Weldless valveless engine?

[insanitys_engineer]

Hey everyone! I'm new here, but I have read around the subject a bit...

I'm looking at building a valveless pulse jet without any welding - there's a story behind this!
My mate has bet me £100 I cannot make a jet engine. So I have a £100 budget with which to build an engine, but no welding kit and no easy access to fresh new sheet metal...
The engine doesn't have to be anything more than a proof of concept at this stage; I was looking at making it out of tin cans and riveted/bolted sheets from baking trays etc.

1) Has anything like this ever been done before?
2) Any ideas on which valveless design is going to be easiest to produce using the basic materials I have?
3) Any general rules about engine proportion I should follow when designing this thing?

Cheers for any help!

Timmy

[larry cottrill]

Timmy -

The easiest "grab" answer is to make a threaded pipe jet, like the "Pipewood" described elsewhere (Valveless Forum). In your case, though, this isn't going to work for the simple reason that you have to impress somebody. That throws cold water on any jet that weighs 15 or 20 times as much as the thrust it delivers.

The basic problem with riveting in sheet steel is that you'll have to do a heck of a lot of it to make your engine work, because of the leakage. If you're willing to put that much effort into it, you should be able to make it work. Your rivets will have to be VERY closely spaced -- on regular round-head rivets, the edges of the heads will be practically touching the adjoining ones. That is going to be a LOT of careful drilling and riveting, but it can be done. Another thing that should be considered is using "locked seams" like in regular HVAC duct work. That can save you a lot of effort -- but only where you have straight seams, like along the side of a cone or along the length of your tailpipe.

You could use almost any of the plans, with "slight" modifications - ha. A good and simple one would be Eric's "Advanced FWE", your main problem being that in its original design it is SMALL, which would make riveting really difficult. You could scale it up to something more workable (and more impressive). Proportions might have to be adjusted slightly, but that would depend on the size you think you need. Any place where the plans show things butted together to weld, you would have to lengthen, and then hammer a "flare" to make a kind of "socketed" fit, then drill all around to run in your rivets. Note that your rivets will need to be steel type material that will take RED HEAT without breaking down! Aluminum alloy "aircraft" rivets won't cut it for this job. A particularly difficult area will be around the point where the intake runs into the chamber, since leakage there is critical and the matching angles vary wildly all around the intake pipe. I'll try to attach a drawing showing a simple way to do the intake (welded) that could be adapted to riveting, since you can work in the clear attaching the straight bottom lip of the intake to the chamber, then add the saddle-shaped "fairing" on (with the addition of appropriate lapping flanges) and rivet the heck out of it.

As long as you're wiling to use mild steel, you shouldn't have any trouble finding stuff that will work. Find an old washer or dryer at the junkyard and cut pieces from the cabinet. A little rust won't matter at all, as long as it isn't enough to really weaken it. Or, just buy some ductwork pieces of reasonable size from Home Depot or someplace similar -- try to get the black painted stuff in lieu of galvanized, if possible. With this stuff, you'll be getting half the locked seam that you can use, and you can probably get a simple hand tool to form the mating edge so you can pull your cone or cylinder together and just lock it up. There IS a way to do it all, you just have to be clever in how to design the connections, and very careful with your drilling and riveting.

For a sparkplug mount, get a small square plate or very thick washer and thread the big central hole to fit the plug (or just use a matching nut) and drill a line of many holes all around for rivets. Clamp it in place on the side or end plate of the chamber (after hogging out a big hole, naturally), drill all the holes through the sheet metal and rivet in -- again, they will have to practically touch each other, all the way around!

Man, if you actually go ahead with this, be sure and get LOTS of photos as you go along and post them. You will not only "amaze your friends", you will amaze all of US if you can actually make this work! It will probably be only about three or four times as hard as my description makes it sound. Ha.

Good luck!

L Cottrill

[metiz]

It has already been done, check this post viewtopic.php?f=3&t=5003
GRIM has made a succesfull engine like that, runs great. Instead of using rivits, simply go with bolts. use automotive gasket sealant to get rid of any leaks. Also, you can use the focused wave engine plans but to make your life a bit easier, make it linear (straight intake bolted to the endcap)

Look for some pipe steel for the intake and exhaust to make it easier still. for the intake and exhaust, use a flare. Make another round plate for both the intake and exhaust and slide it between each seal. so you have combustion chamber, intake and over that the round plate so you have the intake "sandwiched" between 2 plates. this helps keep it where it's supposed to be and also helps prevent leaks (GRIM's idea)

Read that topic carefully.

