um...pulsejet?

[larry cottrill]

I don't know why no one has asked you what construction skills and tools you have available. Is at least one of you a weldor, with reasonable skill working with fairly thin steel? That would make a difference to what designs you should consider. It is possible to learn basic welding fairly quickly, but it takes some experience to weld with high enough quality for pulsejet building - you can't end up with a lot of little gaps and holes, etc. Do you have access to your school metal shop? That would be the logical place to find the tools you need for forming metal cones, etc., as well as welding equipment.

If you don't have those skills and tools available, and especially if you don't have a lot of time to prepare, the threaded pipe jets might be your only good option. Such an engine will work well, as Bruno has already shown, though it will be ugly [in my opinion] and quite heavy. It will also take a LONG time to cool off after running, before you can handle it safely. But, it's about the best option if your skills and tools are limited.

If you ARE capable of welding, a couple of my early designs are very cheap and easy to produce, and they run very well, though the thrust is not very good. They are rather long [about 1 metre], but are not heavy to move around. The amount of welding is very limited. There is, however, a lot of hand work sawing, drilling and filing. The simplest and easiest to build is the Elektra I:
http://www.cottrillcyclodyne.com/ElektraI/ElektraI.html
You can build that one exactly 1 metre long. But, the second one is better looking and better running - a lot more hand work is required, though:
http://www.pulse-jets.com/phpbb2/viewtopic.php?t=856
http://www.pulse-jets.com/phpbb2/viewtopic.php?t=941
http://www.pulse-jets.com/phpbb2/viewtopic.php?t=1102
You'd need to build it 915 mm long, not the 23 inches [585 mm] shown on the original plan.

You can simplify either engine by omitting the engine mount lugs, and just hold the engine in a vise for test running. Both these engines are much simpler to make than my later FWE design.

L Cottrill

[Bruno Ogorelec]

Aluminum plumbing parts are no good. You need iron and steel.

OK, some practical advice if you want to build another type of engine from scratch. Use this forum to the full.

First, buy the tough parts ready made. By tough parts I mean the conical transition between the chamber and the tailpipe and the bent tubes (if you want to build your engine bent). You are not trying to prove that you are excellent welders, but that you are smart, right?

If I were you, I would not make a bent engine. Do Larry's FWE or a 'Chinese' or a mixture between the two instead.

Instead of the conical chamber, find a whipped cream dispenser in a supermarket and use it. They are made of stainless steel and have a perfect shape. The price is usually around 20-25 Euro. Throw away everything but the bottle itself. It can all be unscrewed.

Once you have the bottle, measure everything and post the measurements here. Larry or someone else will give you the necessary measurements for the right kind of a FWE-style tailpipe and the intake pipe.

Go to a place where they repair old and fit new exhaust systems on cars.

Ask them for the appropriate size tailpipe and intake pipe.

Let them weld a tailpipe to the narrow end of the steel 'bottle' and the intake pipe to the part where the bottle narrows into the tailpipe. If you ask them pretty please, they may not even charge you. They will almost certainly be vastly entertained by the idea of you building a jet engine.

If they do charge you, it will not be very expensive.

The same approach can be used if you are building a bent engine (like Anders's Lockwood, but you are likely to need more persuasion at the exhaust shop, because there will be more work involved.

All the other information will be available from this forum -- down to the very last detail, so don't hesitate. Just do it, as Nike says.

[leo]

Hallo nina & elise maybe you can use a old exhaust from a moped (brommer) to make a combustion chamber, maybe you now some fellow students who have something laying around.
If you find something post the dimensions and the people here will help you with the size off the exhaust and inlet pipes to get a running pulsjet.
At this post is a very easy to start pulsjet witch you can build from a moped exhaust.

http://www.pulse-jets.com/phpbb2/viewtopic.php?t=1801

don’t underestimate building a pulsejet sometime people don’t get their designs running, look at this post for a example.

http://www.pulse-jets.com/phpbb2/viewtopic.php?t=1125

or the get very low power outputs, here is a example.

http://www.pulse-jets.com/phpbb2/viewto ... light=duco

this are projects from the Netherlands for similar purpose a you have, I like you to do better so accept the help from the people on this forum please.

