Mitch's Newbie Valveless jet thread

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m1tch
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Mitch's Newbie Valveless jet thread

Post by m1tch » Fri Aug 28, 2009 11:54 am

Hi everyone, I thought I post up a thread to show the development of a newbie valveless pulsejet, I will try and post up as many tests and ideas as I can and comment on how I got certain bits lol

Here is my first test with a jamjar jet, I did have a larger on, but it has a plastic lid that melted! oops, the jet is too small to sustain itself, but you can hear it try and start:

http://s93.photobucket.com/albums/l49/m ... V00638.flv

I need to get a proper sized jamjar to be able to keep it running, but I found on youtube this:

http://www.youtube.com/watch?v=fciwFk0IfF8

Which shows how to upgrade the jet with a plumbing part reducer and some wire, which I will have a go at on a later date :)

My next idea when I was thinking about a 'no-weld' pulsejet as I can't weld at the mo, was taking inspiration from Ghrey's glue pot experiment, I found in the cupboard this:

Image

I have tried to get this to be like a jamjar jet, but I can't get the whole the right size at the moment, might need to be a bit bigger to let enough air in.

My plan with this container is to make a no-weld pulsejet out of it, using the container as the combustion chamber, then, as I can't weld, I will find a tube that fits snuggly over the cap and remove the centre of the cap so that I can wedge/glue in the screwthread part to fit onto the screwthread part of the container.

Then I can make a hole on 1 of the sloping sides to make the intake - it will be kinda chinese style, then I can flare out the end of the intake and put the tube inside the container and feel it through the intake hole from the inside - meaning that the more pressure pushing on it, the tighter the join - perfect lol

I can then mount a spark plug on the end, or in the top and feed propane (still need to get that lol) via some copper brake hose into the combustion chamber.

What do people think of that idea so far? I will be posting up pics of what I have been trying in the hope that this topic might be linked when a newbie asks about certain problems and can't weld.

vturbine
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Re: Mitch's Newbie Valveless jet thread

Post by vturbine » Fri Aug 28, 2009 3:30 pm

m1tch wrote:
I have tried to get this to be like a jamjar jet, but I can't get the whole the right size at the moment, might need to be a bit bigger to let enough air in.
Looks like it from the photo. Try 3/8", 7/16", and 1/2". My guess is 7/16" on this one, but you never know. Generally small simple jars of this size like just a little under 1/2"
My plan with this container is to make a no-weld pulsejet out of it, using the container as the combustion chamber, then, as I can't weld, I will find a tube that fits snuggly over the cap and remove the centre of the cap so that I can wedge/glue in the screwthread part to fit onto the screwthread part of the container.
Most glues won't handle the heat if you do get it going for more than a few seconds. Muffler repair goo, or furnace cement may be more suitable. They don't have much strength, but do work well as filler. Also if you drill your jam jar too big, you can always glue a smaller washer back over the hole with muffler sealer, I found.
Then I can make a hole on 1 of the sloping sides to make the intake - it will be kinda chinese style, then I can flare out the end of the intake and put the tube inside the container and feel it through the intake hole from the inside - meaning that the more pressure pushing on it, the tighter the join - perfect lol
Beyond my level of experience here, but you could try it. I think pressure won't hold it in place alone, remember an intake is subjected to more vacuum than pressure, as well. Otherwise, it isn't an intake! Remember, pulsejets pulse. :D
I can then mount a spark plug on the end, or in the top and feed propane (still need to get that lol) via some copper brake hose into the combustion chamber.
As was mentioned before, the devil is in the details. But solutions are in trial and ingenuity -- solving problems. And perhaps you will find something interesting works that no one else thought to try.

I do recall a pulse jet here somewhere made of a can with pipes stuck into it and held in place by angle brackets -- pretty flimsy, but it actually did run -- there's a video of it. A little iffy for me. Safety is your responsibility -- remember that before trying anything -- protect yourself and others with good shielding, good construction, and safety gear, among other things -- like common sense, good practices, and good planning. You should think about these things at least as much as designing and building something.
No problem is too small or trivial if we can really do something about it.

