Big Forklift power steering problem, turns to one side only

I have an older Towmotor 30,000 lbs forklift.
It does have power steering where a hydraulic cylinder provides assistance. It has a power steering gearbox of unknown (to me)
construction.
The problem that it has developed is that power steering works great when I turn steering wheel to the left, and it does not work when I attempt to turn it right. Instead, turning right requires an enormous effort.
What could the problem be here, thanks. Maybe there are some valves in the power steering gearbox that malfunction?
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 02 Sep 2014 22:03:18 -0500, Ignoramus16252

The steering valve is malfunctioning (or shot)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 02 Sep 2014 22:03:18 -0500, Ignoramus16252

That unit will LIKELY use a manual box with a linkage mounted valve like on a '63 Ford Galaxy etc -
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 02 Sep 2014 22:03:18 -0500, Ignoramus16252 wrote:

AFAIK, power steering works by having the force transmitted through a set of valves, that make the thing torque one way or the other depending on how it's being pushed.
If the valve is clogged, or stuck, it would cause what you see.
--

Tim Wescott
Wescott Design Services
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/03/2014 4:28 PM, Tim Wescott wrote: ...

Or the linkage broke...
--




Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Or the cyl is bypassing in one direction (or one cyl is bypassing on a dual cyl system (vs dual acting cyl)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 03 Sep 2014 21:50:45 -0400, snipped-for-privacy@snyder.on.ca wrote:

Right. They use a center-normal spool valve and strong springs on either side. When you turn the steering wheel, it puts force on the valve, opening an orifice for power (hyd) assist. When the force is lower, it allows the spring to close the valve, removing the assist. But I don't have to tell _you_ that. ;) This is for the others.

It sounds like the assist valve sat under water, according to Ig's description of the replacement scenario.

Ayup, 2 more possibles on the descending order of probability. Lack of maintenance is highest on the list for stuck valve causes.
--
Let no man imagine that he has no influence. Whoever he may be, and
wherever he may be placed, the man who thinks becomes a light and a power.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I bought an all-hydraulic replacement for this system today. It was at some point damaged by water and rust and was beyond repair.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus16243 wrote:

Just be careful to check your hydraulic pressures, the hydraulic steering systems often don't operate at the same pressure as the hydraulics for the rest of the system, i.e. the mast.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Pete, as far as I understand, the power steering hydraulic system is completely separate from the hydraulics on the forklift lifting system.
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus18095 wrote:

Good, if I recall the last hydraulic steering machine I worked on used pressure from the charge pump to operate the steering and brakes, about 1/10 the pressure of the main hydraulics.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

The auto industry range was 1200-1800psi awhile back. I wonder if it differs from industrial vehicles.
--
Let no man imagine that he has no influence. Whoever he may be, and
wherever he may be placed, the man who thinks becomes a light and a power.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 04 Sep 2014 18:02:42 -0700, Larry Jaques

The old towmotors used automotive power steering pumps on most of them - Some had the pump on the end of the generator- like on early cadillacs.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

glad you can find parts.
i have an old hyster, no parts available. When it breaks, its scrap.
Got a DEAL on an international backhoe. Found out i couldn't get parts so i sent it on down the road before i got caught with it.
I'm surprised you can get anything for a tow motor.
Karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This is my second towmotor. I can get some parts. This hydraulic steering replacement is a very universal item.
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus18095 wrote:

Exactly, for much of these type of machines if you don't mind fabricating a few brackets and whatnot you can retrofit off the shelf modern parts into them and keep going. The hydraulic steering stuff is readily available from SurplusCenter and others.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 04 Sep 2014 14:21:28 -0500, Ignoramus18095

Likely fits an early Ford car or pickup truck too.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@snyder.on.ca wrote:

Highly unlikely and not street legal. Iggy is talking about an all-hydraulic steering system as typically found on construction equipment. No mechanical link between the steering wheel and the wheels, just hydraulic hoses.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

If it is a full power steering unit instead of a power assist, the job gets a LOT easier. Lots of "generic" parts availability. I thought he said it had a steering box AND external cyls. He did say he COULD steer it, but it took a lot of force the one way. With a full power system you cannot "armstrong" it.With a power assist you can - which also led me to believe he was talking about the power ASSISTED steering system
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@snyder.on.ca wrote:

From what I gather the original was a power assist system that was rusted to death, and his replacement for it is a full hydraulic system with off the shelf new parts. For a slow moving off-road machine full hydraulic is nice and simple.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.