Cox 550 fuel formula?

Greetings,

I've been using Norvel NVX25 in my Cox Baby Bee type engines for the past year (what I could find locally). I tried to run an OK Cub .049A on this stuff and it wouldn't keep running; it would stall out after starting.

I found an old (25 years in the basement) can of Cox 550 fuel; the label says it is for sport flying and contains 50% more nitro than other fuels. The OK Cub ran fine on it but I only have 1/4 can left [photo not recovered: cry.gif] So I'm wondering what the formula for this stuff is or what is comparable?

Later,
Greg in PA

IIRC cox 550 is 15% nitro, not sure of the oil content but it is castor.

I knew that Cox used castor, just wasn't sure about the nitro level. It occurred to me that the problem with this engine might be the plug. The NVX25 (made by Sig) works in another OK Cub .049 just fine. This one is picky though. I ought to swap out the plugs and try it again. I think I have a K&B plug in the one that works. I have no idea what plug is in the .049B, it might be from the '50s as far as I know.

Later,
Greg in PA

Greetings,

...I tried to run an OK Cub .049A on this stuff and it wouldn't keep running; it would stall out after starting...
Later,
Greg in PA

Greg, has the Cub been run before? Some Cubs come with a very blunt needle and adjust much easier with additional taper. I had one that went from slobbering rich to full lean in about one turn. Also, to get top performance (?) from them, they should be broken-in.

That fuel should work, although I add a little castor to mine. I THINK NVX fuels have 18% lube.

George

Edit: Most OK Cubs come with an OK plug installed.

try 25 % caster 25 nitro Cubs Run great i run all my motors on that formula .Regards joh

The Cox engines run fine on 15% nitro and 20% castor. No synthetic.

The old (1950's), .049 glow plugs heat ranges were in the "pretty hot" region. You should try locating some Wen Mac or OK short glow plugs.

You might try a short-reach, 4-cycle plug. Just make sure the "hose-nose" extended-reach plugs don't interfere with the piston.

These l'il critters run COLD! More nitro would help. Try 25%. I'd recommend Fox Missile Mist.

Hey Bud,

The NVX25 is 25% nitro, the Cub didn't like it. That is when I switched to the old Cox fuel and it ran better. I swapped out the plug with a K&B 1S which is a medium/hot plug. I was using these in the Baby Bees with a plug adapter head with the NVX25 to good effect. Will report back on the OK Cub.

Later,
Greg in PA

Greg,

Just for the heck of it, why don't you swap plugs between the two Cubs and see what happens?

George

Hey George,

I wasn't clear. The K&B plug is the same as on the other Cub .049. I just ran it and it worked fine with the NVX25. That stuff is 25% nitro and 18% oil. Now to go fly this again!

[photo not recovered: 29146.jpg]

Later,
Greg in PA

Attachment #1, (jpg file)

Greg,

As others have mentioned here, Norvel fuel probably needs more Castor oil content to properly lube and cool your Cub engines. They may run well on straight Norvel fuel, but may not last as long.

Norvel fuel is formulated for a much different engine technology, than was used in the old Cub engines. Eighteen percent oil might be good enough if it were pure Castor oil, but I'm not sure the Norvel Castor/synthetic blend is up to the task.

If it were my engine, I'd measure off six ounces of the Norvel fuel, and add a half ounce of Castor oil to that. That will bring six ounces up to twenty-five percent total oil. Note that the nitro content will decrease to just over twenty-three percent (23.1), so you may see a slight drop in RPM.

Run that in your Cub for a few flights to see if it runs well, and then decide if you want to treat the rest of your fuel to a similar dose of Castor oil.

Bill

Greg,

Your Cub appears to be what was dubbed an .049C, which is an "A" tank connected to a "B" engine by means of an aluminum plate. The engine has been rotated 120 degrees from the "standard position.

I have run mine in the upright position and wondered how well it would run in the position you have it. Let us know how well it flies.

George

Hey George,

I wasn't aware that there was a term for my engine, I put it together from an .049B and the A tank and adapter. I put together this arrangement to put the prop shaft closer to the wing level. I mounted the cylinder in the 7 o'clock position to protect it better in a crash. Since I took that photo I put a long needle valve on it to keep my fingers away from the hot cylinder (I'm a wimp). I also found that the spinner pulley is great, especially on Cox reed engines. The plane, a Blackhawk Models American Boy flies nicely with this Cub.

Later,
Greg in PA

Greg,

Here are some of my Cub .049 engines. Lower left is an .049A, upper left is the .049C. This version that came that way from OK. I bought this one from Brodak (~10 years ago). This engine never existed while OK was in full production.

The others are .049Bs. The upper right one came in a "Sabre 44" by Comet in the mid fifties. Some have glow heads instead of plugs. Note the flywheel that is on one. These I believe I got directly from OK. Apparently they were from ARF's. I currently have one of these in a formerly tail heavy VECO Scout.

George

[photo not recovered: 29163.jpg]

Attachment #1, (jpg file)

Hey George,

Old thread but figured I'd give you an update on my 225 degree rotated OK Cub. The plug change did the trick, the engine runs great now. I took the American Boy out today and was flying off a little league field using a stooge. This plane may be too heavy for the motor, I could get it airborne but it was a struggle to do much beyond fly level. Heck, I was nearly able to hover it! Perhaps a prop change will help, I was using a 5 x 3.

Anyway, the big thing here is that the extended needle valve bends in a crash. I had a couple of "bad landings" and bent the valve 90 deg. Luckily it is bent back with the correct needle setting so I'm not too concerned I also feel that the 225 deg. cylinder was beneficial in preventing dirt from entering the ports during a "bad landing".

Later,
Greg in PA