One third scale Ready Motor work in progress

[myrickman]

I started on this back in 2019 as a project to teach myself CNC. I went to view and measure the original Brayton engine at NMIH in Bethlehem. From there I used the CNC to make all the patterns. It is a unique engine in that it is a constant pressure combustion cycle. You get a pilot flame burning in a small chamber above the main cylinder. As the engine goes through TDC, a valve opens, forcing air through a petrol-saturated gauze which burns and expands into the cylinder.…much like a modern turbine, but using a piston. The cylinder closer to the flywheels compresses air for the combustion process which is stored in the hollow legs.
I‘m able to get some intermittent series of fires, but working through issues of fuel delivery, cam profile and timing to get sustained running.

 

[Alyn Foundry]

Very nice indeed.
Way back in 2004 was when I started on pattern making Brayton’s exhibition vertical engine. Finally after many ups and downs the patterns have reached the foundry. A very special thanks to Jason Ballamy for help with the flywheel and various small parts.

I look forward to seeing your engine running.

Cheers Graham.

 

[myrickman]

Thanks Graham. Mine has a 2” bore. What size is yours planning to be? The pilot flame chamber is about 7/8 diameter x about 0.4 high.

 

[Alyn Foundry]

Hi.
It has a 3” bore and 4-1/2” stroke. The model will stand approximately 2 feet tall with a 15” diameter flywheel. The cylinder and ends were cast many years ago and are fully machined. As is the beam. The closure of my local Iron foundry back in 2007 stopped me for a long while but now I have access to a new place. Thankfully they are “ old school “ and very capable moulders. The second picture is a recent batch of castings for my half scale Robinson “ X “ type gas engine.

 

[kf2qd]

Sounds likw a flame-licker or vacuum engine.

 

[Alyn Foundry]

Sounds likw a flame-licker or vacuum engine.

Hi.
This engine is very different. The Brayton cycle is best known as the modern day Jet engine. However the pressure generated by the expanding, combusting gasses acts upon a piston within the cylinder. Effectively a two stroke/cycle engine. My model has the power and compressor piston common to a single cylinder whereas myrick man’s model has a power cylinder and separate compressor cylinder.

With my model the vertical column is the air and fuel receiver. After several revolutions of the flywheel the receiver is charged with a combustible mixture of town gas and air. With the piston set at just after TDC a pilot light is lit within the cylinder end. The admission valve is opened and the mixture of fuel and air is ignited by the pilot light. The following combustion and expansion acts upon the piston creating the power stroke and compressing the next charge. At BDC the exhaust valve opens and the spent gasses are cleared from the cylinder on the downstroke and also pulling in a fresh charge of fuel and air above it. The cycle then repeats over and over until the engine is stopped. It can be likened to a steam engine where the expansion acts in the same way.

The efficiency wasn’t great by comparison to the later Otto/4 stroke cycle but was a massive leap forward against the current atmospheric gas engines of the day. As far as I’m aware there’s but one, maybe 2 working full size Brayton cycle engines that exist today.

Cheers Graham.

 

[chrsbrbnk]

whats keeping the pilot flame lite? seems like a really small space to keep a flame in?

 

[Jasonb]

Graham has a cunning plan for that, I'll leave him to post details.

 

[myrickman]

I think I know Graham’s plan…mine was to make the breech plug into a spark plug and use a bbq ignitor to light the pilot flame. In this video, you can hear the ticking of the spark plug, then the flame light and the dull roar through to the exhaust.

 

[Alyn Foundry]

Graham has a cunning plan for that, I'll leave him to post details.

Thanks Jason.

I think there’s probably several cunning plans that might need to be employed eventually but here’s the first.

Obviously I’m still waiting for the remaining castings from the foundry to complete this model.
Cheers Graham.

 

[Steamchick]

Well done Graham! What a cunning plan! Do you have more details of the Braun foil and burner? I couldn't quite catch all you were explaining in the video. (It is me that is 1/2 deaf and 1/2 daft).
K2

 

[Steamchick]

Would an alternative igniter be a glow plug - as used by the model aircraft Glow-plug engine folk? - That is my cunning plan for a (Small) 1" stroke Otto/Crossley gas engine... - at some time about 3 projects away!
K2

 

[Alyn Foundry]

Well done Graham! What a cunning plan! Do you have more details of the Braun foil and burner? I couldn't quite catch all you were explaining in the video. (It is me that is 1/2 deaf and 1/2 daft).
K2

Hi K2.
I’m old enough to remember the the principle being featured on Tomorrow’s World, a science and technology television program, decade’s ago. Not being involved with the “ glow plug “ scene I didn’t really have any idea of how the Platinum was involved. Thankfully, now older and a little wiser ?? I remembered it again. One of my daughters is a hair stylist who was quickly able to source a couple of the cordless styling wands from her client list.

