Hmm, I think I’ve found a bit of a problem, which might just explain the problems I’ve been having with the new engine.
After the first outing at Snetterton I’d noticed that the chain had needed adjusting quite a lot. That seemed a bit odd but I didn’t think too much about it. However, I’d noticed that the same thing applied after the Silverstone race. At first I was wondering why the chain was stretching so much, or perhaps the sprocket was moving slightly. However, I think I’ve found the problem…
While looking at the sprocket I noticed rather a lot of wear. You can see the issue in the photo at the top of the page. On the left is the sprocket I took off the car today, and on the right is a new one ostensibly of the same size. You can see how the aluminium has been pushed aside from the chain lands into a quite appreciable mountain of aluminium.
What’s more, the same applies to the drive sprocket although is steel! Here’s a similar photo of those.
The thing is, why is this happening? I strongly suspect that when fitting the new engine I’ve got the sprocket alignment slightly wrong. The worst of the wear is one just one side of the driven sprocket which I think is caused by the chain pulling essentially on the corner of the chain lands.
The problem is, there are a number of directions in which the misalignment could apply. The most likely one is that the engine is just translated slightly left or right compared to where the ’07 engine was. As I had to m0ve the engine in this direction to make the sprockets “line up” that would be unsurprising. There are at least two other degrees of freedom though, equating to sprocket rotation about the vertical and longitudinal axes. It’s easy to measure the first one and ther sprockets are within 0.2° of each other. I need to think how to check the other direction though…
Hmm, I suspect this is going to make getting to the next race rather difficult…
While I’m here, here’s the complete (!) video of my race at Silverstone. Listen carefully to see if you hear the sprockets wearing:
Oh dear, the engine swap seems to have thrown more problems. though i guess you’ll get em sorted.
as for your sprocket issues, is your chain too tight? you should be able to lift it off off the rear sprocket, a little A few links from where it leaves the sprocket. with the diff being fixed you can run tighter than on a bike, but still need slack. As for alignment if the sprockets are out the chain will be running on the side of the teeth. Giving tell tale wear marks. the best way to line them up is with a straight edge, you may need to make spacers if things are in the way.
Good luck, and hope you manage to sort things and make the next race.
Indeed. Does make you wonder why I changed it in the first place, doesn’t it?
The chain’s not too tight, although I have been wondering if the relatively short chain run makes alignment more critical. I suspect (I need to do more checking) that the rear sprocket is just translated a mm or so to the right with respect to the engine sprocket. That would certainly fit with the wear on the teeth (the little pile of aluminium is only on one side of the sprocket.
I think I’ll miss the next race anyway, just to give myself a breather… 🙂
just had another thought. check if the sprocket is running true, especially before using it for alignment. maybe a spacer will fix it.
In fact it’s a new sprocket. The old one is too munged to use as the damaged teeth mean that you can’t run a flat edge on it anyway. The new sprocket sits flat on a known flat surface so I reckon it’s OK. (Crosses fingers…)