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Jan 10, 2023 11:45:49 GMT
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Decades ago, I used to have a couple of pulsejets as part of my university projects: (Edit: that was 21 years ago) Starting them required a blast of air from the leafblower and some sparks from a sparkplug. I made a little Veroboard with a 555 timer putting a 100hz square wave through a chunky 2N3055 transistor, into a car coil. All running on 12V. This is it:  At some point I blew something in the circuit and replaced the 555 and whatever the original transistor was with the 2N3055. But it never worked again. Back then, I didn't have a scope and I was relying on cheap eBay 555s from China. I could see at least one or two out of my batch of 10 didn't work and I ended up putting it back in my electronics box in the loft. Since I'm currently on a lunchtime roll with all this electronics malarky, I thought I'd dig it out and find out what was up. First I had to work out what the 2N3055 was because I can't remember all this stuff, so hit the datasheets online. It's a chunky NPN transistor. Then sketched out what was going on after the 555:  So it looks like I basically copied how the points worked on my Anglia. Ok, that makes sense. I don't know if that's good or not, but it works. Next I connected a 100k resistor between the +ve supply rail and the transistor body, which is its output. That completed the circuit and made it do this when I connected it to the scope:  Ok, so it was working after all. I must have tested it with one of the dead 555s whenever it was I last played with this. Since it is now working, I figured with all these spare project boxes I've now got I might use one to house this. I'll use this one: forum.retro-rides.org/post/2717609/thread Inside that box, I'd made a couple of angled Veroboards that drop into the slots. I just had to remove the transformer I'd soldered to one of them:  I've got these other things to make proper connections and to be able to switch it on and off and stuff:  A quick mark-up and drill leaves me with this:  I'm having 12V DC going in the screw-down terminals at one end, through the on/off switch, then coil connections out the screw-down terminals at the other end. My old board will be mounted on the angled one with some stand-offs and I'll wedge it in with something so it doesn't rattle. Then I think I'll crack out the Dymo and make some labels so I don't forget what connects where.
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Last Edit: Jan 10, 2023 11:50:27 GMT by Jonny69
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75swb
Beta Tester
Posts: 1,052
Club RR Member Number: 181
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Jan 10, 2023 20:41:38 GMT
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Then I think I'll crack out the Dymo and make some labels so I don't forget what connects where. And presumably then whip up a pulse jet engine to test it right? Interesting project! |
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Jan 10, 2023 20:45:05 GMT
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I remember the pulse jet scooter you took to le Mans  |
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Jan 10, 2023 20:58:14 GMT
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And presumably then whip up a pulse jet engine to test it right? Interesting project! I’ve still got the pulse jet. It’s screwed to a scooter in the shed! I remember the pulse jet scooter you took to le Mans Yup, good times! It was the same jet as in the video at the top. Don’t know if you remember all the croc clips and stuff and getting electrocuted if a connection got knocked off! |
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Last Edit: Jan 10, 2023 21:00:55 GMT by Jonny69
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Jan 11, 2023 13:10:19 GMT
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Can't remember that but I remember the tennis ball cannon!!
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Jan 11, 2023 13:42:42 GMT
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Wired it in and it still works.  Just needs some labels |
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Jan 11, 2023 13:45:01 GMT
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I think there's a J69 spud cannon at TAB somewhere...
