Who knows this pulse-jet?

[stefan]

Hello,

I got this pulse-jet on a garage sale. Does anyone know the manufacturer? Overall length is about 545 mm, diameter 63,5 mm.







Thanks a lot for your help.

Greetings from Germany

Stefan

[MANOLO]

dynajet

[Rocket Man]

From that tiny photo it looks like a Dyna Jet.

That reed valve will last you for about 1 engine run. You can make your own real easy for about 65 cents each or you can pay $10 each on ebay.

If you trash the factory reed valve retainer and make a new improved reed valve retainer the engine will run many many times and show very little sign of being used. I have one Dyna Jet engine with 30 hours of run time on the same reed valve. The aluminum head will get reed valve dents where the reed valves hammer the aluminum. The aluminum head needs to be made smooth and flat again if you want the valves to seal and cause no damage to the reed valve metal. You can make a steel protector plate to put over the aluminum surface of the head if you want, the protector plate will not get dents in it.

I have bought several Dyna Jet engines, several came direct from the factory. Some came with .008" reed valves spring steel and some came with .010" reed valves spring steel. .010" thick blue spring steel is what you want on your engine. My very first Dyna Jet engine direct from the factory 1976 came with .008" blue spring steel. All the later engines came with .010" blue spring steel. The 1955 model I bought brand new in original box never started off ebay came with .008" blue spring steel reed valves.

[stefan]

Thank you for your information. I found the Dyna-Jet plans and compared sizes. Now I'm sure it's a Dyna-Jet, but I don't know if it is a rebuild or original. Mine has glow plug instead of a spark plug. Left-click on the images above for seeing them in full-size on imageshack.

Do you have some links to instructions on making reed valves?

[dynajetjerry]

Stefan,
You show a 1947 Dyna-Jet. They were never manufactured with glow-plugs but the V-l spark plug often disintegrated after several hours of operation because their rear position exposed them to tremendous heat. The 1948 move of the plugs to where they are now are greatly improved plug life and an increase in static thrust of about 1/2 lb.
Jerry Wiles

[stefan]

Jerry,
thanks a lot for that information. So this Dynajet is quite antique, 1947... 42 years older than me! Do you know if there were any reproductions or is it probably a genuine Dynajet?
-Stefan

[dynajetjerry]

Stefan,
I'm absolutely sure no one ever made any reproductions of the Dyna-Jet. The 1948 and later D-Js were almost identical to yours except they were 1/4 in. longer, had the spark plug near the front of the comb. chamber, and were anodized red. Also, their thrust was about 3/4 lb. greater than yours and the 5/16 in. dia. ball was machined off the fuel injector.
I worked for Bill Tenney @ Aeromarine Co. for 3-1/2 years and for Russell Curtis (who bought out Aeromarine in 1952,) for another 1-1/2 years. I left in May, 1954, because my wages were cut, R&D was shut down, and I was moved into production.
However, I'm still interested in p-js and those who work with them, having 35 different models and makes including a Globe/Solar 105 lb. thrust version. I sold my second Globe to NASA in 2002 for their research into pulse detonation engines. When they ran it @ Wright-Patt AFB (35 miles from my home,) in 2004, I was allowed to watch from a sound-proofed room. God! It's loud! Aeromarine also developed a 205 lb. thrust jet in 1952 that was much more efficient than the Globe. I donated one example of the latter to the USN air museum in Pensacola, where it still resides, and have kept several tailpipe assemblies for them.
I'm finishing the writing of a "book" on the Dyna-Jet (including 100+ pictures,) and the companies and people who worked with it and several follow-on p-j machines. I have several of the latter, including the very first Dyna-Fog generator. It was made in 1950. Smaller versions are still manufactured by the Curtis Co. as well as a few D-Js. You can buy new reed valves for your D-J from Curtis but I think JetBill sells his for less. Curtis Dyna-Fog Ltd. has an internet web site.
Remain very careful and cautious when you fly your jet RC and wear good hearing protection!!!
Jerry Wiles

[Kool]

Hallo mr. Wiles

I read the topics where you mentioned the Aeromarine 205lbs a while ago, this engine seems for a valved pulsejet pretty efficient. Are you also including blueprints/pictures of this engine in your book, or is it only about the DynaJet history?
Does the tailpipe only have one tapering section from the combustion chamber to the tailpipe, or more(see the picture attached, from http://www.pulsoschmiede.de).

Thanks in advance

[dynajetjerry]

Stefan,
I'm not absolutely sure as to the origin of your Dyna-Jet because yours does not appear to have the two shallow grooves in the straight portion of the valve head. They were on Dyna-Jets for easy clamping of "hang tanks" and remained until Curtis Dyna-Fog, Ltd. removed them in about 1960, to reduce machining costs. Your jet may use an original D-J combustion chamber/exhaust pipe assembly (1947, from Aeromarine Co.) but appears to have a non-Aeromarine valve head ass'y.
Thrust will improve if the ball on the fuel injector is machined off and the spark plug is moved forward, to 3/4 in. downstream from the valve head. Of course, if left as is, your D-J will be more valuable as a collectible.
Jerry

[ROHAN]

It’s great that we can come to the forum and get help like this where we can get to identify the pulse-jet shown in the picture that goes back to 1947!! I was really excited to read about this here and it was really enlightening to read about the details!!

[dynajetjerry]

Kool,

My book will contain many pictures of pulse-jet products in addition to the Dyna-Jet. The 205 p-j was 8 inches in diameter over most of its length with the discharge flare being about 9.5 in. For most of those we sent to the USN, the combustion chamber and tailpipe were the same diameter. (I gave one of the latter to the Naval Museum of Aviation in Pensacola, FL, where it still resides.) A few were made that had a slightly smaller tailpipe (about 6.5-7 inches,) and several of the original designs included an internal "venturi" near the middle of the engine's length. It was included to help retain combustion inside the p-j as flight speeds increased. I never saw on of those operate but learned that the venturi and several other internal alterations reduced the fall-off in thrust at high flight speeds.

I'm trying to finish my D-J book and get it to a nearby publisher. Inserting the 100+ pictures and adding captions has become quite a chore but I hope to finish this year.

Thanks.

Jerry Wiles (Dynajetjerry.)