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fail-proofing full hydro steering

Unforgiven

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Looks like the hydro-max system requires between 3.2-5GPM and 1000PSI, and according to gringeltaube, the 5-ton multifuel PS pump puts out 5-6GPM and 1000-1500PSI. I need to make some decisions about what components I'm going to use in the steering system before I'll know whether the 5-ton pump is going to be able to keep up with the steering and the braking systems.
Jesus,

GM originally had a dual power steering/hydromax pump. But it had problems of losing braking power on full steering deflection. Imagine going downhill, offroad, with a tight hairpin turn & limited brakes because all the pressure is going to the steering.

So they switched over to a dedicated Hydromax pump, keeping the steering pump separate. You might want to learn from GM's mistake & keep them separate as well.

The Chevy C7500 medium duty trucks from about 2000-2003/2004ish had a 6x4 tandem version with hydromax. The tandem rears ran drum brakes. The fronts ran 4 piston calipers. I'll bet dollars to doughnuts the Hydromax master cylinder from that truck would be perfect for the 6x6 Deuce if you wanted a dual-circuit version. I don't have the parts numbers, but I'm absolutely certain it exists.
 

m16ty

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Jesus,

GM originally had a dual power steering/hydromax pump. But it had problems of losing braking power on full steering deflection. Imagine going downhill, offroad, with a tight hairpin turn & limited brakes because all the pressure is going to the steering.

So they switched over to a dedicated Hydromax pump, keeping the steering pump separate. You might want to learn from GM's mistake & keep them separate as well.

The Chevy C7500 medium duty trucks from about 2000-2003/2004ish had a 6x4 tandem version with hydromax. The tandem rears ran drum brakes. The fronts ran 4 piston calipers. I'll bet dollars to doughnuts the Hydromax master cylinder from that truck would be perfect for the 6x6 Deuce if you wanted a dual-circuit version. I don't have the parts numbers, but I'm absolutely certain it exists.
My '98 Dodge Cummins has Hyd boosted brakes that runs off the PS pump. Haven't had any trouble with one affecting the other so you should be able to do it with the right setup.
 

jesusgatos

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I don't know yet. Think it's really just a matter of figuring out what kind of demands each system is going to place on the pump. Still don't know what the specs are on the pump that I've got either. Hope I got one of the 'good' pumps...
 

Kalashnikov

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Very interested in your steering progress. I would also like to add full hydro steering mainly for offroad use and the 395s I'll be adding. I cant see buying an air assit for $1500 when I could got full hydro for about $1000. I also like the idea of no restrictions of suspension due to the pitman arm.

And like previously stated, the type of hydraulics used on these systems don't blow out all the pressure at once. If you inspect on a regular basis you'll see any leaks or signs of wear. These hoses usually develop leaks around the fittings unless cut. Dry rot takes many years to take a toll on good quality hoses. The rams you'll see wet if they leak and get progressively worse if left alone.

As stated in the thread, lead-reaction valves will allows the wheels to return to center with the correct caster and turning the steering wheel without pressure will still act as a manual valve. The chances of any failures would almost appear less with a hydraulic system than linkages if drag links were to go unchecked!
 

JasonS

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The whole "direct mechanical linkage" thing is bull****. I haven't been able to find anything about that anywhere. I'm not sure where that started, but nobody has been able to provide a source. There's just no such requirement.
Maybe this has already been answered but I have not read through all of the posts. I have an old codified law book somwwhere and the requirement did exist for a mechanical connection. I suspect that this was quietly repealed to allow for drive-by-wire.....
 

sandcobra164

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For what it's worth, the Marines are receiving the new Terex MAC 50 Crane which uses full hydro steering and it's street legal. It does have a secondary steering circuit and that pump is powered by the transfer and only works above 3 mph.
 
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Hobart, WA
I'd keep it simple - as noted there are 4 parts

pump with reservior
orbital valve
hoses
cylinder(s)

Any source of high pressure fluid from a pump will work - if you are concerned about belts just use one of the 5-ton gear driven pump which will bolt up to the forward side of your injection pump drive. (you will need to trim the radiator shroud) The reservior should hold enough fluid so you have proper cooling and your cycle rate (aka pump output) is somewhere around 1:5 or larger - this means the fluid only runs through the pump once every 5 mins - larger is better (a cooler never hurts either)

Pick your steering cylinder or cylinders - you can find force outputs for given cylinders online or just calculate the area and determine your operating PSI to get your applied force. Remember to subtract the area of the cylinder rod from your area calcs.

