Stirlingengineforum.com

I've been having some issues with trying to keep my foamed glass displacer secure on the SS shaft.

At first I tried high temperature silicone, but that took too long to cure, so I tried supper glue, but that didn't want to work over the silicone.

I cleaned off the silicone as best I could and put some supper glue back on, but it was a problem getting the glue down in the displacer then pushing it onto the shaft, the glue set too fast and the displacer got stuck before completely on.

So I tried glueing with the supper glue after the displacer was already on, but that didn't hold.

Then I tried the supper glue and baking soda.

That worked great for a while, and allowed me to take a "fist run" video, but then afterwards, I was running the engine without the LED.

Without any load, the engine speed increased quite a lot and I wanted to see just how fast it could go and turned up the torch. The engine was flying, then bam... It stopped.

The displacer had come loose. The supper glue had become too hot and softened up.

So, I tried using the high temp silicone again. But just let it set overnight

When I finally tried to run the engine, the silicone smoked and swelled, breaking apart the displacer from the inside
HELP!!!

I'm starting to pull my hair out in frustration.

I've been thinking that the best method would be to have a barbed shaft and fuse the foam glass displacer right onto the shaft in the microwave as it is being formed.

I'm afraid high temperature epoxy would likely have issues at such really extreme temperatures.

At least the displacer did not suffer any damage with the supper glue failure. It didn't swell and destroy the somewhat fragile foam glass, it just softened, but it was not down at the really hot end either.

Maybe some stove cement ? Water glass ?

Anyway, the displacer is ruined. I'm not entirely happy that it was not strong enough to take the pressure.

I think, it is probably possible to make a foam glass that is extremely heat resistant and very strong, but most foamed glass is not formulated for use as a high temperature component in an engine.

This stuff was intended for rabbits to chew on.

I wonder if perhaps silver solder would bond to the foamed glass, maybe even into the pores a bit?
Bumpkin

Bumpkin wrote: ↑Sun Oct 09, 2022 9:07 am I wonder if perhaps silver solder would bond to the foamed glass, maybe even into the pores a bit?
Bumpkin

Worth a try.

If it at least bonds to the metal, it may just fill into the gaps.

Thanks!

I just realized, silver solder is now used for stained glass windows, since getting away from lead.

Another thought is just using some actual crushed glass and put it around the area and fuse it with a torch or in a kiln.

Or, maybe just mix up a batch of foamed glass starter mixture, which is just crushed glass and a foaming agent, which may be just water. Damp crushed glass. Maybe a little glycerine and a pinch of baking soda, calcium carbonate or whatever. Some Silicon carbide might make it heat up in the microwave.

I've always heard it is not good to put metal in the microwave, but apparently SS is ok as long as it is not enclosing a space, like the tines of a fork. It just reflects the microwaves, but fork tines can "trap" the microwaves between the tines.

Anyway, people use Stainless Steel moulds to shape fused glass in a microwave kiln all the time without any problems.

https://youtu.be/qL5nJaiXZjI

SS moulds are also sold for use in a microwave kiln.

I've seen a few videos on the subject of the safety of stainless steel in the microwave, but they elude my search at the moment.

Getting the glass to stick to the SS is probably not a problem, as the topic is usually how to avoid having the glass stick to the SS moulds, using release agents or kiln paper etc.