My Valveless Pulse jets...

[Bob]

I did a bit of playing around with the PJ's the last couple of days , when taking a break from cutting and burning brush...
 so far I have got the Old big PJ working but only by adding a piece to the tailpipe.
... I got the "Old reliable" running the other day
so that left the Funny looking one  and the super tiny one...
 so I took the "funny looking one" and was thinking about it and desiced to shorten the INTAKE pipe  to one inch (just eyeballed it and lopped it off)  the theory being that it is a bit too small to begin with , shortening it may give it that much more flow... not much but maybe enough...
... also there is the aspect of tail pipe length to intake pipe length.... I got to thinking that
sense the Logan study only messed with intake pipes as a short side line study that an intake pipe wasn't needed... and if you think about the operation of the PJ the shorter the intake the shorter the tail-pipe can be..... sense I did get this one to run using an addition to the tailpipe but not without it... that told me the tail pipe was too short to begin with... so shortening the intake served 2 purposes.....(more fuel air and shorter exhaust)
 so I lopped off the intake ...
the results were fairly good it ran easier, if you can call it that...but it was still hard to get started. adding just a short section of tailpipe in addition made it run fairly easy.
....
I have made up 3 diferent lengths of additional exhaust pipe that I can just clamp on with my welding vise grips...flaired at one end they clamp on and are simi-air tight and the results show imediately
....
I have the electric sparker working good now and the Propane supply works fairly good... the fan however is still weak but the PJ's shouldn't need the air to begin with , it just makes it easier.
...
I've studied the Logan report at length now and I have come to the conclusion that a Combustion chamber connected to a slightly smaller exhaust pipe is the best set up....for thrust
...intake pipes are not needed from the looks of things  and in the Logan report they gravitated to larger and larger exhaust pipes to attain the most thrust... the end results were strange... with the tailpipe/exhaust pipe being only .9 of an inch smaller in diam than the C.C. ! but the INTAKE Hole/stub.... usually drawn as about 1" long... was increased to half the diam of the C.C. ... a huge increase as well...
...
taking these changes I can't help but wonder if a straight pipe with a 1/2 Diam intake stub out the side ... cut to slightly longer than the over all length... wouldn't work?
the slight reduction of the C.C. diam going into the tailpipe is the cause for the sonic wave... without that reduction in there it may not work... but there's only one way for me to tell and that is to build one! <Grin>
...
... Backing up to my"Funny Looking" PJ. it looks like a Pea-can with a pipe welded to it on both ends and a spark plug in the middle.... one pipe being small and short ( the intake) the other being 2 times as large and about 5 times as long is the exhaust.
you can look right down through this PJ... its a hollow tube ! .... but it does indeed work !
... if I take that simple design and stretch it to the Logan Reports direction of Exhaust and intake changes... it should be just as good as their fancy 50+hp PJ at 300fps airspeed
...
I want to try this on a smaller diameter than 6" however ... I have some 2.5" conduit/chain-link fence posts... that is my prime target.....
... if my suspicions are correct, this could be a very strong small PJ that is easy to make.
perhaps we shall see...<GRIN>

[Bob]

LOL re-reading what I just posted I realized that what I am describing is just a ram jet....
but I want it to Pulse as a pulse jet...a very distinct combustion stage
that should be achievable by just extending the exhaust pipe to the proper length
...
Bob....

[Bob]

Well, I took a old Ramjet that never worked and re-worked it to make a Combustion chamber for a PJ
and tried something new... I tried a Larger intake and larger exhaust pipes on it, I did this because according to the Logan report as the PJ's got better and better thrust the intake and exhaust sizes increased in comparison to the C.C. size... so I thought I'ed try it and see what happens.
... it came out looking like a "Straight Lockwood" and ran after abit of persuading...never ran real good but it did run.
  I left the intake and exhaust pipes long so I could trim them to "Fit" the PJ.
the 1.25 or 1.5" intake and 2" exhaust seam very large for the 2.85" C.C.
 the C.C. is 5" long so I cut the intake pipe to 5" (taking off about 1 1/4") and tried it again .. this time it fired up almost immediately ! ... and I'ed say it's about 2 times as loud as my other PJ's LOL.
  I ran it for a few seconds but could not get it to throttle very well
... I then cut the exhaust to 8 times the C.C. length ...cutting it extra long to be sure I don't have to weld on a section on later ! ...
 that however didn't seam to work as I couldn't get it to run again after that !...but that may well be because of the propane tank is almost empty!...ALREADY!
so I placed a extension pipe on the end of the exhaust and it took off running almost immediately again
.... seams this puppy needs to be very long!
the thrust seams very good.... the best yet out of all of my PJ's!....
... I tried to run the PJ on gasoline but couldn't get it to run... it would POP and flame but not run. but ONLY after it was pre heated by the propane... once the pj was Hot and switched to gasoline it tried very hard to work.  more tinkering is needed to get that to work though .
....
 I have never seen a "Straight Lockwood" before but I opted for this shape so I could use it on a rotor tip.... where the intake is faced into the oncoming high velocity air so I could get the RAM-AIR effect and increased thrust as the blade spins up ...
I dunno if it will work or not but its sure fun to play with.... Noisy but Fun !
...
LOL
Bob....

