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Old Dec 08, 2011, 05:47 PM
"Unnecessary Necessity"
coriolan's Avatar
Canada, BC, Vancouver
Joined Sep 2006
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The timed pressure fitting on TD's engines work, but its very hard to keep the tubing from slipping out. The back plate pressure fitting is better in that respect, the bladder option is best for c/l combat and consistency! The back plate pressure fitting produce a constant pressure while the timed timing act like a pump and increase pressure over time.
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Old Dec 08, 2011, 08:32 PM
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San Bernardino California U.S.A.
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Yeah, thats true .....

..... Thank God for CA glue!

Thats how I keep the tubing on the plastic nipple!

Also, drilling the case is real fun (not!). On the other hand, the pressure doesnt really come on until the Eng. starts. That helps making it run easier .....

Laramie.
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Old Dec 08, 2011, 08:55 PM
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Hi Laramie. I've got a tapped backplate but haven't used it because now I'm running on a Texas Timers surgical tubing bladder and it works very well. A bit of a pain in the ass at first, but with the proper one way valve in the rear to push fuel through into the bladder, and a tap teed off to let out any accidental air, I'm getting the routine down pretty well. And cranking with the high pressure is super easy for me. I do still come home covered with fuel, but I'll get the hang of it. And I bought new safety glasses.

I still haven't quite got the needle right though. After reading Earl's above post, I think I'm trying, out of old habit, to set it too rich instead of just letting her rip.

Many people have said the pressure at the back of the crankcase is easier to use than the front tap. Something to do with over pressurizing... I don't remember exactly.

If you're interested I'll post a picture of what I'm using. It's unbelievable how much fuel a 1-1/4" long piece of surgical tubing can hold. More than an ounce and a half.
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Old Dec 08, 2011, 09:03 PM
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Good on you. Dunno about the effete valving nonsense. Furrin to me.
But? if that somehow makes it easier for you.
Never had any luck and subsequently use for the pressure taps, carb or backplate. Why? bother when the bladder works so well :-)
Get some 30% and try not to break the crank, need I remind that these are fragile.
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Old Dec 08, 2011, 09:47 PM
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Sig doesn't have 30. I ordered some 35, but I'll put about 4 copper head gaskets in it. I'm using a Gallbreath head.
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Old Dec 08, 2011, 09:51 PM
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I train the front end to expand and then I can push the fuel right up its butt through the check valve. The syringe screws onto it. The side tap makes it easy to get any accidental air out. But I'll probably leave that off the next one. No need to over complicate. I flew it up the other day and lo and behold there was a pair of hemostats swinging from the damn thing.

I bought some Sullivan twisties but that's dacron in the picture.
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Old Dec 09, 2011, 06:11 AM
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Coriolan is correct in that the side fitting on the TD engines results in a timed pressure, that increases over time. But the biggest problem is the plastic nipple is slippery and quite fragile and can break off easily on you. Drilling out the hole has to be done carefully as it is easy to break off the drill bit in it. You need to use a drill that lets you spin up the drill bit to higher RPMs so it doesn't get a chance to catch the tip and break off and you have to be sorta gentle with it, especially when it just starts to break through to the inside.

The backplate pressure tap is much more uniform in its pressure output. You can make you own by using a small brass pressure tap. You fill in the hole with solder and redrill it. You want a small or very tiny hole through it, but the trick to the hole is it is a rocket nozzle shape, with the tapered part facing the crankcase and the flat straight end facing the fuel tank. In this way it allows pressure pulses out, but the flat straight tip serves as a resistor to the reverse flow back in on the suction portion of the 2 stroke engine cycle.

The bladders work great. It is just tricky getting down all the methods needed to use it. Once you do, it isn't a problem, but it can be a hassle at first as you learn how to do it all and get your timing techniques down for starting the engine.

Yeah you run the engines on the hairy edge of peak RPMs with a pressure system, as you do not need to worry about the fuel tank emptying out and causing the engine to run too lean.
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Old Dec 09, 2011, 07:54 AM
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Hay, Rusty, .....

..... Im real glad to see your having fun!

Back in the day, I used the Tee Dee piston, Cyl. & head on a reed valve case with great results, & not so many problems, but of course theres no 1/2A Cox like a Tee Dee!

