fail-proofing full hydro steering

[mikew]

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.)

 

[dozer1]

Man, you'll have the best rock crawler-RV combo ever.

 

[jesusgatos]

Oh, that makes sense. I'll post links to where those images are hosted.

 

[Heavysteven]

Interested thread, maybe a list of pros/cons?

My thoughts, I would rather have a problem with an air assit steering than a full hydraulic system while i was off roading back in the hills.

I'm not an expert, but are you thinking of using a hydrualic cylinder, pump, and hyrdro box that controls fluid when you turn left and right?

I would think you could find a setup like this on a tractor.

 

[Jones]

JG, you're probably right on the set-up. These were thrown together out of then available parts when guys were exploring rear steer set-ups too... usually with nothing more than a push-pull lever to control that.
Then after you cobbled your rock crawler together; you drove, not trailered, to your favorite off road spot. A few trips like that could make a guy think twice about the relative sanity of anything hydraulic.

 

[jesusgatos]

Interested thread, maybe a list of pros/cons?

My thoughts, I would rather have a problem with an air assit steering than a full hydraulic system while i was off roading back in the hills.

I'm not an expert, but are you thinking of using a hydrualic cylinder, pump, and hyrdro box that controls fluid when you turn left and right?

I would think you could find a setup like this on a tractor.

Feel free to discuss this, but my mind is already made up.

Yeah, the system is similar to what you'd find in a tractor and a lot of other heavy equipment, but using components that were designed specifically for off-road motorsports.

JG, you're probably right on the set-up. These were thrown together out of then available parts when guys were exploring rear steer set-ups too... usually with nothing more than a push-pull lever to control that.
Then after you cobbled your rock crawler together; you drove, not trailered, to your favorite off road spot. A few trips like that could make a guy think twice about the relative sanity of anything hydraulic.

...and that's why full-hydro steering gets such a bad rap.

 

[Hammer]

I like the power and steering of my 5 ton, power steering gear box, and an assist ram from the passenger frame to the passenger steering. Not crossover, but everything has great clearance.

Btw, the CEMENT TRUCKS I drove had FULL hydro.
Had to drive full speed on the road, and go VERY slow moving around job sites, and they have BIG front tires.
The ones I drove had two single ended rams with a tie rod connecting the whole setup.
Might want to take a look into those kinds of setups.

 

[jesusgatos]

Yeah, that's a cross-linked setup using two unbalanced rams, and that's basically what I'm looking to duplicate, while possibly building-in some additional safety through redundancy.

 

[jesusgatos]

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.)

Thanks for posting, but I want to eliminate any/all linkage from the driver's-sider frame to the driver's-side steering knuckle. That type of drag-link arrangement just isn't going to work with the type of suspension modifications that I'm planning on making to this vehicle.

 

[jesusgatos]

Jesusgatos: Even after I pulled up the Billavistas Tech Article, the images below 403 on me.

After considering all the options (at least that I'm aware of), I think I'd like to use two cross-linked rams, mounted sort of like this:

But can I use unbalanced rams that aren't cross-linked?


Not sure how I'd use one (or more) of these, but I thought it was pretty cool:

Oh, that makes sense. I'll post links to where those images are hosted.

These images are both from that series of tech articles that I linked to, but I've downloaded them, and I'm uploading them so that you can see them here.

 

[Hammer]

Yeah, that first image is how those cement trucks were setup.
Some had the rams on the axle like that, others had them on the frame like the assist on the 5 ton is setup, but both sides.

 

[jesusgatos]

Right, I gotcha. But one of the reasons why I'm going full-hydro is to eliminate the mechanical linkage between the chassis and the axle, so that it won't be affected by suspension travel. After I re-work the suspension, a stock-type drag-link would be a major problem.

 

[Wrench Wench]

I hacked this together because I was bored. I wish I could have CAD'ed it, but I just mutilated one of the CAD renderings of the 1:10 scale R/C axle from RC4WD instead. RC4WD - The Ultimate RC Products

Okay, what is this supposed to depict? A tandem steering ram mounted to flanges welded to the front of the front axle. The ends of the ram are attached with end linkages with Heim joints to the underside of the steering knuckle arm to keep everything as in-line as possible.

I left the original tie rod in place in this diagram primarily because I was too lazy to erase it. I wouldn't imagine it would be left in place, but I can't readily think of a reason it would need to be removed at this time of night.

For the safety factor, I would take the two hoses for the passenger's side of the ram, bundle them together and bring them around the passenger's side of the pumpkin, and bundle the hoses for the driver's side of the tandem ram and bring them over to the driver's side of the chassis and only bring them all together when necessary, at the dual helm pump.

Keep in mind, this depiction was originally for an R/C truck, not a full size truck. The devil's in the details. By installing the steering ram on the front, I would imagine, would make it easier to install a four-link on the back side at a later date, if so desired.

