[31zook]

sorry for the vague title, but im not sure if what im about to explain exists or if it does what it's called....

ok, so i have a 12V hydraulic pump and i want it to become in-active when my wheel speed goes above 30kph. I have VSS in my sierra dash, so i was wondering if i could get some sort of computer that cuts power and locks the flow of the lines off (yes i know there would be another electronically controlled valve for the lines) when that speed is reached...

Here is the reason why im asking this. Im going to try and fit rear steer to my lwb with a stock sierra WT front housing. It will run cromo's, and im guessing this will be strong as or stronger then a stock rear end. It will be full floater, so thats a reason in itself. i plan to run a 2x6" ram with a 12V hydraulic pump, so there is no reason for my cressida power steering pump to be slowed down, plus no expencive valves or massively long high pressure lines... im only pushing around 29's with no intention of going bigger, so strength wise i think ill be fine, but im still not sure....

and why im going to all this bother, because i want to get it engineered, and see if i can trick things up enough to be capable on rock with the big boys....so does anyone know of a simple computer that can read the VSS and cut power off to the pump? does jrzook wanna make me a simple computer?

This is the pump

comments and questions welcome

[atari4x4]

only 29's??? why bother....

[ball]

A small PLC will do it.

Wouldn't be too hard to wire your speed sensor as an input. Program the PLC to turn on a relay to power your hydraulic pump at low speed.


You could also rig a toggle switch as an input so you could manually switch the pump on or off if required.

[Fatzook]

I thought rear steer was illegal on a road driven vehicle, unless fitted from factory? And I know that hydro is frowned upon.

[royce]

speed switching is piss easy, Jaycar do a kit at the very basics but there are probably nicer ways

your also going to need the controller to recenter the steering before shutting it off, or you could get mega tricky and grab the 4WS gear from a 626 or prelude and wire it in, they would turn the rear opposite to the front at low speed and with it at higher speed

you could also use 4wd as the lockout, IE wont engage in 2wd

[atari4x4]

the 2nd gen MX-6 also ran the switching RWS, the old dear had one & it was cool to park & it switched to crab steering at around 35kph

[rick1970]

How are you planing to control the cylinder with this? A seperate (manual or electric) control valve of some sort or solenoid valving built into the unit?

The powerunit appears to be a DA unit with inbuilt pilot operated checks which can give very snappy response, maybe not the best thing for fine steering adjustments. Std solenoid valving is either on or off, again not real good for fine adjustment of the cylinder position. Picking up a pilot signal from either side of the front PS box to control a pilot operated valve for the rear steer could be an option, solenoid valve to switch over the pilot signal and change the direction the rear steers compared to the front at speed.

You will have no choice but to turn the unit off when not needed as the duty cycle on the motor with these things is very poor and you will fry motors if left running for too long and suck bulk juice from the battery. Check the specs 120amps @ 500 psi and 200amps at 2000 psi.

[31zook]

atari: because tyre size doesn't mean as much as a well set up car, and some believe that unless it has 33's it will be sucky on the off road

ball: Is this what you were referring to? it sounds like a electronic hydraulic stop on a brake press or a punch or anything else that reads stuff for hydraulics....

fatzook: will have a mechanical lock out, i can't automate this but it will stop anything from moving while im driving along the roads. yes it's not taken lightly, but im getting as much information together before i see an engineer, then ill bring him all my ideas and just see what he has to say.... so im prepared for a certified engineer to tell me no, just figured i would try....

Royce: i had thought of the 2wd lockout system, but when i take it out of 4wd to burn the rear around, it will not work so good... there is too many flaws and things i can think of for that to work. the centering thing is still a bit up in the air, i will need it to be spot on, as the mechanical lockout will be a pretty snug fit. if there was a flow reader in both lines, and i could plug them back into the computer then thats the only way i can think of getting it all centered once i hit 30k's...

rick1970: you sound like you know what your talking about, so a signal from the power steering box to give it the fine control, thats how allot of people do power steering and hydro assist, so it would work for sure, but thats if i want the wheel to follow the front, sometimes ill need it to crab sideways and operate separately to the front, so if i destroy the front somehow i can drive to camp with only the rear there would be a elec toggle switch that i have next to my hand brake and as for as i know the motor would only run when the toggle switch is on. i plan to run 1-2 deep cycle batteries in the tray for this.

