A Pipe Fitting Robinson Engine

One day my friend Captain Carl told a tale of woe. However, it eventually came to a happy ending. Here is the story in pictures.

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After buying a small Robinson hot air engine from the estate of the late Al Cropley, he decided to stop off on his way home and show it to one of his friends.

His friend thought it would be fun to see how well the engine ran. Captain Carl went along with the idea and it wasn't long until they lit a torch and applied some heat to the hot cap.


Carl's friend was determined to make it go 'round. Being the "get a bigger hammer" type of guy, he figured that a little more heat would surely do the trick.

It didn't.


When Captain Carl opened up the the little rascal, he discovered why it didn't operate; the power piston was not hooked up to its connecting rod! All the heat in the universe couldn't have made it work.

Further investigation revealed the consequence of pouring all that heat to it. The displacer piston melted!

Disgusted, Captain Carl tossed the whole works into a corner and tried to forget the whole sorry episode.


When Carl told me of his new "toy" being destroyed before he even got it home, I saw this as a challenge. I asked the good Captain if I could take a crack at fixing it. He gladly consented.

This little jewel had been loved to death. All pivots had been worn completely out and the piston was worn seriously undersize.

The repair job seemed like a perfect time to try out my wife's Sherline equipment. All egg-shaped holes were made true and bushed to size. The power cylinder (originally a bronze bushing) was lapped true and a new piston fitted to it. Coming out of a damp climate, The displacer rod and crankshaft were badly rusted, necessitating new ones.

Displacers for "pipe fitting" Robinsons are made out of aluminum cigar tubes. I don't smoke, so you can understand why I choked when the cheapest "tube" cigar cost me $7.00! :-)

Here, you see the finished product, spinning merrily.


The little bugger runs like a champ! Wow!


This picture shows a copper font for the Robinson's alcohol burner. The original one made of glass was cracked. It's a long story, but the easiest fix was to make a new one.

No, gas tank sealer won't work if exposed to straight alcohol. :-(


The little tank was made out of a scrap of copper pipe. For the top and bottom caps, a length short length was split down the side, flattened, cut into disks then spun to the shapes shown, here.


So that is the story of Captain Carl's Robinson engine. His investment finally paid off. Not only does his engine run, he got a $7.00 cigar in the bargain! :-)

My enjoyment came from the satisfaction of bringing a basket case back to life! Satisfaction. Doing a job to the best of one's ability. That's the key to a rewarding life.

By now, you are probably wondering what this "pipe fitting" thing is all about. Well, the main frame is made out of a bell reducer, a close nipple and a pipe coupling.

This is one of the best running hot air engines I've ever toyed with. If you think you'd like to try your hand at building one, e-mail me and I'll put you in touch with someone who will sell you the plans.


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Revised -- 1/18/07