Hi there. You have a worthy project. One of the problems you will bump into is the fact that there are several things which affect the output of your machine.

The first and most important of these is the temperature difference between the ‘hot’ and the ‘cold’ ends of your engine. As you want to make a low temperature engine this temperature difference will also be low and so will be its output per unit volume. Typically this is about 500 Watts per square meter for each degree Kelvin (Wikipedia)

The second factor is the pressure of the system. A difficulty with pressurization is that while it improves the power output, the input heat required also increases proportionately to the increased power. This heat transfer is made increasingly difficult with pressurization is that you have to make the engine more pressure resistant – beef up the structure. The thicker walls of the engine also increase the resistance to heat transfer. You also have to make certain that the working gasses do not leak out of the ‘Hot-Cold’ cycle area. Phillips did this with a ‘roll sock’. Rule of thumb – More pressure the bigger the engine.

The third factor is the working gasses. Advice –stick to Air/Nitrogen, other gasses are either expensive or dangerous.

Don’t forget friction it is always with us!

First I would try to estimate the output you require then the ‘guesstimate’ Temperature Differential and use the figure of say 300W/(M².K) – I have allowed for friction, leakage and all the rest. That should give you a feel for the size of the thing.

Good Luck

Dick.

Edited By Richard Parsons on 02/04/2012 10:00:34

My HTC charger is rated 5v 1amp which seems about average for mobile chargers for lithium ion batteries. So you’ll need about 10w of mechanical power with a 50% efficient generator.

This is not a wind up but how about the little wind up torch. no batteries, efficient , enviornmentally friendly. Whatever way you go good luck

Bob

double posting

Edited By Ian S C on 04/04/2012 15:16:35

Third thoughts. If you put some AC across the coils you could also use the engine to cool your tubes of the 'Amber Nectar' and warm up your meat pies. The Stirling cycle is reversible. Two uses from one machine. May be if you fitted a bicycle with one of those little alternators you could convince SWAMBO to pedal it.. By the way the you could also use the TMG to drive the bicycle alternator which could then drive a fan. Alternators can also run as a motor if you spin them up to synchronise with the AC frequency.

Regards

Dick

Andy Ross's 35 cc ALPHA type motor delivers about 44 watts at atmopheric, would be more with pressurisation. Ian S C

Hi Richard,

There is no noise coming from the generator it all comes from the diaphragm which acts as a loudspeaker.

If you look at my Youtube channel you will see that I have made two TMG's one using a moving coil generator which is also very noisey with the other using a moving magnet set up.

The diaphragm do's not touch any parts of the engine I went to great lengths to ensure clearance together with minimum dead space.

The material used is Berylium Copper which is very good for the job but difficult to form due to it's springiness, I found Stainless steel to be not stiff enough and Phosphor Bronze failed due to fatigue after about ten hours running.

The first springs I used were Hacksaw blades they lasted about five mins.

I hope this info wil be of help. Cyril

Cyril, Is that your TMG Stirling on that Youtube video? Looks like it would be ideal for the purpose mentioned at the start of this thread, just put on the camp fire to charge up your battery.

Cyril, just had a look at no.,3964, congrats, a bit belated but never the less. Pitty no photo of the the winner. The competition needs to be resurected, that and the gnat power one too, these are more than models. It was model Stirling Engine building that led to Dr Don Clucas and others firstly studying (for his Doctrate), at Canterbury Uni, then forming the company Whispertech, to develope, and build the Whispergen. Now theres a thing that would charge your batteries, but you would need a good bank ballance to buy one. Ian S C

The heck with the decorating, I'll be most interested in the diaphragm forming. I can't do anything much until I find a pair of containers, some where between 100 mm and150 mm dia. Ian S C

Ian The diaphragm forming is easy. What you need is a set of ‘Jennies’ and the necessary ‘formers’. If you look in MEW no 188 Dave Fenner has written up an article on making a set. You would need to make the bead rollers (dies for making fold up edges) which he illustrates in the article. You might also need to make a set of cutting rollers unless you use a bottom out of a tin for the job. Do not forget that tins are made of high quality steel. I have just had a look at a tin of ‘Dogo-Knosh’ which is about 3 ½ – 4“ diameter and it would be OK for the job.

You will have to make a modification to Dave’s machine by adding a bar attachment below the lower roller housing sticking forward of the rollers to give you a centre for your disk to run round.

Rdgs

Dick