Stirling Egg Cup Engine

[ace]

I have decided next to build a rather small Stirling engine from plans supplied by good friend Jan Ridders. This engine is as its says egg cup size will be the smallest engine I have built. There are only 16 parts to this engine the smallest being link pins that are 1mm dia by 4mm in length and I have already made most of the parts, the most complex is the crank shaft which I have made and tried to solder up but its that small and fiddly that after soldering the first set of crank webs and attempting to do the other set the whole thing got too hot and fell apart so it was back to the bench where I cleaned all the parts free from solder, turned out a new crank shaft (2mm dia rod) and silver soldered the whole thing again but this time with success.
Now for the fly wheel see you soon.....
Pics will be on display shortly.

ace

[Tel]

I'll be watchin' for them pics Ace - sounds an interesting project, albeit one a bit small for the current state of my eyes.

[ace]

Movin on

Fly wheel completed. Not spoked like the plans but full of holes instead.... actually looks quite good. Obtaining the glass was a bit of bother as it appears to be an odd size, however I have sourced some but it only comes in 1 mtr lengths so I'll have to make a lot of little egg cup engines as I only need a 20mm length ;D ;D.

Tel
I do have a large magnifying light over the lathe that will also swing to the milling machine as well, hope the engines big enough for you to see on the pics though. ;D ;D ;D

[Tel]

Blimey mate, 1m divided by 20mm means you can make .... erm ... lots and lots!

[ace]

I ended up with 2 mtrs, so that's ...erm.....anyone want to buy some...........

[ace]

Almost there

I decided that I would build a base for the engine so that it could be run on a tea candle although it will run on an egg cup full of hot water the candle option is easier to set up to show people.
The timber base is almost done just needs an edging putting on to finish it off, I'll do this on my router later. I managed to get it to run today after a little bit of fettling and then sat back and watched.....satisfied.

A few specifications -
Fly wheel = 65mm dia, Crank shaft 2mm dia rod, piston 7mm dia, displacer 44 dia x 2mm thick. The smallest pin is 1mm dia.





Note the needle point bearing design.


ace

[isc]

Hi Ace, what did you use for the power piston? Think I might make a similar sized one for my next project. Just finishing a Ross Yoke type rider engine. Built a 6" dia LTD engine earlier in the year, that brings the total to about a dozen at last count. isc

[ace]

Hi isc, I used 'Plexiglass' but Perspex is as good. After maching the edge all I did was to use a red marker on the edge to highlight it when its running, left clear you can't see it moving very well.

ace

[Tel]

Very tidy job Ace - congrats.

[isc]

No Ace I was after the power piston (the little one lapped into its cylinder). Is perspex not too heavy? I would be thinking of balsa, or foam plastic for the displacer, but if Jan specifies hard plastic it must be OK. isc

[ace]

Cheers Tel for the kind comments, I have over 1 1/2 mtrs of tube left so................. lets make another one or two or three. ;D ;D

Sorry isc, the piston is just mild steel and then highly polished as with the cylinder. The displacer is approx 1.5mm thick but it works well, it ran for over 3 mins last night after the candle was blown out, however there is a very slight wobble in the fly wheel but I put that down to the crank being slightly bent, not bad for my first crankshaft, well one that size anyway ;D.

ace

[isc]

Thanks Ace, I usually make mine out of cast iron from old window weights, thought perhaps you may have gone to using graphite or some thing. It sounds as though you'v got it running well,as it ages it should run even longer on removal of the heat. Don't worry too much about the wobbly wheel, if you try staightening it you stand a chance of stuffing it. I,v just been looking at glass cutting, think a bottle cut into a ring will make the displacer cylinder. isc

[davidp]

Ace,

Nice job.
Would you be able to point us at the plans source please.

Dave

[ace]

Hi isc
What size displacer glass/plastic do you need? if you are after 50mm od with a 2mm wall thickness then funy thing is I have large supply now ;D ;D. Would be happy to mail you some. As for the piston I am building a couple more but intend to change the design by removing the fly wheel and putting a water wheel design on instead and one with a propellor so I will also be experimenting with materials, Graphite is one of them plus I have just finished a jig to hold the crank in place while I silver solder it this time.

Dave
Try heetgasmodelbouw.ridders.nu/

Jan will be happy to forward plans for any of the engines on his site, and they are good plans with build details.

ace

[isc]

Hi ace don't think so, apart from the cost UK to NZ I'd proberbly end up with crushed glass. Seem like you'll be able to flog of a few to help expences. With the great stresses in the crankshaft you'd be alright glueing it, high strenth locktite or similar. One of my engines has a shaft with pionted ends, it runs in tiny ball races from the tone arm of an old reacord player. isc

[ace]

isc
Yep your right, the 'fragile' marker on posted items must mean to the postman 'break with force' as I've received items in the past that even when wrapped in bubble wrap and thick cardboard but has still ended up broken. I tried out the new crank jig this evening and it worked ok apart from the fact that I soldered it up forgetting to put the connecting rods on first 'Durrr'.
ace

[davidp]

Ace,

Thanks - good site and I will follow up.

Dave