Stirling phone charger

[Tom Booth]

... I would be looking at the kind of "buck-boost convertor" that is used to power things like Arduino's and Raspberry Pi's from a single battery.

Kinda looks like that's what this is. At least it appears to have the same basic components.

On that current build, I see that you still have a relatively large pulley on the generator - they are often run with the driving band going straight on to the axle, but even a small reduction in size would improve the revs.

I actually did, though it's hard to tell the difference. It's just a plastic disk with a groove, so I went round and round it with a file and the edge of some sand paper to make the grove deeper, reducing the diameter. I think it might also improve traction due to the rubber band going down further in the grove.

I just finished making a new piston.

As it turned out, a broken hot cylinder from another engine almost fit perfect but was just a hair oversized, which is better than undersize as it could be lapped in.


https://youtu.be/jyiVc3URBC0?si=qwebvfwci6MJXvWT

[Tom Booth]

I've been having trouble with the LTD.

Extending the throw didn't work out because the connecting rods are too short and the new angle formed causes the connecting rod to hit the top edge of the power cylinder, so the crank would have to be raised higher as well.

Then the displacer came loose. The cement held but the rather fragile grill block broke from around the cement.

I fixed that displacer and put the engine back together using high temp JB Weld paste as a gasket, but that doesn't seem to have made an air tight seal, or perhaps something else is wrong, but the engine wouldn't start.

So, I gave up on that and put the bigger pulley on the high temp phone charger engine .


https://youtu.be/sjDE4pf1zNY?si=ZUZL4Rcr6bUHSccp


That got over 8 volts open circuit, but when I tried to get a video of that the plug that was used to seal the transfer tube where it was drilled out popped out.

The plug popping out can be heard in the video, then the engine stops running.

I didn't know what had happened, I thought an O ring blew, but checked all those.

Finally I noticed the little plug in the end of the transfer tube was missing.

I couldn't find it anywhere. I'll just have to plug the hole with something else.

Sorry to disappoint about the LTD, but maybe I'll work on that again another time. Or, I think maybe build another from scratch as the modifications I have in mind are so extensive, and this engine is inherently so NOT modification friendly, it seems like it might be easier just to build one to my own specs from scratch

This phone charger will need to be better balanced and will also need a heavier base to keep it from jumping around. It puts out more voltage when held down preventing it from moving

[VincentG]

Pretty impressive, that was quite a pop from that plug blowing out. Good spot for a pressure testing port then.

[Tom Booth]

On advice from several YouTube comments, and just assuming there are probably much better choices for small generators, I was looking...

Not really what I was looking for but, these small hand crank phone chargers turned up.

Resize_20240205_013657_7478.jpg (101.28 KiB) Viewed 4179 times

My guess is that they probably don't have terrific low RPM generators either, but internally are likely geared up and may be difficult to crank, but, they are, from some outlets at least, though online prices vary tremendously, under $5

So... They likely have gears, circuitry, USB port, some kind of generator, everything necessary to turn low RPM mechanical rotation into a phone charger.

For a few dollars, why not? It might just work. Crack one open and dump out all the parts, try to rig up something that can be turned by a small Stirling engine.

[MikeB]

I'm sure it's worth looking at one of those, but from what I've seen in the past, they are _too_ highly geared - intended for a crank speed at least one-tenth of what an engine would run at, but maybe that can be overcome with different gearing?

[Tom Booth]

I'm sure it's worth looking at one of those, but from what I've seen in the past, they are _too_ highly geared - intended for a crank speed at least one-tenth of what an engine would run at, but maybe that can be overcome with different gearing?

Right. It would just be for parts. The gearing would very likely need to be changed. Reducing the gear ratio is less of a problem than increasing it, I imagine.