.049 td on pressure bladder starting procedure?

Makes sense.  I'll look for the NVA  I THINK I might remember where it is.  I have a few old clamps and needle drivers around here too.

Phil

Found the NVA, and some glow plugs for my bigger engines!
Phil

You'll need the fine thread NV.

Here's my method:
Open the needle about 3 turns, which is usually too rich to run, but a good place to start hunting. Prime, crank, unclamp when it screams. And when the engine tries to die rich, quickly pinch the line to keep it going as you lean the needle(I rout the line so I can keep my thumb ready to pinch it). You can keep pinching and leaning to keep it running until it stays lit and there you are. Never move the needle again except for minor adjustments, even between outings, and it'll always be an easy starter.

After a flight, it usually gulps a little gas after it stops, so it's possibly already pre-primed for the next crank. After you get the hang of it, just prime it by opening the clamp for a split second and flip the prop a couple of times, then hook up the glow driver and crank. I like to set the prop at 9 and 3 and back flip to crank. This makes it easier to crank when it inevitably gets flooded from fumbling. The more you do it, the less you'll fumble.

Fine NVA installed. I might get to run this tomorrow, maybe. I'll try the clamps I have on a separate piece of fuel line to make sure no damage happens.

So to sum up:

set up run:
clamp line
fill bladder
fine NVA 2 1/2 - 3 turns open
prime venturi
prime cylinder
flip to start, unclamp when catches on prime (be quick)
lean until is running strong, but accelerates when the line is pinched.

engine should remain setup unless messed with.

flight run:
clamp line
fill bladder
do not touch NVA
prime venturi (first run only)
prime cylinder
flip to start, unclamp when catches on prime (be quick)
verify it runs strong, and accelerates when the line is pinched
FLY!

Thanks for the help. I'll let you know how it goes, tomorrow hopefully.

Phil

Just out of curiousity how does one hold the model flip the prop and release the clamp at the same time?

Ron

I anticipate a leisurely 1.2 seconds of time to unclamp the fuel line like a reedy with the NVA closed and near flooded.

No problem.

Phil

Cribbs74 wrote:Just out of curiousity how does one hold the model flip the prop and release the clamp at the same time?

Ron

I use a wing stooge so that answers the "hold the model" question. Up untill this week I was using spring starter. Wind the spring with your right hand then hold the prop with your left hand after winding. With hemostats now in your right hand release the prop. Easy once you get used to it. My Yaking Clown ate the spring the first time I test ran it in the carport. I don't know why some engines have a taste for springs and some don't. So now i flip with my right hand and hold the hemos just below the finger rings with my left so they are easy to grab quickly with my right hand when the motor fires. I'm suprised how easy a TeeDee is to start without a spring once you know what you're doing. BTW, I can't imagine doing this without the plane securely in a wing stooge or a second person holding it for you.

Jim

pkrankow wrote:I anticipate a leisurely 1.2 seconds of time to unclamp the fuel line like a reedy with the NVA closed and near flooded.

No problem.

Phil

Yep, thereabouts:lol!:  It gets easy with a little practice.

Jim

Right, what Phil said. I hadn't thought of that, because my plane is always trapped by the stooge, so I don't ever have to restrain it. Most important, make sure your clamp is in a position easy to access, People use all sorts of line clamps. I just use plastic hemostats.



http://www.ebay.com/itm/Hemostat-Plastic-Line-Tube-Clamp-Lot-Of-5-/120507296622?pt=LH_DefaultDomain_0&hash=item1c0ecb6b6e

JPvelo wrote:

pkrankow wrote:I anticipate a leisurely 1.2 seconds of time to unclamp the fuel line like a reedy with the NVA closed and near flooded.

No problem.

Phil

Yep, thereabouts:lol!:  It gets easy with a little practice.

Jim

Yeah, you know how I always say, Once you go Tee Dee, you'll never go back... the same goes for bladders on 1/2As.

I've heard that saying another way........

Hey, you know what gets me is the larger engines and planes have no problems running on steel tanks and don't require pressure. I suppose larger engines pull fuel better. You can usually run standard vent/uniflow or whatever for CL stunt, but once you start doing serious combat even the big guys need pressure.

