MM-5 Coffee Cup Engine Kit - Made in USA


Out of stock

Stirling Engines

Ready to assemble. You only need to purchase superglue and silicone sealant. You will also need a few common hand tools to assemble your engine. It’s a pleasant two or three evening kit and a fun way to learn about Stirling engines. Click here for a video clip. If your computer can run Flash you may enjoy a Flash animation of this engine.

You may also want to buy a Spare Diaphragm. This is the only wear part in the engine.

The United States Naval Academy once had all of their mechanical engineering students build one of our kits.

If you want a very easy to build kit, we recommend this electric motor kit.

Martin Waugh
Great kit, excellent instructions. First time out, it ran for about 70 minutes on a cup of boiling water. Two observations: (1) The bottom section of the crankcase was slightly bent, I suppose from the bending required to form the right angles of the ends. I chose to spread the ends of the crankcase (at the top) while I glued the cylinder to the crankcase and the cylinder bottom to the cylinder. I used a 4 3/16-inch piece of wood (same length as the brass tube handle) gently clamped in place. This made the cylinder assembly quite flat. I did need to bend the cylinder bottom a bit to flatten it as well, as you cautioned I might. (2) I chose to de-burr the inside edge of the brass washer. It seems that the sharp edge against the diaphragm could lead to premature failure. I used some 400-grit Wet-or- Dry sandpaper. I received it as a gift, and it is a good one.
Matt Silberglitt
From: Mr. Silberglitt's physics class at Mora High School, Mora, MN To: model MM-5 designer and future builders We just finished to MM-5 and are watching it run. We did have a little difficulty with the seal around the cylinder. We used silicone caulk for everything except the reducers, which we attached to the crankshaft with epoxy. We also had trouble getting the pistons to move through the correct range of travel. We would like to suggest the following. 1. Leave the rubber tubing that goes on the Upper displacer rod a little longer than suggested. 30 mm would probably work well. 2. Get the piston side of the crankshaft adjusted first, then worry about the displacer travel. Put the crankshaft with the middle down (over the displacer). Attach the tubing to the diplacer's piston rod, with a bit rolled back (on top) so it is doubled over. With the displacer all the way down in the cylinder, snap the rubber tubing over the Upper displacer rod. Now the displacer will just miss hitting bottom. 3. We just noticed that the displacer, at its upper limit of travel, bumps into the piston, at its lower limit of travel. Is there any way to avoid this? If anyone figures this out, let us know! It's a great kit, and a great learning tool.
Henry Beitz
Like Matt Silberglitt from Mora I have the problem of the displacer and the piston kissing each other. Other than this one problem the engine runs beautifully. A solution that I intend to try is to put in a thicker gasket. Since this will not increase the volume of the airspace by much I doubt that it will effect the running of the engine. It will hopefuuly stop the two components from bumping in to each other.
Gordon McCall
Hi. I recently purchased one of your MM-5 kits and I am completely satisfied. The engine runs for 1 hour and 5 minutes on a cup of boiling water as shown in the picture. The minimum running temperature is 140 deg F at a room temp of 68 deg. For the displacer chamber I used 5 minute epoxy with out any problems. Why would this make a good gift? My answer to that is it is simple to operate because anyone can heat water. Not everyone wants to mess with alcohol burners required for the higher temp Stirlings. Nice kit. Thanks.
Paul Fishwick
I enjoyed building the coffee cup engine, but had some problems (and solutions), which may benefit others. My engine operates for about 8 minutes on a coffee cup of boiling water, which is thrilling! I used 90 minute epoxy since 30 minute was not available, and the bond broke down somewhat after my first trial run. To see if your cylinder leaks air, try pressing your thumbs on either side and press up on the edges of the blue disc with your other fingers. If the piston latex rises signficantly, you have a leak. Instead of tearing off the old glue, I used 2 C-clamps on either side, and this appears to give a tight connection. For some reason, my epoxy gluing experience just didn't produce a good seal. I did the work outside in humid weather (Florida), and wonder if that might have caused the glue to not harden correctly. I also found it useful to reduce the rotational drag on the crankshaft by adjusting the rubber tubing somewhat. Another reader seemed to suggest tweaking the tubing. When the propeller is rotated, there should not be significant drag, otherwise the thing won't get going properly, or may not run very long. I wrapped some ice in cellophane wrap and placed it on the top to increase the temperature difference, and this works well. I feel, in retrospect, that working with a kit like this is the best way to appreciate the working product. I had similar experiences 15 years ago when my wife gave me a boomerang. The boomerang did not work correctly, and it turned out that one arm needed to be shaved to create a working airfoil. Then, it worked perfectly. 15 years later, I have carved 15 boomerangs, and have a collection of about 50.
5 Units Built and going strong.
I enjoyed building my first MM-5 so mush that I bought 4 more and gave them to my friends as gifts. They all loved them and they are going strong.
It worked first time!
Assembly was easy but for one point - the fitting of the rubber tubes to the piston and displacer rods. I found making the 'sock' roll difficult, especially on the piston rod, where I was worried about causing damage to the delicate diaphragm. It ran on a cup of hot water at the first attempt. Getting it to run on ice cubes took a bit more effort but I succeeded with the help of some salt to depress the melting point. Thank you. I am well satisfied with the little machine, which will amuse some people and amaze others. George Henderson St Albans, England
It runs on my hand!
I've just built my coffee cup engine and it ran the first time! After all the horror stories I'd heard about non-working Stirling engines this was great, but even better, it runs on the heat from my hand! Not fast but it ticks over and is a real talking point. Many thanks for a great kit. Alistair Grant Carnoustie Scotland [Alistar has done an excellent job of assembling his kit! Running on the heat of your hand is not guaranteed. For suggestions from other builders on how to build a great MM-5 kit, read our model engines bulletin board. -- Editor]
