ABS/ Fiddle brakes

tristanp · Post by **tristanp** » Sat Jul 09, 2005 9:27 pm

has anyone tried to adapt an ABS unit to be a push button fiddle brake setup?
other than running a second brake line to each dif and figuring out how the wiring on an ABS unit works.. it cant be that hard.. or can it?

Post by **mike** » Mon Jul 11, 2005 10:12 am

well Im thinking it wouldnt be simple either. The way I understand ABS works is that each wheel has a sensor and when that wheel locks the computer tells that wheel to realease the brake for 1/10th of a second and then re-apply hence the shuddering through the pedal. So the computer controls everything and you would need to do something with the computer to stop it getting confused. If it was possible an external interface into the computer with a button telling the computer which wheel to lock would be quite cool, no need for running second lines etc

Mike

DieselBoy · Post by **DieselBoy** » Mon Jul 11, 2005 10:32 am

That is pretty much how electronic traction control works.
Computer locks the wheel thats spinning via the ABS system, making the other wheel spin instead.
If you could get an interface to control that manually, you would have electronic independant brakes.

tristanp · Post by **tristanp** » Mon Jul 11, 2005 3:06 pm

ok. a standard ABS pump has two inlets (front/rear) and 4 outputs(each wheel)
im guessing that by powering up circuts in the pump you can hold/release individual brake circuits.
the only thing im concerned about is ,does the pump take the pressure you have provided by putting your foot on the brake and release/apply/realse/apply or can it do it without the brake pressure being applied-
maybe i should look for an ABS pump out of a car that also has traction control?

DieselBoy · Post by **DieselBoy** » Mon Jul 11, 2005 3:26 pm

Yeah, that could be the go.
You make a good point about how the hydraulic pressure is applied to the system in traction control.

I think the ABS compressor just makes the pressure in the brake system pulse, not actually pressure on , pressure of pressure on again type thing, just a slight reduction in pressure, enough to let the wheel unlock???????

I'm getting out of my depth................................ :lol:

Rotazuk · Post by **Rotazuk** » Mon Jul 11, 2005 4:49 pm

Been thinking about this for a while and have come up with another solution , but lets stick to the abs . I am no car mech so could be wroung .
Abs pump makes its own pressure , as it drops it and re-applies it very quickly . your pedal pressure would run out in the first stroke .

Some abs systems do not do all wheels independantly , channels . The older suzuki systems have three channels , two front and one back . If you want 4 wheeel brakes you would need a 4 channel abs unit .

Then it is seems to be a matter of figureing out what vavles dump and what valves apply pressure . Wire a switch to the corect valve that applies pressure and ditch the computer .

Now if you want traction control , as some aussies are building , that is another kettle of fish . You would need to keep the computer and install a wheel speed sensor at each wheel , mess with the sigan from left to right , detect the faster wheel , make sure its not going around a corner and then lock the faster wheel ( ie brake on and off again )

I think the manual button idea is ok

Maybe I need to spend some more time on it :-)

Chris

Heath · Post by **Heath** » Tue Jul 12, 2005 5:21 pm

What about individual line locks?

Just put your foot down, flick the switch to lock it down and release the pedal. Result one locked wheel which unlocks at the flick of a switch.

Just need a couple of electric solenoids (or valves) one for each rear line.

Seems easy but you are messing with the brakes so not certifiable I guess. Also not the sort of auto system you might want.

Wouldn't a locker be easier?

Heath

tristanp · Post by **tristanp** » Tue Jul 12, 2005 7:29 pm

i was thinking about putting it into an offroad only 4x4 so certs dont matter

and im pretty sure lockers arnt available for the 60 series patrol that i was gonna retrofit this setup into

Rotazuk · Post by **Rotazuk** » Tue Jul 12, 2005 8:46 pm

Line lockers could be a haasle as you have to hit all the brakes then lock the line etc . Also diff lockers don't help in going around a corner .

It would need some sort of overide , locking on wheel at speed would be a bad thing . Would not put this into a road machine , thou .

I have heard that they could be certifiable if you run and extra caliper that did the individual locking . Also if your car had abs already you may be able to tap into it without a cert but as I said I would not want to run this on a road machine until its proven itself a bit :-(

Chris

De-Ranged · Post by **De-Ranged** » Wed Jul 13, 2005 6:16 pm

I know this is a bit off the line of your ABS unit but in reply to Rotozuk
I've got my local certify'er to agree to fiddle brakes on my Rover by welding on an extra set of calipure posts and putting an extra set of brakes plumbed up to hyd clutch master cylinders and its all on a low level cert "visual inspection of my welds..." now i haven't got this fully pass'd yet as I haven't finished the truck, so ..... :roll:

If you can do it from ABS

you could be on a real winner! Save a hell of a lot of work!!

Cheers Reece

SupraLux · Post by **SupraLux** » Thu Jul 14, 2005 12:39 am

Just thinking about this and I would think DieselBoy is right. ABS only works when the brakes are applied, so why would the valve block have a pump in it? I think its just a valve that blocks one brake line, then slightly reduces the pressure in it so that wheel can spin again, then releases again allowing the pedal pressure to take over once more.

I had given this a lot of thought since the MU has ABS and I didn't want to have to totally re-plumb the brake system - but I just don't think its going to be any use at all so I probably will have to pull it.

Steve

Rotazuk · Post by **Rotazuk** » Thu Jul 14, 2005 6:59 am

As the abs system modulates the pressure to the brake , evedent when you jump on the brakes and the pedal rises and falls . If it only had master cylinder pressure everytime it dumped pressure the pedal would fall . It then re-applies the pressure ( lets say from the pedal pressure ) then it dumps pressure . More pedal travel , etc etc until you would run out of pedal , like you have a brake leak .

In when you are on the brakes in an abs car and you lock it up you feel the pedal rise and fall slightly quickly ,

Will see if I can find a good explanation on the net somewhere .

Chris

Heath · Post by **Heath** » Thu Jul 14, 2005 4:41 pm

The haultech system I read about in the Aus4wd mag sounds like what you want to make.

Heath

tristanp · Post by **tristanp** » Thu Jul 14, 2005 6:13 pm

http://auto.howstuffworks.com/anti-lock-brake1.htm

for good info on how it works