Stirling Engine : Laura

Brian you seem to be blaming Bengs again, YOU chose to deviate from Bengs instructions, you cannot now say it is their fault.

Making changes/not following instructions without the necessary experience/knowledge has led us to where we are.

My suggestion at this point would be to assemble everything as it should be.

Disconnect the work piston from the flywheel

Provide heat to the end of the glass displacer cylinder ( wait for 60 seconds at least to get some heat in) then slowly turn the flywheel over which should move the displacer piston as you turn the flywheel you should see the work piston moving in and out due to the action of the displacer. IF this does not happen then something is wrong somewhere. Either air not getting through or air leeks.

Is there supposed to be an obstruction left in the end of milled groove between the 2 cylinder supports?

Howi : NOBODY on this forum has got this engine to run yet so it cannot be just my deviations that are to blame. The point I was making is that the seal between the cylinder holders is VERY important. It should not be left to chance using liquid sealers of any type, particularly since the instructions call for these parts to be then soldered in to the base plate. Where would I be had I followed those instructions ? I would have to de-solder and resolder every time the engine had to be disassembled.

pgk : do you mean on the D. piston side ?

Edited By Brian John on 22/02/2016 09:43:10

I am inclined to agree with Howi This engine has been sold as Drawings Instructions and materials If these instructions had been strictly adhered to particularly the drawings and the supplied materials I feel that this engine would have had a reasonable chance of running

Well I've just watched about 8 of these engines on youtube and all look to be soldered, you can even see the solder on some so looks like at least 8 people got them to run by following the instructions.

Looks to me like the front plate is soldered on but the rear can be removed should the need arrise so no need to unsolder

J

Just for info, I have made this engine EXACTLY to the plans, and not got it to run. I don't think there is anything wrong with the design, but my tolerances may not be up to spec, although they're as good as I can get them.

The problem appears to be friction/ misalignment on the displacement cylinder connecting rods with my engine. I'll remake various bits when I have time.

Hylomar state let the solvent evaporate. When I've used it on cars that has happened by the time I get it on.

They do 3 grades. I assume light is the thinnest one. It can be brushed onto metal surfaces but the solvent evaporates pretty quickly in my experience.

A more watery semi setting variety maybe easier and better to use. Red Hermatite is one brand. A very thin coat which ever is used. These products are gasket lubricants not substitutes for them really. Red Hermatite less so.

Now the obvious things have been ruled out other than maybe distortion when it's bolted down I suspect you need to remake one or two parts. All those pillars aren't a good idea. Most likely the displacer con rod bearing and con rod and maybe the power piston after honing it's bore. The bearing will need an accurately set tailstock. One of the problems with making holes on a lathe is the fact that things tend to produce larger holes than their diameter so do try it on some scrap first. Tailstock misalignment generally makes the hole even bigger.

John

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Could i just ask the technical question of how those two frame parts would be soft soldered together? I'm guessing fluxed and then thin solder wire placed around the edge/inned circle of the cylinder supports between the two halves; then heat and allow to flow. or would it be better to place some thin spacer between the two fluxed halves for caplllary flow and apply solder all around once hot? Or tin both parts, place together and reflow?

Jason, I only see two components of that main frame..once soldered access to the cylinder spaces is via the covers. the only way to clear solder blockage into the channel would be via a new drill hole from one side that you plug after or poking bits of bent wire in via cylinder support.

The two plates are not soldered together. The rear plate is soldered to the base, and the front plate is then bolted to the rear by means of the cylinder bolts and a single 2mm bolt at the bottom.

PGK : larger aperture is the work piston. There is a hole in the end of the frame which connects to a hole which has been drilled down the side of the cylinder. This hole exits at the top and so connects the two cylinders. I am not sure if that is clear ?

Tomorrow I will make paper gaskets for all cylinder covers. If that does not work then I will try an aluminium flywheel. I may also make another work piston/cylinder assembly but this will not be ''drop through''. I will keep as much compression as I can this time.

I am not sure why soldering as per the instructions is any better than bolting the cylinder holders to the base ? True, my engine does not work but I cannot see this as the cause. The only other modification I have made is to make the work piston rod adjustable by cutting a thread on the end and installing two lock nuts. The original design called for this to be soldered to the connecting rod joint which would not have allowed any adjustment to the length. Again, why should this cause any problems ?

I also used a small nut and bolt for the working piston joint instead of a rivet.

NOTE from the instructions : '' After deburring, cleaning, and adapting the parts the base plate can be soldered softly.'' It does not really specify what is to be soldered.

Edited By Brian John on 22/02/2016 12:08:46

Edited By Brian John on 22/02/2016 12:14:05

Edited By Brian John on 22/02/2016 12:15:19

Edited By Brian John on 22/02/2016 12:18:03

OK.. I didn;t see that hole before you pointed it out.

