How can you make a no-weld valve?

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How can you make a no-weld valve?

Post by newbieflyer » Thu Jun 11, 2009 9:24 am

I was just wondering when I saw the "no-weld" jets at aardvark. How can you make a reed valve without welding or lathing??? Also, please tell me if you can buy aluminum ball valves. I believe ball valves are simpler.

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Re: How can you make a no-weld valve?

Post by dynajetjerry » Thu Jun 11, 2009 4:17 pm

I assume you are asking about a valved pulse-jet, not just the reed valve. For a reasonably efficient p-j, welding the pipe assembly will permit a much more compact and light engine than almost any other method of assembly. If you MUST avoid welding, be prepared to have a massive, low-thrust p-j; even then, the reeds will not last very long unless the engine is more than 30 inches in length. A cast valve head is feasible (see those from MEW,) but they require a smooth valve surface.
Theoretically, a ball valve can work but will require a carefully-machined seat and will be short-lived due to the violence with which it slams against the seat. BUT, as has been mentioned on this forum many times, its mass and a usually-desirable spring will prevent operation at the frequencies of many small p-js. Its resonance will be very low, preventing its closing at the proper time unless the engine is very long, on the order of about 5 feet.
Examine the many small p-js that are (or have been,) manufactured since 1946. They represent the results of much research and technology over the years, making it rather unlikely that their successes can be duplicated in simplified designs.
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Re: How can you make a no-weld valve?

Post by vturbine » Wed Sep 23, 2009 3:12 am

I just came across this. I've only considered valveless engines for running the stationary radial fan turbine I built because of limited valve life. I have read about the webpilot/GRIM valveglide success, so have been a little more encouraged to consider valved engines. But here I also see valves other than reeds can be used if the engine frequency is low enough to allow more valve mass.

In my case, engine weight and to some degree, length is not a problem (stationary engine), and I can also weld, cast, and machine. So what are the alternate types of valves that might be considered in a long, heavy engine. You mentioned a ball valve. What about poppet, and disk valves?
No problem is too small or trivial if we can really do something about it.

Richard Feynman

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