russiet

I have my first TD .049. I lusted after these when I was a kid, but only ran Babe Bee's. 44 years later I've built two 1/2A trainers for my daughter's amusement (and mine, too), the first using an old reed valve I had. It still runs great. 4 Minute runs with one of the bigger tanks on the back.

The second plane is a beam mount. I found an never-started 1974ish vintage TD on auction and I bought it to use on the trainer.

Now a couple of questions.

On a test stand the engine starts & runs fine, but I have a hard time hearing the differences in engine pitch for the needle valve adjustment. This was never a problem with the reed engines! The Babe Bee always stepped up in pitch as I slowly closed the NV. On the TD it seems like I can twirl the needle valve in & out with very little change. Only when I lean it out too much does it begin to die. The prop is a 6 x 3 (I don't want this thing screaming on the trainer).

Am I doing something wrong?

The next observation: I'm only getting a 2:15 run on the same amount of fuel that the Babe gets nearly 4 minutes out of. Am I right in assuming that the larger transfer porting on the TD is gulping rather than sipping?

Thanks.

Jon

Dan Vincent

Jon,

The TD has a much larger venturi and dual exhaust grooves in the cylinder. It will move a lot more mixture through the engine with more RPM and power.

The TD also has a stronger crank, should you wish to add a Davis Diesel conversion head.

lfinney

My Feedback: (44)

the 6x3 on the Td is too much, and how much nitro are you running, this makes a huge difference, the Td wants no more than a 5x3 or 5x4, or even less, its a revver , now i know someone will chime in about how they run 6x3 props on TD's but they werent meant to run slow do you have a high compression head on the TD if not it wont really sing ...

Jim Thomerson

Take a look at your needle and be sure the point hasn't been broken off. A TD will turn a 6 x 3 OK, but does better on a smaller prop. For your purposes !0% nitro and a 6 x 3 are OK. More nitro and a smaller prop will run better.

russiet

Nice. Thanks for immediate input.

The engine was NIB. It has a high-compression head. The NV isn't bent or broken. I'm using SIG's 25% nitro, same as with my Babe Bee engine.

I'm thinking it might be the prop holding it back with too much loading. I looked up props & found the 5" diameter ones (combat props) costing almost twice as much ($3.95 vs. $1.83). If the first trainer is any indication, we are going to break quite a few props! This is for a trainer, and as much as I want the engine to scream like it was built to, It needs to be a little gentler & cost effective for the moment.

Do you think a 6 x 2, 5.7 x 3 or a 5.5 x 2 would help without being too wild? These props all have a $1.83 price tag.

Are the Combat sized 1/2A props built better/stronger that it causes them to be more expensive?

controlliner

If you are concerned about too much thrust on the trainer, put the prop on backwards. It will work well but it won't bee too agressive.

Toad

I would suggest the apc 5.7x 3 or , if you can find one, the black 6x3 cox (rubbery)
That engine will turn 'em fine on that fuel. You should get over 18k rpm if you have a way to tach it (maybe a friend at the field can tach it for ya?) I know I dont hear as well as back in the babe-bee days..

GrahamC

The APC 6x2 would be a good choice. I like the 5.7x3 for general sport use but the 6x2 will allow the engine to unload a bit more and keep your lap times down a bit.

I have a little 1/2a control line trainer (21" wingspan) that has had a TD 049, TD 051, PAW 049 diesel, AP 061 and currently a CS/Brodak 061 for power. It has never flown better than it does now using the CS 061, APC 6x2 and 35 foot .012 size lines - good line tension, and comfortable lap times. The APC 5.5x2 might let the TD run a bit faster and still give tension and lap times - try them both. APC also makes a 5.5x2.5 but I have not tried that one yet.

cheers, Graham In Ottawa Canada.

russiet

I now have a handful of various smaller props on order. I'll give 'em a try. Thanks!

