Steering...high steer, assist, full hydro

[vetteboy]

With the load reactive valve and return to center, does it return to center with the single ended cylinder each time, or does the centering move a little as the steering wheel moves a little? If so, how do you get it back? I wouldn't care about the steering wheel moving around, but what about the return to center?

IIRC, the load reactive part of the orbital means that the little torsion rod can be activated by pressure feeding back from the ram, and then spin the wheel. The returning part comes from your standard caster/ball joint inclination just as a mechanical system does. The steering wheel center and actual center aren't mechanically related at all so there's no real adjustment to be had there. If you were really anal about it you could put some sort of set screw on the orbital valve to be able to set the wheel independent of the orbital, but it would be off again after a few good hard-lock turns - anything from pushing some fluid past the pump bypass, to getting some air bubbles in there from agitation, to fluid expansion from heat can cause this.

 

[Goatman]

Oh, I got it. The return to center feature is the ability of the valve to sense pressure and react, so the centering will come from the castor angle just like in mechanical steering. Basically correct?

 

[vetteboy]

Oh, I got it. The return to center feature is the ability of the valve to sense pressure and react, so the centering will come from the castor angle just like in mechanical steering. Basically correct?

Yes...but I wouldn't use it with a single-ended ram (unequal area). If you think about it, even with equal caster forces centering the wheels, you're gonna have more area acting on one side of the ram than the other, and I dunno what kind of effect that'll have. BillaVista has this to say about it:

Load Reaction

THIS is the hydraulic circuit feature that is of interest to us. Load Reaction is the infamous "return to center" feature. Note however, that this feature only allows external forces on the wheels to cause a reaction in the steering wheel. That is, it is only permitting the transfer of force, not actually creating it. This means, how well the steered wheels will return to center after a turn will still very much be a factor of steering geometry / alignment - most notable caster. Without sufficient castor or proper geometry, even with a Load Reaction steering unit, "return to center" and road feel can still be very poor. On the other hand, with good geometry and alignment, and a Load Reaction steering unit, road feel and return to center can be excellent.

Note: Some manufacturers refer to these functions as "reversing" and "non-reversing."

Here's what Eaton says about it:

Non-Load Reaction
A non-load reaction steering unit blocks the cylinder ports in neutral, holding the axle position whenever the operator releases the steering wheel.

Load Reaction
A load reaction steering unit couples the cylinder ports internally (in the neutral position) with the meter gear set. Axle forces are then allowed to return the steering wheel to its approximate original position. Comparable to automobile steering, gradually releasing the wheel mid turn will allow the steering wheel to spin back as the vehicle straightens. The cylinder system used with load reaction units must have equal oil volume displaced in both directions. The cylinders should be a parallel pair (as shown) or one double rod end unit. Do not use with a single unequal area cylinder system.

Excellent article all around, if you've got some time on your hands.

http://www.pirate4x4.com/tech/billavista/PR-Hydro_Steering/index2.html

 

[vintagespeed]

Yeah you've got it on the return to center part. I think alot of the bad experiences out there with full "hydro" steering are related directly to the steering valve that used. I think alot of guys are just taking a forklift valve or whatever they can find at their local hydraulic shop and running it. These just aren't built to provide what we want.

As for the cost. I probably had about $600 in my setup. If I had it to do again I would go with a double ended cylinder like most of the comp guys are running, just because a balanced system is really the "right" way to do it. I was cheap and I figured I could just buy 2ea of the $55 single ended cylinders instead of one $200 double ended cylinder. The single ended cylinder does turn a little less to the one side because of the difference in volume on either side of the piston. It was never an issue though and on a trail rig it's a no-brainer.

Assuming that everything is working the way it should and built stout, you should have no failures on a hydrostatic steering system, other than perhaps blown seals in the cylinder or a cut/melted hose (doubtful to burst 3000psi hose with a PS pump). The seal kits are like $8 and I just carried one in my trail junk and carried enough hose & some fittings to splice in or repair a split. But I never had any issues with the steering once I added the cooler. When Dave/Paul/Ryan & I did Jack my steering whined a bit when it was on it's side because it sucked in some air (too small of a reservoir) and then got hot, adding the cooler increased the overall volume of the system and solved this problem.

I dont think there's any good reason NOT to run full hydro on a trail only rig. It's certainly easier to change a few seals or a hose than it is to weld a sector shaft back together or try to bolt/weld a steering box back onto the frame.

 

[Goatman]

Thanks....makes sense.

Yeah, Bill's article is on my list, when I get some spare time.

 

[vintagespeed]

.......BillaVista has this to say about it....
http://www.pirate4x4.com/tech/billavista/PR-Hydro_Steering/index2.html

Recommended reading. I think there are actually 3 different parts to the hydrostatic steering article that Billavista wrote on PBB. I read them all before I took the plunge and it does take some time but is well worth the investment.

It's great to have that kind of information available for free.

 

[Mr.OverKill]

so what did you decide??

 

[Goatman]

so what did you decide??

Who, me?

Since I had limited time and I have a trip next weekend (New Years in Calico every year), I didn't decide anything yet. I straightened the bent tie rod and added a section of half round tubing to the middle, and I fixed the broken track bar. When I get back I'll take the new PSC pump off and send it back so they can check it out.

I'm right in the middle of the desert wheeling season, so I'll likely get new high steer arms and move the tie rod higher keeping the ram assist. After that, who knows, but it could be full hydro at some time down the road.