Another Adventure in Hot Air

I've made a bit of progress in the last day or two.

I decided to make the displacer rod bush from two pieces so it would screw in right up to the shoulder - seems a nice fit for some 3mm drill rod. The water jacket was a troublesome. Getting it lined up and soldered wasn't too difficult but tracking down some tiny leaks was - it took another three visits to the flame to solve! If I do it again I'lll use one of those small 'Humbrol' paint tins instead of fabricating from scratch.

I made the power cylinder from two pieces of brass as well, soldered them up then did some lapping.

Made the bucket-type piston from cast iron (a bit more of the pig recovered from the local canal!) as I didn't have any suitable aluminium. Seems to be a nice fit but I could have made the walls thinner I guess. Also drilled the cross hole for the writ pin.

Finally I sprayed up the water jacket in matt black. Here it is with the hot end still masked up until the paint cures and some long temporary screws in the water connections.

Made the crank disk for the power side, sawed and filed the base-plate and the attachment upright to size then spent most of today piddling about with clearance holes and screws to make sure surfaces mate together nicely. Found a suitable piece of steel tube (from an old Ikea table!) to make the water tank from and completed enough of the plan at the flywheel end of things to allow those parts to be made.

It's getting there, nice to see it coming together, what are you making the water tank from?

Quote from: Sanjay F...what are you making the water tank from?

Rest your eyes Sanjay!  (see above). Should be using brass or stainless but I don't have either.

Quote from: PaulR

Quote from: Sanjay F...what are you making the water tank from?

Rest your eyes Sanjay!  (see above). Should be using brass or stainless but I don't have either.

Oh yeah! Definitely too long in the workshop today - I knew it had to be something you fashioned from something else; hope you haven't ended up with a 3-legged table! 

Quote from: Sanjay FI knew it had to be something you fashioned from something else; hope you haven't ended up with a 3-legged table! 

Nah, it was used by the kids for doing homework so it's long gone but with amazing foresight I knew I'd need the legs to make water tanks 

Decided to change the way in which the parts would be attached to the bed-plate, lifting things a bit to allow for a slightly larger flywheel. It would have been a whole lot easier to have made the entire frame from a single block although I'm not sure I would have been able to hold it for the various machining operations with my little lathe.

Look, there's one of the 'Red Arrows' 

Looking good Paul, although you are fitting a water jacket for cooling  I think I would still try to fit a heat resistent gasket  between the displacer chamber and mounting plate if possible.
Andy

Quote from: Spinner21Looking good Paul, although you are fitting a water jacket for cooling  I think I would still try to fit a heat resistent gasket  between the displacer chamber and mounting plate if possible.

Thanks Andy. Yes I'm trying to find something suitable but ideally it would need to be <1mm thick so the projecting part of the displacer tube still locates in the hole to keep things square and air-tight.

Made the standards/fixing plate and bearings, roughed out the second crank disk and just about got the tube to length for the water tank. I'll probably reuse a flywheel from one of the previous failures, other than that it's connecting rods and fiddly washers next.

Decided to reuse a flywheel but it was previously on a 4mm shaft whereas this one is 3mm so made a threaded 6mm plug, faced it both sides then drilled/reamed it to 3mm. Forgot that this would also block off the radial hole used to secure it to the shaft ( ) so I had to plug that as well then make another further round the rim. also had to reduce the diameter by about 1.5mm - that chatter while mounter on a 3mm mandrell was horrible until I used a wooden pad and live centre to remove any wobble.

Sprayed up the standards with some primer and since I can't do much else until that's dry, drilled and tapped some holes for connections on the water tank. If I understand correctly, the water itself will actually circulate, not just transmit/dissipate the heat and it's best to have a bit of a head above the top connection and the bottom one as low as possible. I've seen some where the connections are angled towards the engine rather than perpendicular to the tank presumably to eliminate the chance of any bubbles forming(??). Either way, it would be a lot harder to make like that and probably wouldn't make much difference.

Quote from: PaulRDecided to reuse a flywheel but it was previously on a 4mm shaft whereas this one is 3mm so made a threaded 6mm plug, faced it both sides then drilled/reamed it to 3mm. Forgot that this would also block off the radial hole used to secure it to the shaft ( ) so I had to plug that as well then make another further round the rim. also had to reduce the diameter by about 1.5mm - that chatter while mounter on a 3mm mandrell was horrible until I used a wooden pad and live centre to remove any wobble.

The joys of recycling! You've done well to reuse the flywheel; my scrap box if full of oddments which I hope to reuse in future ........and it's getting bigger! 

Quote from: Sanjay F...my scrap box if full of oddments which I hope to reuse in future ........and it's getting bigger!

It's always my first port of call and I save the tiddliest little bits

I thought it would be easy to soft solder a thin piece of steel sheet to seal the bottom of the water tank. Wrong. I tried three times but just couldn't get the solder to run properly. In the end I cleaned off most of it, flipped the sheet over and silver soldered instead which went fine. I don't know why the soft solder didn't work; I have two types, one "best for plumbing" and the other "best for electronics" but I obviously need the "best for incompetents" version 

This is how things stands at the minute - there's an awful lot of metal in the middle bit again, I hope it doesn't hold too much heat...

Quote from: PaulRI thought it would be easy to soft solder a thin piece of steel sheet to seal the bottom of the water tank. Wrong. I tried three times but just couldn't get the solder to run properly.

Steel can be soft-soldered, but there are (at least) two important conditions.

* The steel must be clean. Some plating will work and some will interfere. In either case dirt, rust, or other crud will cause problems.

* An aggressive flux is needed. Typically something like zinc chloride (Ruby Fluid is one brand). Electronic solder with a rosin core will usually not work.

Pre-tinning the parts, perhaps with considerable scrubbing action, will often help.

Gene