World's smallest pulsejet?

[Mike Everman]

so what you are saying is that even if I was to make a smaller version, the frequency wouldn't increase much because the flame speed remains constant?
several of you have used water jackets to cool reynst combustors. Will exess heat cause the engine to die if run too long without it? I have seen pictures of Mark's snorkeler glowing from heat and apparently still running so I don't know what to think.

What Sam was saying is that the operating frequency is figurable from the length of the pot and considering the flame speed, which is constant, but the length is not, so a smaller one will have a higher frequency.

I think that the smaller ones getting too hot kills them by boiling the meth too fast and the mix gets too rich. Big ones can cope with this, because within reason, the meth can't boil fast enough to make a large volume too rich. (so the theory goes).

[Mike Everman]

Oh, by the way, nice work on the rendered design. Looks good!

[steve]

I should probably make another movie- the lighting on that one was terrible and you really couldn't see what was going on (blury too!)

[steve]

I'm going to try to make them smaller! (because what every teen wants is a pulsejet that will fit up your nose)

the sizes shown are 5/8" and 1" but I will also make one from 3/4" (all conduit). The original is slightly over 1"

[Mark]

For some reason this project reminds me of the old movie, "The Incredible Shrinking Man", watch out for any fog that may engulf you. I wonder how long a very tiny chamber could run on a drop of methanol?
Now that would be small.
Mark

http://images.amazon.com/images/P/63009 ... ZZZZZZ.jpg

[steve]

Sucess!
both the sub-micro (made from 3/4" copper tubing) and pico reynst (5/8" conduit) run!

they are a little tricky to fuel and start but I have worked out an effective system and can do it reliably now. The pico reynst has run for about 6 sec on .2 mL of methanol but I think I can eventually get it over ten sec with a little coaxing.
I'll post sounds when I get a chance later this week.

[Mark]

Good work Steve. Imagine such a small engine that you would hardly use that much fuel with a nearby gas tank, you might put it out on the porch and wake the next morning with it still running.
I once heated a platinum wire over methanol in a jar with holes in the lid. The platinum wire would glow to a red heat, ignite the vapor and fire a whoosh out the lid and then die down until the air would refresh the jar and it would cycle again and again. I set it out and the next morning it was still going. Very fine copper wire will do the same, that is sustain a glow, but you can only see it glow when the lights are low, eventually the copper wire melts, but it too will sustain a red heat if suspended as a coil filament over a pool of methanol. What I did was heat the wire over a torch and then quickly lower it into the jar just above the methanol so it is near the fumes of the pool of methanol.
My longest jam jar was a one of my chrome syringes, that ran over 6 minutes, cooled in a water bath in a gallon coffee can.
Mark

[Bruno Ogorelec]

Sucess!
both the sub-micro (made from 3/4" copper tubing) and pico reynst (5/8" conduit) run!

Amazing! I love this!

[mk]

Very nice, Steve!!

I really do need a methanol source here in my region! It's really hard getting methanol. Getting ethanol (spirit) is MUCH easier!!

[larry cottrill]

Steve -

Just wanted to add my congratulations also.

You should get one rigged with a 'tailpipe'. When I first got my Long Tall Sally to run [2 ft long], it was rigged exactly like a jam jar with a long snout [i.e. no other breathing holes - just the long pipe] and it ran for a few seconds on methanol, at a frequency not unlike the Dynajet! Needless to say, I was quite surprised.

Nice work!

L Cottrill

[steve]

It susessfully ran for over ten seconds today (as I predicted before) and I have video for you guys to analyze!

4.30 cm (ID) tall
5/8" conduit
.128" hole (#30 drill bit)

"How to conserve fuel... Build smaller engines!"

BTW, can I claim the official title of "World's smallest pulsejet" yet? ;-)

[Mark]

I wonder what Reynst would have to say?
Mark

[Mike Everman]

fn YEAH, Steve. Very cool.

[Bruno Ogorelec]

So, Larry, your CO2 cartridge jets may actually be feasible after all, if you rethink them.

Anyone old enough to remember this 'turbojet'?

[John Werner]

This is in regards to Ben. Ben you can use the sndrec.exe and the sndvol.exe which are in all of the versions of Windows to capture any sound played on your computer by opening the sndvol program and then goto properties and put a tick in the stero mixer square.

Now when you play the video after you have started sndrec.exe it will record the sound track off the video and then you can save it as a wav file or mp3 or several other file formats.

John Werner