*Cox Engine of The Month* Submit your pictures! -March 2018-

Re-cast

COX SPOOK

Early babe bee with 3 piece piston.

Tee wee half way through it’s conver

Little Traveler and it's Red Scorpion

Black Widow on Baby Ring Master

Custom Cox Tee Dee .020

Wow that was quick

Littlebuzz_97 wrote:Tee wee half way through it’s conver

Well this is interesting. Will you run it with the reed or are you just using the tank with reed dummied out?

Wow, 10 already! I'll get the poll set up.

1/2A Nut wrote:Fast TD .050 RC

Brad I just got my Galbreath heads with Nelson turbo plugs. 3 shims under this setup still leave engine performance a good 1k rpm inferior to the insert plug setup...how many shims do you use with the Galbreath heads? I feed my TD on a 60/20/20 blend...

Thank you

Do you use 3 shims with your insert plug adapter?

Yes three shims is not going to cut it oil the threads of the Nelson plug and the plug adapter
threads that mate to the cylinder and use just 1 shim.

You should be golden, what prop are you spinning? I never use 3 shims for any reason takes too
much compression away. If I was spinning a big prop then perhaps two shims to take some load
of the engine but then you can always just use a standard plug and 1 shim for the same effect.


Vid / 1 shim used also in the speed flights.



AmpAbuser
Published on Oct 22, 2017

Tee Dee RC .050 - All Carbon 4 x 4.5 speed prop.
Best static peak 27,051 / .164hp / 122w / 8.5oz thrust / 115 mph
Nelson plug / aluminum carb body / pressure tap on muffler.

Thanks Brad I use 2 shims on the insert type and added a 3rd for the Galbreath as the seller advised. I use the 5x4 black COX prop.

In my note he said I should start with 1 extra head gasket
Or 2. Larry says that because he does not know what
props you will swing with it. Some folks put 6x3 props on TD's
or a free flight prop such as a 7x2.
With a 6x3 I would use two gaskets if with the Nelson plug
and a sport RC plane.

To truly compare to your insert plug type try equal amount of shims.
With the 5x4 you can safely use 1 shim with your speed plane.

Note I have flown with these props so far:
4x5N / 138 mph
4 x 5 / 141 mph
4.44 x 5  / 132 mph
4.22 x 5.5 / 136 to 139

Thank you Brad. I willtry with a single shim and make sure the threads also will be wet to seal well.

I already had 3 of the Nelson head adapters and use 1 shim on my Norvel .061 and .074 as well.
The Killer Bee Cylinder and Piston / TD Frame engine had 1 shim and did just fine with a APC 4.5x4

Yes the seat of the turbo style plug will conform to the Nelson plug if tight enough
the aluminum shapes to the plug should there be a slight variance, yes oil is the trick.

Thanks for the tip Brad...with a single shim the Galbreath head and Nelson turbo plug produced 1.8k more rpm than with 4 shims. I would have never expected 1 shim is enough because by visual comparison the Galbreath looks to have a smaller combustion chamber than the insert plug that takes at least 3 shims to prevent excessively early ignition timing.

Wow look at the hole size for the element on that insert plug.

So 1.8k with one shim verses 4 shims so three shims less.
The element in the insert plug type looks thinner so hotter plug.


Balogh the gauge and thus temp of the glow element in the Nelson
plug back in the day had been tested against other gauges for best
possible performance. It truly shines unloaded in the air even more so.

What did you get for total static rpm with the Cox 5x4 competition prop?

Unrestricted i.e. without a muffler the black COX 5x4 spins near 21k on the TD. With the muffler used on the TeeDeeVooDoo speedplane it is only 18.4k static due to exhaust restriction and SPI.. I will remove the muffler for later flights but first need to improvise an exhaust deflector to protect the fibre-reinforced plastic fuse from the hot exhaust gases.

Mine will spin with muffler and pressure tap 20,752 rpm static with a 4x6.25 / 123 mph prop speed.
I wish the prop did not break on launch I had too much down trim and skidded in on the toss, snapped
the prop and went with the 4x5 next. See pic actual props tested less the 4x5 that hit 141. The 6.25P
had a very good static result compared to the other props unloaded speeds predict it would have made
it to 145+ mph. Will have to try one again at some point.

Never tried the 3.88x5 too small for that size Nano. The APC 4x6.25 is the higher carbon blend above that
is the new glossy glass mat reinforced FPV racing prop from APC / all props have back cut modified diameters
just for the TD .05 I plan to make a smaller Nano version for the TD .05 the new plane should bust 150 ish then
target weight 7oz RTF.