To determine your orbital valve size you need to calculate the swept bore of your cylinder in either direction (again remove the volume of the rod) - this will tell you the total volume of fluid required for a lock to lock cycle.

Now decide how many turns you would like to have lock to lock - larger number of turns = more control on the road and a smaller displacement orbital valve /// lower number of turns = faster steering and twitchy highway performance

You need to remember the orbital valve has a torsion bar which opens the fluid access to the hydraulic motor (orbital motor) each section will deliver a discreet amount of fluid; so with a larger displacement valve the "packets" of fluid are bigger and result in larger steering changes at the wheels (there are no half "packets" it's all or nothing) This is the cause of the wandering feel of large displacement orbitals used in rockcrawlers when run at speed or the highway (combined with floppy suspensions and tall sidewall tires)

At this point you need to mount the cylinders and the orbital valve - just keep the steering column as short as possible and mount the orbital to the firewall.

Make your connections with hoses - only for the flexible joints - use extra heavy wall rigid hydraulic hard line internally threaded with JIC fittings for all other fluid lines. When using hoses ask for the 4 or 6 wire log skidder hose - use field serviceable ends and carry spares.

I have run a full hyro setup on my rockcrawler for 6 years now and never ever had an issue - even broke the tie rod clean off the axle off road and still had control of one wheel as the cylinder mounts to the steering arm. Just build your system logically and stout - you'll be fine

Matt
 

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jollyroger

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There have been some really good points on this thread, pro and con.

The "new" full hydro systems are really becoming refined enough to feel good on the road. Self centering and feedback. I have been struggling with My "Log 2.0" steering because none of the geometry works with the current position of the box. I can't move it forward like I did the front axle because there is no more frame and it becomes impractical. The best solution is full hydro.

Also I like that the full hydro steering is not trying to push and pull the axle sideways in the Waggy. Not as much a problem on the stock deuce steering but what you get instead is some serious steering "push". What I mean is that if the front tires push up against a rock on one side and they don't want to roll over it the easier way is to turn the tire sideways against the steering which whips the steering wheel out of your hand and spins it to the lock. I have jammed fingers and thumbs and whacked my funny bone in my M-37 and deuce with this problem. That's why you drive these boogers "thumbs out" as my Dad taught me. As I get older I expect to break fingers and thumbs and maybe wrists.

I remember the same physical connection arguments with aircraft when fly by wire was entering that world. Now it's commonplace. All sorts of tripple redundant systems and hydralics and pumps and such. Now that things are refining they just use reactors that have their own "small" self contained resevouirs for fluid and pump at the control surfaces. Put three reactors on and you have tripple redundancy. Then you just run three wiring harnesses out to the reactors rather than three complete hydraulic systems to a ram.

There at one time was a physical connection rule with respect to on road steering for passenger vehicles. I think this was done to avoid the lack of a physical connection on school busses and passenger busses. I think this rule get's prostituted into discussions like this.

As we become more electronically oriented we will have all drive by wire systems in our cars and trucks. I am not afraid of this. It will likely be like the reactor systems on aircraft with the tripple redundancy on critical systems. We already have multiple drive by wire systems on our vehicles today and most people don't know it. Throttles have been wire controlled for a long time. My 96 Ford F-350 Power Stroke is electronic throttle with no physical connection.

As for redundancy and simplicity for your discussion. Run one of the new full hydro steering systems complete and setup how you want it. Comfortable and easy. Then for a backup have a simple ram with electric pump and toggle steering valve on the shifter. Kind of like a self contained reactor type deal. Or just a spare ram on the axle and the seperate pump and controlls remote mounted with the toggle steering. In the unlikely event of a full main failure you can switch to backup and get to wherever you need to. Or have a low pressure arming switch for the secondary system.

