By Jason Ballamy 
Part eleven - ignition
M4. C4n

The Governor latch that engages in the small block I showed last time is cut from a lump of 3/8" steel which was marked out as a guide though I used the DRO to get the actual positions.

The straight bits were easy enough but to ensure the curves met the round pivot boss correctly I used the spinning button method - when the edge of the tool touches the button it turns and you know you are in the right place.
Then onto the rotary table to form the raised boss and round the outside.
And this is the finished part as the drawings would have it.
But as its a casting I spent a while with files taking off the edges to get it more like ones I have seen in photos. Also got the spring post and back lever in this shot.
The ignitor body is another bronze casting, I started by turning the outside dia to the finished size of 1.187"
Then the oblong boss was tidied up and the holes added. It could have done with a bit more metal to play with but nothing that could not be got around.
A small piece of brass was soldered on to form the lug for one of the stop screws.
The inner face was then turned to bring the flange to thickness and the spigot formed.
A couple of holes were tapped on the outside to take the spring pins and stop screw. The trip stop and shaft can also be seen in this shot.
The trip is a tricky little thing to make. Most was worked on the end of a bar using the rotary table.
The ignitor needs a tapered spring winding so I started by making a mandrel.
Then wound the music wire spring onto the mandrel.
Then a quick bit of work with some pliers and the spring is done
The other bits are quite straight forward so I won't cover them here, other than to say that I use 3/32" TIG electrode for the contacts on the hammer and anvil to reduce the erosion caused by the spark. This is the finished item on the engine.