Using a power beyond steering valve without the PB function?

   / Using a power beyond steering valve without the PB function? #1  

BadDecisions

Silver Member
Joined
Sep 5, 2019
Messages
106
Location
Wittmann, AZ
Tractor
Ford 8N
Non tractor application, but it may become a tractor application depending on what happens with this valve...while I've used and repaired the hydraulics on the tractor, this is my first venture into building a system from scratch.

I converted an off road 4x4 toy to full hydraulic steering, using a Char-Lynn 291-5012-001 - 5 port, non load reaction power beyond steering valve, with a double ended balanced steering cylinder and fed it all with a stock automotive power steering pump. I used the PB valve because I had gotten a new one dirt cheap from a shop that went out of business. I initially had just plugged the PB port, found the pump got to be in excess of 400*F within 30 seconds, and had a pump failure shortly after while trying to figure out what was going on.

I did a bunch of searching, learned that the tank port is effectively blocked off when no steering input is given, and blocking the PB port made the valve a closed center. I now have the hoses from the PB and Tank ports tee'd together at the filter input, and filter output flows to reservoir tank. Pump seems happy, steering works well in garage.

1st test drive - front end is all over the road at anything above 25mph, acting as if there is extreme toe in/out. Virtually impossible to keep it running in a straight line. I've played with the alignment a bunch, and got it better, but still nowhere near "right". This isn't something that I intend to be able to run down the freeway, or on pavement at all really, but running access roads to the trails at 10mph is gonna be a bummer too.

Now I'm wondering if using a PB valve without having a need for the PB function is somehow causing an issue with all this? Is my hose routing, with the PB and tank hoses tee'd together causing a problem? Is it possible that the PB is somehow now back feeding pressure through the T port?

I had read where there is a PB sleeve that's supposed to be installed, but I also couldn't really find a clear answer on whether this is a requirement on all PB valves, or if it's needed when not using the PB function. It also doesn't look like either the PB or T port on my valve could have that sleeve added anyways, as in the ports aren't machined in a way that would provide room for a sleeve to drop down in to them. I have considered just ditching this valve, and buying a non-PB valve, but I really dislike just throwing parts at a problem without a clear understanding of why.
 
   / Using a power beyond steering valve without the PB function? #2  
<< ASE Master Tech who teaches steering/suspension/alignment for a community college.

Have you ever driven the vehicle in the same configuration without hydro steer?

When you played with the alignment a bunch, i assume you mean.. not on an alignment machine?

Regardless of how you, the driver, put steering input into the vehicle, if the vehicle won't go straight on its own then the vehicle itself (alignment etc) is creating steering forces that it probably shouldn't be.

So I would focus on making the vehicle stop trying to steer itself instead of focusing on making the steering system constantly fight off the vehicle wanting to turn, if you know what i'm saying.

Depending on how much is custom or how much has been changed on this vehicle, it's a decent chance there's something very 'off' about the alignment angles due to the suspension design, or how it's been changed from stock. Got any pics?
 
   / Using a power beyond steering valve without the PB function? #3  
Steering issues are probable alignment issues as Vigo327 states.... THE power beyond valve thing is probable a misunderstand in how valve operates Its my understanding that PB port with correct plug/valve should NOT cause valve to act as a closed center. I believe open or closed center is a function on main control valve before PB port... I am of opinion you do not have correct plug/valve in PB port... The PB port should just be to supply next valve in a a whole bunch of "series" connected valves.... IF it only valve in system or last valve in system proper PB plug should dump flow to tank port...
 
   / Using a power beyond steering valve without the PB function? #4  
The issue with jumpy steering likely has nothing to do with the orbitrol. There is a thing called "bump steer" which is the geometry of the linkage between the steering and axle. If that is dicked up bad enough, the vehicle will be all over the road.
 
   / Using a power beyond steering valve without the PB function? #5  
Simple answer is should be no issue on connecting the PB to tank since this how the steering unit would be configured without the PB option. Can you see the steering cylinder or linkage while driving? If it is moving back and forth you have a steering cylinder - system problem that could be amplified by steering linkage - alignment issues.
 
   / Using a power beyond steering valve without the PB function?
  • Thread Starter
#6  
<< ASE Master Tech who teaches steering/suspension/alignment for a community college.

Have you ever driven the vehicle in the same configuration without hydro steer?

