Hypothetical Brake Q (Kombi)

fatboy Disciple of Kol

603 posts · joined Nov 2002 · 16 Feb 2004, 10:22 pm

#140706

I've heard you can put commodore breaks on a Kombi - does this mean there is the possibility of ABS ?

" Captain Picard, why are there no Indians on the Enterprise ? Don't you need IT Support ? "

modulus Veteran Volks Folk

2,009 posts · joined Jul 2003 · 16 Feb 2004, 10:29 pm

#140708

Yes and no. Commodore rotors (and clones of these by companies like DBA) are often used in e.g. 4-wheel-disk conversions.

This, by itself, doesn't get you very far towards ABS. For ABS at the very least you need to measure the rotation speed of each wheel and compare it to some (independent?) measure of vehicle speed, then limit braking to each wheel independently.

Yes, there is the *possibility* of ABS. No, I'm not going to do it. Of course, you could always design it, install it, test it and write an article for
http://www.aussiekombicampers.com
😉

hth

Peter Hill
1975 Type 2 Double Cab
modulus.com.au

555bug WRX Bug Boy

1,123 posts · joined Aug 2002 · 17 Feb 2004, 2:04 am

#140755

simply yes, this was covered in one of the very first zoom mags. It works out just like a brake swap + the ABS unit, control bax and the funky sloted disks (behind the rotor) so the control unit can deternin if a wheel is locked up. Sounds like a fun project 🙂

vw54 Administrator Always Waiting 4 Friday

16,723 posts · joined Aug 2002 · 17 Feb 2004, 8:37 am

#140795

ABS would be nice to have on a 65 Beetle... then again the wiring would be a nightmare

I read it on FACEBOOK so it must be true

http://forums.aussieveedubbers.com/viewtopic.php?tid=91278&page=1#pid848630

http://forums.aussieveedubbers.com/viewtopic.php?tid=63561&page=1#pid624099

http://forums.aussieveedubbers.com/viewtopic.php?tid=4832&page=1#pid452603

http://forums.aussieveedubbers.com/viewtopic.php?tid=60650&page=1#pid574409

modulus Veteran Volks Folk

2,009 posts · joined Jul 2003 · 17 Feb 2004, 11:19 am

#140848

555bug wrote:... so the control unit can deternin if a wheel is locked up...

What happens when, as is quite common on wet or gravelled surfaces, you've got all four locked up? Where does the reference vehicle speed come from? The spare wheel?

?

Peter Hill
1975 Type 2 Double Cab
modulus.com.au

555bug WRX Bug Boy

1,123 posts · joined Aug 2002 · 17 Feb 2004, 11:49 am

#140867

to the best of my knowledge each whel is fitted with a disk with X nimber of slots cut into it. (very much like an optical hall effects distributor) as such the ABS control unit does not need to know the vehicles speed all it needs to know is that if the wheels were turning and you just hit the brakes and all of a sudden all four wheels have stopped then it will just reduce the breake fluid pressur until it get a signal from each corner again. I will dig out the article to double check these statements but I am pretty sure that this is how it works.

Purple Martin Fahrvergnugen

913 posts · joined Feb 2003 · 17 Feb 2004, 12:18 pm

#140877

So if I'm already stopped, and I put my foot on the brake, will it release the brake pressure until I start rolling? I think that's why modulus wants some other reference speed.

1959 red & white Beetle
1975 Kombi camper

fatboy Disciple of Kol

603 posts · joined Nov 2002 · 17 Feb 2004, 12:57 pm

#140895

If possible could you scan a copy of the article - I'd love to read it

cheers

" Captain Picard, why are there no Indians on the Enterprise ? Don't you need IT Support ? "

modulus Veteran Volks Folk

2,009 posts · joined Jul 2003 · 17 Feb 2004, 6:09 pm

#141010

The wheels can be skidding under braking without being locked up.

If my true road speed is 120 kph, and LF thinks it's doing 60 kph (skidding) and RF thinks it's doing 90 kph (skidding) and LR thinks it's doing 100 kph (slightly skidding) and RR thinks it's doing 0 kph (locked) -- who to believe?

One of the reasons for my curiosity about this is that the first ABS released in Australia were dead dangerous on gravel roads; they'd keep kicking back the brake until you speared off, as they would tolerate no skidding....

[Edited on 17-2-2004 by modulus]

Peter Hill
1975 Type 2 Double Cab
modulus.com.au

555bug WRX Bug Boy

1,123 posts · joined Aug 2002 · 17 Feb 2004, 9:06 pm

#141103

OK I have just read the article and it appears I was incorrect in regards to a vehicle speed sensor input. In my defence however the article is from the Feb/March edition 1997 Zoom. Anyway here is teh blurb:

A typical ABS unit is made up of a number of input sensors reading wheel speed, an Eletronic control unit (ECU) and a Hydraulic control unit (HCU).
The wheel speed sensors are usually inductive sensors, using a permanent magnet surrounding a wire coil. On four channel systems, sensors are used on all wheels. Triggering the sensor is a toothed ring ( called a tone wheel) attached to the wheel hub. In some systems a G-sensor is used to measure deceleration.

In the most sophisticated systems the ECU compares the wheel speeds of the two diagonally opposite wheels - say the front right and the rear left. From this it works out a reference speed and then compares the speeds of the other wheels. When a wheel starts rotating a lot slower that the reference speed (because it is starting to lock up) the HCU pulses the brake fluid pressure for that wheels circuit. This pulsing can vary in frequency between 4-10 times a second.

so there you go 🙂 do it and let us know how you went.

[Edited on 17-2-2004 by 555bug]