Mike's Build Log

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Mike Everman
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Re: Mike's Build Log

Post by Mike Everman » Sun Aug 06, 2017 3:44 pm

I'm back and cleaning up all the camping gear. Good trip, nice to have a week with just our younger boys home from college.

Mark, "it comes to mind that I could be missing something that exists but would never find unless you created the conditions for it to work."
Classic. I've always thought some billionaire should fund a project to put everything up against every other thing, with every possible chemical and mechanical interaction, ad infinitum and see what happens. My success with fidgeting with a handful of flotsam and jetsam would indicate that it would make for far too many discoveries to possibly develop. Then we die and the sun explodes and the universe loses all those cool projectile weapons. (wow, where did THAT come from?) Oh no, now I'm imagining alien forensic archaeologists finding a paintball gun and concluding it is a weapon intended to annoy someone to death.

Nick: nice 3d renderings of your jar! Print! Print it! Put some fuel through that thing today! The flare at the top of the annulus looks wrong to me, though. Like in the Reynst, it is there to encourage breathing. Or maybe it's brilliant, raising the overall pressure near the exit. ha. In the same vein, Mark's cupped hands are doing what Reynst's ejector was doing, making his pots heard miles away.

In contrast to my comments about breathing being all it's about, ha, I think the good part of the aerovalving going on here is because of the vena contracta in the exhaust phase. All of these snorkels have sharp entries maximizing this. You can imagine the exhaust choking itself as the velocity builds, and making for higher pressure...if in fact this is a good thing. At least one experiment should be done adding a flare on the inside. What I cannot see is what possible benefit there would be at the tip, choking the ingestion. It makes me want to make a flare to screw on the end of one of these paintball snorkelers. I am certain it will change some things.

In other news, I've got access to one of those million frames per sec cameras. An energetic quartz jar would be great for this. From experience, I think some effort should be put into a fuel additive for better visibility.

Also, I am reminded of jar experiments from a few years ago where I put a disk of fabric in the bottom of the pot, soaked, the thought being it presented no turbulent weirdness of a pool. With the further thought that a fuel feed was below it, keeping it soaked. Kind of a wick fuel feed like a candle.
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Re: Mike's Build Log

Post by Mark » Sun Aug 06, 2017 9:32 pm

Welcome back camper. I ordered some powdered charcoal thinking it'd be good for making lots of sparks to observe the flow and just for the sake of art if it works. I want to accentuate this interesting effect in the video. Probably have to keep the charcoal dry and have it sucked or fed in to work.
https://www.youtube.com/watch?v=A8HqY0eLiVU

I was wondering too if this slow whirlwind down-the-drain effect happens with robust snorkelers to any extent or if a skirt around the intake with a side tangential intake would help swirl/prepare the fresh air around the intake in some coherent beneficial manner? Or skirt and spin up some air into a vortex around the intake with an air compressor and see how it modulates the snorkeler. Just some weird things to try with high and low pressure gradients ...
https://www.youtube.com/watch?v=odZAqQgx08M
https://media.licdn.com/mpr/mpr/AAEAAQA ... ZTFiNA.png

"Oh no, now I'm imagining alien forensic archaeologists finding a paintball gun and concluding it is a weapon intended to annoy someone to death." "Look at this, it's almost human-like". "Quickly, shoot now Jarred!"
https://www.youtube.com/watch?v=cph0D7Vdjp4#t=2m51s
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Re: Mike's Build Log

Post by Nick » Mon Aug 07, 2017 4:53 pm

Welcome back Mike :D

I'll get to the printer but busy playing with my new mill at the moment !! I need more tools- more tools :lol: :P

Talking of 3D resin printers have you seen this one - (Kickstarter) $259!!!!!! it does casting resin too!
https://www.kickstarter.com/projects/24 ... e+-+public

This will set the cat amongst the pigeons!

