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Author Topic: Cox stunt tanks?  (Read 1375 times)

Offline Andrew Tinsley

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Cox stunt tanks?
« on: August 13, 2011, 08:06:55 AM »
Hello,
 I am looking for a couple of 8cc Cox stunt tanks. Does anyone know of a source of supply? Bernie, at Cox International, has 8cc tanks but they are of the non stunt variety. I assume that this means that the filler and vent are in the backplate? Is it possible to convert this type of tank? They look as if they are plastic....so a conversion may be possible with a filler and vent tube and the correct adhesive?
  Mind you, I would prefer the metal variety if they are available anywhere.

Regards,

Andrew.
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Offline Bootlegger

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Re: Cox stunt tanks?
« Reply #1 on: August 13, 2011, 08:20:32 AM »
Andrew, you might try this, make a loop of fuel tubing from one tank vent to the other, then cut a notch in the tubing and in effect you have a single vent tank.. DV^^ DV^^
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Offline Andrew Tinsley

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Re: Cox stunt tanks?
« Reply #2 on: August 13, 2011, 09:25:50 AM »
Hello Gil,
  Now that has got me confused! I sort of remember something like this, that I did on a Baby Bee once, a long time ago. I can't for the life of me remember how it worked! Does this mean that you can fly inverted with such a setup? I assume that the fuel pick is in it's usual place for a control line pickup?
  Thinking about it a bit more, I can see how this would work for inverted flight, but I can't see how it works for normal flight!

Thanks,

Andrew.
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Offline john e. holliday

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Re: Cox stunt tanks?
« Reply #3 on: August 13, 2011, 09:51:16 AM »
The pickup in the tank has to be to the outboard side of the tank.  You can take the solid tanks and drill for tubing to make a fill and overflow.   That is if you have the back plate that holds the needle valve only.   I have some backplates with the tubes on each side of the needle valve.  By the way I have replaced the over flow with a longer peice of tubing to get to the top of the tank.  A little sanding and J-B Weld works wonders. H^^
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Offline Bootlegger

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Re: Cox stunt tanks?
« Reply #4 on: August 13, 2011, 05:26:00 PM »
  Andrew, best I remember we too did this on the Baby Bee, anf yess we were able to fly inverted, abain as I remember.  (The mind is a terrible thing to lose!!)  And so is the memory!!
  Try it and see if it works.. ~~>
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Offline George

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Re: Cox stunt tanks?
« Reply #5 on: August 14, 2011, 10:16:35 AM »
Yes, with two fill/vent tubes on the backplate, you run tubing from one vent, under the tank to the other vent, then put a hole in the tubing at the bottom. At least that's how I remember it.

George
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Offline Larry Renger

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Re: Cox stunt tanks?
« Reply #6 on: August 14, 2011, 06:58:52 PM »
That is how it is done, and it works just fine.

Better would be to JB Weld shut the nipples in the backplate and mount tubes into the tank, again with the JB Weld.  You can even make the tank uniflo, if you are good with a tubing bender!
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Offline Andrew Tinsley

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Re: Cox stunt tanks?
« Reply #7 on: August 18, 2011, 02:04:27 PM »
Are the 8cc tanks from Bernie plastic or metal, if the former, then would the plastic be good enough for JB Welding in some stunt vents? My immediate reaction is that it may not work too well?

Regards,

Andrew.
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Online kenneth cook

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Re: Cox stunt tanks?
« Reply #8 on: August 19, 2011, 07:31:39 PM »
           As much as I love those engines, they just about put me over the edge with my patience trying to get them to work. I've posted my success and failures with the integral tank Cox engines. I'm curious Andrew if you could put a tank on the plane. I have purchased engines that someone drilled holes through the tank. I use an external tank feeding small fuel tubing onto the pickup. The engine runs much more consistently and longer. It just seems so much easier. Having used the latest and cheapest Sure Starts, I've had some incredibly successful runs that surely wouldn't of been possible using the stock tank. The biggest problem I've found using the integral tank  is the screws leaking at the backplate where they seat. I've tried silicone, Permatex, teflon tape you name it without success. It seems to all eventually leak air or fuel. Keep in mind though if you do purchase the newer tanks and they're plastic, you will probably need the reed adapter as well due to this being the newer style which doesn't use the circlip. I'm not really fond of the newer style as it seems the reed really flops around inside. It works though. I did find some tubing though that worked very well for the pickup on Cox engines. It's diameter is slightly smaller than the Cox style but works on both the .049 and the .020. Davis Diesel provided me with an order I placed and they gave me this sample for free. I believe they called it nitro tubing. The tubing is the best I've found as it holds its shape, doesn't need the spring inside as it doesn't collapse when flexed. The material doesn't degrade getting hard or soft when exposed to fuel. It holds its shape when placed in the curve needed inside the tank. If interested I will dig up the paper work and get the stock number. Ken
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Offline Andrew Tinsley

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Re: Cox stunt tanks?
« Reply #9 on: August 20, 2011, 07:36:19 AM »
Hello Kenneth,
 I have a couple of trainers for my grandson, They are to a Marvin Denny design and I must say that they fly well on a standard Baby Bee. I just wanted a slightly longer run time out of them. Marvin has a super idea re mounting the engines. The planes are profile with a built up front end. Instead of retaining bolts, there are 4 wire stubs that are let into the front end. The engine is slipped onto the stubs and then elastic bands are used to retain the engine. The planes ROG and are not hand launched, any in advertant arrival on the tarmac and the engine bounces free. Pilot is not up to hand launches!
  Now I don't seem to have had tank problems yet, in fact, I never have with the tanked Coxes (must be luck!). Hence my search for decent metal 8cc tanks. They seem to be on the rare side on this side of the pond, I only see them on eBay as part of a complete engine, I have not seen any for sale as a spare! If Bernie's tanks are plastic, I think I will give them a miss, I can't see them lasting in the usual carnage!
  Looks as though I will have to go the separate tank route, but mounting close to the engine is a problem with the tapered built up front end.
Maybe I will just bumble along with the existing 5 cc tanks. If the pilot shows signs of improving, then I can build something different so I can use an external tank. The tubing sounds a good bet, I will probably get some from Davies Diesels when I am in the US next month. Nitro tubing should nail it, so don't worry about sorting through your paperwork.

Many Thanks,

Andrew.

P.S. I have several butchered 5 cc tanks I can use with an external tank, if only I can get it mounted on Marvin's little masterpiece. By the way I highly recommend the design. Best Cox trainer I have ever seen! Thanks Marvin!
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