As for tapping the case under the plastic nipple, yeah, it took me at least an hour, by hand with a pin-vice, & then of course I had to de-burr the inside, but I do like how it came out! As for the pessure tube slipping off, thats an easy fix, just clean everything with laquere thinner, & glue it on with crazy glue! Oh yeah, always use brand new tubbing too!

However, once you get used to the whole bladder thingie, I doubt if youll ever look back! I remember at the contests I used to go to back in the 60s & 70s, thats what the die-hard FF & combat fliers did.

Laramie.
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Old Dec 09, 2011, 12:24 PM
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Originally Posted by Laramie View Post
. I remember at the contests I used to go to back in the 60s & 70s, thats what the die-hard FF & combat fliers did.
Laramie.
Ermm... Still do :-)
Rusty: Fit and ..Use.. a Baby bee Glo head it gives Better/easier needling on 30%+ than the TD one...lower compression is easier on the engine too.
In theory you might lose a couple of hundred revs, but at 26k? less than insignificant imo..
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Old Dec 09, 2011, 03:06 PM
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I will try that, I need this engine to last.
I have 35% fuel coming from Sig. Is hotter fuel more finicky to needle?
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Old Dec 09, 2011, 04:59 PM
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We used to run 40% in TD mouse racers with backplate pressure and got it to where it was very reliable and worked to suit me. Mouse racing requires refuelling pit stops on the watch, so the restarts have to be one hit to be satisfactory.
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Old Dec 09, 2011, 08:37 PM
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Yes when I ordered it, I was expecting the 35% to be easier to needle with the TD. And hopefully to breathe some extra muscle into the Black Widows. They are a bit underpowered when I use 6" props. You can hear them bog when I change directions a lot, like multiple loops all at once and figure 8s. But the planes won't make nice tight loops and maneuvers with the shorter props.

Jim, and all you guys that have done lots of 1/2A C/L flying; do y'all find the longer 6" props are best for loops, stunts and such? Or might I be missing some other adjustment that would make shorter props more useful. As old as I am and as long as I've been flying, I'm still a noob at stunting (as is evident in my videos ).
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Old Dec 09, 2011, 09:15 PM
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NO...use.. the 5 x 3 rubber ducky prop.
Preferably the original design/production sans the spring stater nubs.
It gives THE best perf on a TD with 30/35% Nitro.. period.
6 x3 is a poor perf choice :-). From what I've seen over the years, going past 35% in a TD is more trouble than it's worth, certainly so for Combat. PITA and only a very few 'more' revs.
However I don't know about running Flat circles .. like 'carrier' it's of no interest whatsoever.... Zzzzzzzzzz.
If yer not getting decent instant 4/5' loops, the 5x3 isn't the cause... yer pore engine not giving enough rpms is the real problem OR yer plane is Crappy ..you decide.
Smaller prop/ decent revs usually gives the best small loops.
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Old Dec 09, 2011, 09:16 PM
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I used to use the Top Flite 5.25x4 nylon props on my Tee Dee's for RC pylon racing. We all were running 24 inch wing span planes all streamlined really well too. Everyone else was using it too. The TF bylon prop tended to flex out to a smaller pitch at slower airspeeds and flex back to a higher pitch when the plane was going full speed down the straights.
For all my other flying, I was using 6x3 props most of the time. It had better pull for aerobatics of course. I forget what we used to run for props on the Black Widow engines when we were doing Q-Tee RC Pylon Racing.
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Old Dec 09, 2011, 09:24 PM
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Theres 6" props, & theres .....

..... 6" props ... 6"X what? And what material? Wood?

I used Top Flight 6X3 props, & I used to shave them down a bit in the balancing, they were fragile, but really turned.

I suppose I could mail you a re-worked Zinger 6X3, so you could see what I mean.

Do you have one of those balancers, you know, the ones that have 2 magnets to suspend the shaft between for a frictionless balance? Mine is by Top Flight, I got it on ebay in a lot of stuff. The lot included everything you could need or want to cover planes with that abomination known as Mono-kote, just what every old school silk & dope man wants (LOL)! Well, I gave that a try, now I KNOW I dont like the modern way ... but let it not be said, I dont have an open mind!

But do you have the where-with-all to re-work your props?

Laramie.
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