Please put your "I am new and need help" question here.

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Mike Everman
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Re: Please put your "I am new and need help" question here.

Post by Mike Everman » Fri Jun 22, 2018 4:22 pm

You do have the BBQ igniter that has a battery, right? The manual pushbutton type is a pain. I usually put a rubber band around so it tiks without an assistant, though it is a fun way to get my kids involved.
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Re: Please put your "I am new and need help" question here.

Post by hermanpj » Fri Jun 22, 2018 6:14 pm

yes - I got a AA battery powered one. It wouldn't work except to spark me until I figured out you have to ground any un-used terminals. So not I have grounds wires, and I feel like the spark is quite significant. I have the plug gapped such that I can see quite a nice long blue spark when I look into the intake. If I return suspicion to the spark, I'm just going to get a Hobby King ignition that they sell for the Dynajet reproduction they were selling. It's about $33 and I've already probably spent that much on ignition related parts. :-)

So I'm ruminating over this but I think you are entirely right - this is coming down to too much fuel even with tiny orifice. Despite good spark, its just getting too much fuel per volume of air, and so it won't light unless I position the stinger right at the intake opening.

will play with getting the fuel dialed in over the weekend. Q: what PSI do you find seems to work best on your air supply? I'm trying 60 PSI from compressor but have also tried hair dryer and a heat gun at various speeds. I backed off from the heat gun bc I didn't think I was getting enough air flowing in comparison to how much it was pre-heating the fuel.

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Re: Please put your "I am new and need help" question here.

Post by Mike Everman » Fri Jun 22, 2018 6:41 pm

pressure is irrelevant. I've never used a heat gun, personally. Have a compressor and a blow-off gun with a nice smooth trigger? Fine low-end control is required.
I've seen a leaf blower used on a tiny motor, but it was a study in getting just the very fringe of the flow to sneak in the outer edge of the intake so it is not too much. And it was so noisy itself you can't hear the growl you want.

That sparker is fine. I've used them for all sizes. It's not that.
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Re: Please put your "I am new and need help" question here.

Post by metiz » Fri Jun 22, 2018 9:05 pm

Hi, welcome to the forum!
I've been reading your questions and I have some feedback. Fair disclaimer: I have never worked with an ugly stick.
In your first post you describe you get a pop or two but mostly yellow flames from the exhaust. To me that sounds like your ignition isn't up to scratch. initially, a lean mixture will allow your sparker to spark just fine, but when the gas ignites, it might "smother" the spark (you did mention bbq igniter right?). That will result in a pop, and then flames from the exhaust, as the fuel now only ignites there.
The second thing that caught my eye when reading your post is that you use quite a "complex" fueling system. Your neddle valve might restrict the flow of gas, and can hinder your reaction speed when trying to throttle. When you hear it's almost going, in my experience, you need fast control for your gas flow.
Keep trying with Mike's suggestions but if you are not succesfull I would suggest hooking up a propane tube directly to your tank, and then a pipe straight in your intake (OD=6mm, ID=4mm) with a Rosscojector at the end. you can then control the fuel flow directly from the tank valve.

You could also consider changing your igniter for something a bit stronger. That way you'll get s strong spark all the time. I use this igniter https://www.ebay.com/itm/50KV-Ultra-hig ... SwQz1bKUhm it's very cheap, runs on AA batteries and gives off a ridiculously powerful spark, many times a second.

Lastly, some starting tips (I start like this, milage may vary):
Turn on spark, blow down intake with compressor (try limiting airflow by gentry pressing the trigger), turn on gas, wait for the gurgle. When you hear a bang and then nothing, or when big flames come out of the exhuast, shut of gas for a second while still blowing air inside the intake. Quickly turn the gas back on (don't be shy on how much) you'll hear more banging and gurgling. When doing this, the engines heats up, making your life easyer. Eventually you'll turn the gas back on and the engine will ignite. This video (kinda) shows how. Notice how I twist the gas valve.
https://www.youtube.com/watch?v=9gQRvX1gTvg

One final piece of advice: when you think you have enough gas, you don't!
Good luck.
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Re: Please put your "I am new and need help" question here.

Post by hermanpj » Fri Jun 22, 2018 9:46 pm

Heh heh. Thanks I will experiment with incorporating all of these suggestions as I narrow down the solution. I saw those step up electronics as I was looking for a solution. Pretty neat. 50,000 volts... Overkill is always worth major overkill!

Has anyone died from home made pulse jet detonation? Just curious. 😀

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Re: Please put your "I am new and need help" question here.

Post by metiz » Fri Jun 22, 2018 9:57 pm

hermanpj wrote:
Fri Jun 22, 2018 9:46 pm
Has anyone died from home made pulse jet detonation? Just curious. 😀
I can guarantee no one has, since a pulse-jet deflagrates and not detonates :D
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Re: Please put your "I am new and need help" question here.