(btw, if you just want to win your 100 pounds, get a jar, drill a hole in the top, between 11 and 13 mm. put a TINY amount of volatile fuel on the bottom of the jar, like methanol ((alcohol works to)). screw your lid on, keep your finger on the hole and shake. place of floor, clean of any excess fuel from the top of the lid and light the hole. putt putt, there's your pulse-jet. 100 pounds bagged ))

[insanitys_engineer]

Cheers larry for such an in-depth response!

(btw, if you just want to win your 100 pounds, get a jar, ... there's your pulse-jet. 100 pounds bagged ))

That was the first thing I tried, but we kinda decided that it wasn't in the spirit of either the challenge or Science in general, so the bet still stands!
Cheers for the link to the thread about the already made one, I'm looking to do something a little more Heath Robinson in the short term until I can find a good scrap yard nearby. I've done some stuff with tin cans, but haven't managed to get more than the initial blast due to the fact I've spent all of £3 on the whole thing so far (excluding the cost of baked beans!).

In the short term I was looking at a capped tube design as I can make the blast chamber and cap from tin cans, and the exhaust from a length of scaffolding tube or increasingly large cans to get the flared shape, with the transition between combustion chamber and tailpipe being jubilee clipped and bolted piece of metal cut and hammered to shape. This one wouldn't have to last long, just prove an engine can be made with cans

In terms of a final design, the FWE looks nice; I reckon given some time I should be able to make flaring parts (not necessarily the combustion chamber though!) and possibly attach recuperators to squeeze that little bit extra performance.

I'll post some pictures of my dabbling so far later this evening.


Edit: my camera isn't behaving, I'll get photos up as soon as I can!

[larry cottrill]

It has already been done, check this post viewtopic.php?f=3&t=5003 GRIM has made a succesfull engine like that, runs great. Instead of using rivits, simply go with bolts. use automotive gasket sealant to get rid of any leaks. Also, you can use the focused wave engine plans but to make your life a bit easier, make it linear (straight intake bolted to the endcap)

Yes, I completely forgot about that one -- pretty recent, too! Of course, I suffer from Oldtimer's Disease (symptoms: You can remember anything that ever happened to you, as long as it was more than five years ago; Everything you say reminds you of something). With the high temp sealant, you could get by with moderately spaced riveting, or even pull it all together with sheet metal screws! Crude but effective - ha. A basic caveat would be to make sure you keep the inside contours smooth, especially in narrow regions where the gas speeds are high, like where the tailpipe joins the chamber.

L Cottrill

[Mark]

Hey everyone! I'm new here, but I have read around the subject a bit...
I'm looking at building a valveless pulse jet without any welding - there's a story behind this!
My mate has bet me £100 I cannot make a jet engine. So I have a £100 budget with which to build an engine, but no welding kit and no easy access to fresh new sheet metal...
The engine doesn't have to be anything more than a proof of concept at this stage; I was looking at making it out of tin cans and riveted/bolted sheets from baking trays etc.
1) Has anything like this ever been done before?
2) Any ideas on which valveless design is going to be easiest to produce using the basic materials I have?
3) Any general rules about engine proportion I should follow when designing this thing?
Cheers for any help!
Timmy

I vaguely remember some paper plans I came across, it was how to make a valved pulsejet out of a can and piece of fence post. The fellow used plates and long lengths of all-thread to hold it all together, along with some fabric gasket material and a hose clamp perhaps. It was just a typically shaped valved pulsejet but nothing to write home about. I forgot what he used for the valve material. But the jet was certainly cheap, it couldn't have cost very much.

I built a small valveless pulsejet that ran on methanol, and later MAPP gas and acetylene. The methanol version didn't even need a spark plug. There was one hole to drill and tap, that being the side port for the 1/8 inch plumping pipe nipple to screw into. No welding of course. I doubt the pipe parts cost more than $20.00, the largest/widest piece being a 3/4 inch nipple for the combustion chamber. I made some larger versions, but the little one was my favorite, loud and about as sure starting with methanol as a jam jar, if not more. After you prime it, it goes almost everytime you light the tail, full grease in an instant. In the pictures you can't really tell the methanol designs are running but I started them up and took the pictures, the fuel tank being a silicone fuel line, which gave me about 10 seconds. But it was simple and loud. I used a fly tying clamp to hold the little copper fuel line in place on the methanol version, kind of makes it look a bit odd.
You probably don't want to build something like this, but it was fun for me.