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sbwhart:
Nick

As a one off you could make a D bit chamfering tool, nice and cheap and effective.

Have fun

Stew

NickG:
Good point John, I have done it before but as you say, this is my biggest and (hopefully) best project so far so I will definitely finish it. It just seems like more work making another base but better than messing up the real thing!

One of the good things about Jan's design is, because the columns are a flat bottom and screwed up from underneath, there is a slight margin for adjustment with slotted holes which would be hidden by the column bases.

Another good point of using a dummy base is so that I can see the overall , what's the word? Not foot print, but the overall max. dimesions of the assembly as I always like to try and leave an even border around each side.

I feel a bit apprehensive about this one, but other people have got them running and I know the only issues could be the fit of the pistons so it's just fingers crossed time I guess.

Nick

NickG:
Oh yeah, why didn't I think of that seeing as we've been discussing D bits :doh: :bang:

Actually, haven't got any big enough silver steel though, only got 3/16" is any other steel hardenable?

Nick

NickG:
Made a little more progress tonight. I thought I’d better turn that awful looking bit of brass plate I’ve been staring at for the last month into something – the connecting rod.

Started by finding a drill that would suit the 7mm bearing. Found one just under and did a test drill. It was ok, a sliding fit but I would loctite it. The brass was bloody hard stuff though.

Milled it square, to width and to length:

Then marked it out a bit – well I knew what it meant! Incidentally this rod is 20mm longer than the drawings to account for my larger flywheel, slightly different design too.

Back into the mill to drill the holes while it’s a uniform shape and more rigid.

Wasting away the sides to give the narrow section:

I then flipped it flat in the vice and milled the radii making sure I wasn’t climb milling. Stupidly, I decided I’d take a lick off the end but because it was only gripped by the narrow centre section the mill tried to pull it upwards. :doh: :wack: I really do some silly things sometimes! Luckily I backed off straight away and was able to clamp it back straight in the vice. There is a tiny machine mark on the end now but nothing to worry about really.

Fitted to the piston and the bearing loctited in:

Another trial mockup, nothing is bolted down here but it seems pretty good and if I bolt the bits in the right place it will be very free running so that’s the first tick in the box.

It was really the first time I got to try the ‘pop’ test with the piston on the rod and something to pull on. The vacuum was more than I thought with the valve covering the port it took quite a bit of force to pull the piston out which resulted in quite a tuneful pop! So that made me a bit happier – ½ a tick in the box I reckon – don’t want to count my chickens!

Base, burner and brown stuff left to do! :ddb:

Nick

Stilldrillin:
That`s taking shape nicely Nick! :thumbup:

David D

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