This is a very impressive machine, with superb craftsmanship and flawless mechanical operation. It is a very attractive display item that I plan to keep on my desk at work, with a supply of fuel and a lighter handy to demonstrate to curious passers-by. My fellow engineer coworkers have also been very impressed with it. It runs surprisingly fast, and is not overly loud, but does make some noise.

I am so impressed with its good qualities that I did not deduct a star for the failings of the instructions that came with it. I'll never understand why Chinese companies do not take the simple extra step to have someone who has English as a first language proof-read and clarify the almost universally poor English translations that ship with their products. The instructions that come with this are quite typical of that problem. For example: "Heating 20 seconds, and then began to gently turn the flywheel, (follow the starting direction shown in the figure) until the flywheel can since Dynamic operation so far." Yes, most will be able to figure out what that means, but why not state it in proper English? I'll note that the instructions cover both a Stirling engine and a steam engine. Paper is cheap, why not have separate instructions for each model? And the instructions for the Stirling engine include a figure of a different type of engine than this, leaving me wondering initially if I received the wrong instructions.

The model comes with several loose parts, some of which are spare parts, like and extra of each glass cylinder and generator drive belt, which is nice But there is no list of parts with a description, including those needed for operation. Again, it was easy enough to figure out, despite no instructions. But should either of the cylinders need replacing, there are no instructions for how to do this. There is an LED light that also came loose. This is a very cool, color-changing LED that demonstrates that the engine converts heat into usable electricity. Why it is not assembled to the model as delivered, nor even mentioned anywhere in the instructions is a mystery to me. It may also be a mystery to anyone who is not mechanically (or electrically) inclined that you have to spread the LED wires apart and bend the ends so they can fit into the holes in the terminals on the outside of the generator. The alcohol lamp had 3 parts, the glass bottle, wick, and lid. The lid is not threaded and just sits on top of the bottle, so be careful not to knock the bottle over while lit, or you'll have a little Molotov cocktail on your hands. When feeding the wick through the hole in the lid, some instruction as to how far the wick should extend would have been nice. I found that about 1/16" is sufficient, and more extension to give a larger flame did not seem to make the engine run any faster. So far, I've transported it back and forth to work a couple times and put a piece of plastic wrap over the wick and wound a rubber band around the bottle neck to seal it. A bottle with a seal-able lid would be a nice improvement. But I suppose the alcohol is cheap enough that you could just dump out any unused fuel if moving it. As is, all the alcohol in the bottle will evaporate rather quickly with the wick exposed to the air. (Here's a tip for filling the bottle from a can of alcohol without spilling more than goes in the bottle: dip a straw down into the can of alcohol, seal the top of the straw with a finger, then put the straw into the bottle and release your finger. Repeat until bottle is full.)

Despite the above nits, I think this is a very cool "toy", especially being a mechanical engineer with a deeper understanding of how it works, and am very happy I bought it. But I don't think you need to be an engineer to enjoy this. I thought the price was a little steep, but feel better about the price after seeing the high quality design, workmanship, and materials used. Oh, since I plan to keep it on display at work, I am concerned about dust collecting and possibly gumming up the linkages and power cylinder that is open to air, so I bought a mini-football helmet display case that it perfectly fits in...see the picture. The case is a "Ballqube Mini Football/Helmet Display Box".

tl/dr: To keep it from walking put some little squares of this stuff on the feet: https://www.amazon.com/gp/product/B07GL9MHW7

OK, read on if you want ;)

The unit is just exquisite. Very well put together and very pretty. Runs on either 91% isopropyl alcohol or a small hexamine tablet. The hexamine tablet left a big sooty chunk on the cup that normally holds the alcohol burner, but this is not a knock against the toy; just a note what to expect. The residue wiped clean.

Everything except the fuel cup that holds the alcohol burner is bolted together, but the cup is only glued down and came off. Possibly because of the hexamine burning directly in there heated it up enough to melt the glue they used. A little dab of silicone and it's solid as a rock.

To keep it from walking, just add some of this stuff "Adhesive Black Rubber Pad Sheet Thin Silicone Rubber Gasket Sheet 12X12 inch,1/25 Inch Thick Gaskets DIY Material, Supports, Leveling, Sealing, Bumpers, Protection" https://www.amazon.com/gp/product/B07GL9MHW7 to the feet. It's super high friction (as long as you don't let the dog hair accumulate!). Without it the engine travels across the desk while running. With it, it does not budge a millimeter!

This is a delightful little engine. I'm amazed by the precision of the craftsmanship and the reliability at this price point. It comes fully assembled, works flawlessly every time, and is very fun to watch and tinker with. If I could improve anything about it, it would be:

1. A heavier base, or some sort of counterbalance: The engine does vibrate at high speed and will occasionally try to walk off my desk. The base, and the engine itself are already quite heavy, so I think the right solution would be some sort of counterbalance to eliminate the vibration. But simpler solution might be to add some balast.

2. Power connectors for the little generator: I've enjoyed powering small items with the generator. LEDs, a little heating coil, some motors, etc. It would be nice if this came with terminals and a switch for connecting various items. Clearly this is something you can add on your own, but it would be a nice addition.

Overall it's been wonderful fun. I think the electrical power output tops out somewhere in the 2 watt range, which is enough to do some nice demonstrations. And it looks beautiful sitting on a desk or shelf when not in use. Overall I'd highly recommend it to someone looking for a fun, easy Sterling engine.

So. My disappointment in this little unit is that it is made in China which I didn't pick up on from the description. I love the little thing nonetheless. My 4 yr old grandson is thrilled by it and that is all that matters to me. The directions are laughable and I picture the poor workers over there trying to write competent translations. I am having fun with it.

!!! I absolutely LOVE this engine! It's beautifully cut AL billet. HEAVY! (for it's size, of course). I laugh loudly every time i run it. BUY IT!