 

[mikew]

Is there any way to design/build a system that has two separate hydraulic circuits without using two pumps? I just don't have enough room to install a 2nd pump (at least not one that's engine-driven).

I think the engine driven pump IS your most likely single point of failure.

It's not because of mechanical failure of the pump, but the engine stoping while in motion. Engine failure, stalling or simply running out of fuel will kill the engine and you're toast!

A hydraulic accumulator with a low pressure warning system, a hydro version of the brake air reservoir system that would give you a few more turns before you're out of juice, could be a possibility but better yet an electrically driven hydo pump as a backup.

 

[Unforgiven]

Jesus,

If you are absolutely heck-bent on full hydro, but still want fail-proof redundancy, why don't you use concentric cylindrical tubes for the steering shaft from the steering wheel to the gear box.

The inner shaft is separated from the outer shaft by grease-able bearings for smooth operation. It connects directly from your steering wheel to the full hydro system.

The outer shaft is your own custom "rag joint." It connects directly to your stock manual steering box. But instead of only 1/4 inch of play like a normal rag joint, make the outer tube detatched from the steering wheel (inner tube). Have an adjustable tab that allows you to custom set the "play" before the rag joint engages.

That would give you anywhere from 0 to 360 degrees (180 degrees left & 180 degrees right) before the manual steering outer tube had any physical contact with the steering wheel (inner tube).

Any bump-steer in the manual steering caused by suspension flexing would never reach the steering wheel unless it was in excess of 180 degrees ... which is highly unlikely. Therefore, 99.999% of the time the steering would be full hydro.

The other 0.001% of the time you would have the custom rag-joint tab as a redundant, fully manual, just-in-case backup system that would be sufficient from keeping your wheels from locking fully left or right in an emergency. It wouldn't be perfect steering that's for sure. But in the event of a hydraulic failure it would be enough to get you to the side of the road without veering into oncoming traffic.

It could be modified with electric solenoids or clutches (instead of a rag joint) to automatically switch to the full-manual tube in the event of a hydro failure as well. That would be more challenging to do compared to a very loose rag joint, but it would instantly give you 100% manual steering without slop in the event of a failure. A pressure switch activated clutch locks the outer, manual steering tube to the inner, hydro tube in the event of hydro failure. It adds to the complexity, but it would give you 100% hydro & 100% manual in the event of a problem.

And it doesn't matter which is which. You could use the outer tube for hydro & inner tube for manual. It all depends on the connection points for the hydro activators.

The manual steering would not have to be disassembled. Sure it would rotate back & forth during normal hydro use, but who cares? It would be a fail-safe redundant system in case of an emergency.

I say use concentric tubes for the steering column. With proper planning it could give you 100% hydro & 100% manual backup without interference between the two.

That's my

 

[m16ty]

I think the engine driven pump IS your most likely single point of failure.

It's not because of mechanical failure of the pump, but the engine stoping while in motion. Engine failure, stalling or simply running out of fuel will kill the engine and you're toast!

A hydraulic accumulator with a low pressure warning system, a hydro version of the brake air reservoir system that would give you a few more turns before you're out of juice, could be a possibility but better yet an electrically driven hydo pump as a backup.

The hyd steering will still work if you loose pump pressure. It will be hard to steer but it would be enough to get safely off the road.

 

[Hammer]

Mike W, there are some heavy equipment pieces that have the emergency electric pump for backup.
M16ty is right though, you CAN still steer without the pump running, just a lot worse then stock for arm strength needed. Plenty to control the vehicle and exit a road though.

Unforgiven, it is the manual connection that he is trying to get away from. The manual connection requires linkage that doesn't work for how he want to redesign the front suspension.
Btw, that is how the steering works in my 818. Basically full hydro unless I loose pressure. But I don't have to turn the wheel THAT far to engage the manual portion of the steering.

 

[jesusgatos]

I hacked this together because I was bored. I wish I could have CAD'ed it, but I just mutilated one of the CAD renderings of the 1:10 scale R/C axle from RC4WD instead. RC4WD - The Ultimate RC Products

Okay, what is this supposed to depict? A tandem steering ram mounted to flanges welded to the front of the front axle. The ends of the ram are attached with end linkages with Heim joints to the underside of the steering knuckle arm to keep everything as in-line as possible.

I left the original tie rod in place in this diagram primarily because I was too lazy to erase it. I wouldn't imagine it would be left in place, but I can't readily think of a reason it would need to be removed at this time of night.

For the safety factor, I would take the two hoses for the passenger's side of the ram, bundle them together and bring them around the passenger's side of the pumpkin, and bundle the hoses for the driver's side of the tandem ram and bring them over to the driver's side of the chassis and only bring them all together when necessary, at the dual helm pump.