Cribbs74 wrote:I've heard that saying another way........

Hey, you know what gets me is the larger engines and planes have no problems running on steel tanks and don't require pressure. I suppose larger engines pull fuel better. You can usually run standard vent/uniflow or whatever for CL stunt, but once you start doing serious combat even the big guys need pressure.

I remember when I first started flying the SS, and I used to yank full up loops it would cut the engine off. But now with the uniflow tank working, the other day when I had finished the pattern I tried everything from flying really high to tight loops and it wouldn't die for anything. I just had to fly it out. But I've heard the "pros," or probably just aspiring pros, talk about doing a kill loop so they don't go over time. The experienced guys know how much fuel to start with. Which reminds me, I better go order some juice.

After a couple flights...

I started with a 6x3 prop which broke on the first...landing(?) And. switched to a 5x4 cox rubber ducky.  I was getting then exact opposite performance expected.  It would 2stroke and scream level, but would 4stroke when I maneuvered.  I had the engine set so it would accelerate before slowing when the line was pinched.

The clip I was using works real good.  Tag it with a finger and it let's go.

Phil

This plane is an honest pig weighing in at 240g, or 8 1/2 oz.

Phil,

Could it be possible it was going overlean? As in sagging?

On the ground it may still show up as rich lean until the prop unloads.

Phil, that sounds opposite what I would expect too. In any case, mine run best with the venturi bored out to about .140". It really needs the air. For launching, I only back it off peak only until I hear the slightest slowing. You don't want the bladder pumping gas in faster than the engine can burn it or it will wet the glow plug. I've had that happen with my Big Mig, launch it rich and after a few loops which might have slowed the prop, it goes into a slow wet run, and either stays in it or shuts off. I just let'm scream.

Listen to JPvelo's launch and engine runs. He has bladders on his Tee Dees and they always run great, except the one he posted on 8/19. His needle was wandering, but his 8/20 video was its usual scream.
https://www.youtube.com/watch?v=-vV3bFQ98E0&feature=youtube_gdata_player

EDIT: Or, what Ron said before I posted this.

pkrankow wrote:I started with a 6x3 prop which broke on the first...landing(?) And. switched to a 5x4 cox rubber ducky.  I was getting then exact opposite performance expected.  It would 2stroke and scream level, but would 4stroke when I maneuvered.  I had the engine set so it would accelerate before slowing when the line was pinched.

The clip I was using works real good.  Tag it with a finger and it let's go.

Phil

This plane is an honest pig weighing in at 240g, or 8 1/2 oz.

Sound exactly like what was happening to me a couple weeks ago and it turned out to be bad fuel. Also slip some tubing over the needle to make sure it seals well.
https://i.imgur.com/dm0Tk5Q.jpg

Assuming you can test run the engine with suction feed, one way to determine the initial needle setting with pressure is to first measure the run time with (say) 5 cc's in a regular tank, suction feed.  You can use your fuel syringe with the plunger out as a temporary calibrated tank.  This works well as you can see that the engine burned through the whole tank. It may help to borrow an extra set of hands.

Use the same prop and fuel you intend to use with pressure.  You can do this with a fine needle, or the stock needle, it matters not.  What you want to know is the fuel flow rate.  Divide seconds of run time by 5 to get how many seconds it takes to burn 1 cc.  (using 5 allows for averaging engine warm up, tweaking needle, etc.)  Write this number down, email it to yourself, or post it in the cox forum, as you will wish you knew it again when you replace the engine or NVA or use different bladder tubing, etc.

Now fill your bladder, and clamp it off.  Pull the plunger out of your fuel syringe, and plug the end, or clamp the tube.  You now have a graduated cylinder.

Invert the venturi into the open syringe, unclamp the bladder, and tweak the needle until it takes a little less time to drip out 1 cc (less time=richer) than you calculated for the fuel rate under suction.

Example: Engine runs 2 min. 10 seconds (130 seconds) on 5 CC.  So it is using 1cc every 26 seconds.  So tweak the needle so the carb drips 1 cc in about 20 seconds give or take a couple of seconds.

