Mike's Build Log

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Nick
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Re: Mike's Build Log

Post by Nick » Sun Sep 23, 2018 9:55 am

This is going to be so much fun!! :D
On the edge of my seat now Mike!

Mark
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Re: Mike's Build Log

Post by Mark » Tue Sep 25, 2018 5:15 pm

That looks like a nice pickle slicer. I looked for various steel/heat resistant impellors to spin up but never found anything suitable or low cost.. But the jet ski prop idea seems like something fun to try. Is that a skateboard wheel on the end of the shaft?
As an aside, I bought a few sets of wheels long ago to use for their bearings, how they spin so freely. I mounted a skateboard wheel onto the center post of a six cup holder spinning serving tray thingy and the thick six steel arms that hold the cups spin for almost 6 minutes, the hub of the 6 spoked array just resting on top of the wheel. It's odd how long it spins after it slows down somewhat, you'd think it was about ready to stop. The whole thing is stainless steel and the tray itself has a pretty mirror polished surface. The 6 arms that were meant to hold cups remind me of the rings on a chemistry ring stand. In other words it's somewhat pleasing to look at, a high end appearance if you will. I was thinking to spin it with a quartz jam jar one day.
Good luck with the jet ski jet drive approach. Ought to be interesting to see how it does.
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Mike Everman
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Re: Mike's Build Log

Post by Mike Everman » Tue Sep 25, 2018 5:30 pm

yeah, this is a fun one, Mark. With the skate wheel driving the side of the bike wheel, it will be a bout 1700 RPM per 10 MPH. I think it should take the heat, and part of it is going to be pumping cool air, so maybe it won't get as hot as I fear.
I got the right angle gearheads today. Pretty beefy. Just took one apart because they have a lot of drag. I'm soaking it in alcohol, as it has probably 50 yr old grease inside. Popped the seals off the bearings and it freed up pretty good. I'm thinking the rubber has swollen in all this time.
Gearheads.PNG
I'm a little worried that this aluminum housing will be so close to the pjet, but maybe it's not a thing. Certainly I won't be running it for an hour at a time.
Mike
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Mike Everman
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Re: Mike's Build Log

Post by Mike Everman » Tue Sep 25, 2018 10:22 pm

We may be wondering: Why, Mike, Why?

Well, reasoning goes like this:
I don't want a big horribly loud motor that wriggles my gizzards to push me around if I can create some mechanical advantage with a smaller one.
I could technically push myself around with this 5 lb thrust, but it would not tolerate even 1 degree of incline. (250 lb weight all up with rider)

So I have to gear down a turbine, and it matters very little what diameter. Better yet, if driving a bike wheel, the wheel becomes an idler, and my driving wheel of 2" diameter's tangential velocity is the bike velocity. Use a smaller driving wheel for more torque.
Mike
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Re: Mike's Build Log

Post by Nick » Wed Sep 26, 2018 6:06 am

The spirit of exploration!

Mike Everman
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Re: Mike's Build Log

Post by Mike Everman » Tue Dec 15, 2020 2:55 pm

Gawd, I have to make time for more fun! Happy Holidays, those still watching his thread.

I ran my 5 pounder on Saturday. I had to quickly figure out the auto start fuel again, since at the shop we got rid of our air compressor and switched to a nitrogen tank for blow off, which doesn’t work so well for starting a pulsejet! I had people standing around and wasn’t really prepared for a dual fuel feed, I didn’t remember that the last time I did this I use two tanks. I literally had to throttle one of the feeds by pinching a plastic line!

Using 3-D printing nozzles in the end of a tube instead of a Rossco Jet seems to be working really well.

I’ve come to the conclusion that there’s two places and styles for fuel introduction, with different goals.

The thermojet only has the first style, The auto-starting, air entraining version that needs to be a high(ish) velocity jet. If you only have that, your pulsejet will work but with terrible fuel economy and so-so thrust, and I think that is mostly because the exhaust phase pushes unburnt fuel out the intake.