[Bob]

 I got more propane... have it about half used up already ! 5 gal don't go very far on a big PJ !
...
 I added a loop back to the straight lockwood ... to make it a proper lockwood.... could Not get it to run at all...no matter what I did...
 so I cut it back off and tried to get it to run as a straight lockwood again... I cut the intake and made 4 add on pieces of different sizes to see if I could get the intake the right size... couldn't get it to run on any of them...
I did the same to the exhaust side and the same problem... although the results were more promicing
when playing with the exhaust side ....
 I read where the intake should be at ODD multables of the exhaust/C.C. combonation and I tried enough odd things to get it to run that if it was going to it should have !
... I think I will flair a long 2" piece of pipe and stick it on the PJ's tailpipe and then Play with the intake again and see if I can get it to run...  its odd because I even tried putting it back the way I had it earlier ...where it ran... but now I can't get it to run at all...
...
 I was so impressed with the thrust coming off that PJ that for the first time I could see it turning a rotor.... it had enough thrust for that !.... now if I can only get it working again !
LOL
Bob......


 

[Bob]

I found a small tube, a chair leg from the 1950's steel and tapered to a point, so I cut it off and decided to make a small PJ out of it.... I calculated the size of the CC from the exhaust diam and came up with a 1" x 2" piece of tubing for the CC, I took some time and threaded a nut to fit the spark-plug I had... so it would thread into the nut properly ... and drilled a hole in the center of the 2" tube and welded the nut on it.
next I found 2 washers for the end plates of the CC and welded them on the CC... cleaned that up and then welded the "chair leg" tube to the CC as an exhaust pipe...leaving it as long as it came!
it is 1/2" at the cc and about 3/4" at the far end  about 22" long.
I then took another of the chair legs and cut a 1/8" slice out if a 2.5" long piece so I could shrink its diameter down ( the intake needs to be smaller than the exhaust!)  i re welded that and cleaned it up and then welded it to the CC.... and it was purdy much done.
... I played with that silly thing for hours today  but could not get it to run ...not even breefly!
it would pop and act like it wanted to run but it never did take off.
even after I slipped on a long 1" pipe over the tail pipe (which I thought for sure would make it run easily) it never would take off... I then desided that it must be the intake that is the problem so I added a 1/2" piece of tubing that pressed on to the intake snout to act as a sort of cone and give it a bit more length.... it still wouldn't run !
... I am beginning to wonder if it will run (being so small) on propane at all.... i may have to use Accetiline on this little thing!
... it is cute though ! its about as long as my arm and has potential of being a Night time PJ.... one that is small enough to not make too much noise at night! LOL
...
this little guy would make a dandy spinning arm test engine because of its small size I can use a quart bottle and valve to power it, and have the bottle on the arm spinning with it!
....I'm interested to see if a PJ can spin a rotor fast enough to obtain flight... and this might be a good one to start with  being its so tiny !  LOL
...
  All I gott'a do is get it to RUN ! HAHAHAHHAHAH!
...
Bob.....

 

[Bob]

ok...
I built a big PJ....
its 6 3/4" Diam by 13" long in the Combustion chamber
has a 3" exhaust pipe  well over 7ft long ....(havn't measured it yet)
the intake is 1 3/4" diam and aprox 8~10" long.
... when this baby pops its like a CANNON going off ! it leaves your ears ringing! HEHEHEH
.... starting is super easy however and all that is needed is to get it burning inside and getting it to "RUMBLE" then slowly increase the throttle... its operating frequancy is probably around 80 hz very LOW
it lets out a rather loud GROWL that will grow to an even Lowder growl ! when throttle is given.
... however I could not "rich extuinguish " it at all , infact I get the feeling it was only just above an idle
 when I had it going for a few minutes....
thrust is not as strong as I had hoped... but its too big to use on anything anyway ! LOL
if you can imagin mutable shot guns going off trying to get it warmed up, when it finally takes off running it is far quietier than it was popping! <GRIN>
....
... 
the GROWL of this thing running sounds so neet its unreal, the combonation of the Hiss of the propane going into the intake at a hellasious rate and the shaking of the earth is quite something to see!
... I was going to run it again and get a red hot picture of it for ya but I only have 1/2 a 5 gal propane tank left....figured I needed it for more experiments!
...(just running it long enough to get it red hot would probably take the rest of my fuel !)
...
for all intents and purposes its a "ROUGH Lockwood" of 6 3/4" in diam for the CC with a non-conical exhaust
I expected about 50 to 80 lbs. of thrust but so far its only about 10~20 lbs of Static thrust.
...
it probably weighs 35 to 40 lbs. and is "over built" with 1/16" steel and 3/16" plate to cap the end of the old air tank I used as a Combustion chamber.... the heavy 3" tubing I used for the exhaust is from old waterheaters
the center flue on gas units, I picked them up when I worked at Hoyte water-heater co. in Reno,Nv. they were throwing them away !  I got 2 pickup trucks of steel from them ! HAHAHAHAHA!
 ....

