Tee Dee success

Hello cstatman,

sorry for the wound inflicted on your finger, "been there, done that"...you fuel line seems to be too long, even if the tank and the carb of the 020 TD are level..even there were some geodetical head between the tank and the carb that would drive the fuel by simple gravity to the engine, the surface tension of fuel in the fuel line adds some resistance..I would recommend you shorten the fuel line and check results again..

I have noticed with some TDs I have assembled and had minor problems with fuel draw that its really really important all of the venturi, NVA, needle, and press on carburetor body seal perfectly. Sometimes when I screw the Venturi in, I have had to use a small washer between the venturi and the carburetor body to get the seal I needed. Also parts being a bit loose can leak pressure/suction. Not saying thats the problem, just that I have had that happen to me and had fuel draw problems. The assembly of the venturi, NVA, needle (with fuel tubing over it), and carburetor body on a TD is tricky as they are quite delicate and you dont want to strip the threads out, but then you dont want them loose or leaking either. I tried using some sealant once, but found later dissasembly too difficult and have since found it unnecessary anyway.

Sometimes the leadup to competition can be disasterous then on the day it just all comes together
Good Luck in the FF Competition

GaryB
'Yabby'

Yabby wrote:I have noticed with some TDs I have assembled and had minor problems with fuel draw that its really really important all of the venturi, NVA, needle, and press on carburetor body seal perfectly. Sometimes when I screw the Venturi in, I have had to use a small washer between the venturi and the carburetor body to get the seal I needed. Also parts being a bit loose can leak pressure/suction. Not saying thats the problem, just that I have had that happen to me and had fuel draw problems. The assembly of the venturi, NVA, needle (with fuel tubing over it), and carburetor body on a TD is tricky as they are quite delicate and you dont want to strip the threads out, but then you dont want them loose or leaking either. I tried using some sealant once, but found later dissasembly too difficult and have since found it unnecessary anyway.

Sometimes the leadup to competition can be disasterous then on the day it just all comes together  
Good Luck in the FF Competition  

GaryB
'Yabby'

Yabby, my go-to solution to prevent TD carb leakage is a teflon tape used by plumbers, wound around the venturi threads...this will help seal and add some thread tightness too to endure vibrations without the venturi loosening up...

Excellent idea Andras! @balogh Never thought of using it. thats what its sort of made for in the first place. Sealing threads and helps tighten without ruining thread. Ive even got the stuff in my draw here. I wrap my hinges with it when I paint. Now I can use it as its intended.

GaryB
'Yabby'

Blood = badge of courage Charles....................

Charles, I did the same thing 35 years ago, was firing up my .020 TD on my House of Balsa (I think that's who made it) 48 inch wingspan Nomad single channel glider. It was mounted in a pod above the wing. Accidentally got my finger in the way, had 5 slits cut into my finger tip equally spaced about 1/8th of an inch apart and about 3/8th inch long each, about 1/8th inch deep. Those Cox 4.5x2 competition gray prop ends are sharp!

Why can't the TD .049 s run what have you did to them ? run on prime / cleaned the engine ? getting fuel ?

GallopingGhostler wrote:Charles, I did the same thing 35 years ago, was firing up my .020 TD on my House of Balsa (I think that's who made it) 48 inch wingspan Nomad single channel glider. It was mounted in a pod above the wing. Accidentally got my finger in the way, had 5 slits cut into my finger tip equally spaced about 1/8th of an inch apart and about 3/8th inch long each, about 1/8th inch deep. Those Cox 4.5x2 competition gray prop ends are sharp!

Been there, done that, except that my finger was sliced by a 5x4 on the shaft of a beloved TD051..with the naked finger bone visible,  it was bleeding like hell so I had to rush from the field and ask for some medical help.....the ER doc on duty did not want to stich it, just added some adhesive plaster, and that is how the scars cured like this...(in fact I am sort of pervertly proud of these COX-inflicted wounds!!)

thanks Team CEF for awesome advice

the fuel line length, since its FF, and I am old skool stupid, its not pressurized and the plane launches vertically, so that motor has to DRAW the fuel. I use small aluminium washers on the venturi, but NOW! I am gonna try some teflon tape, I LOVE that idea

no clue why the .049 or .051 wont kick. new fuel, 35% Sig, clean motor, 1.5v from the glow clip, finger over carb, 3 or 4 flips to see fuel drawn in, 2 drop prime in cylinder, and just nothing.

but the .020 kicked off and ran properly, so I know I am getting there - and I am back to excited.

at 58 (i know, I know, young - feh) I dont need anymore badges.

Cstatman try the radial gap on the crankshaft of those 049 and 051 TD-s..excessive wear will reduce crankcase pressurization and fuel draw.  I suppose you may have cleaned the carburetor,  including the 3 smsll orifices on the venturi neck and the opening on the spray bar that feeds these orifices?

when I have an engine being real trouble starting, I disconnect the fuel line from the engine and run it on prime ony. Util it will run a bit on prome its not going to run on the tank. it takes away a lot of variables and proves if or not the engine can run as a unit itself or if the tank, tubing, etc,. is a problem. is it suddenly flooding who knows. thats why I go back and just make it run on prime only . If it wont do that then I need to look at the basics of why it wont run on prime. Volts, plug, head gasket, barrell tight, head tight,..... sometimes plugs light up when you test them, but fail under load when you put them in and try running the engine.

GaryB
'Yabby'

Hey Charles @cstatman did you get your TD sorted out for the weekends competition? Its great to know that someone is competing with their Cox engines!

GaryB
'Yabby'

the .020 is running great

none of my .049s will kick. and yes, all venturis and ports cleaned, washers, no crank wobble,
some will bark on prime, but not light off and run

Ive got a few bees that run great. but very hard to time the fuel in a tanked motor, and I have not setup bladder tank, etc. for postage stamp/horseshoe. it may come to that while sitting in the van in the field

I'm leaving really early in the morning anyhow, even if I just fun fly em.
my pal/mentor from the Oakland Cloud Dusters will be there, also with a bunch of cox motors,
We will get something in the air. I hope.

All the best with it Charles, I dont love that your having problems, but I love that your still got it in you to compete and to be there with a friend/mentor and know you will put something together and you will compete! Sometimes the unknows of competition are what make it so worth it, but often that is AFTER the competition and you look back on it all a day later.

the TD 049 document     Tee Dee .049/.15  (Provided by Cox International)   found in the CEF Info section, left margin/column - Instructiion sheets  https://www.coxengineforum.com/h24-instruction-sheets   is very very good. Link to download that sheet https://sites.google.com/site/nitroengine/TD049_051_09.pdf?attredirects=0    I had problems starting TD 049s at one stage and went back and read this document and followed it exactly and my engines all start really well when this procedure is followed. The troubleshooting is also very good and explains the sound difference between a needle not open enough and one too far open. Both stop a TD starting. The needle must be right in the sweet spot.  Once I have them running, I dong close the needle though as the instructions say. I pinch the fuel tube with my fingers when I fill the tank so as to not flood the engine. but I did at first do exactly as the document said.  Hope it maybe helps.

Have a great weekend and competition.

Garyb
'Yabby'