You can make a real jet engine for five minute's work and the price of a spoonful of meths - how cool is that?!?
I doubt there's a better way to re-use all those jars under the sink. Much more fun than a trip to the bottle bank.
Step 1: Materials and Equipment.
Step 2: Making It (the Lucky Way)
Jam Jar Jets are by no means my idea, and I knew very little about them:
Knock a hole in the lid of a jar, splash some meths in the jar, give it a shake and light the meths.
So that's what I did, and it worked first time.
After running for a short time, with a noise like an angry moped, the temperature got too high for the jar and it gave way.
That was expected.
Then I tried to repeat the thing...
Step 3: What Goes Wrong...
"Daddy, show us how you made the jet engine!"
"Not a problem", thinks I.
I grabbed another jar, smacked a hole in the lid, splashed in some meths and lit it.
Foosh, then nothing. It didn't work. (There's not much point watching past the first few seconds of this video.)
After some research, it turned out that the hole was too big. If you make a jam jar jet, and it goes foosh and then does nothing, like it does in the first video above, then the hole in the lid is too big. Go make another one.
If your jet lights, goes foosh, and then goes RRRR for a moment, like it does in the second video, then your hole is not quite big enough.
Step 4: Getting It Right.
People that do this properly use proper tools, but it is possible to get it right with just a hammer and an inappropriate spiky thing.
If your fuel is meths (recommended), and you're using a pasta sauce jar, then the hole needs to be about 10-12mm across.
When I prepared a new jet, with a roughly circular hole about 10mm across, it nearly worked. It lit, went foosh and then RRR for a second.
A couple of minutes prodding at the edges of the hole with a screwdriver made the hole about 11mm across, and it ran well. Really well.
But I forgot to video it!
Never mind, I put the flame out and let the jar cool for a few minutes, then tried again. Yipee! It worked!
Step 5: How to Do It Properly...
Drill a nice, circular hole in the lid of your jar.
Splash a few millilitres of meths into the bottom of the jar and screw the lid on tightly.
Put your thumb over the hole and shake. This coats the jar with fuel and adds vapour to the air to aid ignition. If everything is going well, the jar will make a sort of sucking noise when you take your thumb off the hole.
Stand the jar of a heat-proof surface (it will get really hot), wipe spilled meths off the top and light it.
If the jet works, and you want to use it more than once, don't let it run too long. Extinguish it by dropping a spare lid over the hole of the jet - let it cool before you pick it up!
If you get one running, add a video to the comments. One day, in the distant future, I'll make one out of metal and add a fuel-feed. I wonder how loud it will be...