this is WHY I am trying so hard to make a small PJ that runs strong, rather than a BIG one....because its just TOOOOOOO BIG !
...
One thing for sure , the larger the PJ the easier it is to start them... they seam to like being LARGE !
....
I had the exhaust SHORT at first to the seam just before the bend in the pipe, it would not run on that...
I made the bend and used another almost 4ft pipe to extend the pipe out in  front of the intake.
it started easy then and its sound was much subdued compaired to what it was with the short pipe
I doubt I could have stood for the noise had it started with the Short Pipe! LOL
with the pipe longer though its really not so bad.... but I did have cotton stuffed in my ears real tight so I'm not sure how accurate that assessment is .<GRIN>
....
Great Sport at any rate ! LOL
...
Bob......

 

[randy]

Put some wheels on that large tank in the background, mount up all your pulse jets and see how fast you can get er goin. hahahaha Just don't hit anything.

[Bob]

thats the propane tank fer the house Randy I can't snag that.... but I do have a 250 gal tank up the road a bit by the quanset hut .... but I am thinking of making a submarine out of it !
HAHAHAHAHAHA
...
Bob...

oh... you may have noticed the site being down for a day or so.... Pair network did some changing and  told us about it.... our fault for not fixing it right off OOOPS !
.... (didn't know we had to however)

[Bob]

I changed a few things on the big PJ... I cut the end of the exhaust pipe off level with the intake...
that means I cut off about 5" of the 3" pipe.
I also added 2 steel supports to that long exhaust pipe.... it was really RINGing.... so I added the supports to stiffen it up to quiet it down some... and that worked quite well...quieted it down a huge amount.... well when it was Running... the bangs and pops still have my ears ringing!
....
 however shortening the exhaust by 5" made it harder to start... it didn't want to burn inside...just pop or should I say KABOOM !  really loud booms but would not burn like it usually did... I finally got it to run after about 15 minutes of BOOMS and pows by getting it to where it poped in succession and then quickly increasing the fuel and it jumped into Resonance and started shaking the ground!
its low ROAR is quite something !
 I thought I'd make a fan to set behind the exhaust of this beast to spin and see how fast it makes it go.... if I had a 120:1 gear box it might be useful as a turbine powered winch or something LOL
...
 its just something to play with, but I'd like it to be USEFUL ! HAHAHAH
...
 If I've learned one thing about PJ's in general it is this ... they like to be HOT to run so getting them Hot at the start is almost a prerequisite to getting them to run.
...
the air blower I use is not very strong at all and is mainly used to get the fuel air flowing through the Pulse jet.... once any of them are running you can remove the sparker and the air blower and they will continue to run just fine.
...
I find it extremely interesting that this big PJ uses less fuel than the other 3" ones I've made
 I think mainly that is because I am running it very slow... it idles very low and  that is not like most of the others with their higher frequency... this thing cycles at 50 to 80 Hz ...I'm guessing but its very  LOW in frequency unlike most of the others which are in the hundreds or more HZ
...another reason for this "running it SLOW" is that my 1/4" line feeding the PJ is just that ...a 1/4" copper tubing line... this PJ could probably run on 3/8" or even 1/2" fuel feed line before it would "Rich Extinguish" ...
...
By the way... Rich Extinguish, is just a method the PJ experimenters use to determine weather the engine has enough fuel or not.... if you cannot turn up the valve far enough to "Rich extinguish" the engine while its running (which mean the engine will suddenly quit running) then your probably not
getting out all the thrust you can get out of it, because your not giving it enough fuel....
  so its obvious that I'm not giving this big PJ much fuel , in fact its kind of amazing that it runs on what little I do give it ! LOL !!!!!
...
 Bob...


 

[Manta]

Just out of curiosity,  what are you going to use this monster for ?

Or is it to prove the saying ' how do you become a milionaire ? Start out as a multimilionaire and buy fuel for the pulse jet.'

Just looking at the top picture,  is that Mercedes in the background still a runner ?

Dave
(Manta)

[Bob]

Hi Manta !
Yah the Mercadies still runs its a 240 Diesel but the transmition has problems it likes to lock up in 2nd geer and you can't get it into any other gear no matter what...I've got it un stuck 3 times now but it gets stuck when ever it wants to so it sits till I can repair it !
HAHAHHA its my sisters car gets 45~48mpg at last check  but she's scared to drive it now with the tranney acting up.
...
as far as the PJ's go.... well their fun to play with...  but that's about all!
I was thinking of using 2 smaller ones on the rotor tip of my helicopter instead of using the Rotex 447... but I don't think I can get enough thrust out of them so they will more than likely just hang on the wall as sculptures! LOL!
....
Bob....