Cox .049 Inverted flight

[jimmy Hnat]

Not sure where this goes,Picked up a little jumpin bean with a cox .049,flies great over the snow but when i try to loop it the engine stalls.What's the trick to getting these engines to fly inverted.Tryed flying it into 5 foot snow drift didnt help much.....Thanks in Advance....Jimmy in ohio

[Robert McHam]

Jimmy, It would help to see a picture of your set up. Cox made more that one type .049 and which one could make the answer different. Need to see the tank as well. Some of the integral tanks were not made to be used for inverted flight.
Another thing to check would be the pick up in the tank. A clear detailed picture could be the easiest way to help us help you!

Robert

[Warren Leadbeatter]

Found this pic that may help. 

You also need to be sure that you have a tank setup with stunt venting, ie golden bee or black widow.  The babe bee tank is no good for flying inverted as the fuel will fall out.

Cheers

[Wayne Collier]

The tanks with fuel fill and vent like the one shown below are designed in a way that allows good inverted flight if the internal fuel pickup is placed correctly.  I you look at the drawing posted by Warren and imagine yourself looking at the tank from the front, the pickup placement shown is about perfect.  The tanks that have the fuel fill and vent on the backplate rather than the tank itself are not well suited for inverted flight.  If using an engine with plastic back plate and a remote tank, it may be just a matter of plumbing.

[kenneth cook]

      The Babe Bee really shouldn't stall in a loop. A Babe Bee will fly inverted for a little while before it quits. I'm sure there could be numerous reasons here as to why its stalling. The Jumping Bean is a very maneuverable plane. Therefore, the loops should be rather quick. I had a problem with a Jumping Bean recently. I had blocked the airway to the intake due to the rubber band that holds the gear in place. I had a very large  rubber band and this was wound around the knob on the firewall multiple times causing the air blockage. One thing I would check for is that all gaskets are intact with this engine. A rebuild kit is easily obtained and this can save a lot of headaches. I like to screw the needle all the way in, pressurize the top vent while holding my finger on the bottom to check for leaks. This can tell if the tank venturi gasket is making the correct seal.  This is if the needle valve is seating correctly of course. You can listen and hear where the air is coming from. I've also had air leaks from the backplate screws. These leaks can happen in the metal an also plastic tank backs. Cracks can form in either style which are not noticeable to the eye until you pressurize the tank. I use a drop of oil on the heads while pressurizing to detect if the screws are leaking. A plug even though it appears to be glowing can also be the culprit. Its amazing how a new plug performs. You didn't mention any particular fuel you were using or nitro content. I prefer the higher nitro in the 25%-35% as I've found this keeps things going quite well. Your problem may even be a simple replacement of the pickup tube. As they age they don't seal well around the nipple and they usually don't stay in the corner. I found Davis Diesel tubing to work very well and it retains its flexibility. In the event the plane is quite aged, make sure no paint chips are getting sucked off the firewall and getting wedged in the venturi screen. You also didn't mention the orientation of the cylinder to the plane. I prefer the cylinder to be laying horizontally and to the outboard wing. I've had the cylinder in the vertical position and they would drown out in the outsides like a Fox burp so to speak. Let us know your findings. Ken