fail-proofing full hydro steering

[mxrider99]

having driven many, many ,many, many full hydro sterring vehicles at 100+mph i do not see any reason why it cannot be done. Only thing that can go wrong, is if you lose a hose or all your fluid. even if your pump completely stops, they still steer. it takes muscle, but its do-able.

 

[Unforgiven]

Full hydro is not the same as hydro assist. This is a full hydro thread.

 

[mxrider99]

Full hydro is not the same as hydro assist. This is a full hydro thread.

hydraulic ram connected to the turnbuckles is full hydraulic is it not?. nothing but hydraulic lines going to the ram... If i am mistaken, ill shut up and just go sit in my corner again.

 

[LTLDEMONZ]

Check into the MTVR trucks by oshkosh they use dual steering boxes with a single pump and they don't have mechanical input into the boxes. It is not full hydro as most are used to seeing it as it doesn't use hydraulic rams, but the steering wheel just controls a valve on the firewall so it is definitely fully hydro.

 

[jesusgatos]

hydraulic ram connected to the turnbuckles is full hydraulic is it not?. nothing but hydraulic lines going to the ram... If i am mistaken, ill shut up and just go sit in my corner again.

No, we're all talking about the same thing.

Check into the MTVR trucks by oshkosh they use dual steering boxes with a single pump and they don't have mechanical input into the boxes. It is not full hydro as most are used to seeing it as it doesn't use hydraulic rams, but the steering wheel just controls a valve on the firewall so it is definitely fully hydro.

Thanks. Love hearing about other applications that have creative steering arrangements. Anybody have any pics?

 

[Unforgiven]

No, we are not talking about the same thing. In traditional power steering you can still steer the vehicle if the pump or a hose goes out. This is what you refer to as "taking muscle". It is common for off-roaders to add an assisting cylinder to the system. This is the type you are referring to.

Full hydro will have zero steering ability if a hose blows. All the steering wheel does is open & close hydraulic valves. A 100 mph malfunction will, at best, give you no steering. Hopefully you will continue in a straight line with nobody in front of you until you can slow down. More likely is your wheels will spike to the left or right. At 100 mph that will probably flip the vehicle. Hitting the brakes hard will likely have the same effect. Drum brakes are notorious for pulling to one side or the other. A full-hydro failure with drum brakes doesn't sound too fun.

I'm not flaming or trying to beat the dead horse of full-hydro. But facts are facts. If fully hydraulic steering loses pressure, then you don't have any steering at all.

 

[jesusgatos]

Just re-read what mxrider posted, and am still not sure what he meant. Was giving him the benefit of the doubt.

 

[hilton850]

My experience with full hydro steering is mostly with farm tractors. We've had less trouble with the hydro part of the system than the mechanical part. in 20+ years of operating farm equipment we've had zero catastrophic failures from broken parts that instantly prevented all steering control. I'm not saying it can't happen but I will say it doesn't happen often. Usually parts of these systems fail slowly....a hose gets a pin hole in it (the don't usually blow apart all at once), seals leak, the pump wears out over time, etc. You'll know you need to fix something long before you lose the ability to steer the vehicle if you do regular inspections. The biggest problem as others have already mentioned is stalling the engine, I have done that a couple times and it's a little sketchy...big tires + heavy tractor make the steering very slow and difficult. The other big thing is no brakes on that particular set up without the engine running. I was glad I was going VERY slow when that happened and thankfully did not have a close call out in the middle of the field. I would hate to be going 60 in a deuce and loose hydro steering..... We also have some dump trucks that are hydro assisted and work VERY good. Too bad the linkage doesn't work out because as other have said, that's the best of both worlds.

My personal opinion is design the system to operate at a lower pressure....say 1000-1500 psi and use parts that are rated to something higher...say 3000 psi to give as much safety factor as possible. I think a gear driven pump is a good idea. I would not use an electric pump for anything more than a backup since most of these are not designed for 100% duty cycle and it's more moving parts which = more chance for something to go wrong. Use hoses rated for more pressure than your relief valve setting and protect them anywhere they might rub on anything with sections of radiator hose zip tied around the outside of them. Then I would use either a double ended steering ram or the cross connected ram setup mentioned a few posts back....Done. That along with a good sized tank to keep the fluid cool and keep it from aearating. You probably already have all this in mind though. Just keep it simple, you'll be fine.

