Thursday, November 13, 2008

Fly Off Handbrake Conversion

One of the things I've been wanting to do for a while now is to fit a 'fly off' type handbrake. Obviously, there's nothing wrong with the standard arrangement, it's just that I prefer the way the 'fly off' type works.

So I started off by looking at the options. Early Spitfires came with this type of handbrake as standard, so I could get one of those or I could modify the one I had. I took a look at which illustrates how to convert an MG handbrake. In theory it's relatively straightforward to convert from one system to the other. The only difference is that on a normal handbrake the rod with the button attached connects above the pivot point on the pawl whilst on a 'fly off' it attaches below the pivot point.

With this in mind I took off the old handbrake to see if it would be possible to convert it. Unfortunately the Spitfire 1500 uses a linkage where the rod arrangement hooks around the pawl at the top and there isn't any way to change it.

With that in mind I set about looking for an early Spitfire handbrake. These seem to be impossible to get from my normal parts suppliers but Ebay turned up a nice but chronically overpriced example. With time of the essence I just spent the cash! A couple of days later I my neighbour came round with a package and I could finally see if it would fit!

At first glance it looked almost exactly the same as the Spitfire 1500 arrangement, the only difference being that the grip part on the 1500 goes up at a slight angle whilst the early one is straight. I thought I might be lucky enough to be able to do a straight swap but it was not to be! With the cable fitted nicely and everything else looking okay I realised that I couldn't seem to refit the pivot pin. I realised the problem was the ratchet part of the mechanism not being in quite the right position so I tried moving it about with a screwdriver and various other things with no luck. It then dawned on me that something was obviously wrong and it might not be possible to get the hole in the ratchet and the holes in the handbrake to align.

With this in mind I tried fitting just the ratchet on the pivot pin. It wasn't possible and I realised that something wasn't quite right! Comparing the two ratchet mechanisms showed up the problem.
Bizarrely, despite the fact that the two set ups are otherwise completely compatible, the hook part at the bottom on the older mechanism (on the left) is about 2mm longer than the same part of the newer mechanism (on the right). This ever so slight difference meant that the hole wouldn't line up right. After a few minutes with the Dremel I ground back the hook part to the same profile as the Spitfire 1500 one.

With that done, the rest of the assembly was straightforward with the only other slight problem being the pivot pin. On the Spitfire 1500 the pivot pin has a recess around it but, oddly, is retained by a clip that passes through a hole drilled close to the end. Sadly, the hole was drilled so close to the end that it had started to 'pull out', rendering it pretty much useless. Interestingly the older pivot pin was not drilled for a clip but still had the recess. An 'E clip' from my collection fitted securely and, apart from refitting the interior, the job was done.

I gave it a try and discovered something was not quite right. The pawl didn't seem to want to pull away from the ratchet. I greased up the mechanism but it made very little difference. It was then of course that I worked out that the handbrake didn't have a spring in it! Luckily for me the 1500 spring is a perfect fit!

There we go. With the interior back in it looks pretty good. I just need to make my mind up about what type of grip I want to fit and it'll be perfect! At the moment I'm torn between going for the early style grip, which looks more comfy, or the later style, which would keep my car looking standard. Maybe there's another car that has a grip that's even better? I'll keep my eyes out for something suitable!

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