Stirling phone charger

[Tom Booth]

That seems too good to be true lol! What is the rated output of that wall charger? Maybe you have a 2 amp fast charger to try as well?

Even though the little dc generator is not efficient, there's no loss from a rectifier or charge controller like other setups use so the overall efficiency is higher than other efforts online. It could probably benefit even more from a capacitor to smooth the output ripple.

The efficiency of these tiny motor generators improves a LOT at higher RPM. I was looking at some specs online when I was thinking about buying a dozen or so and they really don't even kick in to produce anything at all until they reach quite a high RPM.

I had commented about that on the forum a while back.

That there are all these little toy Stirling engines that you can just barely get make a little LED flicker at full throttle using a blow torch or something.

It isn't that the engines aren't putting out power, it's that the generators supplied with them have to turn at 2000 RPM.

Well here is a typical example for some similar small generators on Amazon:

Parameter: Different voltages correspond to different speeds. Voltage: DC 3V, rated speed: 1500 RPM, voltage: DC 4.5V, rated speed: 2500 RPM, voltage: DC 12V, rated speed: 6500 RPM

So, to get 5 volts for phone charging requires about 3000 RPM. Just to light a 3 volt LED 1500 RPM

Here's another video just wired direct to the generator:

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https://youtu.be/PMYmvOKGsFs?si=YYuEjxUWJwwMfiRu

That thing is cranking fast enough it could probably charge three phones at the same time geared up a little bit.

Does anyone besides me get the idea that "someone" wants everyone to THINK Stirling engines are not good or useful for power production?

I mean, 1:1 gear ratios, aluminum displacer, plastic and styrofoam parts that melt.

And all these DIYers charging cell phones but several Kickstarter campaigns can"t manage this with whatever they rake in?

And what happened to this one?

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Just strikes me as weird somehow, everybody seems to want one but nobody's making any, unless they resort to making their own.

[Tom Booth]

This one has a USB port in the base.

Doesn't say it could charge a phone, but I wouldn't doubt it at this point.

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[Tom Booth]

Yet another:

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USB, but again, just says it can light the supplied "night light" in the photo. And that little 1:1 ratio pulley.

Why?

Of course, it's possible to make a low RPM generator, so... maybe somebody can buy one and see if it can charge a phone.

You mentioned your working on a generator? How about some 3D printed pulleys? Or pulley adaptors?

Gear some of these engines up a little and they might actually be useful.

[VincentG]

You mentioned your working on a generator? How about some 3D printed pulleys? Or pulley adaptors?

Gear some of these engines up a little and they might actually be useful.

3d printed pulleys would be easy, but at this scale I think quality gears may be a better option. Perhaps a nylon spur gear and a brass or Teflon pinion gear for ultra low friction. I could send you some 3d printed gears if you are interested.

I'll make a generator specific post soon. The eventual goal for my little generator is direct drive for the highest efficiency. I've managed 5 volts plus at around 1000rpm so far and there's more room for improvement still. So far it has reached 60 peak volts at much higher rpm and enough current to blow the 10-amp fuse in my multimeter. Fortunately there are good generator options for low rpm 500 watts and up, but not for sub 100 watts with minimal cogging loss. I'm focusing on the quality of flux change instead of maximum frequency of flux change like most small generators use. The tradeoff is a low frequency output v. speed, but I think this can be solved with capacitors.

I'm really curious if you can do the same setup on your high temp LTD conversion to compare output.

I'm still blown away that an unmodified Gamma can charge a phone like that. Ordering one today!

It's very possible that a lack of external cooling is beneficial to the small Gamma. Like ROCKNTV1 found, less air mass in the engine can be more ideal for the available heat transfer rate of a given engine.

[Tom Booth]

You mentioned your working on a generator? How about some 3D printed pulleys? Or pulley adaptors?

Gear some of these engines up a little and they might actually be useful.