 

[bill2444]

This may not be popular: But I operate a fully hydrostatic rig, As compared to our older mechanical rigs. I put my life under loaded hydro systems daily. And i consider them safer than mechanical systems. Hoses just don't blow. They will be torn/frayed/smashed/swelled/ etc. but you will see signs if your observant. Most of the "good " hoses are tough buggers

I think some people overemphasize blowing hoses and other failures, meaning out of all the mechanical joints that wear/fail on a normal steering system. I believe that a hydro is inherently stronger/more wear resistant than a comparable mechanical systems. Never have i had a problem with off road construction equipments hydro systems, But have had to replace many of the mechanical attachment hardware. ( no hose or pump failures yet)

Not saying that they are better/safer just not as trouble prone as compared to the mechanical linkages that they will replace.

I must admit that none of our hydro systems go over 30 mph. And i don't travel the highways with them.

 

[Unforgiven]

Fan belts can shred. It happened to a friend's truck while we were on the freeway. He had manual steering in his truck so it was no big deal. We pulled over, put on his emergency-splice fan belt, and proceeded. If that happens with full hydro you're done for ... no pump = no pressure = no steering.

Engines do sometimes stop working at highway speeds. Granted, that's mainly a problem with gas engines. Losing engine at highway speed might be okay with a manual transmission. But if you panic and push the clutch in, then the hydraulic pump stops pumping. It only takes a fraction of a second for those wheels to lock sideways and roll you.

Pumps do fail, as do hoses. One failure and you're heading into oncoming traffic with only Jesus to stop you. You're trusting that Billy Bob at the hose shop crimped down those fittings properly. Personally, I don't trust Billy Bob enough for that.

A properly designed ram-assist will give similar benefits without the worries associated with full hydro.

Do what you want. It's your truck. I just want the kid to be educated before he does anything.

 

[mudguppy]

... Full hydro will have zero steering ability if a hose blows.

...I'm not flaming or trying to beat the dead horse of full-hydro. But facts are facts. If fully hydraulic steering loses pressure, then you don't have any steering at all.

yes, you are beating a dead horse; you say if "a hose blows." ok, which hose? is it a high pressure hose from the power steering pump to the steering valve or a hose from the valve to the cylinder? what about the low pressure hose?

all these generic statements have proven is that most of the persons making them don't have a clue how hydraulic systems work.

 

[hilton850]

not trying to start any arguments here but some of the stuff above could happen to a normal power steering setup...lose a belt and poof no power steering...that will suprise you. It has happened to me on the interstate while I was driving my pickupand it was hairy getting to a place to stop, but yes I did have steering. I also have an off road buggy with full hydro steering...that will steer without the engine running and I would say it's comparable effort as my old chevy when I lost the power steering belt. That being said, both of those require considerably more effort than a regular manual steering system when the pump isn't running. Mechanical parts are also prone to wear/failure, just ask the off road guys. I think each system has its strengths and weaknesses and neither one is LIKELY to fail suddenly but either can fail suddenly. My personal choice would also be ram assisted steering but to each his own.

 

[Unforgiven]

Geez, you're up late tonight. The kid said full hydro still steers when it fails. That is incorrect.

Fan belts, even new ones, can shred. I gave you a true personal experience with that. No pump = no steering, no matter how leak-proof your hydraulic lines are. There's only so much fluid in the system. Once it's on the ground it's on the ground. A 5 gpm pump is going to put that on the asphalt in short order.

High pressure, low pressure, who cares? Maybe a leak on the low side will allow you 20 seconds of extra steering before the fluid runs out. But if that's the case, you probably wouldn't even notice the leak until all the fluid is gone.

No fluid = no pressure.
No pump = no pressure.
No pressure = no steering.

It's not rocket science.

And speaking of rocket science, NASA assured us that the Space Shuttle was perfectly safe. I think that two blown up shuttles proves that any mechanical system, no matter how well engineered, can fail.

If NASA with a multi-billion dollar budget still has unexpected failures, then what makes you think a $1000 off-the-shelf hydraulic steering system retrofitted to a 40 year old truck is immune to failure?