Keep in mind, this depiction was originally for an R/C truck, not a full size truck. The devil's in the details. By installing the steering ram on the front, I would imagine, would make it easier to install a four-link on the back side at a later date, if so desired.

That's a great way to illustrate an idea. That's also a pretty standard way to mount a balanced/centered ram. I like the packaging (nice and simple), but I'm a little bit concerned about the side-loads. There are several manufacturers that have designed/built rams to stand up to those type of forces, but I'm still kinda leaning towards using two cross-linked rams. Mounting those rams might get tight though, and it's entirely possible that I'll end up using one balanced/centered ram. If I do, I would almost certainly do like you're suggesting and have a custom tandem one made.

I think the engine driven pump IS your most likely single point of failure.

A hydraulic accumulator with a low pressure warning system, a hydro version of the brake air reservoir system that would give you a few more turns before you're out of juice, could be a possibility but better yet an electrically driven hydo pump as a backup.

It's not because of mechanical failure of the pump, but the engine stoping while in motion. Engine failure, stalling or simply running out of fuel will kill the engine and you're toast!
Sure, you're right. But I'm not concerned about that at all. Like m16ty and Hammer have already pointed out, if I lose pressure/power, I'm not worse off than I am right now (manual steering). And I'm planning on sizing the components so that the steering wouldn't be too much more difficult to operate without power than the stock setup.

Someone on pirate also suggested using an accumulator, and that's something that I'll look into. I hadn't considered it because I figured that if you lose a hose, you're just going to spill more hydraulic fluid. But I guess that all depends on which hose you lose, huh?

Jesus,

If you are absolutely heck-bent on full hydro, but still want fail-proof redundancy, why don't you use concentric cylindrical tubes for the steering shaft from the steering wheel to the gear box.

The inner shaft is separated from the outer shaft by grease-able bearings for smooth operation. It connects directly from your steering wheel to the full hydro system.

The outer shaft is your own custom "rag joint." It connects directly to your stock manual steering box. But instead of only 1/4 inch of play like a normal rag joint, make the outer tube detatched from the steering wheel (inner tube). Have an adjustable tab that allows you to custom set the "play" before the rag joint engages.

That would give you anywhere from 0 to 360 degrees (180 degrees left & 180 degrees right) before the manual steering outer tube had any physical contact with the steering wheel (inner tube).

Any bump-steer in the manual steering caused by suspension flexing would never reach the steering wheel unless it was in excess of 180 degrees ... which is highly unlikely. Therefore, 99.999% of the time the steering would be full hydro.

The other 0.001% of the time you would have the custom rag-joint tab as a redundant, fully manual, just-in-case backup system that would be sufficient from keeping your wheels from locking fully left or right in an emergency. It wouldn't be perfect steering that's for sure. But in the event of a hydraulic failure it would be enough to get you to the side of the road without veering into oncoming traffic.

It could be modified with electric solenoids or clutches (instead of a rag joint) to automatically switch to the full-manual tube in the event of a hydro failure as well. That would be more challenging to do compared to a very loose rag joint, but it would instantly give you 100% manual steering without slop in the event of a failure. A pressure switch activated clutch locks the outer, manual steering tube to the inner, hydro tube in the event of hydro failure. It adds to the complexity, but it would give you 100% hydro & 100% manual in the event of a problem.

And it doesn't matter which is which. You could use the outer tube for hydro & inner tube for manual. It all depends on the connection points for the hydro activators.

The manual steering would not have to be disassembled. Sure it would rotate back & forth during normal hydro use, but who cares? It would be a fail-safe redundant system in case of an emergency.

I say use concentric tubes for the steering column. With proper planning it could give you 100% hydro & 100% manual backup without interference between the two.

That's my

That's a really creative solution, and I appreciate the suggestion. Only problem is, it's the actual drag-link that's most likely to end up binding and affecting the performance of the modified front suspension. Otherwise, I think that's brilliant.

 

[Flat Black]

Though I have never driven a rig with hydraulic steering on the road, I have to say that you may be over thinking this a bit....

Hydraulics are in use in thousands of applications from manufacturing facilities to cranes to steering on cars and trucks. Hydraulics typically do not fail catastrophically. Pumps dont explode or blow apart at random any more than steering shafts or drag links break in half while driving down the road. If you are comfortable with your abilities to design a robust and safe system, why complicate with things like double or triple redundant systems.

The few hydro failures that I have seen were hose or fitting related, again not catastrophic. If you use good quality components from a company like POS or PSC and have a reputable hydraulic shop make hoses and fittings there really isnt any chance for failure.

If a fitting leaked or a hose split, you would still have some steering control so again this would not be catastrophic failure. A hydraulic system is very simple and if correctly designed with quality parts, there is no reason to worry about the safety of your steering system.

 

[jesusgatos]

I agree with you for the most part Flat Black, but why now try to make it a little safer? If I can, great. If I can't, no harm done.