managed to get some time in the workshop yesterday and actually started making something!
forgot to take many photos along the way but it was mostly only basic turning so nothing new.
original plan was to follow a Jan Ridders design, but due to parts availability things have changed somewhat and I designed it as I went along.
the glass displacer cylinder was cut last year by rotating on the lathe and using a dremel on the tool post to cut through and clean up.
first I cut out the base and top plates with a large hole cutter in the mill, these were then turned to size on the lathe to end up with these.
these are thicker then originally planned so i bored out the base to extend the displacer cylinder and give a 2mm thick base for quicker heating.
the top plate i left thick to allow attaching of parts, and the center hole is bigger then id have liked but there was already a threaded hole in the plate and once cleaned up it was 16mm diameter
working upwards i turned an old motor brush into a central bush for the top plate, ill center drill it later on the mill.
with the base done i moved onto POWER piston
im using a 12mm test tube for the power piston, which I managed to cleanly cut on the 3rd attempt, good job I ordered 10!
seems to be nice and cylindrical with only the top 2 mm being slightly smaller, the main part is fine.
so now the tricky bit of making the piston
first i chucked up a bit of plastic rod to use as a mandrel (its actually a pin from a large plastic chain) this i drilled and tapped 3mm
i then cut another bit of brush to rough shape and tapped it 3mm, mounted it on the mandrel and started turning.
high speed but slow light cuts was the order of the day, with lots of checking against the tube. i had planned on stopping a few thou oversize and polishing it to a perfect fit, but my last cut was a tad deeper then i wanted and it ended up slipping inside the tube easily
pulled it off the lathe to se what it was like, and was pleasantly surprised when it actually floated with the end of the tube blocked, and fell with it open
edit: just tried again and it slowly sinks with the ends sealed, takes about 8 seconds to go from top to bottom - might have to re do that
next up was the crank assembly, these bits i salvaged from a couple of old valve actuators from work, lots of shiny bits perfect for modding
to make all the cranks the same i made a holder from the bit of plastic and offset it. 5mm was the plan, but had to go to 7 to clear the central boss. hopefully the extra throw wont cause an issue.
with the part in the holder i secured it with a wood screw and carefully drilled it. worked well for 3 but the last one came loose and snapped my drill bit.
also the hole is so close to the gear teeth iv managed to break one tooth off
but ill live with that for the moment.
and that's about up to date. next job it the bearing blocks. i did make an attempt last night but they looked terrible so back to the drawing board for those. ideas anyone??
