Manson Hot Air Engine Build

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Harold_V
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Re: Manson Hot Air Engine Build

Post by Harold_V »

It's easy enough to use a square, or to even use the spindle to run a DTI along one of the two slots that you'd machine first. The piston would be held in the vise on your mill. The piston would have to be offset in the vise, but that shouldn't present any issues assuming your vise closes parallel, as most mill vises do. Faster and easier than providing a plate.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
pete
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Re: Manson Hot Air Engine Build

Post by pete »

Yeah heat of about 200-300f will release most super glues, locktite etc. Just do it in a well ventilated area. I'm no expert but I've read heated cyanoacrylate based glues give off a gas much like cyanide. Whatever it is the fumes aren't healthy.
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rmac
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Re: Manson Hot Air Engine Build

Post by rmac »

Harold wrote: It's easy enough to use a square, or to even use the spindle to run a DTI along one of the two slots that you'd machine first.
My picture doesn't show it very well, but the piston is hollow (like a tube) and those slots go all the way through to the inside. So there's not really a good surface there to register against a square or to sweep with an indicator ... just sharp corners at the ends of the slots. I suppose in theory that would work, but somehow it seems iffy.
pete wrote:Yeah heat of about 200-300f will release most super glues, locktite etc.
I ran a little test this morning with some Loctite brand gel super glue, and it released after a couple of minutes in boiling water. Hopefully it will behave the same when it's time to unscrew the indexing plate. If not, I have a gallon of acetone at the ready.

-- Russell Mac
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Harold_V
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Re: Manson Hot Air Engine Build

Post by Harold_V »

rmac wrote: Wed Aug 04, 2021 6:16 pm somehow it seems iffy.
It would still work. All you need is the two points of contact, the rest doesn't matter.
It can be iffy, but only if you don't have a decent square, or you have poor eyesight. You can set the angle to a high degree of accuracy this way, all depending on the distance between the two points of contact. One degree @ 1" equates to about 17 thou.

No matter---so long as you don't mind doing it another way, so long as you achieve your goal, that's really what matters. Lots of ways to get to the end point.

H
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rmac
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Re: Manson Hot Air Engine Build

Post by rmac »

Success.

piston.jpg
pete
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Re: Manson Hot Air Engine Build

Post by pete »

:-) Congratulations.
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rmac
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Re: Manson Hot Air Engine Build

Post by rmac »

:D Thank you.
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rmac
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Re: Manson Hot Air Engine Build

Post by rmac »

I finished up the rest of the parts for the Manson engine yesterday. Most of them were enough like the Moriya engine that I didn't see any reason to show them here individually. But here is a group photo, arranged sort of like an exploded parts diagram:

exploded_manson_parts.jpg

I had only one mishap along the way. That was when, for the first time ever, I accidentally ran a drill into a parallel. Oops. The parallel now has a battle scar, but remains functional after honing to remove a bit of a burr. The tip of the #50 drill broke off and got stuck in the part. I was able to save the part itself, but the drill is history.

The first test run with heat from an alcohol burner was a partial success. With the engine mounted vertically (hot end on the bottom, crankshaft on top), it ran, but only for a minute or two after it first started. After that, the "cold" end got so hot that there wasn't enough temperature differential to sustain operation. I saw the same thing happening with the Moriya engines, but never so bad that they quit running.

For the second run, I oriented the engine horizontally so that the cooling fins were not surrounded by hot gas rising from the heat source. That worked a lot better, but eventually the cold end still got hot and the engine quit running.

So what to do? The first thing I want to try is to set this new engine up with the parabolic mirror to see if that makes any difference. If it does, problem solved. (Of course it's supposed to be cloudy and rainy here tomorrow, but oh well.) Then if it doesn't work any better with the mirror than it does with the burner, maybe a small fan to cool the fins (driven by the engine, of course) would be in order.

We'll see.

