Author Topic: Number 83, a Hot Air Engine  (Read 256 times)

Offline vtsteam

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Number 83, a Hot Air Engine
« on: March 08, 2023, 05:26:34 PM »


Number 83 was a hot air engine I built for my father fourteen years ago. It wasn't named as my 83rd engine, it was his 83rd birthday, and I built it in the two weeks prior to the celebration. My father was an engineer. We'd been estranged for over a decade, and in this way, I hoped he'd understand how much he meant to me in making this for him. Six years before, I had taught myself hobby casting and machining by building a Gingery lathe and many other projects. Thus he had no idea I could do something like this.

For me, a relatively slow builder at the time (and since, really), making it was done at a very hectic pace, and I only finished the engine and tested it late at night prior to the day, when we drove several hours to his house in Connecticut.

The engine featured an overhung crank, with second offset throw for the displacer, and a crank driven through two sets of sealed ball bearings. It was mostly made up of aluminum castings and scrap brass and steel. The power piston was of graphite and ran in a carefully honed brass cylinder. The displacer cylinder was stainless steel, and the displacer was a thin wall hollow aluminum cylinder.





The displacer cylinder and power cylinder extended in opposite directions from a massive mounting plate of aluminum, which was intended to act as a heat sink. The two cylinders met each other inside that plate, so it was not necessary to have any connecting pipe between the two. This configuration reduced the engine's dead space to a minimum. The cylinders weren't axially concentric, but did overlap by about 25% inside the mounting plate, head to head, creating the zero dead space air passage.

A massive aluminum bedplate was attached to the thick mounting plate (with heat electronic heat sink compound between the two) and two heavy cast aluminum support arms also carried away heat. Fins, fans, etc. were not necessary to cool the displacer cold end, or power cylinder. This gave the engine a clean look, as well as making for a very robust appearance and a stiff structure.





The flywheel was turned from heavy steel bar. The firebox and base were made from scrap structural steel square tube and channel sections, and left roughly finished and linseed oiled, as a contrast to the running parts. A smoke stack was improvised out of a chromed brass household sink plumbing tailpiece, set in a turned collar.





The night before presentation, with paint barely dry, fingers crossed I tried the engine out with a can of Sterno in the firebox. I set it on top of our kitchen stove for a fireproof location.

The engine ran right off the bat, and being quite powerful, rapidly accelerated to surprisingly high revs. Vibration at that speed had the entire heavy assembly starting to move across the stove top, so I pulled the fuel can partially out of the firebox to throttle it down to a more pleasant rate.

My original intention of building such a large firebox and stack was to try to power the engine with a variety of solid fuels for interest sake, -- wood chips, pellets, maybe even small chunks of charcoal. But I had no time to try those, so I boxed it up that night, and wrapped it as a present for the following day.

I'm sorry to say, I have no pictures of the construction, and no videos of it running. I have only a few photos left now of the engine at his house sitting on a table on his birthday, as seen here. I had presented it with some trepidation, but I needn't have worried because he was very surprised and admiring on that day, and that made me feel quite happy. We had finally shared a connection.
Steve

Online Kim

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Re: Number 83, a Hot Air Engine
« Reply #1 on: March 08, 2023, 06:02:58 PM »
Steve, that is a nice little engine, and a wonderful story to go with it!  It's great that you were able to do that to build a connection with your father.

Kim

Online Jo

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Re: Number 83, a Hot Air Engine
« Reply #2 on: March 08, 2023, 06:32:46 PM »
What a lovely gift to make for your Dad's 83rd  8)

Jo
Enjoyment is more important than achievement.

Offline bent

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Re: Number 83, a Hot Air Engine
« Reply #3 on: March 08, 2023, 07:16:49 PM »
That's pretty neat, I do like the stoutness of the design.

Online Admiral_dk

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Re: Number 83, a Hot Air Engine
« Reply #4 on: March 08, 2023, 08:04:26 PM »
Lovely gift and an interesting design  :praise2:

Per

Offline RReid

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Re: Number 83, a Hot Air Engine
« Reply #5 on: March 08, 2023, 08:35:31 PM »
Hi Steve. That's a great little engine, and a wonderful story! :ThumbsUp: :ThumbsUp: :cheers:
Regards,
Ron

Offline Dave Otto

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Re: Number 83, a Hot Air Engine
« Reply #6 on: March 08, 2023, 09:00:49 PM »
Nice project and good memories, thanks for sharing.

Dave

Offline vtsteam

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Re: Number 83, a Hot Air Engine
« Reply #7 on: March 09, 2023, 03:05:22 AM »
Thanks kindly Kim, Jo, bent, Per, Ron, and Dave.  :cheers: :cheers:
Steve

Offline Djangodog

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Re: Number 83, a Hot Air Engine
« Reply #8 on: March 10, 2023, 02:03:41 PM »
Thank you for sharing the engine and especially the story.  A fatherís approval can be very illusive.  Six years after my father passed, I still think about whether or not he would approve of a job that I had done.  I think that for many of us we will always seek our fatherís praise.

For what itís worth, very nice job. 

Offline vtsteam

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Re: Number 83, a Hot Air Engine
« Reply #9 on: March 10, 2023, 02:19:48 PM »
Thank you Djangodog. Now we have to make things for ourselves, or for our younger ones. Or teach others some form of capability, locally, which I'm considering.

Having just written about it, and looked at those pictures again, I have inevitably started thinking about changes that I'd make now, fourteen years later!

And then the mind wanders to making it larger, and being able to test it on other fuels, and, and...........

I guess I'd have to call a new one Number 74, now!   :Jester:
Steve

 

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