Cheers Dave/Graham
Well, I've bin quietly making progress not as fast as I would like but progress nevertheless.
Next part the crank but before I can assemble the crank I need a couple of other parts first:- the eccentric sheaves and the bearings.
I had a bit of a false start with the sheaves it was my intension to have them as plain disc the straps being kept in place by adjoining bits but after I made them I realized there would be too much space between the parts and some of the part wouldn't have a smooth face so they would catch, so decided to make the sheaves edged so that the straps would be retained. I also went about making them a different way to the method I've used in the past I've got more confident with the mill so decided to use the mill to drill the off set hole.
First turn a chunk of bar up to the required diameter and put a small centre drill in it.
The retaining the bar in the chuck transfer it over to the mill centre it under the quill.
Zero the dials and off set the table and drill the hole right through the bar, I drilled it letter U to allow a final clean up with a 3/8" hand reamer.
Then back to the lathe and machine the groove for the straps using a parting tool, then part off to length.
Face to length using the back stop in the chuck.
Then drill and tap M2 one thing a learnt from the first attempt was that the taps are to short to get through the thicker section of the sheaf as drawn, (broke a tap) so for these I tapped through the thinner section.
Next bit the bearing no pic of this as they are simple enough.
The crank shaft is fabricated
So to make the crank shaft webs.
Again I changes my method to take advantage of the accuracy of my mill.
Cut a chunk of plate and milled it to size enough to make all four webs.
Than onto the mill drill four evenly spaced holes down one side again letter U move the table over to give the correct throw and drill down the other side
Bring to size with hand reamer.
Cut off with a slitting saw
Then with a couple of same size bars in the holes, mill thickness to size.
Turn up a 3/8" mandrel with a M8 nut and in the lathe radius the ends.
Thats them done.
Now for the crank shaft journals:- first with the bits roughly assembled check the main journal length cut it off the bar then in the lathe face of centre, and turn and thread both ends.
Cut off and face the crank journals to size.
Now to stick the crank shaft together with high strength loctite, its important not to rush this and to do it in stages letting the loctite cure between stages.
Stage one glue the crank journals to the webs using spacers, the main shaft is there just to keep everything lined up.
Stage two glue one of the crank journals to the main shaft the correct distance from the end. (no Pic)
Stage Three glue the remaining crank journal to the main shaft 90 deg to the first at the correct distance. Using 1*2*3 block:-not forgetting to assemble the sheaves and the bearings in-between first.
Next as I keep my trousers up with a belt and brasses, pin the cranks in place, I just put the pins 1/2 way through that will be enough to stop things slipping, but as an insurance against having to break the crank down to change something one of the pins a drilled all the way through so that I can nock the pin out and take the crank apart to get at the sheaves and bearing.
Cut the bit out of the middle you don't want
And her we have it finished in the housings its turns over nice and free
Stew
