Tee Dee on non-pressure bladder

pkrankow Mon Oct 07, 2013 4:20 pm

I took my third Tee Dee, put a newer cylinder and piston on it (not even going to try this one on the original one port, no boost piston/cylinder). The piston/cylinder set is off my diesel, so sure start no SPI.

I then set up with the Texas Timer fine NVA, a party balloon (too big, I need to find water balloons) bolted it to the mount for my RC glider and gave it a bench run. I let it run about 5 minutes. It ran nice and steady. I pinched the line to shut down and had some difficulty with an immediate restart.

5 minutes later it fired right up. Since I did not refuel it was less than steady when changing the direction of the engine. This is why I think I need to find smaller balloons.

A "hair tie" rubber band seals the balloon to the fitting.

At first I used a check valve and T from my pressure setup. However the check valve was allowing air bubbles to form in the feed line. This meant that I would get the engine started and then it would die. Switched to straight small line and no problems.

After several false starts I learned that the magic number of turns is 7 for starting with the Texas Timer NVA on suction. A full turn on the needle is like a twitch on the original needle!

Next up to swap this engine and a non-pressure bladder onto my baby Flight Streak and give it a fly.

Medium party balloons are too big. They hold over 2 oz without stretching. I bet 4 oz might fit without stretching.

Phil

**Cribbs74** Mon Oct 07, 2013 4:27 pm

Let us know how it turns out!

balogh Wed Oct 09, 2013 9:43 pm

This is exactly the size of a party balloon that I use for my TeeDee051 in my R/C Toucan plane. It holds 60 ccm = 2 oz fuel without stretching it. The average rubntime on this amount of fuel is 10-11 minutes.

I removed the white 3-holed rubber plug from this plastic tank http://coxengines.ca/1oz-fuel-tank-for-cox-engine.html and it fits tight in the throat of the party balloon so I do niot need any string or rubber band to make the balloon throat sit air-tight on the plug. For internal fuel and filling lines in the balloon I use a plastic ballpoint pen fill cut to size, rather than the copper tubing that comes with the plastic tank as this would certainly puncture the balloon on an unplanned/forced landing. A very simply made but lasting and reliable balloon tank that also fits conveniently into the fron tank compartment of my balsa planes, and allows all acrobatics without a compromise on the TD051 flight performance.

pkrankow Wed Oct 09, 2013 10:44 pm

I decided that I will "choke up" on the balloons i have and try it. I want it to fit inside my bottle and not hang out. I will not need more than 1 1/4 oz.

I also decided that I am going to try running on suction with my existing .051 setup + 1 layer of nylon mesh (pantyhose) on the venturi. If I cannot get warm re-start performance this way I'll tear down the engine and put a different cylinder piston combo on it. My thought is the engine will draw fuel if it is running, but won't if it isn't. (hmm.... no clamps)

Maybe tomorrow...

Phil

balogh Wed Oct 09, 2013 10:59 pm

There must be some leakage issue with your TD051 if it does not immediately restart. Mines are coughing a bit when they spend the after-run oil I add them after each day of flight, but the consecutive starts after the 1st flight are all fast and flawless. I prime the TD051 by covering the ventury air inlet with my finger and turning the prop around counter-clockwise twice. Well it is true I use a small electric starter but the engine starts up immediately after priming. t wil also suck the last drop of fule from the balloon if you add a second hole just 1/3 inch from the internal end of the fuel line to make sure its end will not suck the balloon in before the fuel is completely discharged.

When I experienced starting problems I had 1
1. either a crack on the cranckase (to my utmost surprise...unwanted vibration may have been the underlying reason for the crack)

2. or a cut thread in the plastic carb body where the venturi screws in. This will lead to air ingress nad lean fuel

3. Or air ingress passing the threads on the venturi needle. A silicone fuel tube that fits over the nipple on the carb and the stem of the needle valve (many posts have published photoes on it) will prevent and cure it.

Remember that all the above 3 symptoms lead to lean fuel mixture that is detrimental to the piston/cylinder fit if occurs repeatedly.

**RknRusty** Thu Oct 10, 2013 1:53 am

pkrankow wrote:I decided that I will "choke up" on the balloons i have and try it. I want it to fit inside my bottle and not hang out. I will not need more than 1 1/4 oz.

I also decided that I am going to try running on suction with my existing .051 setup + 1 layer of nylon mesh (pantyhose) on the venturi. If I cannot get warm re-start performance this way I'll tear down the engine and put a different cylinder piston combo on it. My thought is the engine will draw fuel if it is running, but won't if it isn't. (hmm.... no clamps)

Maybe tomorrow...

Phil

Hey, Phil, I'd suggest using the toe or crotch part of the panty hose since it's thicker and will give you a little more air flow restriction. Have you checked to see if you're using a bored out venturi? If the butt end of a 1/8" drill bit won't pass through it then it's still stock.

pkrankow Thu Oct 10, 2013 7:53 am

It is still too cold out. 44F, foggy and damp.

I dropped the drill bit in both tee dee engines without screened intakes (the third has a screen, I used it for the test run and haven't checked)) and the drill bit drops straight in extra loose in both. I am not sorting the drill index out right now.

On the .051 I pulled the T and check valve. Took the pressure bladder off (I wonder the material again) put the cut down medium party balloon onto the plastic barb with a rubber band (I think this particular package is silicone, they are really stretchy and latex free)

Given the bore is very large I opted for 2 layers of nylon mesh held with another rubber band.

BTW cutting up nylon tights is easier said than done. That material won't stay put to cut. I used a pair of opaque toddler tights so there are no reinforced patches.

Hopefully after lunch. I need to switch back to the 35 ft lines and locate a 3 pitch prop, even if I run a rubber ducky.

Phil

pkrankow Thu Oct 10, 2013 12:47 pm

Dorked about with the .051 for 1/2 hour without a sound. It barked and then was quiet for a while.

APC 5.5x2.5 prop with brass bushing

By golly is that venturi bored out! There has to be another .030 over the .125 drill bit! I swapped to my apparent stock screened venturi.

Fluttering of the prop is over compressed? I added 2 more gaskets to bring it to 5 with a TD head.

Never seen a TD run backwards either, but this one will when flooded. It will also catch and switch direction!

I can restart! Not instantly, it has to cool a minute or two. This is acceptable.

Still the .051 on suction bladder. Still feels like there is no compression on this engine. (exhaust bubbles huge on prime)

I can swap back to pressure bladder in half a minute if I want to. I might swap back since the bladder position is too high and it siphons.

Phil

pkrankow Thu Oct 10, 2013 2:02 pm

Done for the day.

Blew the elevator on the baby flight streak. Bummer. I got 1 sorta flight on suction, swapped to pressure and got 1 flight in with a bad landing / good crash and the elevator split at the horn.

Pulled out the pink plane, also with engine trouble. Swapped venturis (yea, 3 engines, 1 venturi, not good) threw a couple more head gaskets in to total of 5 under the clamp on head. It was fluttering, so I threw my last 2 gaskets in for 7. Still fluttering, but starts. I need more head gaskets. Still has NO compression if you are not vigorous in flipping! (same with the .051) I think I had it set too rich still. About 1 turn out total.

Flying on 45 ft lines in my yard is suicide. I found a tree, broke the prop and almost lost the rubber off the wheel. Packed it up since it was 2:30 already.

Phil

pkrankow Thu Oct 10, 2013 3:25 pm

2 new venturies and a dozen head gaskets on the way from Bernie.

I'll have to see how rubber ducky props run on these. The APC props get expensive when I break them all.

Phil

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