It buys you time to slow down if you are at full speed and if you have a failure off road you can still get to the camp or civilization to get er fixed. The secondary system is not ideal but it does not need to be as it is strictly for backup.

The problem with all the early fly by wire systems were that they were using the old way of thinking but with a new way of doing it. Too much and complicated tripple redundancy of full hydraulic lines and pumps and valves and rams. they took all of that stuff out of the system and made the reactors and made it truly fly by wire.

Full Hydro is evolutionary. Magnetic steering would be revolutionary. I'm just sayin'. Keep rolling my friend.
 

sewerzuk

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jesusgatos,

Hey, BUILD IT! With some time, $$ and effort, you can make a safe, stable system that works well for your application.
Looks like a lot of people have posted in this thread who have had no experience with hydro steering...
I have driven heavy trucks, rock crawlers, and street/trail machines with both hydro assist and full hydro systems, on and off road (though I have not driven or even seen an M35 with one yet). A small lightweight short WB vehicle does tend to feel a little squirrelly on the road. The longer heaver vehicles have no problem with the full hydro system.
The deuce is a long, heavy rig and will not tend to have the "darting" feel that smaller, lighter, short wheelbase vehicles have with hydro steering (assuming a properly balanced system is designed).
I am currently in the process of putting a full hydro system in my Deuce; using a 3" x 9" double ended PSC ram.
As for your question about fail proofing, I'm of the belief that NOTHING is fail proof in any rig. Tires blow, bolts break, fluid systems leak, rod ends and track bars break, etc.. It's ALL a matter of paying attention to the system, using quality components, and frequently inspecting for damage, leaks, etc.
A well designed and properly maintained hydro steering system with quality parts IS SAFE.
 

jamesfrom180

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The little experience I have is with a jeep. No power is my biggest failure issue. Other than that the new gen. orbitals that allow for centering and feed back are the way to go. Only real solution would be a electric back up red. system I think.
 

jesusgatos

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on the road - in CA right now
Thanks for the continued interest and input guys.

sandcobra-
The number of street-legal vehicles using full hydro steering is definitely increasing. There are garbage trucks and all types of heavy duty vehicles, and evidently even the new unimog? And someone just posted this over on the pirate forum.

Looks kind of like what Jollyroger was talking about. I don't know anything about those reactors though. Please post up some more info if you have any. I'm sure we'd all like to learn more.

Wanderingwillys-
Thanks. Looks like you've put a nice system together for your vehicle. If I end up 'keeping it simple' then I know it's a really straightforward deal. I'm putting a 5ton MF engine in Mah Deuce, so I've already got a PS pump, and I'm familiar with all the other components in a typical hydro system.

But I'm probably going to be relying on Sean (Station over on the pirate forum) to help me size and select components. He'd got an idea of how we might be able to use two cross-linked rams with some type of pressure sensors in the lines that would be able to detect a leak or blowout, and then cut-off that circuit. Would reduce power-steering by half, but that's 50% better than nothing. Easily enough to control the vehicle, and probably still better than stock...
 

mudguppy

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Jesse, i think what you are refering to is similar to a 'velocity fuse' that is used in industrial hydraulic applications such as on machines.

my understanding is that when the fluid exceeds a specific fluid velocity, the fuse closes. this is used to prevent whipping hoses and fluid injection hazards.

what i don't know [which is alot] is whether such a device would work on a steering system after the valve - the system would only see max velocity after a hose failure and you turn the wheel as fast as possible. dunno - thoughts?


james' - as mentioned previously, the only way that you would lose steering power is if a belt were to brake. engine failure is not a concern in a manual transmission vehicle. a gear driven pump, as mentioned, is about a fail-resistant scenario as possible.

belts can break and hoses / fittings can fail. understanding the criticality of this type of system and countering with effective routine component inspections (like sewerzuk said) should be taken all that much more seriously.
 

jesusgatos

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I don't honestly know what type of sensors Sean was thinking about using, but I'll ask him next time we talk. He said he was going to take some time to mull this project over, and then get back to me with some ideas. Just based on the conversations we've already had, I'm pretty sure he's going to be able to come up with something better (safer) than the basic setup most guys are running. And his 'basic' setups are just about the best out there, so this could get interesting...
 
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