New Pulse Jet Dude

[Heli-NuBee]

I installed the nose weight today. I had to place a full two pounds of fishing lead weights up in the nose (I used silicone to secure the weights). The plane now weighs eight pounds dry. The weight of Methanol from info obtained on the internet is 6.6 lbs/gal. One quart (my fuel capacity) should be approx. 1.65 lbs which means the take-off weight of my plane should be just under ten pounds. I had hoped to be a bit lighter than that but it is what it is. Next time I will pick a different design where the engine can be installed further forward. Maybe the next project will be a World Models TameJet but we will finish and fly this one first.

[Heli-NuBee]

Wing loading is excessive on this plane at this point. I am working on lowering the wing loading but it is uncertain if this plane is going to be adequate.

[Heli-NuBee]

OK, we put that plane on a diet. I changed the wheels to the small wheels that came with the kit, removed some of the heat reflective tape and removed some of the nose weight. This helped quite a bit and the wing loading is better but still on the heavy side. I reduced the weight more than a pound so we will go ahead and try some test flights in the next couple of weeks.

[Heli-NuBee]

OK, the engine jets and starting coil arrived today. We are now very close to the maiden flight. I have been doing a little testing of the fuel systems and have encountered a couple of bugs. The fuel bladder catches on the sides of the containment bottle and then kinks the fuel line shutting off the fuel flow. I added a piece of strong hose around the fuel line inside the fuel containment bottle to help prevent this condition. I will have to do a bit more testing to ensure that the fuel system will work as designed. With any luck at all, we should be taking the maiden flight this comming Wednesday.

[Rocket Man]

If you have never used a fuel bladder before there is a bit of a trick to getting the engine started. Ignition on first, air on next, release fuel clamp and engine fires up if you have the correct fuel orfice. If you do not have the correct fuel orfice you will need a needle valve to adjust correct fuel flow. Adjust needle valve out slowly giving the engine more and more fuel until the fuel becomes too rich and the engine dies. Screw the needle valve IN about 2 clicks and restart the engine and your ready to fly.

As the bladder gets old the rubber gets soft it does not stretch the same and fuel pressure changes. It gets harder and harder to get a good engine run if you have no needle valve. A needle valve will solve all your problems.

Ram air makes the engine run lean. Lean is not a problem but pulse jet engines do not like to run rich. That is not usually a problem with most engines. If you want the engine to run at full power you need another fuel system for inflight use only or a needle valve. All this fuel system does is compensate for ram air by adding a little more fuel to the engine. If ram air is making the engine run 30% lean then you need 30% more fuel. Connect a servo to the needle valve. Start the engine then throttle it up and take off once the airplane is in the air throttle it up some more.

I assume your going to use gasoline as the fuel. After you fly your airplane several times if you want more speed use 100% methanol. Methanol is expensive but it is a fun experement it is always fun to try methanol at least once. Depending on your engine thrust can be increased maybe 40% and flight time will be reduced 40% if your using the same fuel load. A needle valve will allow you to dial in the amount of extra thrust you like, 10%, 20%, 30% more. I almost forgot, you will need a larger fuel orfice for methanol.

A needle valve is nice for your maden flight you can run you engine at a lower thrust if you want to get the feel of flying your new airplane. Hobby engines are not usually designed to run at lower than 80% or 70% thurst.

Have fun and don't crash. Keep your elevation up pretty high it gives you more time to react if there is a sudden problem.

[Mark]

http://www.primelineindustries.com/natu ... chart.html

[dynajetjerry]

Rocketman's suggestions are valid but some may have several caveats: Adding a eedle valve in the p-j's fuel circuit might help but only if the metering jet is larger than the standard. On the D-J, that would be .039 in. ID. If you use methanol or a blend, as Rocketman says, the metering jet will need to be much larger.
Another caution: For most model-size p-js, a fuel flow that significantly reduces thrust will also lead to early burn-out of the reed valves because the fire moves forward. A truly lean run can shorten reed life by more than half. A rich run will not cause early damage but, as Rocketman says, it will lead to unsteady operation and/or stoppage.
Also, petroleum-based fuels are (usually,) damaging to a designed-for-methanol system. The bladder and fuel lines can weaken and/or rot. Jim Cline's fuel controller seems to be OK for all kinds of fuels.
By the way, Jim passed away several years ago and his widow is looking to sell the business; her health is also getting poor.
Good Luck!
Jerry Wiles

[Heli-NuBee]

It is nice to see that some folks are following this thread. I appreciate everyone's input. I will be using a fixed jet sized as Bruce Tharpe advised. I will be using methanol based fuel that is compatible with the fuel bladder and fuel line used. I am using Bruce Tharpe's proven fuel system design consisting of a fuel bladder, fuel shutoff valve and a Cline fuel regulator. Hopefully, we will see if this works within the next few days.

[Heli-NuBee]

Here are my air tank with the starting wand and my fueling system. My fueling system is a little backyard mechanic but it works well. I used a heavy plastic large mouth 36 oz bottle and installed a robart air retract valve and a Dubro fuel can fitting. I place a measured quantity of methanol in the bottle and them pressurise it with my small portable compressor. There is a fuel line with a clunk on the inside of the bottle, connected to the Dubro fuel can fitting and a fuel line with a shutoff valve connecter to the outside of the Dubro fuel can fitting. When the fuel is all pushed out of the fueling bottle into the bladder tank, I close the shutoff valve and clamp the plane fueling line. I shut down the compressor and then release the pressure on the fueling bottle by slowly opening the bottle cap. I then set the plane on its nose and burp the bladder tank to release any air. I then install the plug into the plane fueling line and remove the clamp. The plane is then fueled and ready to start. See pictures below:

[Heli-NuBee]

OK here is the completed airplane. I made a static engine run today for about 15 sec. to make sure the engine was going to run and that the shutoff valve was going to work. I had a heck of a time starting the engine for the first time. It is quite sensitive to where the air wand is placed. I worked for some time and had not even a single pop but did have liquid methanol running from the tailpipe at one point. I finally figured out just where to hold the air wand and she unexpectly started. WOW! was she loud and made good power. I'm sure the neighbors really appreciated my new pulse jet static run. I ran the engine on straight methanol and it seemed just fine with plenty of power. All I have left to do now is to charge the radio batteries, range check the radio, assemble my flight team and go flying this Wednesday!

[Bruce Tharpe]

Get video!!!

[PyroJoe]

Great build, and look forward to the videos!

[Heli-NuBee]

Completed the radio range check today and did final checks. Everything checks out and maiden flight tomorrow is currently a go. As a side, bracelets and beads - you have got to be kidding - such sales advertisements have no place on this forum - some folks just have no class.

[Kool]

I've followed this thread for a while and you have made a nice pulsejet plane . I'm looking forward to the video, wondering how the balance of this plane would be at high speeds.

BTW.
A big chance you or someone in your house searched for bracelets and beads a time ago, so you are now seeing the result of it. Right on this moment I'm looking to cow feed advertorials in my own language(dutch).

[Heli-NuBee]

Sorry to say, there was no flight today. I and at least 50 other guys at our flying field were very disappointed. I could not get the engine started. I went through two air bottles and a lot of hand pumping and never even got a pop. I am working with the experts on pulse jets on figuring out why I am having trouble starting the engine. I am on a steep learning curve so please bare with me. We will get this figured out soon and get this plane in the air.