[ball]

31zook wrote:

atari: because tyre size doesn't mean as much as a well set up car, and some believe that unless it has 33's it will be sucky on the off road

ball: Is this what you were referring to? it sounds like a electronic hydraulic stop on a brake press or a punch or anything else that reads stuff for hydraulics....

fatzook: will have a mechanical lock out, i can't automate this but it will stop anything from moving while im driving along the roads. yes it's not taken lightly, but im getting as much information together before i see an engineer, then ill bring him all my ideas and just see what he has to say.... so im prepared for a certified engineer to tell me no, just figured i would try....

Royce: i had thought of the 2wd lockout system, but when i take it out of 4wd to burn the rear around, it will not work so good... there is too many flaws and things i can think of for that to work. the centering thing is still a bit up in the air, i will need it to be spot on, as the mechanical lockout will be a pretty snug fit. if there was a flow reader in both lines, and i could plug them back into the computer then thats the only way i can think of getting it all centered once i hit 30k's...

rick1970: you sound like you know what your talking about, so a signal from the power steering box to give it the fine control, thats how allot of people do power steering and hydro assist, so it would work for sure, but thats if i want the wheel to follow the front, sometimes ill need it to crab sideways and operate separately to the front, so if i destroy the front somehow i can drive to camp with only the rear there would be a elec toggle switch that i have next to my hand brake and as for as i know the motor would only run when the toggle switch is on. i plan to run 1-2 deep cycle batteries in the tray for this.

Yep that is a PLC. They can do a hell of a lot more than just act as an electric hydraulic stop.

Look into directional control vales and flow control valves. This will give you the parts to fine tune and control the cylinder. These can be switched on or off by the PLC which will give you the motion you need.

An accurate proximity switch can turn the whole lot off when it is centres.

I think you are going to need a mechanical lock in the centre postion if you want to try and keep the engineer happy.

[mightymouse]

mabe a hobbs switch but dont know if hyd fluid may cock it up

[ZookiMonsta]

If you're going to drive the car on road, IMO you'd be better off with rear cutting breaks instead of hydro. It would suck
if the computer roasted and rear steer did what it liked while driving down the road. Just my 2c

[shep]

ZookiMonsta wrote:

If you're going to drive the car on road, IMO you'd be better off with rear cutting breaks instead of hydro. It would suck
if the computer roasted and rear steer did what it liked while driving down the road. Just my 2c

that's why you would use a mechanical lock on the rear steer, wouldn't stand
a chance of being engineered without one.

[ball]

ZookiMonsta wrote:

If you're going to drive the car on road, IMO you'd be better off with rear cutting breaks instead of hydro. It would suck
if the computer roasted and rear steer did what it liked while driving down the road. Just my 2c

That is why you would set it up to turn on at a low speed. At regular driving specs the thing would be turned off with a suitable mechanical lock to safeguard against computer problems.

[ball]

shep wrote:

ZookiMonsta wrote:

If you're going to drive the car on road, IMO you'd be better off with rear cutting breaks instead of hydro. It would suck
if the computer roasted and rear steer did what it liked while driving down the road. Just my 2c

that's why you would use a mechanical lock on the rear steer, wouldn't stand
a chance of being engineered without one.

Beat me to it ya bastard

[31zook]

ZookiMonsta wrote:

If you're going to drive the car on road, IMO you'd be better off with rear cutting breaks instead of hydro. It would suck
if the computer roasted and rear steer did what it liked while driving down the road. Just my 2c

I'm not a nasty guy, but good on you for reading the whole post before posting yourself yeah i could, but I'm pretty sure that this will look cooler


[quote="ball']

Yep that is a PLC. They can do a hell of a lot more than just act as an electric hydraulic stop.

Look into directional control vales and flow control valves. This will give you the parts to fine tune and control the cylinder. These can be switched on or off by the PLC which will give you the motion you need.

An accurate proximity switch can turn the whole lot off when it is centres.

I think you are going to need a mechanical lock in the centre position if you want to try and keep the engineer happy.[/quote]

A mechanical lock was never out of the question. I'm thinking of just having a speed cut off switch, it will make everything simple and I'm pretty sure once the engineer See's that i have enough brains to set it straight and lock it in place then he will probs not be too worried about auto centering. Flow control valve for fine adjustment of the ram is a great idea, I'm not after something that will snap my wheels side to side in an instant, it's going to be a crawler so i want all the control i can get

can you ball (or anyone else) recommend a good PLC computer?

sorry if all my questions are a bit simple, im a boily, not a hydro computer wiz

[ball]

Go to http://www.automationdirect.com.au/

Click on the PLC's down the left hand side. Look for the CLICK micro PLC's. The software to program them is free, the cable is cheap and the PLC's are very cheap.