Cheers

Nick

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Re: Mike's Build Log

Post by Mike Everman » Thu Aug 10, 2017 4:24 am

printed two fold pocketjet, web size.jpg
I've got to look into a resin printer. I've got two Ultimaker FDM machines, and they run really well. I just printed a two fold version of my 1.25" intake pocket jet. I'm designing the augmenters to throw on there. Base motor was 5.4 lb thrust. I'm hoping to get 8 with augmentation. Making it metal is the thing.
Nick may recognize this motor, as he did that sleeve and silicone rig on the intake when I had it in the UK.
two fold posketjet. abs print.jpg
Mark, you really would have fun with a cheap 3d printer from Monoprice (really), and a free version of OnShape modeling. I have moved all of our engineering to OnShape. Just think. Model and print any shape you want and see how it barks.
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Re: Mike's Build Log

Post by Mike Everman » Thu Aug 10, 2017 5:19 am

And to prove my point, I'll get this printing before I go to bed.
abs jam pot.PNG
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Re: Mike's Build Log

Post by Nick » Thu Aug 10, 2017 9:34 am

Hi Mike,

Hey looks good - nice to see the jet is still Ok :-)

Yes, I think 3d printing is a rapid prototype tech we could only have dreamed of a decade ago.

I looked at Onshape Mike - its nice but Fusion360 is free/lowcost and getting better all the time - don't think its quite as good as Onshape? - but was certainly a fairly painless transition from Spaceclaim and AutoCAD.

Getting into the CAM side of things on Fusion at the moment, its surprising how hard it is to unlearn the way I used to do CAM with stl and dxf files etc

Looking forward to seeing the results of your latest print!

Cheers

Nick

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Re: Mike's Build Log

Post by Mark » Thu Aug 10, 2017 2:07 pm

To hold all the shapes in hyper space in your hand ...
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Re: Mike's Build Log

Post by Mike Everman » Thu Aug 10, 2017 3:00 pm

The capability for rapid iteration has changed everything about the way I design. Just holding designs in your hand can be as important as proving the function in any one area.
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Re: Mike's Build Log

Post by Mark » Thu Aug 10, 2017 7:42 pm

A sense of wonder is one hell of a drug. I'd probably go crazy with rapid prototyping. I was thinking about augmenters, how one time it sped up a dying snorkeler, brought the engine back from the grave after it had run a bit and was starting to flag. When you put one in the air stream, you can feel some force trying to blow the augmenter out of your hand which might produce some extra back pressure on the escaping exhaust. So the notion was that maybe in a sense an augmenter aft of a snorkel could start to morph into an annular valveless characteristic or segmented snorkel, providing a shortcut for the incoming air while hopefully still retaining the compressibility or inertia of a full length snorkel. I recall one jam jar posted on youtube where a tube was situated above the hole in the jam jar lid but maybe it would be better to build up somewhat of a coherent run out the exhaust before introducing a shortcut. Exiting a simple hole in a jam jar lid is somewhat tortuous. Some kind of a funnel shape would be better, like that latest prototype you've got there Mike.
But also it's starting to become just another pulse jet if you take it too far in that secondary port/annular direction. Maybe if it was optimized, something overlooked by Foa, Reynst, Tharratt, Lockwood, and the gang you could discover something new there. I don't think there's much left to be mined as far as thrust though, but who knows? However there's a lot to play with in the creativity department and if you could bang out something infinitely simple to make, that would be nice.

PS Mike, that side view of the white prototype has a nice artistic look to it and so small. The elbows remind me of the jet nozzles on squid and also hint at being tentacles. Paint some eyes on it maybe.
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Re: Mike's Build Log

Post by Mike Everman » Sat Aug 12, 2017 4:47 pm

I think definitely Reynst is on board with this model, ha. He was about breathing more than thrust. This is just a printing demonstrator with completely notional geometry I can hold in my hand.
Most of the "design for 3d printing on cheap printers" has to do with eliminating support material, which is in a single material printer is hard to remove, leaves bad surface finish and is fairly easily replaced by supergluing pieces. Though this time I think I will use ABS glue, and even give it a coat for sealing.

