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Antiguo 18-05-2012, 20:02:05   #1
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Predeterminado Caster en Rear Steering ???

He buscado pro no encuentro el dato especifico, alguien sabe en que rangos dejan el caster cuando se arman bichos con direccion trasera? por mi lo dejaria en cero para que sea liviana , pero no se que tan necesario sea el caster positivo buscando en auto centrado, alguno ha leido algo por ahi ???
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Antiguo 18-05-2012, 20:09:43   #2
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Predeterminado Re: Caster en Rear Steering ???

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He buscado pro no encuentro el dato especifico, alguien sabe en que rangos dejan el caster cuando se arman bichos con direccion trasera? por mi lo dejaria en cero para que sea liviana , pero no se que tan necesario sea el caster positivo buscando en auto centrado, alguno ha leido algo por ahi ???
Wena pregunta. yo tambien habia pensado en cero.
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Antiguo 18-05-2012, 20:34:20   #3
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Predeterminado Re: Caster en Rear Steering ???

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Wena pregunta. yo tambien habia pensado en cero.
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Antiguo 19-05-2012, 00:52:19   #4
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Predeterminado Re: Caster en Rear Steering ???

http://www.pirate4x4.com/forum/showthread.php?t=94654

http://www.icemy.com/thread-79269-1-1.html

Sl2
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Antiguo 19-05-2012, 12:16:47   #5
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Predeterminado Re: Caster en Rear Steering ???

Perfect, no ando tan perdido, el segundo link no me funciona
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Antiguo 19-05-2012, 13:41:16   #6
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Predeterminado Re: Caster en Rear Steering ???

Cita:
Empezado por VSilva Ver Mensaje
He buscado pro no encuentro el dato especifico, alguien sabe en que rangos dejan el caster cuando se arman bichos con direccion trasera? por mi lo dejaria en cero para que sea liviana , pero no se que tan necesario sea el caster positivo buscando en auto centrado, alguno ha leido algo por ahi ???
Interesante... cuenta que traes en mente!

Saludos

Rod
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Antiguo 19-05-2012, 14:39:58   #7
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Predeterminado Re: Caster en Rear Steering ???

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Perfect, no ando tan perdido, el segundo link no me funciona
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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Antiguo 19-05-2012, 14:40:57   #8
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Predeterminado Re: Caster en Rear Steering ???

CJ

There's no reason for any caster with full hydro as the rams don't care about any small amount of steering input that caster could give. Run it straight-up.


Originally Posted by JRThere's no reason for any caster with full hydro as the rams don't care about any small amount of steering input that caster could give. Run it straight-up.

Is everyone in agreeance? I too need an answer.


Originally Posted by JRThere's no reason for any caster with full hydro as the rams don't care about any small amount of steering input that caster could give. Run it straight-up.One advantage to having rear caster is that you can program some lean of the tires when they are steered. This can make them turn just a bit sharper , and can combat tire roll. This is something alot of people don't consider at all when thinking caster angle. Even with negative caster your front steering can still have good self centering characteristics , but the tires will lean out on corners like a Wino on a bicycle and cause the tires to roll really bad. I have witnessed one case of this that was so bad that on a 44quot; swamper the rim would almost touch the ground when steering while moving on smooth flat ground at road pressure.

Just thought I would throw that into the mix.

I may not be creative enough, but I see no way for a rear hydraulic steering system to be completely proportional to he movement of a joystick without electronics being involved. There are actually quite a few options/ways for this, but expense, and system complexity can quickly go through the roof.

Sean


Originally Posted by CJ LagosI 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.

CJ

I have had rear steer for a little over a year now, set up just like this. I agreed with everything you said here. Every time I hear guys talking about thier complex self centering devices I just think quot;why?quot; What a pain in the ass to set up and its just more stuff to fail. If you have the money to spend and you think its necessary, then do it I guess. I'm completely happy with looking at the rear tires to center it. If I'm steering while driving down a trail, I can pretty much get it centered just by feel.


Originally Posted by StationOne advantage to having rear caster is that you can program some lean of the tires when they are steered. This can make them turn just a bit sharper , and can combat tire roll. This is something alot of people don't consider at all when thinking caster angle. Even with negative caster your front steering can still have good self centering characteristics , but the tires will lean out on corners like a Wino on a bicycle and cause the tires to roll really bad. I have witnessed one case of this that was so bad that on a 44quot; swamper the rim would almost touch the ground when steering while moving on smooth flat ground at road pressure.

