Sprocket to me

It’s another of those three steps forward, two back posts. Actually, I don’t know how many back it is really.

First, though, the forward bits. Most importantly, the chassis is now back home again. As you can see, I took the trailer off back up to Soham and collected it. To be honest it isn’t a fantastic job, but it’s good enough. It’s not quite the shade of grey that I was after either, but that’s no big deal. Mind you, I wonder if I want to make the roll cage a different colour from this? In which case, I wonder if it’s possible to paint on top of powder coating? Seems possible that it’s not.

In addition to the chassis itself, I got this big pile of suspension and engine mounting bits. The coaters were not as good as they said about keeping the coating out of the threads, and in one case they’ve got it in the threads and not on the housing around the threads. But, it’ll do. I’ll soon get along to fitting all these parts to the car.

In the meantime, I wanted to finish off the diff carrier. Last time, I said I was a bit concerned about getting the bearings on to the diff journals. After much discussion and thought, I decided to actually have a go at pulling a bearing onto one of the journals. So, using a long M10 stud righ through the middle of the diff and a little dolly I made on the lathe, I had a go. To my delight it pulled in without any great drama. I stopped after a few millimetres because I didn’t want to make getting it off too difficult, which is the state it’s in the photo. However, it was clear that this wasn’t going to be too big a problem.

So, I finished off the various bits for the diff carrier plates. Here’s the first of them here. This is the outer side of the plate and you can see the bearing in situ and the holes that allow access to the bolts that retain the sprocket on the diff.

That looked as though it was going to work so I took the plates apart and pulled the bearings onto the diff with the inner bearing carriers in place. I could then bolt the plates and the outer bearing carriers in over the top of the bearings and I ended up with the whole lot as one piece. As I started drawing this months and months ago, before I got the chassis from Jeremy, this is rather a relief.

At that point I went into a bit of a decline.

I thought I’d try fitting one of the sprockets I bought ages ago to this lot. The plan, if you’ve been paying attention, was to split these sprockets so that I could bolt them to  the diff without taking the whole lot apart. In fact, putting the complete diff carrier together was a deliberate experiment on my part to see if this whole process was going to work.

First, though, I needed to cut one of the sprockets in two. So, with a new blade in the hacksaw frame I did this carefully and then proceeded to bolt it to the diff.

And then I noticed this.

On one side of the diff the gap between the two halves of the sprocket is considerably larger than on the other side, as you can see in the two photos above. Clearly, this can’t happen, as the sprocket should be registered on the mounting points on the diff flange. There’s something screwy about this that I don’t understand at the moment. One possible problem is that the mounting  holes in the diff are specified at 27/64″ with a 14mm registration dowel in two of them. (I’m not making this up…) I’ve got an M10 screw (not even a bolt at the moment) in the 27/64″ holes. That means that there’s 0.7mm of a gap at the side of the bolt. All the same, I thought that the whole thing was put into registration by running up against the body of the diff itself. In fact, there seemed precious little slop when I put it together. The hole size is very strange though. The largest imperial size that’s going to go through it is 3/8″ which leaves even more clearance than the M10 one.

Hmm, I’ll need to think about this. What I’ve got at the moment is clearly unacceptable.