Post by Mark » Sat Jun 23, 2018 11:31 pm

Remember the little high voltage modules aren't meant to run continuously. You could shorten the gap distance and use the lowest power to run them which would help. I was just toying with one and if you put the wires closer together it will turn on with a 1.5 volt flashlight battery. But anyway they make a lot of sound. https://youtube.com/watch?v=1zeWvJsPNJ0

"the high-voltage module should avoid the use of electricity in high voltage no-load . (Power must be adjusted to a suitable distance to the high-voltage output line , battery capacity is proportional to the distance and the use of the high-pressure arc ( not a voltage as high as possible , you must provide enough current ) . Experimental test of the arc distance from short to long , Do not exceed the maximum arc distance electricity, energy can not be released due to high pressure , can easily damage the module."
"Work: intermittent , continuous work does not allow more than 1 minute and the output side does not allow shorting . Improper voltage and long working hours easily damaged module."
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Re: Please put your "I am new and need help" question here.

Post by pulsethug » Sun Jun 24, 2018 2:58 am

I second the recommendation by metiz and Mark to use a spark module. I use them exclusively now.
https://www.amazon.com/Ardokit-3-6V-6V- ... B01GM9B4R0
You can run these off of a single 18650 lithium battery or a 5volt power brick off of a wall outlet.

Here's a couple of observations that others have already addressed, however here's my take:

1 Detonation/Deflagration - On my 5" dia CC rice-jets (Chinese thermojet) with a 2" exhaust tube max thrust comes in at ~12 lbs. The exhaust tube area for a 2" dia tube is ~3 sq-in. That yields about 4 lbs/sq-in average pressure (12lbs/3sq-in). Even schedule 20 PVC can handle many many times that (but not the heat obviously). Of course that 4 lbs/sq-in is only the average that is created by very large but very short explosive-acoustic spikes. But when you further compare that to 650 lbs/sq-in of pressure for CO2 paintball use you can see where 4 lbs/sq-in is really pretty low. Also, if for what ever reason the pipe did break or crack, the system becomes de-tuned and no longer creates pressure. Short answer: It ain't gonna take your hand off by any stretch, but the escaping propane can burn the crap out of your arm.

2 Intake - From what I can see, it looks like the jet could benefit from being flared quite a bit more. The flare should be between 30 and 45 degrees. The jet shown below has two intakes, but the pic shows only one. Fuel is routed through 1/4" stainless tubing. The business end of the stainless tubing is tapped to accept Mikuni carburetor jets.

I usually try to get a wide size range. Smaller jets can always be drilled out.

https://www.amazon.com/Mikuni-Small-Rou ... B0022ZUXEE

intake-jet.png
mikuni-jet.png
Using carb jets allows you to really accurately tweak the fuel amount and velocity. Velocity is key for starting a valveless jet. Seems to me the higher the fuel velocity, the better the venturi effect to bring in more air which further aids in obtaining a good fuel/air mixture. Also, fuel tube/jet placement inside the intake pipe is critical to get the optimum venturi effect and mix happening. Start off with the exit (or jet) end of the fuel tube about halfway into the intake pipe and tweak back and forth accordingly. The fuel tube should be centered axially to the intake tube as close as practical. This means you are going to have to find some way to rigidly mount your fuel tube so you can adjust it's position.

Regarding fuel air mixture, check out this chart for the LEL and UEL of propane.
http://www.afcintl.com/pdfs/application ... tibles.pdf

The LEL to UEL spread for propane is 2.1% - 9.5%. That's pretty narrow. If we average it to ~5%, that means that for every 1 cu-in of propane, the jet wants to consume 20 cu-in of air give or take. That might help you visualize what's going on.

3 Flow control - Let's see, how else can we blow some more of your $$$. Oh yah, needle valve. Ya gotta get a good one with very fine low end control.
needle-valve.png
The valves I've had the best luck with are Parker valves. They ain't cheap but fine control is everything when trying to start a valveless jet.

4 Max flow - Another thing you may eventually run into is the problem of built-in flow limiters in the brass propane tank connectors. There is an inline rubber ball and spring that shut off propane flow out of the 20lb tank to the system if too much flow demand happens. I just drill out the brass connector carefully to remove the ball and spring. This is dangerous however as the flow limiter is there for a reason; to keep from creating a flame thrower should things get out of hand. Don't do this unless/until you really need that kind of flow and for god-sake do it outside. Also don't get to freaked/overwhelmed at the stuff we're all throwing at you, just try to do the easiest stuff first and resist shotgunning it otherwise you won't know what mod had the most effect.

One more comment; a full face mask ain't a bad thing. Singed hair smells really bad.

That's all I got for now. If I think of anything else I'll repost. Good luck. BTW- what part of TX are you in? I lived 15 years outside of Austin on Lake Travis.

-spoon

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Re: Please put your "I am new and need help" question here.

Post by hermanpj » Sun Jun 24, 2018 1:14 pm

ThAnks spoon ... really cool stuff. I haven’t had any time yet this weekend but I have been taking notes from this thread ontona legal pad and kind of prioritizing it.

