Another couple of hours shop time snatched and I managed to get a fair bit done.
This bit was done the other day, but I couldn't progress any further until it was done. I had already mentioned about removing the kick start system. The last part of that job was to make up a spacer and dress the gear lever for a nice close fit to the outer case.
Now the gear lever is out of the way, I could now get the two original bits machined to a finished state.
I used the mandrel that I made the nut with, and mounted the nut onto the RT. I then centred the machine quill up to the nut spigot, using a shortened arm that I had knocked up for my centring DTI. It worked a treat, and it now allows me a little more room to play with on the mill throat depth. The Y axis was then locked up solid.
I could have made this slot using a slitting saw, but if I have the chance, I will always choose an end mill (or slot drill). Me and slitting saws just don't seem to get on well together.
By taking steady cuts in the X axis gave me a nice 3/32" slot, plus a couple of thou clearance, because invariably, the cutter cuts the slot slightly oversize.
Slot cut, now for the bit to go inside it.
This was the easiest way for me to hold the part and to guarantee that each side will be exactly 180 degs apart.
Because of the amount sticking out, I couldn't guarantee that each side to be machined would be at the same height, so I treated each side as a new cut, and touched on first then cut down the required depth. I ended up with a blade spot on 3/32" width, and exactly on centre.
I used a high speed cutter with a 1mm rad on the edge, this reduced the stress on the joint between the blade and the spindle. If it was a sharp cut edge, it would be liable to fracture at that point.
The two parts fitted together just nice, with a couple of thou running clearance. You can just see the rad produced by the cutter at the blade/shaft transition.
Again, I was stopped from continuing any further with the tacho drive because there was another repair to be carried out.
Whoever had converted this standard engine to a racing one had done a bodge job on the crankshaft.
To reduce the swept volume of the crankcase, it is standard practice to fill in the sides of the cast crank webs. They had just bodged on round ali plates. The problem was that when the engine started to reach top revs, the unsupported areas of the ali discs started to 'fly' by themselves and rub on the inside of the crankcase. So I have come up with a repair scheme.
I prised out the loose areas of disc and gave them a good clean up. Then they were given a coat on the inside, and all over the outside edges with JB Weld, a metal filled epoxy resin.
Hopefully, when that is fully cured, I will be able to machine it back and end up with a pair of well bonded in discs.
Just got to wait now before I can continue.
Bogs
