Mike's Jam Jar experiments

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Mike's Jam Jar experiments

Post by Mike Everman » Sat Dec 13, 2008 9:27 pm

Enjoy the video.
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Re: Mike's Jam Jar experiments

Post by metiz » Sat Dec 13, 2008 11:06 pm

Haha! valves on a freaking jam jar! Talk about over-engineering. Non the less, that's realy cool what you have there - makes a nice noise :)
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Re: Mike's Jam Jar experiments

Post by Mike Everman » Sat Dec 13, 2008 11:19 pm

Having the micro spot welder is sure handy. Here's a higher res version on youtube:
http://www.youtube.com/watch?v=KIE8m5dzFO8

I'll post another vid later, showing the frequency of the valves, and see if I can get them humming at the right frequency. Then I'll go over to Forrest's valve thread and see where it should be.
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Re: Mike's Jam Jar experiments

Post by Mark » Sun Dec 14, 2008 1:37 am

That was enjoyable, I love jam jars. I would have liked to seen the little reed valves going. Might the two non-valved holes still offer too much resistance, or be holding the jar back? What if you had say 6 valved holes on the perimeter equally spaced and one big free hole in the center for a dedicated coherent in/out flow? I wonder if perimeter valves would have any cooling power to insulate the sides of the jam jar, if they opened up, such that the tips were pointing towards the outer wall edges. Or to get the flow down deeper, maybe little internal snorkelettes around the perimeter blasting in fresh cold air, to keep the wide part of the blue-flamed vortex,(down near the bottom), away from the fragile glass walls, where the temperature gradient is extreme, at the methanol level/splash zone.
Going back to the 6 perimeter valve design, if you added a snorkel/exhaust tube in the center of the valves, you might have something of a "reversed head/intake" Dynajet facsimile. But that's another adventure. It would just be a valved pulsejet with the reeds in a different location on the combustion chamber.
I enjoyed seeing your jar crack too. ha
Last edited by Mark on Sun Dec 14, 2008 2:17 am, edited 1 time in total.
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Re: Mike's Jam Jar experiments

Post by Mike Everman » Sun Dec 14, 2008 1:53 am

that's exactly where I'm going with this, Mark! the reverse dynajet, that is. first thing's first, though. I've got this .500"x.003" stainless spring strip. The current active length is .76"
The natural frequency of the valve you see in the first video, is 153 Hz.
The frequency of the motor is 58 Hz.

I'm now going to consult the valve guru, Forrest to see which way I should go with it!
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Re: Mike's Jam Jar experiments

Post by Mark » Sun Dec 14, 2008 4:27 am

You would probably get a faster response time with those reeds if you cut them into a petal shape and made the surface they rest upon as smooth and flat as you can. I liked the buzzing sound they made. I've noticed on some of my homemade reeds they really have a hard time lifting off it they are way bigger than the hole, as if a vacuum effect might be forming/ping pong ball in funnel motif.
http://www.columbia.edu/cu/physics/demo ... funnel.jpg
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Re: Mike's Jam Jar experiments

Post by Mike Everman » Sun Dec 14, 2008 6:30 am

Mark wrote:You would probably get a faster response time with those reeds if you cut them into a petal shape and made the surface they rest upon as smooth and flat as you can. I liked the buzzing sound they made. I've noticed on some of my homemade reeds they really have a hard time lifting off it they are way bigger than the hole, as if a vacuum effect might be forming/ping pong ball in funnel motif.
http://www.columbia.edu/cu/physics/demo ... funnel.jpg
Until I make a flat thicker sheet head plate, there's not much I can do about flatness. I was oilcanning it so it would make the valve open a little so I could suck air in to make it buzz.
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Re: Mike's Jam Jar experiments

Post by WebPilot » Sun Dec 14, 2008 5:15 pm

Hey Mike,

You are pushing my model to the 'limits'.

ωdn = (2π × 58Hz)/(2π × 153Hz) gives a dfr (or φ) of 0.379, which is close to the V-1, but way under 0.431 for Valve Glide™ and the upper limit of 0.59 for the valve to close in time before +tive pressure ensues.

However, the uncovered flow holes are effectively 'short-circuiting' the valved ones during the intake phase. Their resistance to flow is much less than the covered ones. Ergo, most of the inflow is going through the unimpeded holes and not the valved ones. This may even cause a corresponding decrease in overall 'pressure drop' across the valves during the intake phase. IOW, the valved holes are just going along for the ride.

Humor me. Spot weld another strip to the top of the jar covering these holes. See if you can 'blow' some compressed air (at low gauge pressure) off angle at one of the intakes to determine if you can set up some sort of a resonance. If so, light the spray.