Jim Thomerson

I have flown TD powered stunt airplanes with Master Airscrew 6 x 3 cut down to 5 1/2. Worked fine.

combatpigg

My Feedback: (3)

These engines will benefit from a sonic cleaning and some had tight crank fits that would give the symptoms described....not much rpm change with leaning the mixture. A 6x3 should only be used on a well broke in engine. 5x3s are the prop, you'll get both more speed and more thrust. 6x3s will give you more heat.

colingw

I've been running an original 1960s TD .049 in a small control line stunter, and have now settled on the 5.5x2.5 as the best prop on the TD for my application.

The other props I've tried are :-

Cox Black 6x3 - good revs (19,000+), moderate airspeed, some variation in revs depending on maneuvers.
APC 5.7x3 - old favourite prop, higher ground revs than 6x3 (about 19,500), and faster level flight than the Cox 6x3, but the engine bogs a little in tight maneuvers.
APC 5.5x2 - screamed but didn't tach it. Constant revs in flight regardless of maneuver. Not quite enough airspeed for my application.
APC 6x2 - as for 5.5x2. Tached at about 21,000 on this prop, but just didn't like how the plane flew with it.
Cox Black 5x4 - similar max revs to the 6x3. Very fast level flight, but hopeless in maneuvers, and tended to bog & fall out of its power band if I threw the plane around.

Then I tried the APC 5.5x2.5 and found it to be clearly better than the others for my model. Revs were bit higher than the 5.7x3 - but nowhere near the 24,000 practical max for the TD, and best of all it seems to give constant revs through maneuvers. The bigger or higher pitched props do not. Level airspeed was about right for the model. This and the 5.7x3 were the only props where consecutive loops were comfortable and a friend of mine was able to get overhead eights & stuff out of the model with it.

We're also getting great results with the 5.5x2.5 on the Norvel .061, although the 5.7x3 is also darn good on the Norvel.

Usual disclaimers apply - these results were for my models, with my flying style. Different props will suit different applications, but for flying C/L sports stunt with a TD the 5.5x2.5 is tops.

I haven't tried the APC 5x3 yet, and don't trust the Cox 5x3 enough to risk sticking one on a TD or Norvel.

cheers,
Colin

GrahamC

Thanks for the comments Colin. I will have get some of the 5.5x2.5 and give them a try. The Canadian online supplier I usually deal with doesn't stock this size nor do any of the two local stores carry them. Ordering direct from APC incurs much $$$ in shipping charges so I will have to work something out. Winter is approaching and I don't expect to get out to much more this fall so there is no immediate need.

cheers, Graham

russiet

Grahm,

If you have a business address you can ship to it might be cheaper. I'm having APC ship to my work address instead of home & the rate dropped from over $10 to just over $5. Still a little overpriced considering how easily props are shipped.

GrahamC

Interesting idea, I will check into it.

cheers, Graham

russiet

While waiting for some smaller props, I cut & balanced a couple of the 6x3'x to 5.5 x 3. With this I also tried a tachometer and got results of 17,400 rpm. Then I found a 5.5 x 4 on an old black widow & on the TD it turned 18,500. These are all good nubers for what I'm using it for. Thanks everyone.

gcb

If you are going to smaller props, you might want to buy a reset tool if you do not already have one. The higher you rev, the more often you need to reset...normal maintenance.

George

VGE Hobbies

My Feedback: (9)

Let me know if you need a reset tool after running those high RPM's, I have plenty of them in stock for Cox 010 - 020 049/051 engines.

Reggie

Tee Bee

I have a fast-turning .049 that's usually ready for a reset after a couple of outings to the field. Around 5-7 flights of 5 minute duration.

EngineCrazy

Great to hear Tee Bee!!! If you aren't needing a rod reset then you just aren't running it hard enough!!

LAter,
Tim

russiet

With APC props, are you guys using fuel tubing over the prop screw to compensate for the wayyyy too large hole in the prop?? Do you use one of the reducers & fuel tubing, or just the tubing??

Tee Bee

For adapting the apc props to an .049, I usually use some nice little machined aluminum adapters I got from Tim Wiltse(enginecrazy). Fuel line will work in a pinch, though.

russiet

Measured for bushing. 0.124" ID x 0.186" OD x .25" long

Anyone care to machine me a few??

EngineCrazy

russ,

I can take care of you. I'll send you a P.M later.

Tim

russiet

yee-haw