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Jan 11, 2023 15:41:06 GMT
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I think there's a J69 spud cannon at TAB somewhere... Ah, I think that's the giant Spudmatic. I forgot where that ended up! The tennis ball cannon was a load of baked bean cans gaffer-taped to some drain pipe that ran on Zippo fuel. It was an evolution of the mess tin cannon that we used to make in cadets etc which was made from mess tins taped together, but a lot more powerful. I always knew stuff went a long way because at university we used to fire onions out of it because you could peel the onions until they were the right size for the barrel. We made one that was about 12 cans on the end of about a metre of drainpipe and it blew the onion up into the cloud cover and out of sight! I'd got a tennis ball to go around 350m out of a smaller one when I was working in SFX. The Le Mans version was basically a longer barrel with the baffles in optimised positions and from the middle of the Tertre Rouge campsite it basically cleared the spectator area and landed in the gravel trap on the other side of the Dunlop Esses. I was aiming for 500m but we got around 450m in the end. The university capers with the baked bean can cannon is actually what led to the pulsejet project I did. Long story short was that I taped the cannon and a pair of boots to a skateboard and lit it. Apart from blowing my eardrums out, it shot the entire length of the corridor in my halls. One thing led to another and my final year project was born. You've got one of the big turbos I had at TAB. The jet is the one in the video at the top and it's on a scooter in my shed. |
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Jan 12, 2023 17:05:38 GMT
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I got it labelled.    Labelling clearly isn't my strong point because none of them are straight or centred even though I marked it up. Never mind, I won't forget how it works now, so it can go back in the loft for another day (though I might hook a coil up and a sparkplug and check it still sparks). |
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Last Edit: Jan 12, 2023 17:06:09 GMT by Jonny69
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Jan 13, 2023 16:25:58 GMT
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And as usual I can't leave things alone. I had 30 minutes between experiments and I was thinking. I've got that adaptor to go on my Makita 18V batteries. Little point having to run this on a PSU or a car battery like I used to, when I could use that. 555s only like 15-18V though and I think 18V Li Ion batteries can hit 21V. A regulator should fix that! Like this:  |
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Frankenhealey
Club Retro Rides Member
And I looked, and behold, a pale horse! And its rider's name was Death
Posts: 3,881
Club RR Member Number: 15
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Jan 14, 2023 21:04:21 GMT
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Following another of your threads again and you've already made me go out and buy an Arduino kit  Anyhoo I'm clearing out the abandoned projects in the Volcano Lair and found this from when I was considering making my own cracker box for the turbines and wondered if it would be any good for a pulsejet starter and if so did you want it?  |
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Tales of the Volcano Lair hereFrankenBug - Vulcan Power hereThe Frankenhealey here |
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Following another of your threads again and you've already made me go out and buy an Arduino kit Anyhoo I'm clearing out the abandoned projects in the Volcano Lair and found this from when I was considering making my own cracker box for the turbines and wondered if it would be any good for a pulsejet starter and if so did you want it? img.retro-rides.org/i/v/frankenhealey/39a4bb22ab30.jpg Lol, intriguing transformer. What’s the spec? So what is the ignition source for your turbines? I’ve been following the thread when it pops up but I don’t think I’ve seen you mention how you light them. |
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Frankenhealey
Club Retro Rides Member
And I looked, and behold, a pale horse! And its rider's name was Death
Posts: 3,881
Club RR Member Number: 15
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Jan 15, 2023 20:11:05 GMT
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Following another of your threads again and you've already made me go out and buy an Arduino kit Anyhoo I'm clearing out the abandoned projects in the Volcano Lair and found this from when I was considering making my own cracker box for the turbines and wondered if it would be any good for a pulsejet starter and if so did you want it? img.retro-rides.org/i/v/frankenhealey/39a4bb22ab30.jpg Lol, intriguing transformer. What’s the spec? So what is the ignition source for your turbines? I’ve been following the thread when it pops up but I don’t think I’ve seen you mention how you light them. Got no idea of the spec, sorry. Here's the exciter for the turbines  Further info here |
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Tales of the Volcano Lair hereFrankenBug - Vulcan Power hereThe Frankenhealey here |
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Jan 15, 2023 23:24:36 GMT
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50 pages of obscure how-to-start-a-jet? Don’t mind if I do!
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Jan 31, 2023 18:05:09 GMT
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I found some old pics from university. This would have been late 2001 to early 2002! One of the cannons (small one by the looks of it):  The scooter up in the halls kitchen:  The skateboard:  Couple of shots of the pulsejet turbine engine I built:   ^ Those are some really rare shots in the metalworking workshop on the Brunel Runnymede campus. It's long gone now; sold off and demolished about 10 years ago.  |
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Last Edit: Feb 1, 2023 10:37:10 GMT by Jonny69
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bstardchild
Club Retro Rides Member
Posts: 14,968
Club RR Member Number: 71
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Jan 31, 2023 18:12:14 GMT
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I thought the scooter looked sketchy till I saw the skateboard |
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jamesd1972
Club Retro Rides Member
Posts: 2,921 
Club RR Member Number: 40
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Batshit mental.
Carry on with more details !
James
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So the potato gun that HARDCORE mentioned, that's this thing:   It's basically a big Spudmatic. It's a small chamber that you pump up to whatever pressure with a track pump and let it all out with the ball valve. There were originally two of them and this was the second one. I built the first one for an episode of Big Bigger Biggest which was on Channel 5 in late 2009. It was originally a scale underwater Polaris missile launcher. See if this video links to the right place, if not, skip forward to 34:45 to see it: It did actually work quite well with the gaffer tape cap on and would shoot the missile up to the ceiling from underwater, but I don't think they used it properly in the shoot. |
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Hahaha, from my notes at the time: The pump is a bit rubbish but 40psi sends a 15mm slug of potato clean over the 3 stories of flats in my building. 100psi sends it right over the block adjacent and 160psi which is pretty much all I can manage with all my weight on the pump goes about 75 metres down the road with a bit of recoil.
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