Considering the fuel is Butane the refills are ridiculously expensive and many of these wands lie unused and unwanted.
They consist of a disposable tank, an on/off switch and a thermostatically operated gas jet. A small Piezoelectric spark is used to first ignite the fuel and air. Once lit the small Platinum alloy mesh tube keeps the process going until the fuel is shut off. I was quite surprised as to how long you could turn the fuel back on after it being turned off for the gas to reignite. Perfect for the current project….

Regarding your Otto Crossley project. I have had the privilege of working with several examples over the years as my main interest is with the restoration and preservation of vintage machinery. When I started producing model IC engines they were mainly of hot tube ignition and I would suggest that you initially try running the engine with a simple, hollowed out, 316 Stainless Steel tube.

For any interested in this particular model and other current projects you might like to visit or join….

https://www.facebook.com/groups/ALYNFOUNDRYMODELS/
Cheers Graham.

 

[SteamChEng]

Hi.
This engine is very different. The Brayton cycle is best known as the modern day Jet engine. However the pressure generated by the expanding, combusting gasses acts upon a piston within the cylinder. Effectively a two stroke/cycle engine. My model has the power and compressor piston common to a single cylinder whereas myrick man’s model has a power cylinder and separate compressor cylinder.

With my model the vertical column is the air and fuel receiver. After several revolutions of the flywheel the receiver is charged with a combustible mixture of town gas and air. With the piston set at just after TDC a pilot light is lit within the cylinder end. The admission valve is opened and the mixture of fuel and air is ignited by the pilot light. The following combustion and expansion acts upon the piston creating the power stroke and compressing the next charge. At BDC the exhaust valve opens and the spent gasses are cleared from the cylinder on the downstroke and also pulling in a fresh charge of fuel and air above it. The cycle then repeats over and over until the engine is stopped. It can be likened to a steam engine where the expansion acts in the same way.

The efficiency wasn’t great by comparison to the later Otto/4 stroke cycle but was a massive leap forward against the current atmospheric gas engines of the day. As far as I’m aware there’s but one, maybe 2 working full size Brayton cycle engines that exist today.

Cheers Graham.

Very interesting combustion engine! In fact, it sounds more like a combustion version of a Skinner Uniflow than a flame licker. Best of luck with the project!

 

[Alyn Foundry]

Here’s a link to Wikipedia on the Brayton cycle. There’s also a picture of the engine that I’m currently working on.

https://en.wikipedia.org/wiki/Brayton_cycle
George B Brayton was really quite ahead of the time, a highly talented engineer but now, almost forgotten.

Cheers Graham.

 

[Steamchick]

MOST interesting! I also like the idea of using the parts from a Gas hair curler... I think my wife has one, but her hair is too short to curl nowadays... Maybe I can acquire that one...? - Or it may be cheaper to buy one off £&@y!
K2

 

[Jasonb]

On the slow turning otto and Crosley engines a model glowplug needs to be wired in all the time which the hair drier part won't require so no need for wires etc which would also look out of place.

Not sure if you could get the hair drier element to work on an enclosed combustion chamber of an Otto or Crossley, OK on graham's open ignition flame which burns externally and is more to stop the flame being blown (sucked) out by the incoming air/fuel

 

[Steamchick]

Thanks Jason. That is most interesting.
I also have an atmospheric gas engine. This relies upon an external flame, past an orifice half way along the stroke, to ignite the gas- air mix. Needless to say, it was designed for coal gas (CO etc. containing free hydrogen in the mix) which ignites readily, but does not work well with butane. An alternative is to use acetylene. Or fit a glow-plug. So I guessed the element of the glow plug must be platinum coated tungsten wire, to add the catalyst effect to the element. I would guess the mesh you are using from the hair heater could also be tungsten plated with platinum, to keep costs down. - but whatever, it works!
Not important, if the glow plug won't work I'll make a stainless steel hot tube.
Thanks for the advice.
K2

 

[Alyn Foundry]

I know we’re digressing a little but here’s mine. A BEECo of Leek Staffordshire Circa late 1890/1990’s.

 

[Steamchick]

I don't mind you digressing. My atmospheric gas engine is a long way from looking that good! Well done Sir!
K2