Just thought I would throw that into the mix.

Sean

From a rock crawling standpoint, it has been discussed to use a lot of positive front caster, like 10 or more deg. The idea being that the front tires flop out and grab more into the rocks on the side when they are turned. On the rear, the same applies only opposite, a lot of negative caster.
I have positive caster on the rear and hate it. On steep up hills, the effective wheel base seems to get shorter when the wheels are turned and makes the car easier to roll ( well, it does for me ).
Hey Sean, I need to talk to you about a rear ram when you have time.


Originally Posted by JRFrom a rock crawling standpoint, it has been discussed to use a lot of positive front caster, like 10 or more deg. The idea being that the front tires flop out and grab more into the rocks on the side when they are turned. On the rear, the same applies only opposite, a lot of negative caster.
I have positive caster on the rear and hate it. On steep up hills, the effective wheel base seems to get shorter when the wheels are turned and makes the car easier to roll ( well, it does for me ).
Hey Sean, I need to talk to you about a rear ram when you have time.

I agree with this logic. I am running (I guess I should say rolling around instead of running ) somewhere around 6* of caster front and rear. Obviously positive in front, and negative in rear. This gives the tires a nice lean into corners which gives the bicycle effect that makes the vehicle steer sharper due to an arc shaped contact patch on the ground. My 120quot; wheelbase buggy ,as it sits, turns ALOT sharper with just front steering than my 95quot; wheelbase , F/R ARB'd TJ does. Mostly due to the awesome steering angle of the mogs , but I do believe the caster helps it out an appreciable ammount.I am always here, just give me a call, or shoot me an e-mail with the best time for me to call you, and I will get with you ASAP. I believe I still have your number here somewhere, so I may give you a call tomorrow evening to see if that works for you.Sean

I definatly agree that some caster in the rear is good, if it was set at 0 deg. it would cause premature wear of linkage. There is always some tolerance of slop in a system so if it is set at zero the wheels will chatter back and forth till it becomes noticable.
It may take a long time to notice this unless you see some speeds once in a while.

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Antiguo 19-05-2012, 14:41:32   #9
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Predeterminado Re: Caster en Rear Steering ???

On the rear steer I also see no way to make the rear self center with a manual valve.
I do plenty of rear steer systems and the guys that have run them say it is one of those things that after having it you never knew how they did with out. I do feel this is more critical for bigger rigs because it may be harder to see everything.
The system can get a little expensice but it ends up around 600$ on top of what parts you need anyways. there is some corners that can be cut though as well to get it down more. If anyone is interested give me a call and I can discuss it, rather than sit and pimp here.


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.
Hey now that you got your star how about a diagram!


Originally Posted by JRHey Sean, I need to talk to you about a rear ram when you have time.

Anything you want to tell us JR? You coming back to AZ this year?


Originally Posted by CJ LagosI 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.

CJ

Ditto....I've been running the same type set-up for two years now and could never go back to front only steering. I fought reservoir volume issues initially and ended up with a double tank set-up that resolved the overflow probs. A fair amount of heat builds up in mine which seems to be controlled well enough by a LARGE tube type tranny cooler up front. You really get a feel for the rears position after a bit of use...you'll feel even a slight bit of crab when your running fast or slow and a quick tap on the joystick will bring you back straight with the world without looking. If you've run cutting brakes before (sandrails, comp rigs?) the quot;second naturequot; feel is similar.

i've only had my rear steer rig on the trail once since building it and by the end of the weekend, i could feel even a little bit of crab walk. just tap the joystick and i'd be driving straight again. a sensing ram is an option but considering the added $600-$700 cost, i can already tell that i just don't need it. it is very easy to tell where the rear wheels are without looking. and to me, it doesn't seem that critical. hell, i don't drive on the street and 40 mph is very uncommon.
besides, it would seem cumbersome to have to quot;holdquot; the joystick in place to keep it from self centering when i didn't want it too. na mean?
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Antiguo 20-05-2012, 01:16:06   #10
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Predeterminado Re: Caster en Rear Steering ???

Excelente info, habra que leerla con calma, y a esta hora la neurona que queda de turno no me va a pescar jaj Gracias

Rod, vamos a hacer este proyecto que estaba guardado desde hace ya varios años en la carpeta de CCG, y como no falta el voluntario hay una Hilux que sera la camioneta de indias una vez teniendo los componentes mas importantes lo tiramos como proyecto
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