Fitting the Handbrake

Today I had one aim. I was going to complete one system on the car, I was going to get one entire system finished and operational so that I could say I had completed something and that the build was progressing, just one system. (Dammit Tim has already got the engine in on his Fireblade Fury!).

And that system was going to be?........ The handbrake :-)

The handbrake operates via single Willwood mechanical calliper which bites onto the reverse ring gear on the diff unit. So this meant that the diff had to be rebuilt back into the car. I'd fully cleaned it up, lubbricated and reassembled it back into the carrier last night. So it was ready to be plonked into the car. It's a two man job so enter my willing assistant Duncan.

Before you can mount the diff you have to remove the driveshafts and the easiest way to do this is to remove the camber adjusters from the top joints on the rear suspension wishbones and pull the wheels out like this.

For some reason I think this picture is rather comical, either the car is a "she" and this is a strangely "take me now" moment, or it's only halfway through it's transformation into a "Back To The future" style hover car.



The brick BTW is the current handbrake mechanism, you jam it under a wheel to stop the car rolling.

The diff is mounted in the car using a series of m10 bolts, mounting plates and spacers, it's a bit of a jigsaw really, and after about an hour of finger trapping, diff shuffling, swearing and bracket fitting madness we decided that next time it would be a really really good idea to make a drawing of the installation before removing it :-).

Still it was in now and the lesson was well and truly learned. Erm "what about the drive chain?" says Dunc. B*gger! So another 10 mins of repeat faffing follows and we get the drive chain in place and the diff bolted up for a second time. Incidentally wherever possible we used new bolts and nylocks as the old ones were a bit "munged." (technical engineering term)

Right, so now we are ready to fit the handbrake calliper

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The calliper is fitted onto the side of the diff carrier using this bracket

The width of the calliper jaws are controlled by two machined spacers, one of which needed to be removed, (in the picture below I've already removed it.)

Here lay the first challenge of the day, the clamp bolts are cap head bolds and take an Allen key of some uncertain imperial size. Certainly none of the standard metric or imperial Allen keys I posses fitted (And I've got more than a few!) Fortunately I managed to get the things apart to remove the spacer and trial fit the calliper to the Diff, but the bolts will need to be changed, because at the moment I can't tighten them up. They've got to be something really odd like 13/32nds

So it was time to bolt up the calliper to the diff, connect the handbrake cable, and hey presto a complete working system.... and I can get rid of the brick!

er No!

As can be seen from the two pictures below (which were taken later without the mounting bracket because I forgot to take them at the time) the mounting bolts on the calliper foul the drive chain!. I'm going to need some bolts with very thin or countersunk heads to mount the calliper and avoid fouling the chain. So the handbrake isn't going to get completed today :-(




The other thing that became apparent is that the actuating lever will foul the mounting bracket and needs to be bent away from the calliper slightly, so I removed it, mounted it in a vice and gave it a solid biff with a hammer...... PING! Bejeezuz it's like Bagdad in here! There's a bit of shrapnel flying all around the garage in true cartoon style..... Ping, bing, , rattle.. the broken bit of lever is really doing the rounds. Duncan an I are protecting our eyes and trying to track the broken bit of lever with our ears so we can retrieve it from my clinically clean garage floor.

The lever must have been hardened to be as brittle as that, but with the broken bit retrieved I'm fairly certain that I can weld the two halves together and at the appropriate angle so it's not the major disaster it first appeared to be. We've run out of time, patience and body heat now (it's bloomin cold) and so the wheels go back on car and she gets put away.

Another weekend has passed without major progress being made.

After Sunday tea I had a brainwave..... I'm sure I have a picture of the calliper's installation that was taken when Tim was first building the car, a bit of digging around locates it and here it is. It's not very clear I'm afraid, but it appears to show that the calliper mounting bolts are not standard Cap or Hex heads and that the calliper has been machined a bit, or Mr Sparky angle grinder has been having some fun to relieve the bolt mount faces.


For those that are interested here's a shot of the Willwood calliper's components. Left most is the fixed side of the calliper, the pad is permanently fixed to it's inside face. On the right is the other side of the calliper which houses the actuating mechanism and moving pad. The (now two part) lever is hinged at the right hand side using the bright hinge pin in the calliper, and has a cam section just to the left of the hinge hole. The operating cable attaches to the left hand end via one of the two mounting holes.
The small "bullet" shaped piece of steel passes through the centre hole of the mechanism side and is moved by the cam in the lever. The bullet operates on the steel back plate of the moving pad, which in turn bites into the brake disk surface. The bullet and operating lever are "pinched" by a threaded stud at the rear of the mechanism to allow the pad to float the correct distance above the disk.