Expect the unexpected.

 

[jesusgatos]

I'm confused. Who's the kid? I'm going to be using the gear-driven 5-ton PS pump that's already on my new LDS engine. Nevermind, carry-on. For all the back-and-forth banter, there's some helpful info in there. Somewhere. Thanks for posting everybody.

 

[bill2444]

I only have two more useful opinions,
First: I have blown many hyd hoses in my time. They were all damaged from normal use ( bucket end of excavators/back-hoe's/dozers) These hoses drag in the dirt and rocks, catch on roots simply by where they need to be located) It is expected that those do not last long. ( critical hoses are replaced as soon as observed to need replacement)
In any event those hoses always blow when highly loaded ( maxed out against a large obstacle) NEVER have i had a failure when lightly loaded.

So i would think a failure of hose assemblies would happen off road with the tires steering into something hard (rock/gully/etc.) and not tooling down the road.

Second: Our U.S. systems are relatively low pressure compared to European systems that use 2-3 times higher pressure and less volume (pump/rams) in the same hose assemblies ( 6 strand) that we use.

Just trying to contribute what i can, not an expert though.

 

[Unforgiven]

I'm confused. Who's the kid?

This guy. I want him to understand the difference between complete hydrostatic versus hydraulically assisted steering:

having driven many, many ,many, many full hydro sterring vehicles at 100+mph i do not see any reason why it cannot be done. Only thing that can go wrong, is if you lose a hose or all your fluid. even if your pump completely stops, they still steer. it takes muscle, but its do-able.

But, as usual, it devolved into a discussion about the safety of full hydro.

I'm going to be using the gear-driven 5-ton PS pump that's already on my new LDS engine.

I think that's a great idea. I'm doing the same; already have the pump ready to go, 1500 psi, 4.5 gpm from a 5 ton multifuel. The only difference is I'm going with ram assist. I like the idea of a drag link ultimately connected to the steering wheel. That's a personal choice for piece of mind.

 

[bill2444]

Sorry guys, one more thought: The Deuce already uses a hyd system for critical systems with an undersized resivoir, THE BRAKES.
No one says OMG we need complex mechanical linkages to each wheel.
And those lines are closer to harm than a steering clyinder would be. And yes there is a mechanical back-up to the braking system ( parking brake)

 

[Unforgiven]

Bill,

Spicergear figured out a great upgrade for that a few years ago. He installed a HydroMax upgrade.

http://www.steelsoldiers.com/deuce-...ro-max-brake-assist-pics-added-long-read.html

I've already got a complete Hydromax system out of a GMC 6500 Topkick waiting in the garage.

I'm going to use Spicergear's pioneering work with one twist. I'm going to make sure it's dual circuit, even if I have to figure out how to proportion the front to the rear.

That's my next major upgrade (even before hydraulically assisted ram).

With the availability of modern parts in junk yards, there's really no excuse (other than orthodoxy of keeping a pristine historical vehicle) to bring these trucks up a level or two safety-wise. By modern I mean mid-90's to present. For example, the HydroMax that I pulled out of the GMC was from 2002. True, that's almost 10 years old. But freshly rebuilt master cylinders are readily available. And they have a reduced-pressure redundancy built into the system via an electric motor.

Just getting rid of that annoying low-air buzzer is worth the upgrade in and of itself!

 

[jesusgatos]

Unforgiven, I'm planning on upgrading to Hydro-Max brakes too. You want to work together on that? If you've already go the parts, I can help design mounts and stuff. Would like to start working on that, but don't have parts yet. So hit me up if you want/need any help.

 

[OPCOM]

Have you considered a hydro version of the air-assist system?

It would give you much more assist power, have mechanical redundancy and be safe (that means legal too!).

You can contact Garrison and they will help you design a system and supply the parts. It will cost more the the air-asssit, but not that much more.

(The second attached image is a PDF, open it in a new window to view all the pages.)

Having put >2k highway miles on an air assist, air-o-matic, I would agree that a hydro version of that would be a good choice if you do not want air for wahtever reason (I was completely satisifed with air). More of a pain to install due to needing a pump.