Gents,

In the other thread “In Flight mixture control” is the theme.
Re-adjust the mixture during flight with an extra servo.

How about Ed, and the contest Taurus. Did Ed have an answer for that, the leaning out of an glowplug engine during flight?
Of course he did! Only he did not tell us the secrets direct, you have to search for that!.

A short story. But please, read it with a smile.

(No reso pipe, so no resonance and a sucking pressure before the exhaust closes by the piston.)

All the air is sucked by the breathing of the crankcase , enlarging the volume before opening the carburetor.
But how about the fuel?
The sucking pressure of the carburetor is the driving force, and especially the venturi of the carb does this job..

What are the disturbing factors?
1 Level of the fuel in the fueltank.
2 Flight position of the plane, so lower or higher fuel tank position when compare with the carburetor position.

The fuel is transported through the needlevalve by the under (sucking?) pressure P venture minus level of fuel.(h x @). And the “minus” changes whatever we do.
The amount of fuel is restricted mostly by the adjustable needle valve!!

What did Ed do to make the mixture as constant as possible without thinking of changing it during flight?

1 First built a light plane with it’s possible to use a little engine. What?, 70 “ span 0.45 engine?
But the sucking pressure is the same as from a big engine (or you need a special crankshaft!)!

1a So with that little engine you can use a small tank and the result is less difference in level of the fuel in the tank. Because there cannot be a big level difference in a small tank!!

1b Because of the little (short) engine the distance between the centre of the tank and carb is also low. So the influence of the position of the plane in the air is less. For that, look at the picture 1 compare the 45 K & B Greenhead with the 56 ST later used.!

1c By not using all the power of the engine, reduce the bore of the engine carburetor, this gives you relative more suction pressure of the carburetor so a lower influence of tank level and flight position. This is done by Ed with the Veco 45, see picture 2! Of course by closing the needle valve a little so you have the right mixture.

What?, 70 “ span 0.45 engine? And a restrictor in the carb? You are kidding!

Reducing the bore from 280 to 250 thousands of an inch reduces the open area with 20 %.
And again that little tank has an amount of fuel that will do the job, for one contest flight!

2 Last point, use a tricycle undercarriage so the plane accelerates and taxies after a flight in flightlevel position.


So, and what did we do later to destroy all these points of thinking
Indeed, all these things again, but than 180 degrees around the other way!
1 Little engine? Bull s**t, 0.60 at least is what we need, I like more!!!
2 But we do not fly contest and want to stay in the air, touchdowns are tricky, so bigger tank.
3 Speed is what we need, so less drag. Away with that old fashioned tricycle undercarriage.
4 Oh yes, we want a short runway for our tricycleplane with taildraggertransformation so the nose must be high, up in the air. (wing incidence. Nonsense!)
5 Preventing the engine starts his own business make the plane and everything stronger, for that, read the thread of foodstick and look at such a engine in picture 3!

This all has a destructive effect on the ratio of air and fuel during flight, but!!!!

No problem, we have a solution, we can change the ratio with our remote fuel mixture adjustment .

Who was that ? Talking about leaving the “pioneer days of RC”! I think we all do jump with two legs in ours at this moment. In the past Ed did had anything “Under control”, now we want to get “under control” anything!

Do not forget, smile!

Cees