A long time combat pilot I fly with, Burt Goldsmith, has a calibrated eyeball and can usually watch the fuel dripping out of the carb, factor in the engine size, and get close enough to keep it running in a try or two.

Also, burt has strong fingers or uses thin wall tubing and pinches the line with fingers until the engine fires, so he is not fiddling with hemostats, which he never uses anyway.

Instead he uses the slider type control line clips.  When the line is in the round end part the fuel flows:



Slide the line into the narrow straight part, and the line is pinched closed:


You can leave the clip hanging on the line, or use a screw and washer through the other end of the clip to secure the clip to the model, which makes it easier to operate with one hand, especially when your fingers are oily.

Leaving a clip on each model adds a small amount of weight, but it makes one less thing to keep track of on the flight line. Also Burt is cheap, and has been flying long enough that he has a lifetime supply of line clips.

Finally, remember it is all to easy to end up squirting fuel in your face, especially when new to pressure bladders.  Have a water bottle handy in case you need to flush your eyes, and safety goggles might be worth the hassle at least for the first outing or two.

All good points, Kev, especially the emergency eyewash. I always place it where I can find it blind. It's a spray pump bottle set to mist. Change the water once in a while. Mine turned green. 
A pinhole in the fuel line can be as bad as a burst. I've rarely had a bladder burst filling it. Just an old one. My cloth net sheath keeps a burst from spraying far.

Thanks Kev,

Good writeup. Burt Goldsmith from Albuquerque?

Ron

Glad I have my windshields on...all the time. I had my bladder come apart twice.

I am following the instructions on the Texas Timer website to use a 1 inch bladder...yea, after I use up the couple I have tied up I am making them bigger.

I never ran this engine on suction. I don't know the diameter of the venturi. Since it had a stock NVA on it I suspect it is not drilled out. I am pretty confident the .051 I have is opened up, would swapping be reasonable to see if it runs better?

Phil

pkrankow wrote:Glad I have my windshields on...all the time.  I had my bladder come apart twice.  

I am following the instructions on the Texas Timer website to use a 1 inch bladder...yea, after I use up the couple I have tied up I am making them bigger.

I never ran this engine on suction.  I don't know the diameter of the venturi.  Since it had a stock NVA on it I suspect it is not drilled out.  I am pretty confident the .051 I have is opened up, would swapping be reasonable to see if it runs better?

Phil

I make them about 1-1/2" long. Lately I've been tying a knot in the back end, cutting it off and using Sullivan wire ties to secure the bladder to the cone. Never had one leak and it's really quick to make. On a stock venturi, the butt end of a 1/8" drill bit will not pass through. I first tried drilling it out with a 1/8" bit and finishing it with sandpaper to polish it. They ran okay. Then I tried drilling them out with a 9/64" bit and polishing, and that gets it in the area of .140". That lit a fire under its ass in a big way. .140" is the most widely accepted size for the sport bladder user.

For a Tee Dee, I recommend at most a 5.5x3 prop(I mostly know Master Airscrew effects), but it will run better with a 5-1/4" prop. After that, it just depends on your plane's weight and your comfort flying. If I have a restricted area like 35', I put an APC 6x2 on it and the engine still screams and the speed is manageable.

On a Big Mig, you can go a little bigger, up to 6x3, but again, it likes smaller better. And for 35', the same APC 6x2 works well.

I am stuck inside 35 ft, although I recall measuring and deciding that I could fit 45 ft if I am very careful.

My neighbor's walnut tree, growing in an abandoned, well decided to fly the airplane a few laps today. That was exciting. No harm to me, the plane, the tree, or anything for that matter.

I might have to measure again and move the existing or install a new paver.

Phil

So how were your engine runs today? Have you been able to use any of the bladder advice you've gotten in this thread? Lots of people with different ideas, you just have to figure out what works for you. 40' is a big difference from 35'. 45' is about the max for 1/2A. Longer than that gets harder to keep tight if there is any wind unless you're really hauling ass.