The other type needs to happen closer to the transition of intake to combustion chamber, and be more like a fan or cone of spray. I’ve taken to using the first style to get a growl, And then ramp up the main fuel feed for resonance, then kill the starting jet. Further down this thread I list the starting nozzle diameters and locations that worked for this motor, but seems to not be very finicky when you’ve got “the touch”. Ha

I tried one of Marks snorkelers, the one with a pipe fitting on a stainless bottle, but it was leaky. I’ll play with one of the paintball tank ones this weekend. Thanks, Mark! Only took two years to start playing with your gift!
Mike
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metiz
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Re: Mike's Build Log

Post by metiz » Tue Dec 15, 2020 10:08 pm

Mike Everman wrote:
Tue Dec 15, 2020 2:55 pm
I had to quickly figure out the auto start fuel again, since at the shop we got rid of our air compressor and switched to a nitrogen tank for blow off, which doesn’t work so well for starting a pulsejet!
Not with that attitude :P

Good to see you back to fin-nicking with jets again!
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Re: Mike's Build Log

Post by Mark » Thu Dec 17, 2020 2:34 am

Mike, the one with the leaky fitting is a bit fussy and the best way to fuel it is to put the least amount of fuel in it, just enough to barely cover the bottom and then screw the snorkel on as best you can and stand it upright to light it and so you don't leak fuel out the reducer by fueling it assembled. Then spray a few squirts of methanol down the snorkel. On a cool day and only on a low humidity day, it will really inspire you when it catches, way louder than a jam jar.
I hold the silver body soap dispenser and roll it to coat the walls of the vessel and then prime the snorkel. Then give it a try. Humid days aren't worth trying but cool days are fun. I was so excited the first time I heard it rev up. Try it standing straight up, that way works rather than at an angle.

The paintball tanks like to run at a low angle but not horizontal, and 50 to no more than 75 ml of fuel for the 12 ounce paintball tank. I'd try 50 ml to start. Sometimes I put my finger or a stopper in the snorkeler and inverted the snorkeler to coat everything for a peppy start. The little air pump is nice to air it out after each try.
One time after a run the paintball tank was very hot and being held with a leather glove, the remaining fuel after flaming out is near boiling so I quickly relit the snorkeler as it fumes out the tip of the snorkel. It will burn like a candle with a foot long flame as the fuel evaporates, and tilted, the tank flashes the fuel when it contacts the very hot snorkel. It can make a 15 foot flame and some thrust from the sudden expansion. Methanol boils at 67 C and it's already near that when it hits the hot exhaust tube.
I felt god-like the flash of heat so sudden and such an attention getting trick. Water expands by a factor of 1600 when it turns into steam at atmospheric pressure - I don't know what methanol does but the flashbulb of heat, light and sound is a kick. If you have seen how fast those water bottles go fueled with liquid nitrogen and water and then angled horizontally/inverted, the suddenness is like that only it's a big flash of fire for so little fuel.
Nitrogen rocket
https://youtube.com/watch?v=ZIWsfglG2uc

Here's the two paintball tanks I sent you.
https://youtube.com/watch?v=boKEWoQsfLw
The 12 ounce one - https://youtube.com/watch?v=hQXrxrnbRDw
https://youtube.com/watch?v=LAudE7ZGkis
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Mike Everman
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Re: Mike's Build Log

Post by Mike Everman » Sun Dec 20, 2020 3:41 pm

Cool, I will try all of that! Happy Holidays!
Mike
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Mark
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Re: Mike's Build Log

Post by Mark » Mon Dec 21, 2020 3:54 pm

This little augmenter or similar shapes if held in the exhaust of the paintball snorkelers makes some kind of vortex street or cavitation that will absolutely blast your eardrums. A strange phenomenon to behold. Happy holidays too!
http://www.pulse-jets.com/phpbb3/viewto ... 530#p77549
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