A wee bit of hot air

My smallest, and newest, it has a 3/8" cast iron piston, in a cast iron cyinder with a stroke of 1/2". The main crank shaft bearings, and the big end bearings are ball races from VHS recorders. The main bearing on the beam, and the little end bearings are plain bronze, the shafts at these places are the rollers out of needle roller bearings 3/32" dia. The displacer cylinder is made from the steel casing of a AA size Nicad battery. The motor is mounted to its base via a 1' dia rubber shock mounting, it can be unscrewed and mounted directly on a camera tripod for experimenting with solar heating.

Nicely done, Ian

A splendid mix of old and new !

MichaelG.

Nice work there, and some clever recycling.

Well done.

V8Eng, Its all recycled, The cold end of the displacer cylinder is made from an aluminium door stop. The 4 rods that hold the crankshaft are tubular spacers out of some old radio gear. The piston was turned up out of a bit sawn out of an old automotive flywheel. The brass bit is from a 12" length of 1" sq that I won from a friend for a job done (I did not ask where it came from). The black raised disk on the base, is a washer from the through bolts on a large wooden cable drum, The 6 x 5/8" through bolts will come in handy some time, they are about 3' long with about 1" of whitworth thread on each end. Ian S C

Wow, that's great stuff.

I usually go to the annual hot air engines gathering at Kew in the UK, the ingenuity of people such as yourself in building the variants of these always impresses.

Edited By V8Eng on 31/07/2012 11:03:01

The main thing I like about these little, and the not so little motors is that I design them as I go, around what ever materials I can find, I don't call them models, they are not copied/ scaled from a prototype. I'v had very few complete failures, the notable one being aFluidine pump as designed by Dr Colin West.

Ian S C

Lovely little engine, Ian.

What did you use for a displacer inside the AA battery casing?

Will a AAA battery casing work, or is it too small?

Hopper

Hi Hopper, I'v forgotten what I used for the displacer, its out in the workshop, I'll have a look tomorrow. Ian S C

I like that Ian, it has the look of an old laboratory balance.

I won't ask what happens to the inside of the nicad

Neil

Hopper, the displacer started its life as a bit of rebar, bored out, and turned down to 11.25 mm, the hot end is a steel disc brazed in, cold end aluminium loctited in, that size leaves a gap of .93 mm. AAA battery would work, its diameter is10.25, that would give a gap of 1.43 mm, it would also be thicker than my home brew tube at just over .005" thick (think I made about 3 of them before I got one without a hole in the wrong place).

Neil, the insides of lots of thing end up on the outside around here, hasn't hurt me yet. Want an aluminium cylinder 30 mm x 165 mm, try a used Paslode fuel cell. When the builder finishes with the cell its still got enough gas to fill my little pencil torch a number of times, then when its empty you can open it, and take the gas bag out of it. I have used these as displacers, but the way I run my motors, they tend to melt. Ian S C

Thanks Ian.

I had not realised you could just use mild steel for the dsplacer. Might make life a bit easier, but I like the battery case idea so might try that too.

Stainless steel is the best, but if you are going to use it to its best advantage, the hot end is either TIG welded on, or the whole thing carved out of solid bar, done that for displacer cylinder hot ends, ie., 1 3/4" bore BETA type has a hot cap 3" long, carved out of a bit of 2 1/2" dia 316 stainless, thined to .010" at the hot end.

You could also use the casing of a alkaline battery, but the closed end has the + tit on it, instead of a flat end of the Nicad. Ian S C