[Mark]

I was thinking you could go to another store, plumbing pipe made of iron is used almost everywhere I should think. I haven't even seen any made of aluminum!
Mark

[Mike Everman]

Bruno, nice pic of a chopped chinese. I've never seen that one.

[pabloenlucky]

Wow...dude...a lot of reactions, we love it!

First of all we would like to thank everybody for helping us out. We have seen so many plans now that we have no clue at all which we should use. However, we are going to the store now and see what kind of whipped-cream dispensers and thermos(flasks) we can find. We will be back in about an hour and post our findings.

And leo, we will beat those noobs at the TU Delft ;)

[pabloenlucky]

O and by the way, we wondered how it is possible to measure thrust if we don't bend the engine (for example: www.vhp.co.uk/turbine/pulsejet.shtml)

[Lawrence]

you'll have to remove the ')' from the link to make it work

[Bruno Ogorelec]

O and by the way, we wondered how it is possible to measure thrust if we don't bend the engine (for example: www.vhp.co.uk/turbine/pulsejet.shtml)

It is possible but complicated. However, the easier way is to bend it You just use a bent exhaust tube instead of a straight one.

[pabloenlucky]

Okay! sorry for the delay, but we did find some thermos(flasks). We also searched for a whipped cream dispenser, but we didn't find the right ones.

We found four types of thermos(flasks), with these measures (see the end of this post for an image with explanation of the letters used):

1. D=6cm D2=4,5cm H=17/18cm
2. D=7cm D2=5cm H=20cm
3. D=8cm D2=5cm H=28cm
4. D=8cm D2=5cm H=24cm

They also differed in the steepness from bottom to top (the punctuated line in the drawing), we don't know if this is a problem? The flasks were made from stainless steel, the walls were about 5/6mm thick (though we think they exist out of two layers steel with some sort of isolation between them).

We also found a cocktail shaker ( http://www.allclassygifts.com/cocktailshaker250.jpg , something like that) from which the lower part might be of some use. The walls were very thin, about 1mm thick. Is this too thin?

We also went to a showroom and got 4 spark plugs.

[Bruno Ogorelec]

I don't think the thermos would work. It probably has a glass bottle inside. If it does, you'd have to remove it and use just the stainless outer vessel. Also, its shape is not really ideal.

The cocktail shaker sure looks sexy. It might be a good place to start, but would require more work to adapt it.

I don't know what to advise further except continue looking for the whipper. Anyone else with practical advice?

[pabloenlucky]

The thermosflasks didn't have glass inside, both inside and outside were made of steel, we only didn't know what was between the two layers of steel. We won't be able to find the whipper i'm afraid, someone from school told us they had been on the market a couple of years ago, but that they aren't on the market right now (in our country that is).

[larry cottrill]

Bruno -

I agree that the cocktail shaker looks pretty nice, but I really like the outer shell of the smallest Thermos. Remember, the only part of the nozzle that really has to be nicely shaped is the narrow throat where the velocity is fairly high - look at how crude the nozzle end of the Fo Mi Chin is. Some dead space around the outer edge really won't hurt anything, in my opinion, except for introducing a little unnecessary high-frequency ringing. Those dimensions are really close to what I would have liked for the original Fo Mi Chin plan, and I certainly wouldn't hesitate to make an engine out of it. The bigger ones are a bit long, I think, though the larger volume should allow you to wring more power out of it.

L Cottrill

[leo]

Maybe you can find something cheap in a secondhand store (kringloopwinkel) that you can use.
If the diameter is around 6 or 7 cm and the length is two times that size you can use it, then you have to find a exhaust and inlet tube to weld on to it, the diameter of the exhaust must be half the size of the combustion chamber diameter, and the inlet a little bit smaller, my experience is that smaller in and exhaust pipes makes starting easier, but trust will be lower.
If you find something post it and you will get advise on the length and placements of the in and exhaust pipes, then use a bend exhaust pipe to measure trust.

[Bruno Ogorelec]

I really like the outer shell of the smallest Thermos. Remember, the only part of the nozzle that really has to be nicely shaped is the narrow throat where the velocity is fairly high. (snip) Those dimensions are really close to what I would have liked. (snip) I certainly wouldn't hesitate to make an engine out of it.

Makes sense, Larry. What do you think is between the inner and outer thermos shells? Vacuum? Do you think they can be taken apart?

Would you work out the pipe dimensions for the ladies on the basis of the small thermos?