So, after Silverstone I had a couple of problems to fix. However, I remembered that I didn’t write up what I did before that race. Most importantly was that I modified the seat slightly so that I sit ever so slightly more upright. I think that I’m a bit too laid back and it makes my neck hurt over the length of the race. So, I thickened the top of the seat very slightly. It certainly seemed to do the trick at Silverstone but we’ll see a bit more in the long run.
As you can see, I’m running short of red gaffer tape…
The other thing I did was to add a small amount of ducting to the oil cooler to attempt to control temperatures a bit better. This did seem to do something at Silverstone which was a pretty warm day. However, I noticed (and I think I would have noticed this before) that the bonnet above the exhaust headers was getting very hot and soft, I presume because the ducting has changed where the air goes under the bonnet.
However, when I started stripping the car to take the engine out to have a look at the gearbox I was starting to worry about the amount of grot around the engine compartment. I had noticed, as I think I mentioned, what I thought was oil coming from the right front damper. However, after looking hard at the whole area I think it’s possible that the oil cooler is leaking and this is spraying the underside of the bonnet with a fine mist of oil. So, in order to test this I’ve taken the oil cooler out entirely and just tried to clean up as well as I can. Time will tell, assuming I can make the car go properly, whether this is a sensible strategy.
So, the important thing was to have a look at the gearbox. Of course, this involves taking the engine out. I have to admit that I’m seriously cheesed off with taking this car to bits and putting it back together again. I’m not sure why, perhaps it’s some sort of late middle age crisis…
With the engine on the bench I started taking it all to bits. Although I was only aiming to get at the gearbox to do this you have to split the engine casing in two, the split line going through the centre of the main bearings and the gearbox shafts. Hence, it’s a pretty detailed job. I’ve done this to ‘blade engines twice in the past, but I’ve never actually reassembled one and then run it again. Still, it’s well within my capabilities but did need some careful thought.
With the sump off I could see the gearbox and the change mechanism. To be honest at this point it didn’t look at all bad, so I was starting to wonder what the problem was.
Pressing on I eventually got the gearbox completely exposed. It still didn’t look awful although it was clear, squinting down the gaps between the gears, that the dogs weren’t in perfect condition. It would have been surprising if they were, though.
What I did at this point was to completely replace the mainshaft with one I took from the engine I set fire to. I then went through every single component on the countershaft (and there’s a lot of bits) and selected what seemed to be the best one in each case. I couldn’t just use the entire old countershaft as it includes the output sprocket drive, which was of course where the propshaft fell off from and it’s been a little bashed up.
However in all of that I didn’t really find a large problem. The only two small things that I did see were:
The shift drum had a very small dinge on the edge of one of the selector fork tracks. Problem is, this particular track isn’t concerned with 3rd/4th gear which was where my problems were. You can see the little mark on the top of the track in the photo on the left.
The other issue was in the escapement on the end of the gearshift rod. One side of this was quite worn, you can probably see it in the photo on the right, especially if you click through to the full size version.
So, I replaced those two parts with other ones from the large collection of bits that I’ve got from other engines that I’ve blown up over the years.
With that done, I reassembled the engine (which sounds quite trivial) and eventually put it back in the chassis. I’ve now finished connecting the electrics, inlet, exhaust, cooling etc. I’ll go out tomorrow and buy some new oil for it and see if it still goes.
This doesn’t really explain why I had the problems that I did have at Silverstone. However, in putting the engine back in the chassis I realised that something was slightly awry in the gearchange itself in that one of the rods was binding, very slightly, on the scuttle. I’ve fixed this now but I wouldn’t be surprised if that could have had an effect. Perhaps I needn’t have taken the engine out at all? To be honest, this is a potential problem with my gearchange which has a moving rod that goes through the scuttle. The scuttle is supposed to be sealed (although heaven knows why as it’s made out of rather flammable GRP) and scrutes have complained in the past about being able to see 0.5mm of daylight around the gearchange rod. Perhaps I should change the gearchange to a cable one, even though I really dislike the push/pull cables.