Cox Dragonfly engine

As Lieven stated, yes they can be used for RC and are in fact designed for it. Not only did they come stock with an exhaust throttle/muffler but they had a flexible weighted "clunked" fuel line in the tank that allowed for extended inverted flight. While not the most powerful Reedy I used to have one of these engines on a sig hummer and it was a fun little bird wish I still had it. (Bandit)

Thanks for the fast reply! The engine I saw had what I thought was just a muffler, so would one of these be a good way to get into RC kits?

RK Flyer

RK Flyer wrote:Thanks for the fast reply! The engine I saw had what I thought was just a muffler, so would one of these be a good way to get into RC kits?

RK Flyer

I enjoyed mine so I would say yes just keep in mind to build the model light it's not the most powerful maybe a little better than a Babe Bee. One thing, If you decide to get this engine, this engine has a clunked tank so I would advise that after getting the engine and any hard landing that results in a sudden hard stop, give the model/engine a slight shake and listen for a clunking rattle inside the engines tank. If you hear the rattle it is OK if you don't hear the rattle, that means the weight "clunk" on the end of the fuel tubing inside the tank has been forced up towards the front of the tank and has likely pinched the fuel line. If it has, you will have to disassemble the tank to fix it if you have to do this make sure that when you reassemble the tank that you have a little clearance between the clunk and the back of the tank. If the clunk touches the back of the tank it will most likely starve the engine of fuel. (Bandit)

If you are at the field, and the "clunk" was forced to the front by a bad landing (yea, I'll be nice and say landing.  A landing requires no repairs).  Try "bouncing" the plane tail down.  No, don't drop it or do anything that will break it, but move it quickly tail first, then jerk it by the propeller and landing gear.  Stand up on something and let gravity assist you too.  Frequently this will be enough to reset the clunk to where it belongs.  

No I have never done this to a dragonfly.  Yes, I have done this to larger clunk tanks. Removing the wing must be done if possible.

Phil

pkrankow wrote:If you are at the field, and the "clunk" was forced to the front by a bad landing (yea, I'll be nice and say landing.  A landing requires no repairs).  Try "bouncing" the plane tail down.  No, don't drop it or do anything that will break it, but move it quickly tail first, then jerk it by the propeller and landing gear.  Stand up on something and let gravity assist you too.  Frequently this will be enough to reset the clunk to where it belongs.  

No I have never done this to a dragonfly.  Yes, I have done this to larger clunk tanks.  Removing the wing must be done if possible.

Phil

Great point! As far as the dragonfly is concerned, I've tried the jerk trick with my dragonfly back when I had one on my Hummer and while it can be done it just didn't work well. (clunk too light in a small tank) It takes a good hit for it to happen so it's usually a good idea to take the engine off anyway to inspect or repair the model (Bandit)

I have one but cannot see how to throttle it.

The excellent Cox .049 Dragonfly engine can regulate its gear all the time, thanks to its rim and throttle regulation chamber. You can do many projects with it and you will really enjoy it!
Here is a video, in case you want to see it .....
https://www.coxengineforum.com/t14703p25-happydad#193209

MauricioB wrote:The excellent Cox .049 Dragonfly engine can regulate its gear all the time, thanks to its rim and throttle regulation chamber. You can do many projects with it and you will really enjoy it!
Here is a video, in case you want to see it .....
https://www.coxengineforum.com/t14703p25-happydad#193209

Thank you. i will have a look.

I see two moving parts on mine, the silver part and the black clip thing on that part. If that makes sense.

MauricioB wrote:The excellent Cox .049 Dragonfly engine can regulate its gear all the time, thanks to its rim and throttle regulation chamber. You can do many projects with it and you will really enjoy it!
Here is a video, in case you want to see it .....
https://www.coxengineforum.com/t14703p25-happydad#193209

I need a close up vid or pic of the engine and the throttle connection, really.

A few details, with dried up castor and stuck on cat's hair!

Here’s a picture of a Dragonfly for reference:



The engine is throttled by reducing its exhaust flow. This is done by rotating the muffler-throttle (the silver colour part around the cylinder). There is a circlip on the bottom part of it, and the pushrod from the throttle servo is connected to on one of its loops.

Note that you need to rotate the circlip in its groove so that when your throttle servo is at ”full speed” position, the exhaust aperture of the cylinder is fully open. Adjust idle speed so that you first adjust the needle valve so that the engine runs good at wide open throttle, then close the throttle to the point where you still get a reliable idle. That’s your ”idle” position.

The spring steel part that can be adjusted to partially (or fully) cover the outer aperture of the muffler-throttle is mainly for adjusting the sound level but will affect the engine behaviour too. It is not meant to be adjusted ”all the time” or in-flight. If noise level is not a concern, you can adjust it fully open or just remove it.

Hope this helps.

Edit: Lieven posted very good pics while I was writing this. These should help you to get your Dragonfly sorted

OVERLORD wrote:A few details, with dried up castor and stuck on cat's hair!

Perfect!

I had not even noticed the ring at the bottom!

kiwichristian wrote:

MauricioB wrote:The excellent Cox .049 Dragonfly engine can regulate its gear all the time, thanks to its rim and throttle regulation chamber. You can do many projects with it and you will really enjoy it!
Here is a video, in case you want to see it .....
https://www.coxengineforum.com/t14703p25-happydad#193209

I need a close up vid or pic of the engine and the throttle connection, really.

Here you have it friend:

Like to find one of those.... Always wanted to build a Cox powered Rc plane.

OhBee wrote:Like to find one of those.... Always wanted to build a Cox powered Rc plane.

Sr., the Falcon Jr. model aircraft or also the Baby, are excellent models for radio control with the Cox Dragonfly engine!


https://outerzone.co.uk/plan_details.asp?ID=2191
https://outerzone.co.uk/plan_details.asp?ID=2226

That looks like a good stable trainer/ Nice build too I got a Falcon kit Goldberg still in the Box sealed .. The one at outerzone don't look to hard to build . OhBee i got one of those engine for sale now , needs cleaning , if interested pM me .

Older cox gtp stocker rc cars use the same parts exaust rc tink wit two bypas no boost port it give extra performance some of the first gtp use single bypas cylinder lots of power Not mutch rpm wit the two bypas cylinder best performance is gain in rpm To like y have alredy explain on those exaust rc like mauricio vidéo it how the exaust opening Must be placed when the opening is placed towards the air can enter a very important factor to consider for the proper functioning of the spi sub piston induction y found cars sufer of that trouble wit the old style gtp cylinder using spi air dont enter that mutch like wit prop kind of presurise exaust stack y was runing m'y on plane 1\3 closed To som reason y gain rpm

Over lord tink the spring on the picturs is reverse try change direction use 1\3 close just for best performance