Project diary

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Pulsejets
Project diary


This page is designed to document my progress with my own experimentation in the world of pulse-jets. ill hopefully add some pictures soon when i get round to it. Project diary - Part 2

----- DECEMBER ----- Started the construction of the tailpipe,conical conecttor and combustion area. The two straight pipes were cut to shape and then formed into shape on some rollers. The Conical section was made by inputting the two diameters into a program which then calculated the appropriate pattern that was required. Once this had been cut it was necessary to mark out every five degrees on the metal, this was so that when i came to roll the cone i only rolled one line at a time, once i got to the next line i repositioned the peice of metal so that the next line was parrallel with the rollers and then rolled again. Once the parts had been formed i then TIG welded the seams and then finally welded them together. The whole process only took a couple of hours but i think it may have taken longer had i used stainless steel, but for testing purposes it wasnt necessary. I also began the construction of the electronic ignition circuit(A full description can be found on this site) after a few setbacks the circuit was finally finished. ----- JANUARY ----- Now that the pulsejet tail section had been completed i could then begin the work on the intake venturi section. i decided that i would machine the intake out of some steel bar(WHY?) which was lying around, because of this decision i think it is taking me much longer than it would if i had used aluminium which is the prefered material for the intakes. I started off with a lump of steel that was first hollowed out and counter bored and then i cut the angle into the inside of the intake. this part clearly shows why aluminium is usually used as it took ages to get through the steel!. once this was done i then put the outside slant onto the intake giving it a nice conical shape. once this part had been done i then cut off the piece i wanted and then turned it round so that i could get to the other side and add the radius on the inside and complete the venturi shape. Now that the venturi was finished i then had to make the valveplate. again this was made out of steel and was simply machined to size and then cut off from the rest of the material. Im now in the process of making the valve limiting plate which again isnt to difficult and should have it finished by the end of the week. More to comme soon! I also finished off the electronic circuit by housing it in a plstic box that houses everything and generally looks alot neater. Now i can concentrate on the pulse-jet which is a relief. I finsihed off machining the valve retainer but unfortunately i think i have made the hole that the bolt goes through too big, which may lead to the valves breaking very quickly but hopefully it should be ok. i also managed to mess up the valve back plate, i miss read the plans i have and drilled the holes too near to the center which meant that they overlapped so im currently machining a new one which hopefully will not take too long. Once i have finished the valve plate and successfully drilled the holes i can then move onto fitting the fuel line and also make some screws to hold the whole thing together. after that and i should be close to getting the thing running!!!!!! Im also having a few problems with my ignition circuit. i think its probably due to all the modifications and refits ive had to make which has lead to some of the copper tracks coming away from the board which has made the connections a bit dodgy so i may have to etch another one. ----- FEBRUARY ----- ive just about finished the intake section(i think) all i have to do now is put a thread on a piece of material and then some more round the outside of the intake to hold the tailpipe to it. Im hoping this shoudnt take too long to do but at the moment i definately hope to be finished by the end of the month at the latest. Weather it will run or not is something else.!!! ----- MARCH ----- Yesterday (28/02) i finally got the whole assembly bolted together and managed to get the fuel pipe which is made of copper brazed onto the steel. The pulse-jet itself is actually finished and all that remains to do is install the spark plug into the combustion chamber which i plan to do this afternoon. ive also decided to remake the ignition circuit as i said earlier so ill have to wait for that before i can start it up. Ive been and bought myself a 6kg bottle of propane only to find i didnt have a propane regulator at home only a butane one( god damn it) but i should be able to get one cheap. Im going to have to find some way of supporting the jet on some sort of frame whilst in use but that shouldnt take too long. anyway for now thats it and hopefully by friday next week ill have my own working pulse-jet and some pictures for the site!!!!! IT RUNS!!!!! Last night i finally tested the engine! i layed it down on some bricks and conected the fuel supply up. I will say however that at this moment the ignition circuit is still causing some problems so i didnt use that last night, i used matches instead. anyway first i dropped in a match where the spark plug was supposed to be and turned on the propane and got it burning then i screwed the plug back in and started my little air compressor. for some reason nothing was happening then i realised the valves had moved and werent covering the holes on the valveplate so i stopped the fuel and re-aligned them. this time i put the match in at the tail end and when this ignitied i got a huge flame burning out of the back of the engine. When i started the compressor again the flame got slightly hotter (i could tell by the blue flame being produced) but still no pulsating combustion. i decided that i would try and reduce the fuel supply everso slightly to see what happened and the flame kept getting smaller until the flame all of a sudden disappeared and a slight wistle ccame from the engine but no continuous pulses, so i reduced the fuel ever so slightly and it burst into life. Even though this is my first engine and obviously pleased that i am getting some sort of pulsating combustion i still think it was working 'properly' but at least it was going anyway. I noticed that the combustion seemed to be taking place right at the end of the tailpipe instead of in the combustion chamber. The reason i think it wasnt working properly was the noise which it was producing, whilst it was quite loud it was nothing that could not be tolerated by my ears without protection, other people have said that theres is unbearable so i still need to do some testing. i plan over the next few days to test different fuel settings as it is the regulator im using allows fuel pressures up to 3 bar down to 0bar so ill try to see if i get a better result. UPDATE...... ive done somemore testing over a week ago now and ive managed to get it working even better but still not perfect. Ive just about used up all the propane in my tank so i need some more. Ive come to the conclusion that i need to get my hands on some proper spring steel material because the pepsi can maybe the reason im not getting proper combustion(it just isnt springy enough!). so until i get my hands on some of that all testing has had to be stopped, and until i get my car fixed i dont think ill get any done this week. Oh well ive also in the meantime begun planning my next project which i want to do over the summer. Its a valved pulse-jet or at least the mk1 version is anyway. It utilises a the pressure wave from one engine to compress the air/fuel mixture in the other engine. In theory it should improve efficiency and maybe produce more power if the latest BCVP results are anything to go by. anyway for now im busy working on this drawing up diagrams etc so expect to see some pictures up within the next week. ---- April ---- Testing has been slow over the last two weeks i cant find any spring steel and i havent had the money to get some more propane. I finally had some money to get the propane on thursday (18th) and also My ignition module arrived from america which JIM COXSTER kindly sent to me so i thought it would be a good time to test again. I also borrowed a leak blower from a freind and hopefully this should sort the problem of lack of starting air. The first thing i did was test the ignitor in the class room and it works brilliantly nice big sparks across the plug( thanks jim) then it was time to get everything together and setup outside. oh and i welded some legs onto the pulse-jet so that it can be stood on its own, im actually quite proud of that bit! Project diary - Part 2

CHeck back soon for more updates!