Super Sterling Engine

So, on one of the occassions I visited John (Bogstandard) last year he showed me some plans he had of a Sterling Engine.

It was a Desk Fan powered by a small alcohol burner. There and then I determined I would build one for my good lady for Christmas. Slowly over the year I gathered together all of the various mmaterials I would need for the build.

Now, without going over the details, towards the end of last year I had a number of issues I had to deal with beyond my control. However - letting my good lady down was just not on the agenda - it was the 21st December when I started this project and thus began three days of very intense machining, I didn't get much sleep!

I had made a few decisions regarding materials and design, the main cylinder on the drawing was round but I left mine square, I liked the asthetic. The Hot Cap calls for Stainless Steel because of the heat transfer (or lack of them) qualities. What is even better than Stainless in this regard is Titanium, and as I had some in stock........
I also used Titanium for the two flywheels and it worked well with a nice finish.

One of the components that I thought was quite chalolenging was the main "hot" piston. It called for a flat bottomed cylinder with thin walls and a very thin base - plenty of room for error. I was pleasantly surprised as to how straightforward this was. Just simple, steady machining paying full attention to what I was doing and it came out allright:

The main cylinder was interesting too, I left it square so plenty of scope to knock a corner off or bend a cooling vane here:

The component came out well and the piston was a superb fit, exactly as the drawing.

I had considered making the conrod out of Titanium too, but with time being a major consideration, I stuck to aluminium. I enjoyed making this part, very fine tolerances and small drills and cutters. Making this part caused me to buy a couple of pairs of those magnifying headsets, wish I had bought them sooner to be honest.

Next up was the Hot Cap, I just went for it:

It was tough to machine:

With (literally) hours to go it started to take shape and here you can see the power cylinder turned round in contrast to the main cylinder:

The fan hub was challenging as I recall but it was towards the end and I was suffering from a bit of burnout by then so the actual facts and what I recall may not have been the same thing

So, was it worth it?
Absolutely, no question, my good lady has it in the Living room - things need to be of a certain "standard" to achieve the honour, excludes me some days) All the Bloke type visitors are very interested in it, how it works and when I explain it is a flame powered desk fan you can see in some of their faces the light going on as they realise how Steam Punk this really is.
I am not a "model engineer" as such, but I AM interested in all things mechanical and the Stirling Engine has been of interest to me for some time, I sincerely believe it could play a major part in so-called "renewable energy". Would I build another? Quite possibly, it was intense but still very enjoyable and that could apply to anything however those of you who have built working models will know the sense of real achievement when it actually works! Very, very satisfying and there is no substitute for that feeling.

My thanks go to Ian for telling me "just do it" when we discussed building this and my eternal gratitude to John for supplying me with some of the components I needed for the build.

graham.

graham, that looks great, your finned section scares me, those nice fine fins. One thing that did worry me was seeing that the plans say aluminium for the displacer, I'v used that on a couple of my motors, one a little spirit powered one I changed to steel to cut down heat conduction, the other took two melt downs to make me change to stainless steel.

I hope it goes as well as it looks.

Nearest I'v got is my stove top, it could easily be modified for a burner.

Ian S C

John, you are incorrigible!

graham.

Superb engine Graham, although having been in engineering all my life, only just started making models the last couple of years ..converting garage, buying lathe / mill tooling, making stuff to make stuff, to make stuff with etc it seems a long way off to matching your calibre, but not deterred, engineering principles are the same the world over so nothing is impossible.

How did you get the superb curvature on your fins.. are they commercially bought or did you make them? if you made them I applaud your talent.

George

Edited By mechman48 on 08/03/2015 12:20:18

George - I made the fins. It was pretty straightforward really, I first cut out four pieces of Brass sheet the same sizeish and clamped them firmly together using a couple blocks of wood. I then filed them all so they all had the same profile and carefully deburred the edges.

I then found a piece of two inch tube and squeezing them one at a time around this ended up with the profile you see. Very much "by eye" and I too was very pleased with the result. Cutting the angled slots in the centre hub was straightforward too - once I had worked out the angle at which to hold it, divided by four.

graham.

Graham, it might be useful to make a cage to go round those blades, Stirling Engines don't have great power, but it could still give a good whack over your knuckles. Some brass wire about 8 or 10 swg, say 2.5 mm would do OK. My fan has a guard made of number 8 gauge fencing wire(galvanised steel).

I didn't have any suitable sheet metal when I made the fan, so I used wood, and they are mounted so that the pitch can be altered. I made another fan motor, it's of the Ringbom type, and is both too noisy, and too powerful! The blades on that are made of sheet steel, the extra weight to give a flywheel effect.

Ian S C

Apparently the Kiwis are building a full-size replica of the Eiffel Tower in Aukland from 8-gauge wire.

Neil

That is a pretty thing, are the plans available for a nosey?. I made something along these lines a few years back but it used tec plates and a small electric motor. Worked a treat on the stove top.