Jonny69's inventing laboratory: New jets p.4

I got brave and got my mate to shoot me in the ass ;D

Take 1:



Take 2:



We couldn't look more gay if we tried ;D

haha, mental!

I need one now!

You could of worn pink.... Highly amusing, do you come with your own personal safety warning sticker??! Oh and we need evidence of the bruise.. I'm assuming it left one?!

I seem to have gotten away with only a small bruise. Must be because it hit the fleshy part ;D

Something makes me want to get one of those cheapy compressors- the twin-plunger types are quite good, will manage about 120psi, but instead rip out the electric motor and fit a weedeater petrol strimmer engine on the back of the pump and drive it with that... no wires, just start it up and off you go...

But that'd be a whole other project in itself lol ;D

--Phil

Oooooo nice.. wanna make me an exhaust! lol (please add video involving lots of noise and fire soon... thankyou muchly!)

Dropfiles has gone and gone bust so I've lost all my pictures. I'll try and get them replaced asap.

I've been toying with some bits for the Mk2 jet scooter, one which will have more thrust, proper throttle control, some brakes and will be realistically rideable. I've built some bits but no way near all of it yet so this is more of a build diary.

One big jet is a bit unmanageable in terms of physical size, logistics of making it and materials cost/availability. Two smaller jets can be made using off-the-shelf materials and provide the same results, so I've opted for two jets similar to the one on the old scooter, running in a valveless configuration for longevity and turned back on themselves for maximum use of the thrust. Similar to this one in fact, but a lot smaller:



Check out the dude on the left

The jets are U shaped which might seem a little strange but I'll explain how it works. In a valveless pulsejet you end up with a portion of the exhaust coming out the intake during the combustion phase, about 40% in total and the other 60% goes out the exhaust end. If the intake is facing forwards then it works against the rearward thrust, but if you turn the intake backwards it works with it. You can't suck yourself along, so during the intake phase the inlet will not take thrust away and we won't be working at high enough speeds that ram-air will affect the intake.

Science lesson over, lets get on with the build. Mine are going to be straight sided tube and I can get two U bends in 2" exhaust tube, shown here cut down so when complete the intake tip will be level with the exhaust:



Extend to the desired exhaust length:



The intake is a single straight section of tube. Previously I've used multiple tubes to get the desired area but this time I opted to cut a slice out the middle of a larger diameter tube and re-roll it to the desired diameter:



Onto the combustion chamber. Some endcaps for the intake tubes:



The intakes weld into these and they are simply drilled with a cheapo Screwfix holesaw and the outside diameter cut and dressed with the grinder:



Welded into place:



The combustion chambers themselves are lengths of 100mm diameter steel tube carefully cut to size with the grinder:



I got a nice square cut at each end to work from where the length was cut at Metal Supermarkets, but ultimately it's going to distort quite a lot when it gets red hot so there's no point being too fussy about it being perfect.

Rough layout is this, before I make up come cones:



And to make the cones you can see a card template on the right which I used to make the shape before transferring to sheet steel:



Forming the cone is quite easy with a bit of practice, just working the steel by hand slowly, checking, work it a bit more and so on. No complicated tools needed here

And that's where I'm up to. I've got a little vehicle from Freecycle that may donate some parts, namely the wheels, forks, headstock, brakes etc:



The engine is scrap but all the bits I need are in fine working condition

how is ignition achieved then Jonny? or are they self perpetuating after they are lit?

(seem to remeber seeing one being lit with a leaf blower on scrapheap challenge once)

I was looking at Puch Maxi videos on Youtube.

Found this one.

At 2 30 theres a Maxi with 2 large pulse jets on the sides.