Reed valves, educate me!

Shnitzl Fri Apr 01, 2016 3:08 am

could anyone provide detailed images on how the reed system works on the cox .049?
I see images of an air intake and a fuel mixture screw, does the air flow freely in and the mixture screw regulates the fuel into a common chamber for the reed to open and pass into the cylinder? no multiple jets or micro passages along the way?

I would like to try to make a inline twin engine, with a one piece crank segragating each crankcase with a mid split bearing.
each crank case would get its own reed valve in hopes to produce a usable power output.

Reed valves, educate me! Tank%20Conversion%208cc%20Alu%201

Reed valves, educate me! Tank%20Conversion%208cc%20Alu%201

can I put a reed valve behind a .049 carburetor and call it good?

Mark Boesen Fri Apr 01, 2016 4:48 am

https://www.youtube.com/watch?v=SnqqksKIufU#t=57

Mark Boesen Fri Apr 01, 2016 3:02 pm

fyi, about 3/4 through they talk about engine operation.

Shnitzl Fri Apr 01, 2016 5:52 pm

I suppose I should ask for the engine in my signature.
if I want to install reeds, do I just need the reed and some retainer to accommodate the cox carb and it should run?

the carb will replace the fuel mixture screw and all should work well? maybe I will sketch something up.

so reed, reed retainer (housing), housing tapped for a 1/4-32 thread cox carb and should run?

ian1954 Fri Apr 01, 2016 6:32 pm

That looks like a Jerry James Hex-2 Cox Twin.

http://www.jamesengine.com/Hex%202%20Drawings.pdf

If it is then it doesn't use reed valves.

Shnitzl Fri Apr 01, 2016 6:56 pm

Yes you are correct, I have built his BUT now I have designed my own internals but utilizing the hex stock for simplicity. everything else has been reworked to the way I want it. 3 main bearings, one piece crank. the crank case is segregated by a main bearing sealing off the shared crank case to essentially make two separate cases, the idea is I can now run the stock reed valves to restore performance!

I just want to know if the way I am going to lay it all out will work.

I suppose its easier to just build it and see?

I never had a stock COX .049 to take apart, so thats why I am asking these questions.

ian1954 Fri Apr 01, 2016 7:26 pm

I see what you are trying to do but you will find it difficult.

The reed valve set up has quite a diameter and although one could be made for the rear of the engine for the rear cylinder, getting one to fit on the side for the front cylinder or the rear cylinder will be difficult but not impossible.

Have a look at this

http://modelenginenews.org/eze/eze-rv.html

The carburetor could "easily" be constructed using TD parts, NVA and venturi, or a home made variation. The build shown above should have produced very good results but read the text for an honest summary and the results of the build.

Shnitzl Fri Apr 01, 2016 7:58 pm

thanks that has all the info I was wondering about!
I think in my case it would help allot to add the reeds, but like you stated fitting them will be a challenge.
originally I thought they would fit perfectly on the side of the engine but it now appears they are larger then I imagined. still worth a look but not sure its worth the aggravation yet!

pkrankow Fri Apr 01, 2016 8:33 pm

I have a Johnson JW-10 3hp twin cylinder 2 stroke outboard motor.
http://outboard-boat-motor-repair.com/Evinrude%203%20HP%20Lightwin%20Outboard%20Boat%20Motor/default.htm

One carb, 2 reeds, independent chambers under the pistons to make each function properly. Nothing new. There are no pictures describing the setup here, and I am not tearing down to get to reeds anytime soon on my engine. A little poking around will give a lot of information.

The key items are air passage diameter to allow proper fuel draw, fuel metering method, crank volumes close to minimum so transfer works well. Keeping air passage length more or less even and as short as convenient is good too.

Phil

roddie Fri Apr 01, 2016 9:46 pm

Would a single reed-system work? What I'm envisioning is an opposed-twin with the stock Cox "Bee" back-end.. and both cylinders timed to fire together. It would require a ported "flow through the case" type of design to get fuel to the forward cylinder.. but the vacuum/pressure cycle needed for induction would remain the same.. wouldn't it? The question would be whether a stock-size venturi would flow enough mixture to feed both cylinders? The venturi could be enlarged easily.. so that would not be much of an engineering hurdle. Wouldn't a 180 degree opposed design balance the engine better when running?

Possibly machining a proper crank and porting the "front-case" might provide good results. There should be plenty of adjustment in a stock needle to deliver enough fuel. If you've ever run your Bee "super-rich".. then you know what I'm talking about. Enlarging the venturi in increments of .010" at a time would be a safe approach I would think. You could also experiment with different cylinder-porting profiles.. by just choosing different cylinders. Perhaps running a more aggressively-ported "front" cylinder might help tune the engine better? Very simple things to experiment with... once you have a base-line.

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