3d printed pulleys would be easy, but at this scale I think quality gears may be a better option. Perhaps a nylon spur gear and a brass or Teflon pinion gear for ultra low friction. I could send you some 3d printed gears if you are interested.

Definitely interested, but for a retrofit to one of these little models there are some constraints, I think, as far as available space.

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There is less than 3/8" between my retrofit pulley on top and the power cylinder.

The little orange pulley on the bottom only has 1/8" clearance under it.

Currently the two pulleys are separated 5/8"

It would be a challenge getting two gears big enough to mesh without running into something else.

What I was thinking of is a quick, inexpensive USB phone charger kit/conversion package.

A ring to slip over the top pulley to increase the diameter, a little bit bigger drive belt and a (fused ?) USB socket, with maybe a capacitor.

But since then I see, little engines with usb's built in are already out there. Probably a dumb idea.

If you already sent for one maybe you can figure something out.

...I've managed 5 volts plus at around 1000rpm so far and there's more room for improvement still. So far it has reached 60 peak volts at much higher rpm and enough current to blow the 10-amp fuse in my multimeter.

What? No way.

60x10 would be 600 watts. Just 5x10 would be 50 watts.

Are you talking about that little LTD?

I'm really curious if you can do the same setup on your high temp LTD conversion to compare output.

Possibly, but last time I ran it at over 1000°F it finally had a meltdown. Just the silicone oven mat gasket on the bottom I think, but it needs a new gasket and some cleaning at a minimum

I'm still blown away that an unmodified Gamma can charge a phone like that. Ordering one today!

It's not entirely unmodified. I did swap out the glass piston and cylinder from a set off another engine, and of course the bigger pulley and drive belt.

I think an even bigger pulley would get higher RPM so even better output, probably.

The little generator, I think puts out a very "dirty" DC. It sometimes makes the meter go a bit wacky. The Ampere app also doesn't seem to know what to do with it until it's at a very high RPM, then it seems to smooth out, but I still have not seen the % of charge go up, so I wouldn't get too excited.

I'm pretty sure there are much better quality models available that would have better output.

This was very cheap when I got it. I see the price has gone up considerably since then, but still basically cheap junk.

[Tom Booth]

Well, I guess if necessary I could build another mount for the generator further back and raise it up.

Ideally I think the small gear on the generator should be a little smaller and the drive gear a little bigger than what I added.

The voltage seems to peak. Then more heat makes the engine run stronger, apparently, it seems to me, but not really any faster. So what I'm thinking is it still has the torque for a higher gear ratio.

The generator may be able to put out 12 volts but not until it hits 6000 RPM which is probably like a 1 to 10 gear ratio at the engines top speed (under load).

I had a Briggs and Stratton lawnmower points condenser / capacitor kicking around somewhere I wanted to try charging up with it. See if it will make a spark.

[Tom Booth]

...I've managed 5 volts plus at around 1000rpm so far and there's more room for improvement still. So far it has reached 60 peak volts at much higher rpm and enough current to blow the 10-amp fuse in my multimeter.

What? No way.

60x10 would be 600 watts. Just 5x10 would be 50 watts.

Are you talking about that little LTD?

Is that a typo maybe... 6 volts instead of 60?

Hope you will clarify or verify because, well, Big clunky heavy 15 watt Stirlings are selling for $500.00 (+$200 shipping) on eBay.

If you've managed to get that, or better out of an LTD that's mind blowing.

[VincentG]

Is that a typo maybe... 6 volts instead of 60?

Hope you will clarify or verify because, well, Big clunky heavy 15 watt Stirlings are selling for $500.00 (+$200 shipping) on eBay.

If you've managed to get that, or better out of an LTD that's mind blowing.

I should have been clearer. I've been powering the generator with a cordless Dremel tool for testing. Sixty volts was reached at high rpm open load. On a separate occasion, 10 amps was seen dead heading the generator into the ammeter. The cordless Dremel tool is only rated at 7 watts, so its not very powerful. The LED's light brightly with just the flick of your fingers, even with 2 in series. The body is 3d printed and all other components are non-magnetic in order to not steal flux from the magnets or coils. The whole thing can be made in under an hour, save for 3d printing time.

