Another pocket-lockwood

[Beaker]

Hi all

I have been browsing the forum from day one and its about time I stepped up to the plate.

After following steves pocket lockwood (thanks steve for paving the way) I thought I should build one my self to roughly the same dimensions.


I'd like to share a mod I made, block the end of the stinger and drill through a 1mm hole up about 3mm and drill a hole(make slight interference fit) into the front side of the CC what I got was about 2-2.5 times thrust, just my 2cents.

Any way here are some pics

[steve]

very impressive build! I noticed that your intake is a bit shorter then mine, do you think that might have had an impact on thrust as well? I also think that it is neat how you spun the CC and intake on a lathe!

It's very interesting to see that a fuel injector in that location will work, since I would have guessed that the fuel an air would not mix well enough by the time the next pulse starts, that's why I opted for the less conventional intake flare injector position since it gives an extra couple of centimeters for mixing to occur. I believe that your fuel injector might have a signifigant impact on the engine's frequency (although any change might also be attributed to the diference in intake length) could you upload a video or sound file for us to analyze?

I noticed that the flame comming out of the intake was yellow rather then blue, inticating that combustion was incomplete, suggesting that maybe the injector isn't mixing well enough in the short amount of time it has to do so. I would suggest gently pinching the injector with a pair of pliers to make the holes smaller. You could probably pinch them down untill they are just slits. this will force the gas to be injected more violently into the chamber while greatly aiding in the mixing process and increasing efficiency.

how are you measuring thrust? and exactly how much is the engine producing? I just aquired a very accurate scale to measure the thrust on mine and I would like to compare it to yours.

please describe the operation of this engine in as much detail as possible and please correct any misconceptions I may have stated above

Finally I would just like to thank you for building this engine, I put a lot of effort into making plans for my engines etc. and it is wonderful for me to see that they are being used!

[Mark]

I'd say you hit a home run Beaker. Not bad for a first posting. Since acetylene is so forgiving, does anyone think that it might be possible to do some straight pipe shape or stretched jam jar shape whereby you could do away with a forward intake altogether? That is, is it conceivable that a repeating pulse could sustain itself by the more rapid combustion of acetylene in a simple straight tube or slight buldging variation of a proper length having one end open and one end closed?
Mark

[Mark]

I noticed that the flame comming out of the intake was yellow rather then blue, inticating that combustion was incomplete, suggesting that maybe the injector isn't mixing well enough in the short amount of time it has to do so.
Finally I would just like to thank you for building this engine, I put a lot of effort into making plans for my engines etc. and it is wonderful for me to see that they are being used!
Steve

I noticed that too, the orange color instead of blue. Here is my Logan running on acetylene, more of a blue color too. As an aside, in Foa's book he says that there has been no better method of mixing fuel found than that of a side-ported Logan. And as we all know who've done the acetylene fueling, isn't it a hoot when you start making those billowing flakes of carbon black soot particles that shoot out like confetti when you go to start your prototype sometimes and combustion is incomplete to say the least?
Mark

[mk]

Congratulations "Beaker"!

You're using an amazingly short inlet pipe! You can be proud of your first(?) succesful effort, IMHO.

I assume the holes are pointing perpendicular to the comb. chamber wall when the "swizzle stick" is inserted properly, aren't they?

BTW Who wrote that the engine depicted in the pictures ran on acetylene?

Still shaking my had when looking at the inlet pipe...

[Rossco]

I love short intakes! That one looks much more like it to me!
VERY NICE, rediculesly small! but very nice.
I would think that this engine with its intake set up should be more forgiving than steve's little screemer, you given any other fuels a shot? (propane)

Just my little note in here about acetylene!
Have you ever played with a multi burner cutting attachment when its fully carboned up? FUN
The carbon creates very hot spots around the tip, and if you bump it up on the oxy, you get a very sticcato, extreemly loud, little detonation engine. (it does burn the tip out pretty bad tho)
I can only assume that a tiny pocket of lean mix detonates behind the tip, and in turn fires the hole next to it, and so forth. The tip i used had six holes in a circle of about 4mm. This produced a great racket of roughly 30Hz!.

Rossco

[Beaker]

Thanks guys for your positive feedback

The engine is running on acetylene and in the picture its just at idle because the camera that is taking the pictures just goes fuzzy and blury when at full power not sure why?, its a brand new digital SLR, good its not mine. The combustion mix can be changed by turning the stinger around, finding the sweet spot can be a pain as too much in any direction can kill it, will confirm best position.
It was just a quick build (30 minutes) and Quick start up but will put more time into it.

I'm open to any suggestions, comments as i'm in no way a pro in this field I just like to try anything and bend rules.
I have been interested in pulsejets for about 11 years and have had successful runs and some failures actually more failures but I think thats whats so interesting about this black magic it keeps you coming back for more.
I have a cool project under my belt but I will say no more untill it is done.
:wink:
Starting the engine is no harder with fuel in this position.
Intake is approx (all ID) 19mm x Ø5.8mm, CC 32mm x Ø21.5mm, tail pipe 215mm x Ø4.6.

I will try and run it on propane tomorrow, not to confident it will run!.
My thrust measuring device is not very accurate i've got another idea and will try it.
I will upload a short movie on the weekend.
Hope this answered most of your Qs?

As for bad oxy tips, I work at a large machine shop and when some of the boilys turn on one of the abused and leaking oxy torches we have a short (1-5second) PDE engine! AWSOME!.
I'm going too look into this further and get sound or video or even try to put something together to recreate this explosive force.

[Mark]

It seems from the torch tip stories of Beaker and Rossco that acetylene won't be too hard to get to stuccato in a hot tube of some sort with a little bit of work. Just be careful and protect your ears if you should start detonating or approaching that end of the spectrum. I remember a shop teacher in high school who demonstrated to our chemistry class a small balloon filled with acetylene and oxygen touched with a red hot rod. And too, I onced puffed in a little pure O2 into a tiny pulsejet and then lit the tail end. Kind of foolish but it made an impression on me.
Beaker, if you get your little Lockwood to run on propane, I will be amazed. Propane would be much more practical but ten times harder to do.
Mark

[rocket_man]

hey Beaker could you post detailed plans of your engine, like the dimentions and like a schematic? i'm thinking of building your engine for a school science fair project.

[thecheat]

same here but for fun. I'd like to know the exact stuff you purchased and what you did to it to make it work. thanks!

[newbieflyer]

Did you need hearing protection for such a small thing? Does it give any thrust?