I use them for the small stuff and the KOYO DL05 and DL06 for more complex stuff. I have the programming software and cable for the KOYO stuff but that is the expensive way to go.

I think you will be looking for one that has DC inputs and relay outputs. You will need to see if they do one that runs on 12V DC. All the stuff I use is 24V DC or 240V AC.

These guys are based on the Gold Coast and they keep a shitload of parts in stock. They do a lot of the sensors that you will need too.

Once you get your head around the programming side, it is really simple to do cool stuff with them.

[31zook]

google says i can buy a 12V-24V converter... i had a look also it looks all like 24V stuff....

thanks for the link, i think I'm starting to get my head around it, if i can get the PLC to cut off power to the relay at a set number of signals from the VSS then turn back on once i go below the set amount of signals.

and what i mean by turn back on is become active, not the motor start up, but just useable.

why would i need sensors? wouldn't cutting the ram short and using the diff bumps be enough to stop the hub's from being ripped off? or are you referring to flow control?

[ball]

The input from your VSS sensor may not be good enough. I don't know what the output is.

If it isn't any good then a proximity sensor with a pickup from an axle or drive shaft can be fitted quite easily.

If you have a couple of extra sensors then you can use them as interlocks/failsafes. i.e. shut off the pump in the centre position and the mechanical lock is in place.

Cutting the rod would probably work, but if you have a few extra inputs, why not use them

[royce]

$100 for a speed switch!!!!!!! the jaycar kit is like $30, do the same thing

I reckon the engineer is going to say to you the lockout will require you to get out to operate it in some way so you might find your gunna end up having a locking pin you put in yourself and a master switch outside the cab to activate the pump

how are you going to steer it? I think youd be dissapointed with anything other than full independent control, sometimes youll only want to steer the rear, sometimes crab etc

[31zook]

Why won't my vss signal be enough? too weak? how would my PLC know it's in the center? like i thought of an electric eye but if mud got on there is would be useless again, and a wire setup, but mud would probably shorten it's life span, then a little bump sensor that could read where it was, but mud again would throw it out.....

is there a sensor that can measure the amount of fluid going through it (not pressure) so i can program how much fluid needs to pass before it knows it's on center? This (if possible) would be fully enclosed and not able to be tampered with, unless there is a hose blowout or something like that....

[ball]

royce wrote:

$100 for a speed switch!!!!!!! the jaycar kit is like $30, do the same thing

I reckon the engineer is going to say to you the lockout will require you to get out to operate it in some way so you might find your gunna end up having a locking pin you put in yourself and a master switch outside the cab to activate the pump

how are you going to steer it? I think youd be dissapointed with anything other than full independent control, sometimes youll only want to steer the rear, sometimes crab etc

One is an industrial quality switch, the Jaycar one will be a hobby/handyman one.

Steering, rotary encoder under the dash attached to your steering shaft. Use that to feed the PLC an input, then have it actuate a directional control valve for full independent steering.

Starts to get expensive though.

[ball]

31zook wrote:

Why won't my vss signal be enough? too weak? how would my PLC know it's in the center? like i thought of an electric eye but if mud got on there is would be useless again, and a wire setup, but mud would probably shorten it's life span, then a little bump sensor that could read where it was, but mud again would throw it out.....

is there a sensor that can measure the amount of fluid going through it (not pressure) so i can program how much fluid needs to pass before it knows it's on center? This (if possible) would be fully enclosed and not able to be tampered with, unless there is a hose blowout or something like that....

I am just not familiar with what the output is. It may work fine.

You don't use an electric eye for a sensor, you use a proximity switch. These detect either a piece of metal or an absence of metal. Some work with a magnet, some just a piece of steel. Plenty of choices, just have to work out what you have under the car to use. Think outside the box.

If you buy a decent industrial stainless steel sensor they will live in acid, a bit of mud and water won't hurt them.