I tried printing it in halves, which was a fail.
Capture.PNG
Capture2.PNG
Capture3.PNG
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Re: Mike's Build Log

Post by Mark » Sun Aug 13, 2017 1:55 pm

I wonder if air flow would segregate in an intubated snorkel, sort of in the way the flow rectifier inside a Reynst combustion chamber skirts/biases exiting air around the perimeter of the necked region. But I was thinking in a snorkel within a snorkel the incoming air would be traveling on the outer path, the inner tube be for ejecting the exhaust. It would be a mysterious effect if it worked, as if a snorkeler were running as a full-fledged pulse jet. To some extent the concept is a distant cousin of a typical annular pulsejet only the outer tube longer and the inner tube maybe not the full length of the outer, just enough to guide the air flow, part of the outer snorkel could share the road for two way traffic.

Scroll down https://media.licdn.com/mpr/mpr/AAEAAQA ... MTQ5Mw.png
https://media.licdn.com/mpr/mpr/AAEAAQA ... ZTFiNA.png
Last edited by Mark on Sun Aug 13, 2017 2:01 pm, edited 1 time in total.
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Re: Mike's Build Log

Post by Nick » Sun Aug 13, 2017 1:59 pm

Looking forward to seeing the test Mike!! :D :D

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Re: Mike's Build Log

Post by Mike Everman » Mon Aug 14, 2017 3:47 am

It works well! Another failed print out of ABS (settings need tweaking); switched back to the lower temp PLA and a perfect print. Here's a short video.
notional printed reynst, small.mp4
(1.99 MiB) Downloaded 14 times
Cold frequency is 282 Hz, running frequency is 82 Hz
If I let it go a few seconds too long, it gets warpy down near the base. Sounds like I can go a little smaller on the hole, but already runs better than any of my old stand-bys right now. It's warm and more humid than usual.
Thinking about printing a water jacket and see how long a plastic pot will run with a full jacket.
2017-08-12 22.23.44 small .jpg
2017-08-12 23.35.30 small.jpg
2017-08-12 23.39.12 small.jpg
2017-08-12 23.39.46 small.jpg
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Re: Mike's Build Log

Post by Nick » Mon Aug 14, 2017 12:01 pm

That made my day Mike!! :D :D

Cracking little device - I guess once you have finished tweaking it you could get it printed in metal if you wanted to?

If I can clear my decks I'll get onto printing one on the resin printer and see how that stands up to the heat. Trying to get the upstairs spare room finished so I can take my resin printer home and do more stuff in the evenings/overnight.

Brilliant!

Nick

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Re: Mike's Build Log

Post by Mark » Mon Aug 14, 2017 2:32 pm

Looks very pretty. If you're going to run it sideways, it could probably tolerate having a slightly longer or more narrow combustion chamber. To some extent it seems like the closer you get to a square or circle shaped combustion chamber, the less coherent or controlled the feedback, like it gives the flame front too much choice to spread out in random directions.
The flow rectifier is higher up in the combustion chamber than where Reynst has his. There're similarities between barking dog tubes and these engines. In the vertical, it's as if you are lowering the confinement. If you watch a lot of barking dog demonstrations, often before the bark there's some distance where the exhaust merely floats away softly before the effect kicks in but this can even happen in the horizontal. It's tempting to think the that the flame front is calculating the best distance or length to diameter ratio for the effect to kick in. Often it seems like the barking dog tubes are too long for the diameter in a lot of demonstrations but with such kicky oxidizers such as nitrous oxide or the nitrogen dioxide variant, it doesn't matter. But if f you had a barking dog tube that was on the cusp of barking in the vertical ,tilting it sideways to some angle will get you there, as a way to build feedback. And with less kicky fuels, length-to-diameter ratios start to become apparent.
If you find that the PLAJET likes being sideways, it could be that slippery factor or the fuel presentation or both or other factors. Maybe even there's less dampening getting some of the fuel off the bottom where the flame front is reflected.
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