External valve grid

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larry cottrill
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Re: External valve grid

Post by larry cottrill » Tue Dec 09, 2008 12:26 pm

Grim and Forrest -

Gentlemen, congratulations! That is a beautiful piece of work. For both of you, a nice repayment of the effort put in.

Wonderful! Yes, let's see somebody fly one, or get one on a hydro!

L Cottrill

PyroJoe
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Re: External valve grid

Post by PyroJoe » Tue Dec 09, 2008 2:22 pm

Wow,
Nice clean valves and no damage, good work. Alot of work in these engines.
Joe

GRIM
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Re: External valve grid

Post by GRIM » Tue Dec 09, 2008 9:22 pm

WebPilot wrote:PS ... we've still got to make one fly.
ABSOLUTELY ,
larry cottrill wrote:Wonderful! Yes, let's see somebody fly one, or get one on a hydro!
It will be a cannard ,
I know Bruce allready done it , I have no quarrel with him , he done good ,
Viv wrote:Nothing wrong with that motor ;-) sounds nice and clean, I love the fact that you have built this using maths and are getting such good resul
I am thrilled that the math worked out, it is very satisfying ,

Thanks JOE yes a lot of work ,

Thanks to all for the kind words , I still have a long way to go before one of these will take to the air , but it is reassuring to know that the theory is good

G

dynajetjerry
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Re: External valve grid

Post by dynajetjerry » Wed Dec 10, 2008 8:05 pm

Grim,

Your p-j looks and sounds great! I wish I had access to the tools and material to try a few ideas of my own.

Your design is vaguely similar to the 1946 Minijet in that the incoming air and fuel goes straight down the combustion chamber, encountering little turbulence in the process. Your engine might benefit from some kind of turbulence-inducing devices downstream of the reeds. Or, strange as it may sound, you might try reversing the reeds: anchor them at the center of the valve wedge and place their free ends toward the side, where your present reeds are anchored. Of course, such a layout might completely prevent any running, at all.The pattern of heat on the c-c is a good indicator of the path of the hot gasses, moving pretty close to the valve chamber in your engine.

You might also try flaring the exhaust outlet slightly, perhaps to 1 1/8 times the diameter of the tailpipe. This can help stabilize operation, especially when running statically and when fuel rate is not opltimum. As you alaready know, lean runs are death on reeds, though your design is not harmed so much as traditional versions (Dyna-Jet style.)

One of the current Dyna-Fog, Jrs. employ a valve chamber that is separated from the c-c, as I've mentioned before. We went with that feature to cool the valve reeds and increase their livees. It was particularly useful in designs that were much longer than those intended for thrust. Never having tried such a system in relatively short p-js, I don't know if the separate valve chamber is as useful as in the DFG, Jr.

Jerry
Louder is always better.

GRIM
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Re: External valve grid

Post by GRIM » Wed Dec 10, 2008 11:11 pm

Hi Jerry , thanks for the reply , I agree with you that the flow into the cc is probably "too centred" in this design ,
I had considered some kind of diffuser if it were necesary , but decided against it ,

My next attempt will dump fuel in a more spread out fashion ,

Graham questioned about a W shape , strange that , in the drawing you may be able to see some W shape baffles,

This is still only on paper but I got a quote for some 7075t6 today so , sooon , :)
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GRIM
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Re: QCV

Post by GRIM » Sun Dec 14, 2008 10:59 pm

Here is a vid and a couple of photos of QCV (Quasi Chinese Valver )
This started life as a valveless , a kind of straight tail chinese , it started easily ran well , had good throttle , but lacked power ,
I then put the semi bustle on it , didnt do much for the power,

So here it is with valves , cant say much about the power , (to be defined ) but it starts easily and runs on gasoline , so cant be all bad ,

The frequency spectrum looks a mess, so I cant say about the dfr either ,but I thought worth posting,

