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Building Tips and technical articles. => 1/2 A building. => Topic started by: John Castle on March 03, 2009, 03:44:43 PM
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Is there a way to modify a Cox Babe .049 to use an external tank and increase the run time?
John
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John, as far as i know , you could sub a sure start backplate if you have one or cut a hole in the original tank for a fuel pickup hose to run to the external tank. I believe Kavan and some others made tank extenders for Cox tanks, not sure how they worked or the availability.
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I am gambling that this will work, but on the Tech Terror, I have buried a tank in the nose of the plane. I plan to have its fuel pickup go to one of the vents on the Golden Bee tank, and cap the other vent. The engine should drain the extra tank, then its own. We'll see if that works.
Plan B is that Kavan made a tank extender that bolts between the tank and backplate giving well over double the run time. You may be able to find one on e-Bay or a request in the wanted/sale portion of this website.
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Never tried this myself, but I saw a picture once. The guy had drilled a hole in the back of the tank and through the firewall of the plane large enough for a fuel line. He connected the fuel line to the place inside the tank where the pick up would normally fit and then passed the other end of the fuel line through the drilled hole to a tank inside the fuselage of the airplane. The cox tank essentially became a dry engine mount that also camouflaged the fuel line leading to the internal tank. Although he had a larger fuel capacity the tank appeared stock to the casual observer.
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I would vote for the Sure Start or the previous version plastic backplate made for using an external tank. I will gladly swap you one complete backplate mount with needle valve,a good gasket and reed for your Babe Bee tank, and throw in a small Perfect brand wedge tank to hold the fuel.
There is also a guy on E-bay who bought a bunch of Sure Starts and parted them out- he probably has a backplate-but the cost + shipping may be a bit much, don't know for sure.
The Kavan tank extenders worked, but tended to leak, if you tightened the screws some more to stop the leak they sometimes cracked.
I would advise against drilling holes in the tank or backplate - I just don't like seeing good parts modified to do a job that other readily available parts are designed to do.
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Hopefully the picture of my little Babe Bee-powered Deweybird will come through here. Clear plastic tubing exits a hole in the side of the Babe Bee tank to the external tank. It runs very nicely. Check this out: http://www.youtube.com/watch?v=PazRfz_BLb4
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Larry,
That's a nice flying little plane. The engine appears to be a Black Widow front end on a Babe Bee tank. Runs great in the video.
George
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Larry,
Nice video,what size of tank do you have in the Dewybird? I am also assuming that the fuel line goes through the hole in the tank and hooks directly to the fuel pick up by the needle valve?
John
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The tank is a Perfect (now Brodak) wedge of 3/4 oz. I have not timed it but it probably runs five to six minutes. The fuel line connects to the nipple on the backplate inside. I use a small piece of copper tubing as a coupling between the engine tubing and the external tank tubing. I don't know if the front end is a Black Widow or not, but but the cylinder does have dual ports. It runs fairly well. I use 42' X .012's to keep from getting dizzy. I only fly this plane one day a year, but it is definitely one of the most enjoyable planes I have.
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That worked out pretty well. A quick hole drilled in the tank and presto a larger tank. I will test run it tomorrow and see how it does. The tank is a balloon in a small container I found at the Dollar store. It seems to hold about 1/2 an oz. In fact I got 12 of them for a dollar. They were in the wedding section and are used to hold bubble solution. A life time supply of balloons cost a dollar as well. :!
John
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John, as a note, remember to draw all the air possible out of the balloon with your syringe before filling, it will run much better!!
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John
There is a good way to modify cox tanks for longer flights. Look at my post "Cox Pee Wee .020 tank mods" in this section. Go to page 6 of the index to find it.
Clancy
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Is that a Man-Win trainer you have that mounted on. If so, you won't be disappointed.