displacement pumps and a simple rocker switch for steering - there's no way to vary the flow to the steer cylinder. If you were to use an orbitrol-type system it would probably be better because there's flow control and usually a relief valve for the hand pump.

Also, hydraulic steering isn't self-centering when you let go of the wheel....although I suppose you could work something out using an open-centered valve, which should allow the fluid to flow directly back to tank without restriction. How it'd work with an orbitrol, I don't know, I never thought about it before and unlike my Skyjack schematics, I don't have anything for an orbitrol hand pump on my PC in PDF format LOL

[opto]

Good point, I'm not looking for an extreme powerfull steering but a replacement for pitmanarm and idler arm that just lasts for a couple of weeks. The other stuff in the steering setup seems to last quite well. Although the extremly weak idlerarm puts a lot of stress on the saginaw gearbox.

So what I will need probably is enough volume but not so much pressure.
I suppose the RockRam saginaw gearboxes made for external hydraulics have the flowcontrol both for portioning when steering and when centering, does anybody know.
I tried to contact them to get further information but so far I haven't got any.

[DmaxMaverick]

Opto

If I understand you correctly, you intend to replace your existing steering gear box with a hydraulic system, and discard the OEM gearbox.

I'm not familiar with the vehicle safety standards in Sweden, but such a system would not be legal for operation on highways in the US. On a motor vehicle here, the steering must be a mechanically operated type, and can be assisted by other means, hydraulic, electric, etc. Your description would remove the mechanical operation, and be extremely unsafe for operation on-highway. Any failure would leave you without directional control of your vehicle. This is usually not an issue with farm equipment, as speeds involved are not that great.

Another option to reach your goal would be to use a non-assisted type gearbox, and incorporate your hydraulic system into it, maintaining the mechanical ability. It would take some hydraulic engineering, but could likely be done with existing components available for farm type equipment.

Generally, the existing system used in current vehicles is very reliable. If you are having problems with durability, I suggest finding the cause of your issues, rather than replacing it with what would be, stastistically, a less reliable system. If your components are in fact only lasting a couple weeks, something is definately wrong somewhere. A new system may not be any better than what you have. At least until you identify the cause of your current failures.

[opto]

I fully understand your point and sorry for not being clear enough about the setup

This is the case: I intend to keep the saginaw gearbox and use the hydraulic cylinder for assist and in place of the pitmanarm-idlerarm-relayrod setup. The pitmanarm will then be connected with the end of the hydraulic cylinder with a draglink.

You can see it as a RockRam setup but with the RockRam cylinder and stock linkage replaced by the mentioned cylinder.

The reason why my OEM idlerarm won't last is because of 35" tires and the offset used. This is a well known akilles heel.

Indeed you have to have a mechanical connection in the steering setup. In Sweden the lagal issues of vehicles are rather tough actually.

Main reason is for the durability in the more heavydutyish hardware. Pherhaps the first step will be to replace the relayrod-setup with the hydraulic cylinder but not use it for assist, just put oil in it for lubrication, and use the powersteering assist in the gearbox and a draglink.

[NH2112]

Personally, the first thing I'd do if steering component strength (or lack thereof) is such a problem would be to trash the IFS setup and weld in a solid front axle setup. It may be easier to run coil springs and trailing arms like 94-up Dodges or 66-80 Broncos, but then you'd have issues with trailing arm bushings and Panhard bars wearing out rapidly. I just don't think you can beat a good old solid axle/leaf spring setup for durability, strength, and simplicity. This would get you a steering setup with a drag link running from the Pitman arm to the steering arm on the driver's side knuckle, and a single tie rod connecting the 2 knuckles together. No more wimpy idler arms! Although, are you using the newer style of idler arm, with 3 mounting bolts instead of 2? They're supposed to be quite a bit more sturdy.

[opto]

yeah, I converted to the newer style idler arm last year and yes, it is better but still not good enough.

A Dana60 would be nice but the costs are holding me back. This is also a daily driver therefore IFS is a little sweet to.