On jan ridders engine he recommends silicone for sealing .. simple clear builders silicone applied in a tiny amount to covers. I haven't tested for leaks as such but whenever i take the bits apart there's a nicely squashed very very thin even layer of the stuff there (which peels off easily). A lot easier than making sets of gaskets..any diy or builders merchants.

Something like this ?

**LINK**

The instructions mention ''sanitary silicone'' : How does that differ from other silicone sealants ?

https://www.masters.com.au/product/900004549/fuller-770-sanitary-silicone-sealant-300g-mid-grey

Edited By Brian John on 22/02/2016 12:31:03

Edited By Brian John on 22/02/2016 12:31:25

have no idea of the diffrence between builders silicone and sanitary silicone.. I just used the ordinary cheap clear builders silicone comes in those cartridges you pop into an applicator and seal around windows, brickwork, fish tanks etc'. It does coem in a few colours but that shows up my incompetence more

PDK as I see it only one plate is soldered to the base, the other plate (cylinder side) is sealed to the first with silicon.

But if I were soldering two plates like that together I would tin both of them that means apply a thin coat of solder to each, then hold them together and reheat which is known as sweating and then melts the two coatings of solder into one.

I use a silicon type liquid gasket on teh IC and steam engines, as you say just a smear is all that is needed.

Sanitary silicon has antoi bacterial additives to help stop mould and mildew

If you look at this one you can see the fillet of solder along the bottom of the flywheel side plate where it joins the base and also the two reinforcing webs. there is no sign of solder on the other plate and the central bottom screw helps hold the two plates together.

The photos here also show very clearly that one plate is fixed to the base the other just held by the various screws and sealant.

You may also want to translate the guys third post where he talks about the wooden base causing distortion, John touched on this a while ago.

Edited By JasonB on 22/02/2016 13:45:02

Well, his machine goes like the clappers...much faster than the first video we were shown. One thing I noticed immediately was that he has eight bolts on both D. and work front cylinder covers and not the four as per the instructions. I wonder if that was done for a reason...was he having leakage at those points ?

He has also made his support columns from brass and not aluminium. You might remember that I was having trouble machining the aluminium and I did consider switching to brass at one point. I think it looks better too.

I have looked around the internet and settled on this silicone gasket material from Autobarn :

**LINK**

I will try this instead of paper gaskets.

Edited By Brian John on 22/02/2016 13:47:19

Thasnks, jason. Sweating was the word i;d forgotten (hence reflow0..

The acetic acid these silicones give of will do something to brass - that's what was suggested for cleaning the hob burners on a stove we had. It works too even at vinegar concentrations. Probably doesn't matter but if it gets too hot it reverts - to sand. The other question about them is what filler has been used. There is a clear type intended for adhesive type use = more vinegar smell. Often used for making aquariums.

To be honest with these engines especially at lower power levels unless people think about maintaining alignment when parts are made other similar factors there are likely to be problems. Also I suspect some honing will be needed in the power piston area. Not a problem really but info on making hone seems to be far more complicated than it needs to be. There is a Stirling Engine model engineers type book about that shows a simple hone. I bought it years ago but in useful terms there isn't much else in it. The suggestion for finishing the piston is very fine sand paper of a width greater than the piston but there are better materials available these days.

I could post a photo of the hone but the copyright owners might object. They might be the people that run this site.

There is rather a lot about NOT finishing it and applying heat immediately.

John

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Today I made a paper gasket for the work cylinder cover. I need much more practise in making gaskets ; it is harder than it looks. But first I removed the work piston and cylinder to test it : I placed one end on my thigh to seal it up and pushed the piston down from the other end. It gives a very good seal with lots of ''spring'' as the piston is compressed so there should be no problem there. I do not need to make another work cylinder and piston. After fitting the gasket I noticed that the cylinder cover was not quite sitting correctly so I removed the gasket and it was still not sitting correctly. I then put the cylinder cover in the lathe and machined it to a smooth finish then tried it on the engine without the gasket. Huge improvement....but it will still not run !

I was previously getting air leakage around the work cylinder cover ; the engine now makes a different noise...sort of ''put put put''. I am now getting 8 revolutions when the engine is cold and about 24 revolutions with heat applied. When I try turning the flywheel in the other direction it will only turn twice so I have fixed a major air leak but there may be others.

I am still not happy with using Hylomar as there is no way of knowing if all has been sealed adequately between the cylinder holders so I am going to have another go at making a paper gasket for this. I have also purchased some Permatex high temperature silicone gasket compound but I will not be using this just yet. I think a paper gasket would be better if I can get the shape correct.

Edited By Brian John on 23/02/2016 06:50:33

Edited By Brian John on 23/02/2016 06:52:20

Edited By Brian John on 23/02/2016 07:07:42