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Brayton Readymotor.

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Alyn Foundry:
Hello All.

It almost seems like a lifetime ago now when I first started upon the most ambitious scale engine project ever.

A long standing customer that became a good friend, Mike the bike, showed me a picture of the Brayton ready motor. A beautiful piece of Victorian mechanical engineering. A time when aesthetics and functionality were as one. Sadly, Mike passed on and only his photocopies from the book remained.

Upon a whim I thought, wouldn't it be nice to remember Mike with an inspirational and pioneering engine? The Brayton fitted the bill nicely.

George B. Brayton and his engine are almost forgotten but the Brayton Cycle is now used widely in the form of the Jet engine!
In the early 1870's prior to NA Otto and his four stroke the Atmospheric engine reigned supreme. Brayton's " constant pressure engine " design had similar efficiency but later liquid fuelled engines were developed for places where town gas was unavailable.

Picture a canister filled with a pressurised combustible mixture of air and Town gas, a recipe for disaster if ever there was! Well this was exactly how the fuel was stored prior to combustion. At bottom dead centre the admission valve opens allowing the mixture to pass by a burning pilot light within the cylinder head. The result is an expansion of the Nitrogen that presses against the underside of the double acting piston. On the other side of the piston the air and gas that was drawn in on the last downstroke is being moved through a non return valve into the tank that forms the engine's beam support column. At a given point the admission stops to allow further expansion due to the heat generated by the flames. As the engine reaches TDC the exhaust valve opens and the flywheel carries the piston down both exhausting the power cylinder and drawing in a fresh charge of mixture in. The cycle repeats.... Well until sometimes the flames could pass the many safety meshes and ignite the fuel in the column!! The engine was fitted with a large volume safety valve to allow for this condition without an explosion of the cast Iron receiver.

Well, that's the history. George Bailey Brayton continued to develop engines and in the 1890's was the first to directly inject liquid fuel oil into the cylinder just like Diesel did but used secondary ignition. He was the first to control engine speed by quantative means however.

To the point....

I happened to have a pair of " lazy S " spoked cast Iron wheels that had solid rubber tyres bonded to the rim. A quick measure at around 15 inches diameter seemed about right for a one third scale engine. Once a datum has been found you can then use it to measure a picture and start making a three dimensional pattern. After several months I had got most of the engines patterns made and quite a few were cast in Iron. I have the cylinder, piston and heads finish machined too. Disaster struck, my one and only Buckley foundry announced closure. I hadn't quite finished the main engine pattern, the project was shelved.

Having recently found a new and I'm happy to say, competent Iron foundry the Brayton Ready motor seems like an ideal candidate for resurrection?

What does the membership think? Does anyone know if a
" constant pressure engine " has ever been scaled and built?
Is it worth the effort? Over to you....

crueby:
Well, I don't yet follow the way the cycle works (diagram would help a lot, I think), but the engine itself is very interesting looking, with the fluted column and arcs its classic.  Would you make it to run the original cycle, even with the dangers?

Art K:
Like he said, I don't follow how it works. I did follow a link to Wikipedia that explained the cycle and as an open cycle turbine and jet engines. I guess it's just over my pay grade. :ROFL:
Art

Jasonb:
I think I follow how it works the top side of the piston acts like a compressor piston and draws in the fuel air mix on the return stroke and then pumps it into a smaller chamber on the power stroke. The Combustion side of the piston sees that compressed fuel/air mix at the start of the power stroke where it is ignited making the engine fire and on the return stroke it exhausts the spent gas.

Is it worth the effort?

Well as a personal challenge then I'm sure it is. As a possible commercial project then I think the size will be a limiting factor as there are not many engine enthusiasts who can acomodate a 15" flywheel and even those that can may turn their noses up at an engine that is not going to be easy to move around.

As to whether it has been modeled before I don't think it would have been done in a "scale" form but expect someone may have made a barstock version just to see if the cycle can be modeled. I see from Google that Nick Roland (RMC Engines) has a full size later 2-cylinder engine that runs with this cycle so he may have played about with it on one of his test rig models.

Alyn Foundry:
Good morning.

Many thanks to the few that looked in.

The Brayton cycle is basically quite simple.  A mixture of compressed air and fuel ( in the correct ratio for combustion ) are allowed to enter the closed cylinder with the piston at bottom dead centre. A pilot light within ignites this flammable mixture. Two processes act as one, the compressed air wants to expand into the bigger space and at the same time is also being heated by combustion, rapid expansion occurs pushing the piston away, the power stroke.

The engine had a mechanism that controlled the amount of admission, a bit like a steam engine does, variable " cut off " this maintained the engines speed and power.

This particular engine combined both the expansion chamber and compressor in a single, double acting style cylinder, later designs used separate cylinders.

With regard to your question crueby, no. I felt that a potential " bomb " wasn't a great idea so I have made the admission valve assembly with the addition of a separate fuel injection port. In other words the mixture will be made on demand just prior to burning, the column will contain nothing but compressed air.

I've also attached a picture of the Brayton cycle pertaining to an " open cycle " system.

Cheers Graham.

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