When you played with the alignment a bunch, i assume you mean.. not on an alignment machine?

Regardless of how you, the driver, put steering input into the vehicle, if the vehicle won't go straight on its own then the vehicle itself (alignment etc) is creating steering forces that it probably shouldn't be.

So I would focus on making the vehicle stop trying to steer itself instead of focusing on making the steering system constantly fight off the vehicle wanting to turn, if you know what i'm saying.

Depending on how much is custom or how much has been changed on this vehicle, it's a decent chance there's something very 'off' about the alignment angles due to the suspension design, or how it's been changed from stock. Got any pics?

I had a feeling it was still some sort of alignment issue, but as I also don't yet have a firm understanding on the internal workings of the hydraulic issue, I also wanted to make sure I wasn't chasing my tail so to speak, and why I was questioning whether the hydraulics could be playing a part in this. It's not at all a situation of being sure that the hydraulics was absolutely the problem, and more one of "I just don't know". Hopefully that makes sense?

On an alignment machine? No..not unless you consider on jackstands, in my garage, with tape measures, levels, and angle finders a machine, lol. I've found it difficult in the past to find shops willing to work with highly modified vehicles in the first place, and then willing to deal with going outside of factory specs, as absolutely nothing in the suspension and drivetrain is anything even remotely close to factory any more.

What started out as a factory 1987 Suzuki Samurai now has full size Chevy truck axles from a 1985 K20, coil overs front with double triangulated 4 link suspension, Jeep CJ leaf springs rear, running on 37x12.50R17 tires. Front axle was pushed out 14" over stock.

I still haven't yet finished out all the tubing work, axle vents, etc in these pics. But all the suspension and drivetrain is welded in solid.

View attachment 732009

View attachment 732010

I currently have the toe in set at 3/16" at the wheel lip, which I realize that toe is set in degrees, but I've done it this way for 20 some years on the other trucks, and has always worked well...Wheels are brand new, so the wheels haven't yet been chewed up, and I figured that was the best place to get repeatable measurements. Caster is currently 7* positive.

I have gone from 1/4" toe in to 1/4" toe out, 1/16" at a time trying to find a sweet spot, and settled on 3/16" as the best so far. Caster I've gone from 0* to 10* positive, again settling on 7*. I'm thinking with the much larger tires, I might just need to go past 1/4" toe in?

All of the suspension and axle work was done at the same time. I didn't have any kind of power steering on the Samurai before I did this, I knew there was no way I'd be able to deal with 37s on the factory tiny manual steering box, and bump steer would be atrocious with that 4 link anyways. I was driving the Chevy truck that the axles came out of for a while before all this, so I'm confident that the axles themselves are OK, and it's an issue with the way I set things up.

The issue with jumpy steering likely has nothing to do with the orbitrol. There is a thing called "bump steer" which is the geometry of the linkage between the steering and axle. If that is dicked up bad enough, the vehicle will be all over the road.

Bump steer doesn't exist with the full hydraulic steering. There is zero mechanical connection between the steering wheel and axle at this point. I have had bad bumpsteer on the K5 Blazer after a big lift, and stock push pull steering, as well as big lifts on Jeeps when the trackbar and drag link don't match on angles, so I know what that feels like.

Though I have been wondering if the unequal length tie rods could be causing drastic changes in toe during steering movements.

Simple answer is should be no issue on connecting the PB to tank since this how the steering unit would be configured without the PB option. Can you see the steering cylinder or linkage while driving? If it is moving back and forth you have a steering cylinder - system problem that could be amplified by steering linkage - alignment issues.

Not while driving, but I have been all over the front end looking for loose bearings, joints, heims, etc while on stands in the garage, and have none.
 

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   / Using a power beyond steering valve without the PB function? #7  
Well I really want to see those pics but it says i dont have permission for some reason..

I get you on the alignment machine thing, I am lucky to have access to one in an educational setup where something being 'a good learning opportunity' is more important than whether it makes money.

So there are a bunch of factors that cause the wheels to 'start' steering when they're rolling straight or mostly straight down the road. If you already understand caster and have tried messing around with that that's a good start and +7 sounds like a normal number for big tires like that. How are you measuring caster?