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[Tom Booth]

Oh, thanks. That certainly makes more sense.

Still, very impressive for such a small generator.

I'm a bit puzzled how you 3D print a generator. It appears to be just a plastic cylinder with an LED attached?

What are we looking at there exactly? I mean, assuming your not reserving the details for a patent or something.

[Tom Booth]

A comment left on one of the videos on my YouTube channel suggested that if the voltage was high enough, a DC car phone charger could be used.

It might not be needed, but it sounded like an idea with potential. After all, the voltage in cars is prone to all kinds of fluctuation and voltage spikes and drop offs so there must be some protective measures.

Don't know much about circuitry myself unfortunately, but it looks like there might be a small capacitor can or two in there.


https://youtu.be/fD8qYYvHIik?si=xYM6pk446IIROzds


Shouldn't hurt any to give it a try and see what happens anyway.

[Tom Booth]

...
I'm really curious if you can do the same setup on your high temp LTD conversion to compare output.

I'm still blown away that an unmodified Gamma can charge a phone like that. Ordering one today!

It's very possible that a lack of external cooling is beneficial to the small Gamma. Like ROCKNTV1 found, less air mass in the engine can be more ideal for the available heat transfer rate of a given engine.

As far as the High Temperature "Low Temperature" engine. I started doing some damage assessment this past evening.

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When I loosened the screws on the bottom plate it came popping off badly warped. Obviously under stress. Without the bolts holding it, it came off the engine all buckled and warped out of shape.

For some reason the bottom plate is very thin metal compared to the top plate. Anyway, I think some other thicker metal bottom will be needed.

The glass ring was badly covered with sticky soot from the bottom plate silicone oven mat gasket that literally burned to a white ash. Nothing much left of that but a white powdery residue, but the glass cylinder cleaned right up nicely

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The top "cold side" gasket came through just fine, seen in the photo as a purple ring around the rim of the glass cylinder.

Going to post this before my login times out.

[Tom Booth]

The piston had become glued into the cylinder due to the sticky smoke from the burnt silicone. The piston had to be forced out of the cylinder, it had really gotten stuck after the engine cooled down, surprising it could keep running for so long with that gunk all over the piston. It kept running up until the gasket blew though. I'm sure the goo all over the inside of the engine from the burning silicone must have put a drag on the piston.

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The displacer made out of that pumice stone or foam glass grill cleaning brick came through in pristine condition. Looks just the same as when I had just made it.the "glue" I used to secure it, if I recall, high temperature JB Weld, held secure. With all that heat and high speed reciprocation, it's not loose or anything at all.

I have to check that the high temp JB Weld was what I actually used. Could also have been some wood stove gasket cement. Whatever it was held great!

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[Tom Booth]

I decided to add a little more to the drive pulley diameter. This PVC fitting just about fit perfectly over the existing milk bottle cap.

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After installing the larger pulley, I hooked up the meter and gave the flywheel a GENTLE. Spin.

Went over 2 volts easily. A bit of a harder spin got over three volts easily.

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That reading of 3 volts was with the engine just coasting after I gave the flywheel a spin, of course the piston is off so not much resistance.

Not sure what I'll do for a new piston. I think that one has probably had it, though it was working, even broken, before it got gummed up.

Anyway, I'm also curious to see what the high temp LTD might do as a phone charger, so I'm working on getting it back in working order. It won't exactly be the same engine when I'm done though.
.

[VincentG]

Looking forward to this one. You may end up having to use that 12v car charger after all.

[MikeB]

As ever, watch out for quality with car chargers - converting 12v to 5v leaves plenty of head-room for really crap circuitry that might rob all your power at lower voltages. If you are going down that route (sounds like you aren't) then 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.

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.