Fluid flow would not be accurate enough

[royce]

centered is just a magnet and reed switch on something that moves side to side, it knowing which side it is on will be the drama

this is sounding like a lot of work to lock something, when getting out and dropping a pin in will do the same thing

[31zook]

royce wrote:

$100 for a speed switch!!!!!!! the jaycar kit is like $30, do the same thing

I reckon the engineer is going to say to you the lockout will require you to get out to operate it in some way so you might find your gunna end up having a locking pin you put in yourself and a master switch outside the cab to activate the pump

how are you going to steer it? I think youd be dissapointed with anything other than full independent control, sometimes youll only want to steer the rear, sometimes crab etc

31zook wrote:

rick1970: you sound like you know what your talking about, so a signal from the power steering box to give it the fine control, thats how allot of people do power steering and hydro assist, so it would work for sure, but thats if i want the wheel to follow the front, sometimes ill need it to crab sideways and operate separately to the front, so if i destroy the front somehow i can drive to camp with only the rear there would be a elec toggle switch that i have next to my hand brake and as for as i know the motor would only run when the toggle switch is on. i plan to run 1-2 deep cycle batteries in the tray for this.

the outside master kill switch is a good idea, i wonder if he will ask for that....

ball wrote:

I am just not familiar with what the output is. It may work fine.

You don't use an electric eye for a sensor, you use a proximity switch. These detect either a piece of metal or an absence of metal. Some work with a magnet, some just a piece of steel. Plenty of choices, just have to work out what you have under the car to use. Think outside the box.

If you buy a decent industrial stainless steel sensor they will live in acid, a bit of mud and water won't hurt them.

Fluid flow would not be accurate enough

A proximity switch will work really well i think, if i can mount it out of the way (i was thinking above the ram, but im thinking about putting it on the other side of the housing now).

A vss signal is an open circuit, until a magnet comes over the top of it and the reed inside of the tube closes together, there is 4 closed circuits per revolution of the speedo cable. This is so the ECU knows how fast the car is going and can adjust the fuel mixture or something....

so if i can set the PLC up to adjust the ram to center itself once the set signal is reached. Im not going to drive off all of the sudden with it on full lock and try to set world records.... it will prob's just shift it millimeters as i cruise from trail to trail on private property

[31zook]

so i don't burn people out, im going to go shopping and get some stuff together, then put up pic's and show you all. i've found out i can do nearly everthing i've asked, so ill start putting it into reality

massive thanks to ball

[royce]

I reckon get the thing working first, worry about the automagic turning it off second

A good in between may also be when you steer from lock towards center it will stop and center and you have to activate teh steering again to go past, few people have said thats the annoying bit with it, when your in a hurry you just want to get moving and not worry about getting the rear back to center

maybe the engineer might like it not being able to do more than 30km/hr when its active rather than it locking out

[31zook]

royce wrote:

I reckon get the thing working first, worry about the automagic turning it off second

thats a good idea

A good in between may also be when you steer from lock towards center it will stop and center and you have to activate teh steering again to go past, few people have said thats the annoying bit with it, when your in a hurry you just want to get moving and not worry about getting the rear back to center

that will just tick me off, i like smooth seamless operation. And just sticking my head out the window and having a eye ball measurement at it will be suffice till road time...

maybe the engineer might like it not being able to do more than 30km/hr when its active rather than it locking out

that would be just plane hard to do, i can't even think of a way to do that

thanks royce also

[ball]

Ok, the problem I can see with the VSS sensor is the frequency.

How many times does it pules at 30kmh.

The PLC will only be able to pick up a certain number of pules per scan of the program. I can't remember any of the specs on those click plc's

This has caught me out when I was programming the PLC that drives my toolchanger on my lathe. I had a combination of 4 proximity switches and they would only pick up every second switch when the turret moved. I tore my hair out for weeks trying to get that bastard programmed correctly.

[royce]

nothing worse than trying to do something and the rear end is gone all strange, I doubt youll ever steer from one side of straight to teh other in one go but not having to think to get back to center is worth its weight in Vitaras

remember even with caster in the steering it wont self center, actually there might be an option, the hydraulics open so caster can center the wheels and when it does the pin drops in to lock it

speed limit is easy, same jaycar kit and same as a rev limit on an engine, when it sees some many pulses per second or more it cuts the injectors, when it drops under it comes back, instant speed limit

[3cyl]

Years ago I did the control of the rear steer on the mate's Mogrover using a double throw spring return toggle switch to steer it and a single push button for return to centre. Used 1 inductive prox to tell it when at centre and 1 prox the same to tell it when it was right of centre. No PLC required, just 3 identical 4 pole HC4 12v relays. I must have made it in about 2005 and the Mog has changed hands since then and as far as I know it's still working. Also did 1 for Haultech's front engined buggy and a couple of others. It had an LED pilot light that lit when it was centred as the single ended ram would occasionally creep from valve leakage, easy to operate and cheap to build. Independant manual operation was definitely the go and it would be easy to pin it locked at centre.