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Norbert Keeley Robinson Engine Kit

corlissbs

Registered
I have started building the Robinson hot aair engine kit that I purchased in 1987 from Norbert Keeley of Ohio. This engine has a 2.000" bore power piston and is larger than the Poly Robinson engine. However, no one that I know has been able to get this engine to run. I know several people who have built it, with the same result. It is a nice looking engine, with the classic Robinson water hopper. Has anyone in this group had experience with the Norbert Keeley casting set for the Robinson engine?

Brad Smith
Franklin,WI
 

Orrin

Registered
Last Subscription Date
06/25/2014
I've not built that particular Robinson; but, I've spent a great deal of time tuning a quarter-scale. What I've arrived at is a far cry from what the drawings call for.

I threw away the cast-iron piston and made a very close fitting one out of graphite. I very carefully honed the cylinder before fitting the piston.

Because the hot and cold ends of the Robinson are very close together, one needs to make every attempt at isolating them, thermally. I've done this with double-thicknesses of 0.062" of high temperature gasket material between the hot cap and the rest of the engine. I've also put a double layer of cork gasket between the base and the upper portion of the engine.

Water cooling is essential, so I rigged up thermo-siphon cooling between the engine and a copper water tank.

The most spectacular improvement came from my throwing the original brass displacer away, replacing it with a regenerative displacer. Basically, it amounts to perforated spin-formed top and bottom caps. The space in between is packed with a stainless steel scouring pad. The pad us kept from bulging out with a cylinder made of fine S/S screen. I made a wrap of fine S/S wire around the screen in two different places to keep it from bulging out. The screen is held securely by the flanged top and bottom cupped caps of the displacer.

In its designed configuration my Robinson would run for five or ten minutes, at most. Now, it will run all day long. The only time I have to stop it is for topping off the alcohol fuel tank.

You can see pictures of it, here:

http://users.moscow.com/oiseming/lc_ant_p/pic_Prj4.htm

Orrin
 

corlissbs

Registered
Thank you, Orrin for your reply. I do know that the full sized Robinson engines used a porus displacer of "twisted wire," according to the patent information. The Alyn Models, 1/3 scale Robinson uses a porus displacer, but I have never seen a drawing showing how it was made. Robinson engines ran well and I have seen full size engines running at hot air engine shows. But that is a far cry from seeing the engine apart.

The Keeley design is a very nice looking engine. I will try to post some photos. I plan to cut down on the dead air space by using a 1/4" diameter passage instead of the 1/2" diameter that the prints call for. Something makes this engine not run, as several of my friends built it in the 1980's and could not get it to run. And they were experienced hot air engine builders. I worked out the swept volume ratio and it is 1.8:1, which is too low in my opinion, so I am getting the ratio to 2.3:1 by enlarging the displacer cylinder and sleeving the power piston. The stroke, I am not going to change, because it would also change the stroke of the displacer.

Why did you not keep using the balsa displacer piston, as your web site states?

Brad Smith
Franklin, WI
 

Orrin

Registered
Last Subscription Date
06/25/2014
I had to give up on the balsa wood displacer because the rascal kept absorbing water from the humidity in the air when the engine was sitting idle. Then, when ran it the heat from the hot cap would drive out the water in the form of steam. The power cylinder was the coolest place on the engine, so the steam would condense, there, gumming up the power cylinder. Seeing as how the power cylinder was cast-iron, it would rust almost instantly.

I was tickled pink by the performance of the balsa displacer and was so excited about it I posted the results on my Web page. I should have waited until I had more operating experience.

I had thought of trying to find some kind of sealer with which to coat the balsa; but, gave it up. I would cook the balsa in the oven for hours, hoping to dry it out; but, it was the same old story after the engine sat unused for a while.

I think you are onto something by decreasing the dead space. I go to great pains to minimize it. Consequently, my Rider-Ericsson runs great on the tiniest propane flame I can manage. I've re-built the burner three or four times, each time cutting the number of flame orifices in half.

I'd surely like to get my hands on one of those non-running Robinsons. I'd like the challenge of seeing if I could get it to work.

I have the castings for an Alyn half-scale. When I get around to building it I'll probably use a stainless steel scouring pad displacer for it.

Robinsons puzzle me. I've seen full-sized factory-built Robinsons run at shows all day long with not a drop of water in them. Apparently, at low RPM they can dissipate enough heat.

Regards,
Orrin
 
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