using an old ABS set up for fiddle brakes.

[Crash bandicoot]

Any one out there got a fairly good understanding of how an abs unit works and is wired.....

had a fleeting idea today that if you could power the 4 cylinders individually from 4 switches would it provide the required constant pressure to lock individual brakes on?

[Team Tonka]

looked at this one before, each solenoid blocks off its brake. So 4 switches on dash, flick the ones you don't want to work and then brake. Seems simple but I came to the conclusion that it would be hard to use effectively in the real world.

[diogenese]

Here's a link to an American car forum but it has a good set of diagrams of the electrical and hydraulic setup for bosch abs.
You would need a lot of switches... http://www.ls1gto.com/forums/showthread.php?t=417188

[Rotazuk]

You don't need a lot of switches , you need two joysticks . One front axle one rear axle , working in the left right plane only . You do not want to be able to lock both front or both rear at the same time but you may need to lock both left or left front and right back ( if you had no lockers like me )



Inside you have a few relays that do the switching , I have too many here I found out after the first test .



ABS units work by pumping fluid away from the brake that has locked up back to the master cylinder ( I assume thats the bumping of the pedal you feel when its in operation ) . That is not the way you need it to work for fiddle brakes , you need a pump that can put pressure to a brake to slow the wheel . There was talk in the uk of a BMW "abs" unit that did that but I never worked out what one they were talking about .

You need to think traction control , these type of units can work both ways . As I have a landrover I had the diagrams for the rover system and it seems simple enough . I got a complete ABS unit and 6" of plumbing along with the ecu and 2ft of wiring out of a freelander ( they are being wrecked left right and centre ) but they have traction and hill decent control .

At the moment I only have the fiddles side of it wired (no abs sensors in the hubs ) but the next 4x4 will get traction control with fiddle overrides . The traction control is not designed to lock the wheel , like you see the trials truck do , and I have not had it out with the new brakes yet to test it properly . On grass and my concrete floor it locks and drags a wheel a wheel but on my rough asphalt drive it doesn't , they crep around .

Time will tell .
Cheers
Chris

[rotordogg]

Heard Howie's played with ABS units for powering his hydrolic lockers, might be worth a call to him to see what he found out...

He's normally happy to chat about things like that.

I'll look at using that for my next Howie locker!

[churchill]

A NP Pajero has its own power pack on the brake unit and it's designed to brake individual wheels for traction control. This might be a good start point.

[Pedro]

A NP Pajero has its own power pack on the brake unit and it's designed to brake individual wheels for traction control. This might be a good start point.

honda prelude has a pump good for about 2000 odd psi with a accumulator,

i tried the abs for wheel brakes using a subaru abs unit, i could get the unit to lock the wheel and lock it bloody solidly but could not get the valving to release the wheel again, i was going down the line of a 2 stage system, partially lock to full lock, but using a timer circuit to apply the brake for x millisec to off for y millisecs, due to time restriants, trial was the next day flagged it and ripped it all out, even had the abs sensors and teeth machined into the disks and planning to take it to the traction control level. never quite back to it, but it sounds like the rover abs unit would be best as it is designed to apply and release the pressure with out a external pressure source (brake pedal)


pedro

[Rotazuk]

Heard Howie's played with ABS units for powering his hydrolic lockers, might be worth a call to him to see what he found out...

He's normally happy to chat about things like that.

I'll look at using that for my next Howie locker!

Some nissan skyline's came with a factory locker that works in similar fashion to howie's lockers . They worked by the traction control ecu turning on the pump etc . In the boot on the left hand side was the pump and res setup .

May work for you better than an abs unit but would only do one locker not two .

Cheers
Chris

[Rotazuk]

honda prelude has a pump good for about 2000 odd psi with a accumulator,

pedro

If I can't get enough pressure I was going to get some model details off you and merge the two units . The issue I think I have is there is a constant bleed on the rover unit preventing full pressure . When I have more time I will pull a unit apart and see if this can be blocked by a valve or if necessary permanently . If by a valve you could have two stage pressure , with relief open or closed , as you talked about . I expect/hope closed will lock the wheel solid .