Have been watching YouTube’s on the voltage step up electronics

Carb jet is easy to get ahold of

Needle valve would be easy to splice in and I could remove other control valves in my line.

Re the tank ball valve if it come to that I’d probably order a new tank empty to dedicate to this jet. Then I’d feel comfortable drilling the brass on the tank. As it is though I feel like I’m over supplying propane and the tank has not tried to limit me.

Love lake Travis. Went to UT. Was out at Bee Caves road for an interview a couple weeks ago. I live in Plano. My neighbors are going to hate this. 😀

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Re: Please put your "I am new and need help" question here.

Post by Mike Everman » Sun Jun 24, 2018 5:41 pm

Liking all this!

So, what I liked about the Harbor Freight burner (I've had one for years) is it's a cheap way to get a nice high flow needle valve with all the hookup stuff to the tank. Though I mostly use just the tank valve which takes a fine touch when starting a small linear like this with compressed air.

Carb jets are great for making self starting Thermojet styles, so worth the playing. If you really get into it for things like RC aircraft, you'll find the T-jets are terrible fuel hogs, though, I think mainly because the sweetspot for for fuel injection for self starting and for economy are at opposite ends of the intake tube. The outer position loses fuel to the surroundings on exhale, perhaps.

All this is making me want to take one of my pocket jets out and see if I can add the self starting jet on there, and still be able to transition to the normal fuel feed.

There was a guy that made a pulsejet organ for burning man that had self starting jets of several sizes that would instantly autostart so well he could play music. I bet Mark knows how to find that video.
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Re: Please put your "I am new and need help" question here.

Post by hermanpj » Sun Jun 24, 2018 7:14 pm

Dadgum - that organ would be something to see! I bet it sounded like the ancient titans themselves were making music.

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Re: Please put your "I am new and need help" question here.

Post by Mark » Sun Jun 24, 2018 8:25 pm

Mike Everman wrote:
Sun Jun 24, 2018 5:41 pm
Liking all this!

So, what I liked about the Harbor Freight burner (I've had one for years) is it's a cheap way to get a nice high flow needle valve with all the hookup stuff to the tank. Though I mostly use just the tank valve which takes a fine touch when starting a small linear like this with compressed air.

Carb jets are great for making self starting Thermojet styles, so worth the playing. If you really get into it for things like RC aircraft, you'll find the T-jets are terrible fuel hogs, though, I think mainly because the sweetspot for for fuel injection for self starting and for economy are at opposite ends of the intake tube. The outer position loses fuel to the surroundings on exhale, perhaps.

All this is making me want to take one of my pocket jets out and see if I can add the self starting jet on there, and still be able to transition to the normal fuel feed.

There was a guy that made a pulsejet organ for burning man that had self starting jets of several sizes that would instantly autostart so well he could play music. I bet Mark knows how to find that video.
Some tidbits and photos of Lucy Hosking's creation. Type her name in youtube for videos.
"The calliope is centered around a cluster of 17 acoustic pulse jets, tuned chromatically from G1 through B2. Fourteen aluminum organ pipes tuned from C3 through C#4 fan out on the sides and are blown with propane. Fourteen truck horns, lengthened for tuning, are arranged among the pulse jets with their bells across the top and are also blown with propane. Two large accumulator flares blast from the top for percussive effect. This is mounted on an hydraulic jack which raises and rotates vertically to a height of three meters for playing and retracts horizontally for travel."
https://www.leonardo.info/gallery/burni ... sking.html
https://www.pinterest.com/pin/273382639851778282/
https://people.duke.edu/~ng46/topics/lucyfer.htm
https://terrybowker.smugmug.com/Burning ... -h9qxL9G/A
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Re: Please put your "I am new and need help" question here.

Post by ErinTwotails » Mon Aug 06, 2018 3:42 pm

I R newB and want build best pulse jet ever!!! U guys has plAns?

Ok, all joking aside.

I have read "PyroJoes Recipe for Beginners" a few times. My first build will likely be based 95% on that and 5% me playing with the calculators and software you guys have collected around here. What I weld up at first will be a "mild steel monster" for me to learn starting on, as this forum broadly recommends. I'm going to complicate it a bit by trying to run on kerosene.

I plan to order a little Amico TIG-165 this month as my dedicated "pulse jet" welder. I'll nix that idea if there is a major fault that makes that unit unusable. Or if there is a better unit to use in the $200 - $250 range according to forum wisdom.

I have dreams of making a beautiful stainless and chrome Messerschmitt Pulse-Ram Jet, and building a recoverable missile, drone or wind tunnel test to prove the ram stage works.

I'm also fascinated at the possibility a pulse jet, burning atomized coal, could fly. Am I correct in assuming nobody has flown a "coal burner" successfully?

I have been playing with a little HHO "Browns Gas" generator, it might be interesting to build a Pulse Rocket motor throttled by changing DC current to the HHO gen.



35, Enrolled to use GI Bill to learn genetic engineering, looking for more STEM hobbies.

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