Trigger wheel pt.1.

In the last post, I wrote that I needed to attach the trigger wheel to the crank somehow in order for it to be able to be used to fire the ignition system. The logical place to attach this to is the crankshaft damper. This is a big lump of nodular iron that is attached to the front of the crank with the aim of contributing to (1) the balance of the engine, (2) the flywheel effect and (3) damping the effects of the crank's turning the up-and-down motion of the pistons into rotational motion.

The 'easy' option is to bolt it to the front of the damper, but the problem here is that the bottom pulley attaches to the damper. That's OK, but anything the belts touch (alternator, water pump, power steering) would need spacing forward 5mm (the thickness of the steel of the trigger wheel), which is a pain. My solution to this is to turn a register in the damper and attach the trigger wheel that way. I am aiming for an interference fit, so I'll have to cut the register pretty accurately (within a thou or so) I think. I reckon to be having to put the damper in the freezer and the timing ring in the oven to get the two things to mate together.

Probably some of you are thinking about the consequences of attaching the timing wheel now on the timing. So basically the question is "how do you know where TDC on pot one is without the engine together?" Well, I don't. I could build the engine up and do this prior to balancing (and I may yet do), but with the software the Emerald ECU runs, you can supply an offset. So perhaps I position the timing wheel 90Deg from where it should be, I can correct this out in the software.

So, in terms of pics, here we are - the damper mounted in the four jaw on the lathe:

On the four jaw chuck, the jaws move independently of one another.This means you can set jobs up in the lathe with great accuracy. You can see the dial gauge mounted on the cross slide here. It took a while, but the damper spins in the chuck with less than 1 thou run out. That's pretty true.

Unfortunately my digital vernier let me down. It was a cheapie, and it was a bit old, so I got what I deserved - cheap tools always let you down when you want them. This meant I couldn't complete the cutting of the register because I can't measure with anything like enough accuracy how much to take off.

Here's the cut so far:

Lots to go. Here's a pic with the trigger wheel:

There's a slight risk in the way I'm doing this. That ring you can see outside the bolt holes on the crank damper is a ring of rubber that's bonded to either half of the damper. Obviously the wheel will be able to move fractionally. However, I'm betting that in real life, this makes sod all difference.

Got some more inspiration for the Enfield: http://vimeo.com/30586946. Cheers Jim.