-- Russell Mac
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rmac
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Steam Engine with No Boiler ???

Post by rmac »

Yesterday this project suddenly got a lot more interesting!

We had a little sunshine in the afternoon, so I was able to try heating the engine with concentrated sunlight from the parabolic mirror. That didn't work any better than with the alcohol burner, apparently because the cold end was still getting too hot. In desperation, I grabbed the garden hose, gave the cold end a good squirt and the engine almost immediately took off and was running really well.

So I thought, "okay, the problem really is not enough cooling" and decided to cut a couple more fins in the cold end just to see if that would help any. It didn't. By this time it was dark and I was back in the shop trying to heat the engine with the alcohol lamp. Once again I tried to pour some water on the cold end, but this time it didn't help.

It didn't help, that is, until some water accidentally got into the cylinder vent port. Almost immediately, just like outside with the hose, the engine took off and just ran like crazy! I haven't figured out exactly what's going on yet, but I'm pretty sure that some of that water is instantly boiling inside the engine and somehow creating lots of steam pressure at just the right time!

So now there are three questions:
  1. What is actually happening when water gets inside the engine?
  2. Has anybody already built a engine where steam is generated in a heated cylinder instead of in a boiler? Google turned up a sort of obscure reference to something called a "Hall engine", but I couldn't find a description of how it actually works. Other than that (last night for me, anyway), nothing.
  3. Is there some way to modify what I stumbled on and make it intentional, preferably with some controlled and automatic way to introduce the water without just dumping it in with a hose. It seems like a steam engine with no boiler, only three moving parts, and no complicated valve mechanism would be very interesting.
-- Russell Mac
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Re: Manson Hot Air Engine Build

Post by Inspector »

Perhaps a little carburetor in its simplest form metering the water into the cylinder?

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Andy R
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Keep the cool end cool - a challenge

Post by Andy R »

Russel,
Your observation regarding "...eventually the cold end still got hot and the engine quit running ..." is spot on based upon my experience. I have a small horizontal hot air engine that my grandfather built. The cooling fins are oriented vertically (as opposed to yours). The alcohol burner for the heat input is enclosed in a brake fluid can (remember those?) and the can is lined with asbestos, all in an attempt to keep stray heat from reaching the cold piston. But it always runs better with an ice cube melting over the cooling fins. The difference in temperature appears to be paramount for good operations. In cold weather the ice cube is not needed. Without some magic substance to keep the cool side of yours cool, perhaps lower input heat will work? It's worth a try. Nice machining work, by the way.
Regards,
Andy
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rmac
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Re: Manson Hot Air Engine Build

Post by rmac »

Inspector wrote: Perhaps a little carburetor in its simplest form metering the water into the cylinder?
That's an interesting idea. At the moment I'm still trying to figure out what's actually happening when the water gets inside the engine. Questions like: Is the water dribbling into the port by gravity, or is it being sucked in somehow? Where within the engine is it boiling? How is it that the increased pressure magically happens at the correct time within the cycle? Stuff like that. It's a mystery.
Andy R wrote: Your observation regarding "...eventually the cold end still got hot and the engine quit running ..." is spot on based upon my experience.
Yes. There are lots of discussions on the homemodelenginemachinist.com forum about this, and I guess quite a few model Stirling engines solve the problem with some sort of water cooling. Another thing I'm still trying to figure out is what's different between my Moriya engine, which works great with just air cooling, and this newer one which doesn't. The standard Moriya setup has a fan blowing on the cold end, but I have always run mine just with a flywheel, so that's not it. The other big differences are that my newer engine has a much smaller hot end, and it doesn't have the big, chunky aluminum base like the Moriya does. I can imagine that either one (or both) of those differences might be problematic.
Andy R wrote: Nice machining work, by the way.
Thank you.

-- Russell Mac
Last edited by rmac on Thu Aug 12, 2021 12:43 pm, edited 1 time in total.
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