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Engine basics => Engine set up tips => Topic started by: bob whitney on September 21, 2017, 03:12:25 PM
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Ok here is a Brain teaser for u. what is happening when an engine dies on take off ,a little history. I have two full body with 1/2 pan mouse 2 racers with cyclone engines both both planes the same tank. both stock engines on suction. (my venture) the first one worked fine very easy to use ,winning the nats. built a second one and it would die on take off .I covered up the hole over the venturie and it worked as good as #1 ,just as fast ,Mister scale Dave Platt built 6 Barten B team racers to take to England .all with a stock Irvine 25. 5 ran fine but one would die on take off .did the same thing and covered the venturie and same thing worked good.. now he has an Oliver Tigre 15 diesel on a Free Flight doing the same thing .the Oliver is made to run suction with a small diesel venturie .
what is actually happening ,are they running away from the fuel ,are they loosing velocity I have no idea the 1/2A's use a spicket pee tube ,the Barten a cox type and the tigre spraybare through the center of the venturie
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No clue what the spicket pee tube is but if it quits on take off are you implying as soon as centrifigal force takes over ? So why if the fuel being pull away by cf ?
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Saw this happen to a club member. It had a clunk tank and the clunk somehow found it way to front of tank.
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I've had to unsolder the pickup tube and pull it out of the corner slightly due to problems like you mention. This isn't the situation with the Oliver, I can't explain that one.
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this is the second that you release the model
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Hello. If not a fuel or crankcase vacuum leak , I have had this happen often on worn engines with poorer then normal suction . Usually change to muffler pressure helps get a clean take off. Otherwise besides increasing muffler pressure or by adding crankcase pressure or a pacifier tank to small motors like Cox TD's solves this issue . I have also added crankcase pressure to a small diesel to good effect to sort the same issue but with a large venturi. Does sound odd as a small venturi and healthy engine should work fine. Regards Gerald
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Hello Motorman. By running away from fuel and improving the fuel track, what will help him besides shortening fuel line and distance to tank and not going oversize on the fuel line (common problem with 1/2A engines not drawing fuel) , clogged/restrictive filter?. Can you please elaborate too. Regards Gerald
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I have had that happen often enough, never did nail down the cause and it was random. I'd start the motor adjust the needle with everything sounding right it would run until the model was released. It would not get 2 feet. So the next go round I would hold the model and let the engine run for a minute or two and then release, the same thing. The third go around start the engine, flip the plane inverted, hold it on the side, put it down, release and it would instantly quit. Weirdest thing. But as it only happened every once in a while I never gave it much thought.
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Not sure why Tee Dee was brought into this. The Tee Dee engines were very marginal on suction, especially after intrepid hop-up artists removed the screen from the venturi. They really were intended to run on some sort of pressure feed. I never tried the timed pressure tap off the plastic stub thing, but used crankcase pressure off the backplate and pen bladders.
Some of Rad Racer's examples might be explained by spraybar rotation in the venturi bore...said to be that 4 o'clock gave a better draw than 6 o'clock. Hmmm, maybe clear enough. I'd be swapping tanks around between the 6 TR planes or swapping engines, whichever was easier. Another potential fubar is that fuel filters have a correct flow direction, and an incorrect flow direction. Details, it's all about the details. LL~ Steve