MM-5 Ran on the First Spin
The kit was very easy to put together, minimal modifications needed. It ran after the first spin for 45 minutes, the water in my coffee mug had cooled off. I replenished the hot water and it is off and running now. I also notice it does not run at a constant rate but speeds up and slows down from time to time. Next I will try the ice chip heat sink trick after it stops. [Please read Kevin's assembly tips in the model engine forum under the heading, "Assembly Tips for MM-5 - ed]
Look out Energizer Bunny!
* * * * * Five Stars for sure! When my MM-5 arrived I could not wait to get started putting it together. The hardest thing for me to accept is that glue won't dry any faster by watching it. I guess I waited long enough for the glue to dry because as many others have said, my MM-5 ran the first time I tried it, and it ran even better after tweaking the displacer & power piston rod lengths. The cup I use is a QT (Quick Trip) 32 oz insulated drink cup filled with boiling water. I have had runs over three hours. Like the energizer bunny, it just keeps going, and going, and - - . The only lube that I have used is graphite. (I rubbed a pencil on the crankshaft cams & main pivot points.) I think I'll try a drop of machine oil on the displacer tube to slow down what little pressure bypass that there may be. At this point it has not run on heat from my hand. Maybe if I put my hand in boiling water first. (Kids, don't try this at home! - Adults only!) Randy
Worked perfectly the first time!
The good news is that I built it in about 2 1/2 hours yesterday and it worked perfectly first time. I think it's just a case of following the instructions carefully and being careful not to damage the parts, especially the piston membrane.
Stumped 'em :-)
I've finally put my kit together. It's very cool and has upset some people in the office who thought they knew physics :-). Thanks again, F. Daly, Ireland
Ran the first time!
I ordered this on July 27 and received it on July 30th. That was fast shipping! From start to finish, it took about 1.5 hours. I used J-B Kwik Cold Weld to assemble it. The Coffee Cup engine ran the very first time! I would say that it is "highly recommended." William Rushing, Champaign, IL.
Great kit!
I thought it was great! My nieces and nephews love it. --Hugo Tress, Provo, UT
Great Kits and Excellent Service
One hundred of our sophmore mechanical engineering students built MM-5 Stirling engine kits. The kits were great and the service was excellent. Building these kits was a very good learning experience for our students and we plan to do it again. --Professor Angela Moran, United States Naval Academy
Amazing still running strong.
Put together on Monday April 18 running every day on top of my aquarium light 9 hours a day every day replaced nothing great product highly recommended
A Kalashinikov of an engine!
You have quite a Kalashinikov of an engine. That is, I put it together with less than ideal adhesives, left out some parts, and the engine is still a straight shooter. A couple of guys here have worked on automotive Stirling projects and they were really tickled to see your engine running on a cup of hot water. Thanks very much.
Amusing to build, amusing to watch, fun to explain
I originally looked into Stirling Engines a number of months ago, and it ended up on my Christmas wishlist. I received the MM-5 for Christmas, and finished building it in about an hour on the 26th. I think I rushed a little bit too much, but I couldn't wait to get it together. In the process, I did bend the crankshaft a tiny bit, which causes the propeller to wobble a little as it rotates. My suggestion would be to attach the propeller and nut to the reducer prior to attaching them to the crankshaft itself. Since I had to screw the propeller onto the reducer, I applied too much pressure and that is how I bent the crankshaft (pulled down on it a bit, while attaching the prop). Other than that little mix up, the engine worked immediately on a warm cup of water and ran for a few minutes. When I ran it on a boiling cup, it ran for nearly an hour. A great gift for anyone who likes to see how things work, and especially if they are perfectionists. It is the perfect project for someone who wants to get it all exact, as the more exact you are, the better it is going to turn out. Now I hope to get the other models for my birthday.
Very easy to build, and the result is amazing. The engine can run on hot liquids or cold ice. It is amazing to see how fast this spins because it only runs on heat
Up and Running.
Fun to assemble, fun to run, fun to understand. Thanks for developing the MM-5 kit. Horton A. Johnson, MD, New York, NY
Great quality!
I love it! The quality of the instructions and the quality of the parts are all very good! BTW, great product! Norwood Matt, Norwood-Near, Ohio
Amazing engine; it even runs on Ice!
I ordered the MM-5 on 2/18 and received it on 2/28. Started assembling the evening of 2/28, worked on it on 2/29 and finished the morning of 3/1. After final assembly I attempted it's initial run on hot water; it ran just as I was expecting. I let it run for about 10 min. as I marveled at it and then tried it on Ice; ran on Ice too (which I think is incredible). After it's initial run I let it rest and then over the course of several hours ran it off and on with hot water; I timed it once and it ran for 35 min., haven't timed it on Ice as of yet. The LCD thermometer is a nice feature; lets you see how the "cold" side warms up as the engine runs (and I imagine cool down when using Ice). All the parts were in the kit as were easy to follow instructions; the on-line instructions were very helpful as there were additional assembly tips. I took the time to polish the brass parts as I wanted the engine to look as nice as possible. I am very impressed with this engine's simplicity, construction, appearance and performance and I'm eager to introduce others to this engine; this is the sort of machine that will trigger the creative genius in some people and I'm expecting to see that happen. This is an amazing little engine; I highly recommend the MM-5 Coffee Cup Engine Kit to anyone with an interest in energy use, production and conservation. And it really does run on Ice...incredible!

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