Other things that have an impact are wheel offset/backspace which basically determines how much 'leverage' a tire has to turn the knuckle on its ball joints. Pretty much all mud tires are way wider than stock tires so that alone gives the tire more leverage on the steering. You also have to move the tire outward from where a stock one would be so the wider tire doesn't rub something on the inside when turned all the way or with axle at max tilt/articulation. Not as big an issue with solid axle, but still.. big tires are usually set out further from the balljoints than stock tires. Then you have your wheel offset which can set it out even further, and all that adds up to if a big tire spaced further out hits a tiny little something, it will 'jerk' the steering system way more than a skinnier tire set closer in. There's not a way to totally cancel that effect. If one tire hits some kind of resistance and the tire on the other side doesnt, it will put a bigger force on the steering system than stock tires/wheels/offset. A little more toe in and caster like you mentioned are what we can do to partially compensate. There are other things like 'caster offset' which aren't really adjustable without precisely modifying the knuckle or the yoke on the axle.

Then you get into making the steering system itself more resistant to inputs from the tires. Any play in ball joints/tie rods etc is bad, obviously. Bigger/thicker tie rods flex less under these forces. A steering damper, which is basically a shock absorber on the steering, resists FAST movements like from a tire hitting something, but doesn't resist slow movements from the driver turning the wheel. It's hard to measure how much a steering damper is doing, but it's very hard to over-damp the steering so even running multiple steering dampers isn't usually bad, just time and money. Since you have a full hydro steer setup you COULD use the flow in and out of the steering cylinder itself to limit the speed of movement of the steering by using a restrictor in the line (since its a double acting cylinder fluid on both sides has to move to do anything so you only need to put a restrictor on one side) and see if that helps anything.

I don't know for sure if this isn't a terrible idea but there is also such a thing as a cylinder with pilot operated check valves or 'load holding valve'. It blocks the lines going into/out of the cylinder UNLESS there is pressure in one of those hoses. Basically, it means the hydraulic system can push on the cylinder, but the cylinder cannot push on the hydraulics. That would make your cylinder a solid bar any time you weren't actively steering the car. What i dont know is what is the pressure threshold they open at, because if they're only available with a fairly high pressure threshold using one as a steering cylinder might make the steering feel like it is always 'stuck' wherever it's at, until you push on it hard enough to hit that pressure and it suddenly moves. I dont know much about hydro steer so either it's already like this (unlikely), or theres a very good reason its not done (more likely). EDIT: looks like some steering valves already do that Orbital Valves - Orbital Valve Information - Hydraulic Steering Unlimited

As far as bump steer.. it doesn't exactly exist with a solid axle the way it does with IFS. Actual technical bump steer is a change in toe angle from suspension travel. The term doesn't actually mean your steering moving when you hit bumps. On a solid axle if you have cross-steer linkage where both knuckles are hooked directly to each other by one tie rod and only one knuckle has a 'drag link' going up to your gearbox, then the tie rod and the axle are parallel at all times so moving one side of the axle up and down doesn't change toe angle by itself. However, depending on your 4-link arms geometry, if the axle moves forward and backward as it goes up and down and only one side goes up or down, then one side of the axle is now forward or backward of the other side, and the car will steer a little because the entire axle rotated under the vehicle, even though the ball joints never turned. This type of thing (steering doesn't steer but entire axle changes angle) might actually be the majority of your problem, but i haven't seen your geometry and id have to wreck my brain to figure out what the geometry meant anyway so i can't say for sure. Im guessing when people 4link a front end they just stick to what's 'known good' geometry on other builds rather than building scale models or computer modeling to figure out how it's going to move.

Though I have been wondering if the unequal length tie rods could be causing drastic changes in toe during steering movements.
As long as the tie rods and the cylinder are staying parallel to the axle housing it shouldn't cause anything from hitting bumps or dips etc, but the unequal lengths might change your 'ackerman' or how much more one tire steers than the other one when you turn the wheel. Cars always have whichever tire is on the inside of a turn turned sharper than the other one, so even if the car has 0 toe when straight ahead, the wheels are not parallel when turned. The normal tie rod actually gets closer and further from the axle as steering is turned left to right, but its always a straight piece. The hydro cylinder is mounted at a fixed distance from the axle so even if you mounted it where the two tie rods were parallel when going straight, they would never stay parallel once the steering is turned, and at that point if they have different lengths they're going to change how far each wheel actually turns. But that seems like an unavoidable side effect of putting hydro steer on a car and probably lots of them are fine, so i assume it's no big deal at all. Ackerman only really has to be close to maximize tire wear on high-grip surfaces like pavement. If your on dirt most of the time it wouldn't matter much at all. I put drop spindles from a Dakota on my B250 van and now the ackerman is crazy, when im at full lock one side is turned like 15 degrees more than the other side. It doesn't even squeal and it's not killing the tires, plus my turning radius went WAY down.
 
