Cox fuel test plane

JPvelo Tue Jul 02, 2013 1:27 pm

Here's my attempt to test Cox Super Power Fuel against Sig:
https://i.imgur.com/aYjAwjT.jpg
https://i.imgur.com/y8bFSvq.jpg
https://i.imgur.com/diM7uNv.jpg

Inboard engine runs on Sig 25%, outboard gets Cox. Will put a quart through each motor an report on the results.

Engines are dual slit exhaust, dual port, non spi. Venturis are drilled to 13/64 and set up to run on bladder pressure for ease of starting and consistent runs. Heads are high compression.

This was the first flight, glow heads were regular bee type.
https://www.youtube.com/watch?v=vLP36vMP8z8&feature=youtube_gdata_player

Still getting dialed in but I added the hi comp heads and it has a lot more ooomph. Got it to where I can loop and do lazy eights but the out board motor likes to die when I fly it inverted. If I set it rich enough to not lean out in maneuvers it wants to die before I can launch. Very fine line between to rich and to lean. Over compressed? It is the cox fuel side. Sig side runs like a top.

Jim

Jim

**RknRusty** Tue Jul 02, 2013 2:03 pm

Haha, that's really cool. I'm interested to see what the results are. And what becomes of the Cox Fuel engine. Strange that it cuts off inverted. Your takeoff looked pretty tricky. Sort of like that platter plane I made takes off.

**Cribbs74** Tue Jul 02, 2013 3:43 pm

You could always swap the inboard to the outboard to see if it's your fuel or your setup.

sdjjadk Tue Jul 02, 2013 5:29 pm

Great video! There is nothing like the "Bee" swarming sound of multiple Cox Engines screaming away. Thumbs Up

I'm interested to see what your conclusions are with the Cox fuel and I second Cribbs' suggestion.

Shawn

JPvelo Tue Jul 02, 2013 6:02 pm

sdjjadk wrote:Great video! There is nothing like the "Bee" swarming sound of multiple Cox Engines screaming away.
I'm interested to see what your conclusions are with the Cox fuel and I second Cribbs' suggestion.

Shawn

Yeah, it's crazy loud! I have to admit I was a little intimidated the first time I flew it. I don't think I will test run both engines simultaneously in the driveway again or the neighbors might call the police!

I added another shim to the outboard head in hopes of making it easier to needle. If that doesn't work I will try a flight with Sig in both sides and see what I get. It can't be a left/right tank problem as I am running both engines on bladder pressure. The cox fuel seems to have "attacked" and weakened the bladder significantly more than the Sig fuel.

Jim

**RknRusty** Tue Jul 02, 2013 8:59 pm

That's interesting that the Cox fuel bladder is degrading faster.

I used to replace them after every outing, but now I flush them with denatured alky and squeeze them out, and then let it hang down with the fuel line open to dry. I've used some of them several times over the period of a couple of months without a pop. That's with Sig 25 and Glowplugboy 24 and the Texas Timers small latex bladder tubing.

I still never fill a bladder without my emergency eyewash spray bottle within reach. I finally needed it the other day too. We were test running kee88's Brodak MKII and he got fuel in his eye when the flooded engine spit on him, so I sprayed him in the face until he was soaked. lol!

JPvelo Tue Jul 09, 2013 12:00 pm

Well, took the plane out to fly today and was having the same problems of not being able to needle the cox fuel side and having it stumble in loops and die completely when inverted. I decided to try Sig in both sides. Flew like a champ. Loops, inverted, whatever. Did it twice more just to make sure. Same result. As far as I'm concerned the test is over. I want to fly my planes, not get frustrated trying to make them run.
Unfortunately it was windy and I was on 35 foot lines which are to short for this plane when it is running well and I belly flopped it on a loop.
https://i.imgur.com/jHsoIHN.jpg
Already repaired. I have parts on order from bernie to make a clone of my contest engine so next time this thing flys it will have engines that turn 19k on the bench. I will also put it on at least 42 foot lines to start and will most likely make up a set of 50 footers.

Jim

**RknRusty** Tue Jul 09, 2013 12:46 pm

Maybe Google and Bing will index my title.
Sounds like that seals the deal on the poor quality of the Cox fuel. I wish there was some way to spread the word so newbies to Coxes don't hurt their chances at developing a successful hobby. I guess this is as good of a place as any to put the word out.
Thanks for taking the time to evaluate and compare, Jim.
Rusty

sdjjadk Tue Jul 09, 2013 1:07 pm

Thanks for the fuel testing and I'm glad you were able to repair your plane.
I'm not sure how true this is, but I recently read that the new Cox fuel is nothing more than re-branded O'Donnell r/c car fuel. O'Donnell, who (if I'm not mistaking) is owned by Hobbico / Great Planes. Which wouldn't surprise me as Hobbico has a tendency to do quite a bit of product re-branding for Tower Hobbies.
I used to work at a hobby shop as an r/c car tech when I lived in Florida and I've seen several customers with new engines that wore out with in a week or so and the only constant was that they all used O'Donnell fuel and I've heard racers complain of unsteady needle settings, glow plug fouling and over heating problems before switching to a different brand. Also, I think RknRusty has a good idea with getting his title indexed with Google and Bing.

Shawn

sdjjadk Tue Jul 09, 2013 1:16 pm

This is interesting as well.

O'Donnell Speed Blend Fuel
test stands - Cox fuel test plane Odop4510

"Cox Super Power Fuel" Same bottle different label!
test stands - Cox fuel test plane Coxp1010

JPvelo Tue Jul 09, 2013 7:24 pm

RknRusty wrote:
Thanks for taking the time to evaluate and compare, Jim.
Rusty

No problem! I needed an excuse to build a twin. Not only did I get my twin, I got a quart of kool-aid colored parts cleaner as well!

Jim

JPvelo Tue Jul 09, 2013 7:27 pm

sdjjadk wrote:Thanks for the fuel testing and I'm glad you were able to repair your plane.

You're welcome! See above post.

**Cribbs74** Tue Jul 09, 2013 8:03 pm

JPvelo wrote:
RknRusty wrote:
Thanks for taking the time to evaluate and compare, Jim.
Rusty
No problem! I needed an excuse to build a twin. Not only did I get my twin, I got a quart of kool-aid colored parts cleaner as well!

Jim

Lol,

Thanks for sacrificing one of your engines for the greater good.

JPvelo Tue Jul 09, 2013 8:13 pm

Cribbs74 wrote:
JPvelo wrote:
RknRusty wrote:
Thanks for taking the time to evaluate and compare, Jim.
Rusty
No problem! I needed an excuse to build a twin. Not only did I get my twin, I got a quart of kool-aid colored parts cleaner as well!

Jim

Lol,

Thanks for sacrificing one of your engines for the greater good.

I didn't sacrifice anything, the cox fuel engine sat idle and got the spray bar pressure flushed while the plane did flat circles on one engine!

Jim

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