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I am looking for some advice on my caster angle for my RW5ton/14 bolt rear axle, I am going to use full hydro steering on the front with a power beyond port in the servo valve and run the rear cylinder off of the power beyond port(5 port valve). I am going to control the rear hydro cylinder with a seperate hand valve ( spring center) so it should return to center on its own but we'll see. My Question is should I run the rear caster at 0 degrees or +7 or -7 or run less caster angle like +4 or -4 this would be for normaly driving forward.
If you´re thinking that a spring return to center valve will bring the wheels back to center automatically whan you release the lever, you´d be mistaken. The cylinder will just stop where it is when you let go of the lever. What happens from that point will depend on the port configuration of the valve.If you want the rear wheels to straighten themselves out on their own, then two things will be necessary. First, the center position of the valve, independent if it´s a spring return or detented, will have to have all ports open to tank. That way, oil in the cylinder will be free to return to tank on its own. Secondly, you´ll have to have some mean caster to have the wheels return on their own and STAY there.
Personally, I think you´ll have problemas to get this to work correctly and safely, but I have no first-hand rear steer experience here, I´m speaking only from indusrtial experience with hydro systems........
Saying that, I´m sure that you´re not the first to think of something like this, so someone who HAS done it will prolly tell me I´m full of shite. That´d be cool actually, a friend and I are about to embark on a rear-steer project for his rig, so if this IS possible, I´d like to learn how as well.........
treat it like a front end +7 degrees will get return to center when driving forward
......but will it STAY centered, even when taking side impacts?!?!?
I wanna see pics of the 14bolt/ 5ton rockwell hybrid axle.
well i am picking up the 5 tons tomorrow afternoon, i have no doubt about the hydro system not centering itself on the rear steering cylinder you are most likly right BILLJ . I am going to add a proximity sensor on the rear cylinder I am using an aluminum barrel cylinder and I am going to add a .020 ring into the center of the piston to read from, this way I will know when the cylinder is centered, inticator light on the dash comes on. I just don't have to turn around and look at the rear tires to see if they are strait mainly because of neck problems.
That´d work. In this case, I´d go with a spring centered valve with the center position blocked. That way, the cylinder will stay where you last left it, independent of external forces on the tires. And in this case caster angle wouldn´t matter, I´d run it zero to minimize the turning forces.......
In any event, if you street run at all, I´d put some sort of mechanical locking pin in the system. The last thing you´d want is for the rear steer to activate because you accidently messed with the valve.......
Originally Posted by billj......but will it STAY centered, even when taking side impacts?!?!?
no, it will be just like a front end and will need to be corrected, ect
I've put some thoughts into this (but warning: they are just thoughts, no experience yet). I'm thinking some caster is good to keep the rear wheels from wobbling or making the rear-end drift/steer etc if you drive straigt at a little speed, as there will probably some give in bolts, cyl, hydro lines, fluid etc.
Over here it looks like all the comp rigs with rear steering use a small joystick valve for the rear, then a button for it to return to center. I don't think I'll like running that, so I thought up something better (but mainly cheaper). Will need a bit of rods and joints though:
Put in a drag link like you would if you were to run a steering box. Put your hydraulic two-way spring loaded valve on a Watt-link with the drag link on one side, lever on the other (fancy word for a bar with three holes: drag link on one end, valve in center, and connect lever to other end). I don't know if that explanation is understandable, but the point is that you'll get a lever with absolute position of the wheels (instead of relative with a normal set up). I.e. when you push the lever forward (for steering left) the valve will open in that direction, the cylinder (on the axle) turns the wheels, and the lever will follow. Let go and it stops. Make a little tick or something so you can feel center in the lever. I think that'll give me a much better feel and control over the rear wheels as I drive.
how about a paint-brush pic for us not thinking types..
thanks,
--SherpaCheers......
Originally Posted by AmundI've put some thoughts into this (but warning: they are just thoughts, no experience yet). I'm thinking some caster is good to keep the rear wheels from wobbling or making the rear-end drift/steer etc if you drive straigt at a little speed, as there will probably some give in bolts, cyl, hydro lines, fluid etc.
Over here it looks like all the comp rigs with rear steering use a small joystick valve for the rear, then a button for it to return to center. I don't think I'll like running that, so I thought up something better (but mainly cheaper). Will need a bit of rods and joints though:
Put in a drag link like you would if you were to run a steering box. Put your hydraulic two-way spring loaded valve on a Watt-link with the drag link on one side, lever on the other (fancy word for a bar with three holes: drag link on one end, valve in center, and connect lever to other end). I don't know if that explanation is understandable, but the point is that you'll get a lever with absolute position of the wheels (instead of relative with a normal set up). I.e. when you push the lever forward (for steering left) the valve will open in that direction, the cylinder (on the axle) turns the wheels, and the lever will follow. Let go and it stops. Make a little tick or something so you can feel center in the lever. I think that'll give me a much better feel and control over the rear wheels as I drive.
Originally Posted by SHERPAhow about a paint-brush pic for us not thinking types..
thanks,
--SherpaCheers......
Sorry, ain't got the star, can't upload. But I'll see next week, maybe I can draw a proper drawing, hook the scanner up, upload to another server and link etc.
I use an orbital with the power beyond port and a hand valve between the seats. The setup is definately bad ass but on my next one I think I'll look harder at a 2nd pump to keep the two systems separate.
Mine definately does not self-center, and it really doesn't bother me. I just turn back and line the tires up by eye. I've gotten good enough with it that I can do this while moving now, at first it took a while. Rear steer is a lot harder than it looks! I very rarely have a problem with the rear tires moving on their own, they hydraulics hold them in place well. My hand valve is open center. If you drive on the road you can tell that the tires bleed off to one side and slowly turn themselves, but I have discovered I can very quickly tap the hand valve even at high speeds to re-adjust. On the trails, you are constantly turning the tires that is never an issue. I have a feeling this quirk stems from the single ended cylinder, my next one will have a double ended on both ends.
I didn't measure caster, I set the pinion angle. I don't think it matters as much because there can't be the return to center with the hand valve.
If I was racing, the self-centering would be more of an issue. I want to put a light on the dash to indicate when they are centered but it just isn't that important to me.
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