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   / Using a power beyond steering valve without the PB function?
  • Thread Starter
#8  
I edited the post with photos, and just added them again as attachments, rather than trying to insert them inline. It gave me problems the first time too, and I assumed it was because I was on a work computer with stupid firewall restrictions. It blocks a lot of free image hosts, free email providers, etc as spam/malware/etc. I'm a security admin and communications tech with wide open freedom on much of the corporate network, but apparently I can't be trusted to check email or look at pictures of silly cats, lol.

If you can see them now, you'll see that tire clearance is not even remotely close to an issue now, and I set up the suspension links specifically to avoid tires hitting anything at full lock. I spent a LOT of time doing the math on the 4 link to ensure that geometry issues don't crop up. Especially with things like axle rotation/pinion angle changes throughout the travel, or the amount of wheelbase change left to right.

Though obviously some changes will occur just due to the nature of a linked suspension going through an arc during compression/rebound, I just aimed to minimize it. I have a spreadsheet of all the numbers if you want to see it. Hopefully the pics show up, so you can see that I've gone well beyond just the typical suspension lift, or just copying a known OEM style 4 link. I don't know of any OEM implementation of a double triangulated 4 link front anyways.

The "bump steer" we usually see on solid axle rigs comes from big lifts on coil spring front end vehicles that end up with different angles on the drag link vs track bar. This also crops up on trucks with push/pull steering, such as full size Chevys with a solid front axle. The drag link ends up with such an extreme angle that the axle cycling through the suspension ends up causing the drag link to be pushed around, which then moves the steering around.

It was my understanding that non load reaction steering valve/orbitol that I'm running would prevent outside forces on the tires from moving them without active steering input, outside of things like slop in the wheel bearings, ball joints, etc.

The steering cylinder on the axle is mounted so that the tie rods are in a straight line as full lock left/right. At center, the cylinder is slightly ahead of where a normal tie rod would be, so that the tie rods on either end of the cylinder are angling back just a bit.
 
   / Using a power beyond steering valve without the PB function? #9  
Ok, I got confused about what was in reference to who, but i see what you meant now about bump steer.. i was already talking in the context that you dont HAVE a drag link anymore (or a track bar)..

But along those lines, have you sort of 'verified' what the side to side play of the front axle is like? As in, maybe strap/chain the axle up to the frame at ride height, jack it up from the frame or winch up to a gantry crane etc, just some way to get the front tires up without the axle holding the truck up, and just push side to side on the axle? I understand the triangulated 4 link should be handling the job now, but it also seems possible that even a good design might still have as much side to side 'play' as a less than perfect track bar, so its at least worth pushing on it to see what it really is. Even the frame end of the arm might be a slight issue. We can weld stuff to a frame and assume that's as good as it gets, but even stock vehicles sometimes crack their steering boxes off their frames and who knows how much it was deflecting in use for how long before that. Just gotta consider all the stuff that could 'give' a little.

Same thing with the steering.. seems you've already got the proper type of steering valve which should resist 'feedback' pretty well, but have you pushed on the wheel to see?

Between all the moving pieces, it could still just be an issue of 'tolerance stackup' just like death wobble often is.

As far as the caster, what happened when you went higher than 7? I've never really run into the downsides of too much caster, just worsening ride quality. I know some stock cars that go 180mph have 9*, but the trail and tire diameter and a whole bunch of other stuff plays into what that actually means between the car and the ground.

Definitely seems like you've done your homework and avoided most of the low hanging fruit problem possibilities. It looks great. (y)

Unrelated but.. at one time i had a stock samurai divorced Tcase and since they have a 1.4:1 high range iirc, for a while i was thinking about using it backwards on something as a divorced .71 overdrive box.. so read into that about my mental state what you will..
 
   / Using a power beyond steering valve without the PB function? #10  
A panhard bar might give front axle more side to side stability than the wishbone stabilizer.
 

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