That Electric Park Brake Again

[oldtimer]

Hi Mike and All,
Ever since I've owned an S type I wondered how the electric hand brake worked, the mechanical bit that is. After all it is only a winch of some sort! I recently visited my local village garage and noticed a complete electric handbrake assembly complete with cables about to be thrown into the skip. This I retrieved to my workshop, so today, too cold for the garage so into the workshop and a bit of peace and quiet to look at this. I better mention that it was discarded from a Renault. No matter, I wanted to discover how an electric motor converted rotory motion into a linear or pulling action on two brake cables.

In this case the whole assembly is contained in an oblong box. After not too long the contents are spread across the bench to reveal three main elements, these being :-
a) The winch, (a photo would save a thousand words). This is best descibed as a garden fence wire tentioner. You know the sort of thing, a barrel with a bolt in each end. The bolts have an eye for the attachment of the fence wire. Rotate the barrel and tighten the wire. The barrel in question is made of brass and the bolt has a ACME thread (square section thread)screwed into the barrell. Some fancy attachments are used to secure the brake cables to either end. Rotate the barrel in either direction to apply or release the hand brake.
b) The small electric motor rotates the winch barrel via a train of eight plastic straight cut gear wheels the last of which has the winch barrel passing through it's centre.
c) Finally the dreaded PCB (printed circuit board) This is about 12x2 inches long covered in gizmo's which I have no idea what they are.!
Conclusions.
1) I'll put money on it that the principal of operation is the same as the Jaguar one
2)The threaded bolt was screwed into the barrel solid.It took a while to realise that there was a threaded bolt. I put the barrel into the vice and forced the end of the bolt with a molegrip.
3)Bearing in mind that I received it as it came off the vehicle. One has to ask,what switches the motor off when the hand brake is fully on. Answer, the electronics read the electrical load and says that's your lot and swithes off - cos I haven't found any micro switches.
4) I'm inclined to think that the brake pads were excessively worn allowing the winch bolt to bottom out and jam in that position.
5)This appears to be a well made unit with no ingress of water or any sign or smell of burning.
6)Tomorrow I want to run the motor cos I'm sure it's OK.If I had the time and inclination I would like to reassemble the unit and fit it to offending vehicle just to see.
All I need now is somebody to supply me with a dead Jaguar unit to see what it is all about.
I agree with your comment of several months ago what the Devil do we want an electric hand brake for anyway.
Tis pasted my bedtime10.50hrs
Goodnight Oldtimer

[J44EAG]

As I understand it, Phil, the Jaguar unit has gears of some sort which have a tendency to break if a car is allowed to spin its wheels on ice. The unit receives signals which try to put the unit into an on and off state at the same time. End result is a breakage.

Agree we need to lay our hands on an old unit to fully understand its operation.

The bottom line is with these units is that bust means bust as there are no rebuild parts available.

Mike

[oldtimer]

Hi Mike,
Thanks for the reply, you say that bust means bust. OK but did you understand my explanation of how the unit works, if so, would you accept that the Jaguar item(the mechanical bit) is most likely identical in concept?
I'm trying to understand how the thing works. Mechanical and electrical things I can work out but I don't have a clue when it comes to electronics.

Today I extracted the electric motor and it operated perfectly in both directions.
So far I have established that the electric motor is OK, that the plastic gear train is as new.
And the winch device that hauls in and releases the hand brake cables works well.

So, setting the printed circuit board aside complete with the muli pin socket containing twenty three pins of various sizes I would be content to sign a certificate of release and declare this unit
fit for further service.

This Renault unit contains the electronics inside the casing

Question
Are the electronics for the Jaguar unit inside or a seperate module located elswhere?

If the answer is that the electronics are contained in a module elswhere, then based on the example I have in front of me, then bust does not mean bust.

To digress for a moment. I have read about hand brake problems to often and the huge cost of often unsuccesful rectification. This is a cost that I could not justify or if I'm honest want afford. My objective is to try and understand the workings of the system before attempting to analys the problem. This is for my benifit and at the same time share my findings with others but I do
wonder if I'm wasting my time !

Now, where was I

There are a couple of other interesting elements that I discovered today, I'll save that as it is getting close to my bedtime
Oldtimer

PS Mike I noticed you where burning the midnight oil last night, I can't manage that any more

[Martec]

Hi, whilst on ebay looking for throttle bodies and throttle pedals I also noticed on 'JoJags' site an electronic handbrake for an S type with a photo, it may show the bits you are interested/comparing to.

Brian

[J44EAG]

Hello Phil.

Difficult to say really whether concepts for electronic hand brakes of Renault and Jaguar are different, similar or the same without seeing both units dismantled on the bench, side by side.

I do believe the module is separate but to confirm, I`ll have to do some research as the electronic unit does not figure in the early Technicians overview publications. However I recall that the mechanism may have appeared in a later technical manual which I think I may have a copy of. I`m away from base at present so will have a look upon my return.

Dave Marks covered the electronic handbrake at the last Seminar but I missed that part of the day due to being outside getting a tyre fixed.

Back on this subject as soon as I can.

Mike

[oldtimer]

Hi Mike,
You are quite right, until we have the two units to compare it really is all guess work. If I had found a Jaguar unit in the first place we would not be having this daft conversation.Never the less I feel that I moved a short way up the learning curve.

I guess we need a friendly scrap dealer or what ever they are called these days so that we could examine /tear off panels look in and under as required. I would love one at the bottom of the garden. Could you imagine, her indoors would go hysterical.!**?

Mean while look forward to your return to base

Oldtimer

[J44EAG]

I`ll try and get an old one for examination.

Mike