Richard Feynman

m1tch
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Re: Mitch's Newbie Valveless jet thread

Post by m1tch » Fri Aug 28, 2009 3:56 pm

Yeah I will make sure its all safe, a pulse jet that doesn't pulse is a pipe bomb, so I will be careful, I will need to re-think my intake idea a bit, but this is just a work in progress, I am trying to use some dimentions from this diagram:

Image

But just have the intake facing backwards, not sure if it will work, but the CC diameter is 2.5"s, which when I used my excel calulator it says I need an exhaust size of just less than 1", which is about right for the size of the top...result lol :D

I have some exhaust gasket paste stuff as I work on my own cars, so thats ok, I think what I will do is use some gasket paste between the screwthread end and the pipe, and then compress it all a bit so that its all tight :)

Would it be best to mount the spark plug on the top or at the front?

I just got in from trying 2 get the 'mark 2' jamjar pulsejet (using the container as a jamjar first lol) to work lol I get the fizzz..pulse..pulse... so it does start, but can't sustain itself, I don't want to cut the hole too big though, but is the hole too small to allow enough air in?

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Re: Mitch's Newbie Valveless jet thread

Post by Ghrey » Sat Aug 29, 2009 2:00 am

Try putting it in a water jacket before you bore it bigger. Metal jam jars heat up fast. They do not run over heated.

I realize now that I totally blew it in that thread. I showed no, or few construction details. When I get home I will rectify that.

For now suffice as to say it is all nuts washers and threaded tubing. NO sealant just screw down tight.


Cheers.
In the process of moving, from the glorified phone booth we had to the house we have.

No real time to work on jets, more space, no time.

Life still complicated.

m1tch
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Re: Mitch's Newbie Valveless jet thread

Post by m1tch » Sat Aug 29, 2009 9:20 am

Ok im sure I can make a rig that holes the pulse jet underwater or something :) might even be able to ironocally use a jam jar to cool it and perhaps a spacer on the metal lid to stop it floating :)

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Re: Mitch's Newbie Valveless jet thread

Post by Ghrey » Sat Aug 29, 2009 9:21 am

Update completed.

One other thing;

The one thing that can be seen in the very bad video I made is my troff of ice water. I melted several batches of ice cubes filming.
Floating is an issue, so is vibration, be prepared.
In the process of moving, from the glorified phone booth we had to the house we have.

No real time to work on jets, more space, no time.

Life still complicated.

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Re: Mitch's Newbie Valveless jet thread

Post by m1tch » Sat Aug 29, 2009 9:55 am

Im thinking perhaps using wire to suspend the pulsejet, that way its firm, but can handle the vibrations lol

Would a copper pipe be ok for the inlet? or would it melt quickly?

The diagram above shows the dimentions in terms of D for an intake being at the front, can I use the same dimentions but put the intake at the back of the CC?

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Re: Mitch's Newbie Valveless jet thread

Post by tufty » Sat Aug 29, 2009 1:04 pm

m1tch wrote:The diagram above shows the dimentions in terms of D for an intake being at the front, can I use the same dimentions but put the intake at the back of the CC?
The lockwood is a linear jet, which is to say that the inlet comes in at one end and the exhaust goes out the other. No matter what you do in terms of bending it into wierd trombone shapes, it remains a linear jet, and remains a lockwood. If, however, you move the inlet from one end of the CC to the other, you make something that is no longer a lockwood, and it would be naive (to say the least) to expect the lockwood dimensions to hold true.

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Re: Mitch's Newbie Valveless jet thread

Post by m1tch » Sat Aug 29, 2009 1:44 pm

tufty wrote:
m1tch wrote:The diagram above shows the dimentions in terms of D for an intake being at the front, can I use the same dimentions but put the intake at the back of the CC?
The lockwood is a linear jet, which is to say that the inlet comes in at one end and the exhaust goes out the other. No matter what you do in terms of bending it into wierd trombone shapes, it remains a linear jet, and remains a lockwood. If, however, you move the inlet from one end of the CC to the other, you make something that is no longer a lockwood, and it would be naive (to say the least) to expect the lockwood dimensions to hold true.

Ah ok, hmm does anyone have any equasions in terms of D to get the optimum intake for say a chinese style pulsejet? Or should I try and convert to a linier jet using the container I have?

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