Author Topic: Alyn Robinson Hot Air Engine  (Read 423 times)

Offline corlissbs

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Alyn Robinson Hot Air Engine
« on: August 22, 2019, 01:10:48 AM »
I am building the Alyn Foundry Robinsin hot air engine. Everything to this point has been done "by the book" if you will, but I do not like the heavy cast iron hot end (displacer cylinder). I am making one out of thin stainless tubing, with a copper bottom to put the heat into the cylinder and not up into the engine. Has anyone else replaced the cast iron hot end?  Brad Smith, Franklin, Wisconsin

Offline Ian S C

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Re: Alyn Robinson Hot Air Engine
« Reply #1 on: August 22, 2019, 03:49:05 AM »
Brad, I would make the hot cap by making a stainless steel cup by TIG welding a stainless disc on the end of a bit o thin walled stainless tube, foreget about the copper base. The stainless hot cap can be run at red heat, and will last for years.
Ian S C

Online Jasonb

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Re: Alyn Robinson Hot Air Engine
« Reply #2 on: August 22, 2019, 08:15:12 AM »
I seem to remember from the long thread about these engines that Graham reported that one of the best runners worked with a thin CI bottom and ran off a small tea light (candle) so can't see why copper would be needed. With his own engine being able to run all day at rallies there would not seem to be a problem with excess heat getting into the top half of the engine so don't know what you would gain by going for the less conductive stainless steel in place of the cast iron.

As you are new to the forum you may not have seen the thread started by Graham about his engines but worth a read.
http://www.modelenginemaker.com/index.php/topic,7561.0.html

Offline Alyn Foundry

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Re: Alyn Robinson Hot Air Engine
« Reply #3 on: August 22, 2019, 11:42:53 AM »
Good morning Brad.

Welcome to MEM.

I'm intrigued, one of my kits in Wisconsin, wonderful. How did you get it?

The Robinson is as true a replica as we could make it. The original used a cast Iron " hot pot " as I call it and it works very well.

Thanks to Jason for posting a link to my thread you should be able to follow a couple of recent builds.

Sadly a lot of kits by other suppliers used Aluminium which, as you know is highly conductive. The heat is rapidly transferred to the " cold end " and they cease to function. Being of " all Iron " construction ours doesn't suffer the same fate. I used to demonstrate my kits at various Steam rallies here in the UK and the Robinson would run all day long. It would bring the cooling water up to the boil over a period of time and continue to run. I personally think your concerns are unwarranted.

There was one modification that I did on later engines. The drawing shows the " O " ring nearly fully embedded in the platform casting. On later builds we opted to reduce the depth of the groove in both the platform and hot pot castings. This physically separated the metal parts and the " O " ring became the thermal barrier.

I'm sure all the interested members would love to see some photos of your build, please feel free to post them in the thread, linked above.

Cheers Graham.

Offline corlissbs

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Re: Alyn Robinson Hot Air Engine
« Reply #4 on: August 22, 2019, 01:23:02 PM »
Thank you, guys. First, how do I post a pic????? Yes, I am new to posting on the forum and I think I have a lot to contribute. I specialize in building high efficiency Stirling engines. This will be my third Robinson engine. I love the Robinson design. Without the regenerator in the displacer piston, the engine won't run well, unless one extends the displacer cylinder to a ridiculous length, as was done with the Westbury Robinson years ago. More on that later.

I have recently acquired a 55kw Stirling generator (75hp engine) and hope to get it running. Last weekend, we were running a 5 watt experimental Stirling. But these are not models and this forum is about models.

I have used both the SS hot cap and the SS tube with the copper bottom. While both work very efficiently, the copper bottom exceeds the SS cap in efficiency. This time, I am going to inset the thin copper disc to trap the heat from the flame, as Robinson did.

For efficiency in the 1970's, in the US, I used a displacer made out of manmade pumice stone, which works well in combination with the copper bottom hot cap. However with a steel hot cap, much more heat has to be applied which causes the pumice stone to crumble. My Ericsson, Esses and Denny engines from that period are still running fine. You probably know the pumice stone as a grill cleaning stone. It weighs nothing and actually acts as a slight regenerator. Because of the heat factor, I no longer recommend the pumice stone. I used to sell Bremen engine kits and supplied the pumice stone block. We call it "stinky stone" from the smell given off during machining.

Graham, I have looked for this kit for years and found one on British eBay. A friend of mine in the state of Oregon had an unbuilt kit and I am not sure where he got it. There used to be someone in the state of Washington who sold your kits and has a "barn full" of them, but was unwilling to look for a Robinson hot air engine for me. 

Brad Smith Franklin, WI

Online Jasonb

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Re: Alyn Robinson Hot Air Engine
« Reply #5 on: August 22, 2019, 01:34:33 PM »
Brad when the box comes up to type your reply just under it to the left is "attachments and other options"

If you click that more will come up and you will see a box "chose file" click that and then select the image on your computer (there is a size limit)

Offline Alyn Foundry

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Re: Alyn Robinson Hot Air Engine
« Reply #6 on: August 22, 2019, 02:15:34 PM »
Hi Brad.