Apologies for the shaky vid , but this was a hit and run , I was in the driveway to a country estate , ran it and got outa there LOL

G
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Mike Everman
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Re: External valve grid

Post by Mike Everman » Mon Dec 15, 2008 12:34 am

dude, I'm grinning ear to ear!
so it looks like you could put a carb on there. wild, man, wild.
Mike
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GRIM
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Re: External valve grid

Post by GRIM » Mon Dec 15, 2008 12:58 am

Yeah , a couple of Amal mk2 would be cool , Boneville style, :D
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Mark
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Re: External valve grid

Post by Mark » Mon Dec 15, 2008 5:36 am

A rear facing valved pulsejet. Not bad. It made me think that if you cocked the last of the tail up a bit and streamlined the whole thing and stabilized or broaded the "bottom" you could have a torpedo pulsejet boat, partially submerged. It certainly would make for a good Captain Nemo Nautilis if you dressed it up a bit. Might even produce some steamy mist effect too. Move over putt-putt boats. ha
Now that I think about it, a little Logan with ballast could be dressed up and steamship along too, using the same basic formula. Pulsejets being hollow would make for good toy boats. Just keep the "tail and snorkel" out of the water. Think of all the little features you could add.
(Your pulsejet in this basic shell) (with some artistic license)
http://www.vulcaniasubmarine.com/NAUTIL ... age003.jpg
http://www.youtube.com/watch?v=FZVboveW6y0
Presentation is Everything

WebPilot
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Re: External valve grid

Post by WebPilot » Tue Jun 23, 2009 4:53 pm

Some of you are asking questions about valve grids and the like.

Lest we forget, here a man successfully designed and built his very own, with extraordinary valve life.
Image

jayidian
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Re: External valve grid

Post by jayidian » Sat Jun 27, 2009 5:07 am

that's really cool! good job! keep up the hard work!
Butuan City |

Ormoc City

gone2fly
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Re: External valve grid

Post by gone2fly » Mon Sep 21, 2009 10:52 pm

It looks like you have it running now. What did you do to fix the problem?

WebPilot
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Re: External valve grid

Post by WebPilot » Mon Sep 21, 2009 11:36 pm

gone2fly wrote:
The reed valves need to open easy and close fast. If your reed valves are too stiff then they may not be opening far enough this will act like the intake is too small not allowing enough air and fuel into the engine.

The reed valve frequency needs to be higher than the combustion chamber frequency. If the reeds are opening too slow they may be only half way open when combustion chamber pressure slams them shut.

...

If the engine is designed correctly the valves will open and close like a flag on a flag pole flapping in a breeze. The vacuum sucks the valves open and they should be all the way open before the vacuum pressure reaches zero. Pressure starts to build up in the combustion chamber and the valves start to close on their own. The valves should be closed all the way before the combustion chamber pressure slams them shut.
GRIM and I collaborated on this engine.

All you say here can be found in a thread I posted a year ago. I addressed this very problem from an engineering point of view. What I posted was theoretical. What G showed here experimentally was that I was correct.

Now you're confirming it again. Thanks.
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GRIM
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Re: External valve grid

Post by GRIM » Tue Sep 22, 2009 1:12 am

Hello gone2fly Welcome,
To answer your question
gone2fly wrote:It looks like you have it running now. What did you do to fix the problem?
You need to read the thread, the answers are there,
You would do well to read Forrest Eckstein’s excellent tread as well,

Here, viewtopic.php?f=2&t=4984

He explains very well the phenomena you describe,

The valved engine section of this forum is quite slow at the moment, but rest assured there are a great number of people eagerly awaiting more information on your work , some videos / photos would be nice ,

G

Rocket Man
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Re: External valve grid

Post by Rocket Man » Wed Mar 17, 2010 5:36 pm

I see you have several problems.
Last edited by Rocket Man on Thu Mar 18, 2010 12:35 am, edited 7 times in total.

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