I could never get my subaru ABS unit to put out any pressure and reading how they worked ( taking pressure off the brake ) not sure how you got pressure . I'm just not smart enough and will have to try again

Cheers
Chris

[ChurchurDan]

I dont see why it cant be done especially if your truck already has abs. I would avoid the honda units that have an accumulator, as the pumps and accumulators are prone to failure.

[Heath]

I remember a rover based wagon (MOGROVER I think) that used an ABS setup in reverse to lock the spining wheel rather than release the locked wheel. Maybe a search under that name will give some results (was in aussie 4wd mag IIRC). Is it possible to trick the system to switch on when it thinks it is switching off (swap the plugs around?)? Perhaps too simplistic.

[Pedro]

I dont see why it cant be done especially if your truck already has abs. I would avoid the honda units that have an accumulator, as the pumps and accumulators are prone to failure.

to be fair they were 40 bux from a wrecker...... howie uses one to drive his lockers i beleive

pedro

[Heath]

Cut from article about the haultech traction control system.

Nothing to secretive about it exceot how the actual program works. The rest of it is fairly straight forward. It has speed sensors on each wheel, and an air over hydraulic master cylinder for each wheel brake and a computer controlling the whole thing. Its powered by air.

If you saw it working on something like my buggy you would be hard pressed to see that it didnt have lockers. IMO on an axle that is a bit marginal for strength it is by far better than a locker. On an axle that you carnt break then lockers are better (like my mog 404 axles). Basically it stops you breaking as much stuff for a very slight decrease in capability in a few particular types of off road situations (which turn out to be the exact types of situations that will break CVs). So its trading capability for reliability which ultimately means that you can drive your rig so much harder which actually makes the rig more capable.

[ChurchurDan]

I dont see why it cant be done especially if your truck already has abs. I would avoid the honda units that have an accumulator, as the pumps and accumulators are prone to failure.

to be fair they were 40 bux from a wrecker...... howie uses one to drive his lockers i beleive

pedro

At that price it doesn't really matter, just buy a few for parts while you are there.

[Pedro]

Cut from article about the haultech traction control system.

Nothing to secretive about it exceot how the actual program works. The rest of it is fairly straight forward. It has speed sensors on each wheel, and an air over hydraulic master cylinder for each wheel brake and a computer controlling the whole thing. Its powered by air.

hmm the control is relatively easy using small ardino cards or similar, but I would think the reaction time and rate of application would be fairly limited due to the air cylinder response time, bearing in mind a reasonable size cylinder would be required to drive the master cylinders and not to mention the air required. but be nice to find some tech specs on the system

pedro

[Heath]

Cut from article about the haultech traction control system.

Nothing to secretive about it exceot how the actual program works. The rest of it is fairly straight forward. It has speed sensors on each wheel, and an air over hydraulic master cylinder for each wheel brake and a computer controlling the whole thing. Its powered by air.

hmm the control is relatively easy using small ardino cards or similar, but I would think the reaction time and rate of application would be fairly limited due to the air cylinder response time, bearing in mind a reasonable size cylinder would be required to drive the master cylinders and not to mention the air required. but be nice to find some tech specs on the system

pedro

Good excuse for airbags as well - need a compressor so why not multi task it...?

[Rotazuk]

Spent too much time on the couch this weekend so while wasting the day I looked into the Misti abs/traction control setup . It appears that it is a three piece system , Pump , Master Cyl and valve assy . To get it to work you need all three bits as the pump works through the master cyl to get to the valve assy .

So looks like I will have to stay with the rover one I have . This is a self contained unit that just goes in line with a standard type brake setup , ie front and rear brake lines in , splits into four brake lines out etc .

Interesting to note that the rear brakes on the misti are only electric , as in a pump failure means no rear brakes . Expect the front will pull it up eventually but .....

Cheers
Chris