You're obviously well versed in the Sterling "art " !!

I'm looking forward to seeing some of the engines in your collection and in particular the 55Kw generator.

I used to have an agent in the USA, Cliff Schroc?  I'm not sure if I've spelt his surname correctly, I heard he'd had some health issues and wasn't trading anymore?

The posting of pictures is fairly easy but as Jason has pointed out there's a size constraint, if they're too big they are disallowed.

Here's a photo of a machined Robinson platform that was cast for me late last year. They're possibly the best that were ever made!

Cheers Graham.

Offline corlissbs

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Re: Alyn Robinson Hot Air Engine
« Reply #7 on: August 22, 2019, 04:45:34 PM »
Again, thank you for the help. I am attaching a pic of the Alyn Foundry Robinson, in it's current state of construction. Yes, the top plate is a masterpiece, with the great cores. It is a pleasure to work on. What I like most about this engine is it's accuracy to the full sized engine. I have operated two of the full sized engines that are in the US. Nuff said about the accuracy, compared to other Robinson models.

On one of the other message boards, someone has built a Robinson engine that overheats. that shouldn't happen. It should run all day and not overheat, as I am sure this one will.

In the past, I have built my own burners. I use Propane for fuel and have a difficult time buying a burner, such as a backpacker's camp stove burner that is small enough. They put out way too much heat, so I modify them by fitting a thin brass ring or washer to the top that blocks all the holes except the inner ones. But recently, I have been using a gas furnace pilot light to run my engines. I can buy a model that comes with both natural gas and propane jets, although it no problem to modify the jet hole size.

Brad Smith

Offline corlissbs

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Re: Alyn Robinson Hot Air Engine
« Reply #8 on: August 22, 2019, 08:16:12 PM »
Regarding my other engines, I will take pics and post them here. This one, I finished this Spring, in time for our N.A.M.E.S show. It is the Poly Models, Anthony Mount, upright Bailey. There are two of the full sized engines existing. One in a museum in Great Britain and the other in the hands of a collector in Australia. It is a beautiful runner, that runs all day at the shows. I now have a pulley mounted to the shaft and will run something with it. I found that an engine that is doing something attracts more attention than one just sitting on the table, running. Especially the ladies can then visualize what these engines were used for. This engine was a dream to build. The drawings were fantastic. I wish I could say that for their Bailey Bee, which is presently under construction. And yes, the hot cap has a copper bottom and I use a choked down camp stove burner that only heats in the center. The engine runs all day on 0.5 of 1 psi. One other thing that I did to this engine is to use no gaskets, but every seal has an O-ring sealing it. Brad Smith, Franklin, WI

Online Dave Otto

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Re: Alyn Robinson Hot Air Engine
« Reply #9 on: August 22, 2019, 11:31:44 PM »
Nice looking engines Brad.

I had a set of your Bremen walking beam engines that I let my good friend Max talk me out of; it turned out a very nice looking and running model. He wasn't too fired up about the factory color scheme so he did his own thing. I CNC machined the two steel plates for him and made a second set for the other Bremen castings that I have.

Dave

Offline corlissbs

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Re: Alyn Robinson Hot Air Engine
« Reply #10 on: August 23, 2019, 12:29:13 AM »
Glad he likes the engine. It is a great runner. I will be posting pics of my Bremen's of both styles. The factory colors are WILD. I have been to the Bremen factory. It is/was still standing, but of different usage. I helped remove a Bremen from a Sears house in Columbus, OH.  Brad Smith

Offline corlissbs

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Re: Alyn Robinson Hot Air Engine
« Reply #11 on: August 23, 2019, 12:33:08 AM »
For the main bearings in my first Bremen (The normal configuration), I used computer disc drive bearings. When I built the walking beam model, my supply had dried up, so I used Oilite bushings. There was no difference. both ran equally well.

Brad Smith

Offline corlissbs

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Re: Alyn Robinson Hot Air Engine
« Reply #12 on: August 23, 2019, 10:10:07 PM »
This is a quarter scale model of the Denny Improved Ericsson pumping engine, that I built in the late 1970's. It utilizes my pumice stone displacer piston and copper hot cap bottom. When John Ericsson lost his patent to his pumping engine, because he sold engines before patenting them, anyone could build the engine and call it an "Ericsson." Several companies did just that. The American Machine Company of Wilmington, Delaware made significant changes to the Ericsson design and produced this engine in 6-1/2" bore and 8" bore. While the double bearings are an improvement, this is much more complicated than the Ericsson design. and much more expensive at the time that Rider-Ericsson was cutting prices. Shown are three pics of the model and an real American name plate from my collection.

Castings for this engine were made and sold by the late Brad Eisner. His son, Wade sells the castings now on eBay. It is all cast iron and a very nice runner.
« Last Edit: August 23, 2019, 11:24:10 PM by corlissbs »