Something strange in the progress of my engine

Thanks Cribbs74 for your interest in the subject ...
I think I know what is happening ...
The model in the air and at full speed has vibration per unit of the engine and the needle of adjustment of the venturi moves, that causes that it fattens easily because when the model enters in itching and the engine unloads more rpm, it vibrates more and makes the needle move.
I'm looking at how to make sure that the needle is really firm and secure at the desired point.
In addition to placing a neoprene, someone made some locking tab for the needle of Tee Dee .020? ... Any suggestions?

...If this is not the problem, I will continue investigating...

 During hot weather on the ground when I am setting up the engines needle valve the head temp raises fast.
I have to quickly set the NV to avoid over heating requiring a richer setting to get a steady running engine.  However,
once  in the air the engine cools and will go rich. This happens to my engines in the summer. A smaller load will
allow the engine to spin higher rpm for smoother running in the air. The other trick is set the NV lean on the ground
when flying it will quickly cool down and be more optimized. Ground temperatures are hotter then up in the air. The
hot sun creates a layer of humidity and heat which blankets the ground and air above it for several feet before a noticeable
difference in temperature is felt. If you set the NV for best performance on the ground then fly low to the ground heheh.

Brad, thanks for these tips, but this started now in the last flights to happen.
Always the engine worked correctly, but a few days ago I started with this problem, I think, it is possible for me to replace it, but change the propeller for a new one, the new propeller may not be correctly balanced, therefore increasing the rpm increases the vibrations and that's when the needle moves, I think that's the problem at that point, but I'll continue to investigate! Thank you, friend!

Ok best wishes      

 note vibrations create heat too

It's almost winter in Argentina.

Oh yes folks, winter starts here soon.
These are images at 8 a.m. a few days ago...

Okay! ... so to make the needle safer and firmer, I changed the original spring of the Cox Tee Dee .020 for one of bigger size and hardness, also make a bronze cap, the needle makes butt with the cap and the bushing compresses the spring, working not only the bottom surface of the bushing but also the entire internal perimeter, all this makes the adjustment very firm compared to the original, in the running tests, it seems to work, the needle remains instead, allowing a very firm fit, I will have to test the results in flight.
I leave some images...

You must have been a watchmaker in another life.

maybe yes.. maybe no..

one type of hairpin..



safety goggles or plastic bag for cutting..





another type of hairpin..

Friends! Today I went to the club and finally I was able to determine what the problem was.
Well, it is necessary to clarify that this will not always happen to any user of a Cox .020, the reason ... well, this occurs when there are many rpm and the increase of vibrations.
As you know, vibrations are a serious problem, they cut welds, loosen screws, wear the control joints, beat the fuel generating a lot of foam in the tank, etc., etc., etc. And also move the needles of our engines ... I take all the time and dedication to control flight after flight the behavior of the needle of my engine, I realized that if I fly straight and level, the engine achieves certain maximum rpm and everything is normal, but if I make the model climb high and from there I dive, at full throttle, the rpm increases incredibly high (logically), the engine generates a buzz that looks like a mosquito raging, furious, angry; here it shows a greater number of vibrations, which in my case, made move 1 degree, if, 1 degree the needle of the engine, opening it and causing the engine to grow fat. This was the problem.
Place the new spring, (of greater strength), place the bronze bushing, adjust the needle and I left to fly ... it's a pleasure, to hear the engine throttle to full throttle and the sound becoming a penetrating sharp buzz ... to mode to feel an incredible smoothness of march and that the engine continues working after its recovery, perfectly and with the needle, exactly in the position of initial adjustment.
This only happens, when a model reaches a speed above the "normal", I'm sure most will enjoy their Tee Dee .020 engines without having to make any changes to their carburetion needle, but, for those who find with this problem, the fault basically exists in two points to consider:
1) The glow plug may be loose. After several flights at many rpm, it is convenient to check the adjustment or tightening of the glow plug.
2) Check that the carburation needle is really in place and that it remains there, at the point that we have adjusted in advance.
Placing a neoprene tube on the needle may be a first-hand experience, as a sure thing, but in reality it is not like that ... the neoprene tube twists when adjusted and often generates a "rebound" effect, moving the needle to a unwanted position.
Finally I leave by comparison, my two models checked today, Baronet with Tee Dee .020 and Piyurin with Tee Dee .020 ... then:
The Baronet, by its size (greater) flies at much less speed, the engine unloads laps, but they do not get to affect for its greater structure, it absorbs much more the vibrations.
The Piyurin .020, is much smaller, it flies much faster, it increases the rpm of the engine, especially in bites, and its structure absorbs less vibrations, which makes it have a greater impact on all the components of the model, including the carburetor needle.
I am glad to know that, I have been able to verify it and share it with you.

ticomareado wrote:You must have been a watchmaker in another life.

...thank you for your comment!

roddie wrote:maybe yes.. maybe no..

one type of hairpin..

Roddie, friend, how are you ?, Thanks for your idea, but I must tell you that it is a TEE DEE .020, therefore the needle has another type of installation, which is next to the venturi.
On the other hand, the idea of sejetarla in that manner type "clamp", is good, applicable to the line of engines with valve flap, that Yes!

Mauricio my TD 020 works on my Ugly lil stick (similar to your Baroness but looks more than her old butler) and has many hours on it.




While the cylinder and piston seem to be everlasting, the carb body is soft  and its thread has gotten sloppy over time...this resulted in erratic engine runs because of unwanted air ingress bypassing the threads.

A spring itself will be the answer for the needle valve changing position during flights, but will not always and forever improve sealing.

I use the well known fuel tube trick in combination with a spring.. having an oversized tube piece pulled over the carb body threaded end and the needle valve stem still seals well (cut it long enough to reach the inside face of the knob for a perfect seal) and will allow the fine needle adjustment without "rebound", while a small spring inside the tube will keep it firm against vibrations. (With proper zooming you will see the spring inside the tube)

balogh wrote:Mauricio my TD 020 works on my Ugly lil stick (similar to your Baroness but looks more than her old butler) and has many hours on it.




While the cylinder and piston seem to be everlasting, the carb body is soft  and its thread has gotten sloppy over time...this resulted in erratic engine runs because of unwanted air ingress bypassing the threads.

A spring itself will be the answer for the needle valve changing position during flights, but will not always and forever improve sealing.

I use the well known fuel tube trick in combination with a spring.. having an oversized tube piece pulled over the carb body threaded end and the needle valve stem still seals well (cut it long enough to reach the inside face of the knob for a perfect seal) and will allow the fine needle adjustment without "rebound", while a small spring inside the tube will keep it firm against vibrations. (With proper zooming you will see the spring inside the tube)

Hello, friend Andras, yes, that's right, I also always use a neoprene tube on my needles of my engines, but still, this one failed, now it's solved, that is, thanks to the needle now being firm.