Stirlingengineforum.com

I can't find anything suitable for the firebox in the shed and can't get out due to the lockdown, so a change of plan.

Started to have a look at the flywheel and made it slightly heavier. I have some bits of lead roofing flashing that is about 3/32" thick. One layer of this on the outside rim of the wheel has made a big improvement, it runs even faster and a lot smoother.

Pleased with that.

Toodlepip

Congratulations !
I love it too.

This lockdown is essential and I pray for those suffering because of the virus, all I am suffering with is the inability to get to the local stores for essential bits.

Just to keep things moving I had a look round the shed and came up with green and yellow paint, and I managed to find some masking tape that I bought a few years ago and never used, so I played with that for a while.

Nice machine!
I think copper is underestimate, its easy to solder and its look really good.
I found that it is quite easy to solder stainless steel.
https://twitter.com/BenKrasnow/status/1 ... 9517665281
By having a stainless hot end, you should avoid any defiormations of the hot end if it gets too hot. (within certain limits)
A steel thermos might be a good hot end, cut it and allow it to be soldered to the cold part where the temperature is low (no soldering problems)
What do you think good or bad idea?

keep up the good work

exile wrote: ↑Thu May 14, 2020 10:30 am
By having a stainless hot end, you should avoid any defiormations of the hot end if it gets too hot. (within certain limits)
A steel thermos might be a good hot end, cut it and allow it to be soldered to the cold part where the temperature is low (no soldering problems)
What do you think good or bad idea?

Thanks for the tips.

I have looked at soldering stainless before but never used it being unable to get the flux at my usual suppliers.

A couple of points, even if the hot cap is stainless steel then the solder is still the limiting factor for temperature, in my experience copper does not deform at temperatures that are required for soft soldering operations. If you require solder with a higher melting point then silver solder is readily available, however the temperature required to make a joint will make the copper glow a nice cherry red, the exact point where copper is anealed and becomes soft even after cooling. I have a small amount of silver solder in stock for emergencies but I have never used it in anger.

In this instance I only have two joints in the heated zone. The first being a 2.1/2" copper cap to copper pipe, I used "FireGum" just smeared the mating surfaces and pushed the cap on the pipe, it took all of 2 minutes is solid and if you belive the adverts is good to 1000 DegC. The second is the seal for the sliding rod, I have made this with plumbers solder, I believe that the joint will not reach melting point if I am proven wrong then I will give the silver solder a try.

Had a play, reduced the amount of pressure pipe as suggested by Sadi, as a result of which I had to reorganise the conrods and ended up putting in a crankshaft, getting the third bearing lined up is proving troublesome - I need to rethink, but I am pleased with the progress.

I cannot count that fast, but if somebody can manage it, could you tell me how many RPM's the machine is doing?

https://youtu.be/pP0FoHtTuDA

Toodlepip

I managed to get some Aluminium and made a fire box of sorts and a cute little chimney out of bits from my box of scrap copper.
Is there anyone else out there working on a project during the lockdown?

Toodlepip

Quick coat of Bar-B-Q Paint and some copper polish and it's starting to come together, its better than I hoped for.
I am starting to suffer with lack of stuff due to the suppliers being in lockdown and lack of transport. I have sent off to china for some bits and bobs but they will be about a month.

Toodlepip

Just stopped working for a coffee so I thought I would post something.

No pictures of todays work so how about pistons.

This works for UK Tube and pipesizes.

Cut about 20mm (3/4") off the bottom of an empty steredent tablet tube, and fill it with epoxy. Take off the printing and it is a good snug fit in a 28mm copper pipe.

I spent a couple of days deciding how to make doors on the firebox. Ended up making a drawer which was very easy and only took half an hour.

The good news is - the fire box is brilliant, the engine got up to heat very quickly and started so easily I was really chuffed. The engine got quicker and quicker, hotter and hotter, then things took a turn for the worse.

Right before my eyes the solder melted, the lovely chimney slid off the roof followed by the engine locking up and the crank shaft achieving a rather strange configuration.

The remains of the engine were really hot, the fuel that normally lasts for 10 minutes was gone in less than 1 minute.

I will close the shed down for today and carry out a post mortem tomorrow, I suspect that the anchor plate on the conrod which was holding the displacer in position has melted and relocated.

OK - You can all say " I told you so.

I think now is the time to dig out the silver solder.

Toodlepip

Here's a video just prior to the engine going into self destruct mode, if you look closely you can see the chimney sliding down the roof.

I have had a quick look and things are not unrecoverable.


https://youtu.be/t2NVVwjVn-c

Silver soldering is not the answer for me. I tried a couple of small pieces as tests and everything was as it should be and I was very pleased with the results.

However when I tried on my work pieces I failed to get the pieces to the correct temperature, I ended up building a soldering hearth complete with bricks and two propane / butane blow lamps at the same time after 20 minutes I could not get the copper to glow red or the solder to run. Just to much copper and it conducted the heat away. I do not have access to acetylene so it's plan B, but more about that later.

After a couple of days with miserable progress I needed something to cheer myself up so I had a look at the supports or the sliding bearing. When I first built them I used screwed rod, its very useful stuff, very quick but really Fugly. Today I changed them out for some shiny copper and made myself happy. The holding down bolts (8No 2mm) are just for show the screwed rod is still there inside the copper tube.

I've read through the account, I don't think you've mentioned, so I'm curious, what do you use for a displacer in your engines? A "can" (solid or hollow displacer) or something porous like steel wool (regenerator).

Very nice work!

Displacer, I used balsa covered in aluminium foil.

I made the displacer from 1/2" thick strips of balsa glued together. To locate the displacer on the shaft I soldered a flat piece of copper to the brass rod to form a stop, then added the balsa strips on either side.

After forming the displacer and getting to the correct size I coated the wood in superglue, this surface hardens the balsa and provides a good surface for contact adhesive to bond to. If you are going to do this make sure that the displacer is the size you need because once the super glue is used files, rasps and sand paper just bounce off it and any further modifications are very troublesome to say the least.

After my "meltdown" I opened up the displacer to check the state of the displacer and I was surprised to see that it was as good as new.

"After my "meltdown" I opened up the displacer to check the state of the displacer and I was surprised to see that it was as good as new."

Thanks.

That does seem rather remarkable, that an engine hot enough to melt solder, nevertheless, did not burn or char the balsa wood displacer.

I've had problems with lightweight foam displacers warping and melting... well below any temperature that could begin to melt solder. Currently I'm trying some of that rigid foam used for craft, I think mainly for flower arrangements. I'm not at all sure how well that could take heat, but right now I'm experimenting with a cold running engine. ("Powered by ice" so to speak) so I don't anticipate excess heat to be any problem.

I'm always curious regarding the question of using a displacer vs. regenerator (or "regenerative displacer"). I've seen evidence that using a regenerator makes a big difference, but then I've also read accounts where someone experimented with both and found no advantage to using a regenerator.