Be careful, and don't burn yourself.
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Re: Mike's Jam Jar experiments

Post by Mike Everman » Sun Dec 14, 2008 6:00 pm

WebPilot wrote:Hey Mike,



Humor me. Spot weld another strip to the top of the jar covering these holes. See if you can 'blow' some compressed air (at low gauge pressure) off angle at one of the intakes to determine if you can set up some sort of a resonance. If so, light the spray.
When I watch it run, the valves are moving very little for sure. By "these holes", do you mean the currently unimpeded? May seem obvious, but just making sure. I don't want to have an exploder here. the lid is oilcanning so much there's valve gap or not at different times, independent of the pressure driving it. I suppose the fundamental of the lid could also be something to optimize, and why one is better than another for no apparent reason.
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Re: Mike's Jam Jar experiments

Post by Mark » Sun Dec 14, 2008 6:42 pm

"I don't want to have an exploder here."
Mike

You're not trying to make a buzz bomb are you? Ha
Just some meager tidbits here for your interest.
I wonder if in a completely sealed plastic vessel or glass jar of a critical strength, the flame front will go slowly and not burst the vessel, but by setting up a hammer wave, by actually letting some of the pressure out of the vessel during ignition, the latter effect might propagate a bang? Maybe things would go this way, something to do with the mixing/swirling ignition particles or the way a flame front advances. I once likened the supposed effect to cupping a bee in your hand, I've done that, feeling him crawl around inside my tightly cupped hand, but letting "it" sense/see a quick escape route, a crack of light, can cause the bee to sting. (Not scientifically proven yet) More testing required. ha

I recount the time I once drilled a half inch hole in the pointy end of a paper mache ostrich egg bought at a craft store, thinking it would run like a jam jar, instead it exploded and stung my fingers. Again, more testing required. There are whoosh-bangs and then there are the no warning bangs. The no warning bangs are really impressive. Oh!

I think you should try pins in your reed valves. ha
http://jedlik.phy.bme.hu/~hartlein/www. ... +25+17.gif
I'd like to try some sort of modified ping pong ball snorkeler. Yesterday I saw these light stainless steel balls on a long plastic-coated steel leader as a decoration at a hardware store. They were all sizes, from about 5 inch spheres to 1.5 inch spheres, again very light as a slid them up the wire to feel the weight. The "items" were about 4 feet long I guess, just hanging straight down like ornaments on a string. One was $30 and the other with larger sphere montages $60.00. I was really tempted to buy them, the stainless steel was very thin. Another thing that appealed to me was that they had two neat tiny holes for the wire to go through, near perfectly centered if you were going to make something with them.
http://jedlik.phy.bme.hu/~hartlein/www. ... +25+16.gif
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Re: Mike's Jam Jar experiments

Post by WebPilot » Sun Dec 14, 2008 6:57 pm

When I watch it run, the valves are moving very little for sure. By "these holes", do you mean the currently unimpeded?
Yes.

You are going to have a valve strip on the top of the lid, and one on the bottom. The one on the bottom is supposed to open on the -tive portion of the cycle (top shuts), thereby admitting air and the one on the top opens during +tive pressure (bottom shuts), thus exhausting.

I warned you to be careful, because the spraying may cause alcohol to go in places where you may not want it to go. Once you ignite it ... you'll find out where it went.

And yes, this may turn out to be quite more powerful when you get it all worked out.
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Re: Mike's Jam Jar experiments

Post by Mark » Sun Dec 14, 2008 7:30 pm

I've thought about that "reverse/double valving" scenario before, and I concluded that at best the jar would quickly starve itself. But testing is often the best way to know something.
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Re: Mike's Jam Jar experiments

Post by Mike Everman » Sun Dec 14, 2008 8:11 pm

Mark, this one's for you, fun with jam jars and ping pong balls:
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Re: Mike's Jam Jar experiments

Post by PyroJoe » Sun Dec 14, 2008 10:08 pm

That kicked it up a gear, ha.
Had the same problem with the valves only slightly moving. This is why the valves in the metal jar ended up looking odd. Used aluminum and cut them way down.

Yours are doing a much better job. Have you tried small lengths of pipe over the exhaust holes? Sometimes this gives a little bit of pumping action, and keeps the valves open longer.

Good stuff.
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Re: Mike's Jam Jar experiments

Post by Mark » Sun Dec 14, 2008 11:09 pm

Oh! I do like that. A bit of jam jar juggling. ha
It makes me imagine spinoff ideas. Maybe a jam jar lotto machine, or a little light, weighted plastic butterfly to get caught in the updrafts. How entertaining. Or a little kite tethered to the lid. It's really much better than my pinwheels or party extenders. And there's room for a whistling jam jar too.
I could try a tennis ball with my big snorkeler.
Sincere thanks for making my day.
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