Cox .01 /.02 /.05 /.09 /.15 Speed Planes

The OEM backplate weighs 5.8g and this one weighs 8.9g. So that's +3.1g, now subtract the mount at 13.3g and it's -10.2g not counting removing the lugs which is another -2.2g so total 12.4g or .5oz less. That adds up!

Yes very true, 12.4g on the nose of the plane makes a big difference with the CG for .10 to .15 size planes.

TD .020 Tuned pipe would need to be 7.75" from header coupler to stinger.
Engine is imposed into the foreground and is not to scale.


Can do in three pieces if need be.

Proportionately it would look about right, but I wonder if it is too short. The F2A speed pipes for a .15 are a fair bit longer, and they are running around the same RPMs, around 40,000. They mostly have interchangeable tailpieces of different diameters for fine tuning. TBH, I have not seen one for a few years and don't know the exact dimensions. I would think that length with a smaller diameter would be close to ideal, or a good starting point. What kind of pipe parts did you scare up there? Looks interesting.

Here closer to scale:


7.75 plus the distance to the center of the piston.
1675 WS x 140 ET / 7"  = 35k


TD .020 has hit these numbers;

All carbon 3x3
Best Static 30,684 / 87 mph / Per Prop Calc.

Best pass 37,304 rpm
Doppler Reading best pass 107 mph down wind.

3.5 x 3.5
Doppler Reading 105 mph down wind
Best pass 30,742 rpm

3.37 x 4.5N Prop
Best pass 28,585 rpm / 122 mph down wind.

I saw that listing and noted how that pipe was built. It would be an expensive pipe.

Yes fancy pipe AC-29 engine with the tune pipe made by Cyclon out of  Russia.

Alberto is selling the setup: $385
https://www.ebay.com/itm/Speed-Engine-AC-29-with-tune-pipe/323774503905?hash=item4b6276dbe1:g:H4EAAOSw7Khcr3yQ

Given the size for the TD .020 this would be more feasible, say around $65 bucks a pop would be worth it. I am down for
3 of them! 2 for projects 1 for bench testing engines / props. Manifold and header would be a steal at $80 considering the
micro engine cool factor.

Have you already sent the final round of testing for the plug adapters?

That .29 is tempting. A BB OS is almost that much, and not anywhere near the technology. Too bad it's the last one. No parts when stuff breaks.

Tested with a P4 plug KamTechnik turbo plug adapter and a new prop APC made for 1/2A:  4.4x4




Published on Apr 20, 2019
Best Peak 23,498 rpm / 9.2oz thrust / 89 mph pitch speed
.140hp - 104.4w / weight with oil spray 8.8oz / APC 4.4x4
KamTechnik Turbo Plug Adapter / OS Gold P4 turbo plug
Average rpm 22.5k rpm / 86 mph pitch speed.
Will need to unload to 28k to get better use of the pipe.
106 mph pitch speed + with the 4.4x4
Carbon HQ 4x4.5N prop for speed runs est. 138 mph / 32.5k

Tried no pressure tap as an ole wise owl said he gets better
low end idle with no pressure tap when using a RC carb and
pipe combo with TD engines. I was willing to give it a go with
the P4 plug which on it's own should help hold a good idle it
worked fine and gives me some comfort when I go to fly it.
So will see how things go in the air, will set a bit rich at 22k rpm
to compensate for a thirsty unloaded rpm.

The new APC prop is impressive offering a good amount of thrust and
pitch speed can recommend says made for CL planes.


Good weight at 3.9g with attention to rpm via thin tips.
 

Are the plug adaptors still in testing ? i know you had said before they may bee offered at one time .

Yes last round of testing is in the mail go back a page you will see some 2nd round testing those findings
have gained a conclusions for the final compression ratio.

Passed ready to go for: Cox .049, .05, .051. includes .049 and .061 Norvel engines.
This adapter has performed just as well as Galbreath adapters for the Nelson plug.

3rd and final round of testing coming up for these two displacements we are very close to perfect!

Current 2nd round testing for Cox 4.5x2:
.020 / 17.72k (looking for 18k or better)
G Mark .030 / 21,237 rpm  (22k)

Odds are good you may see turbo adapters for:
.074 /.09 and .15 engines

Alrighty then , good deal thanks Brad !

Doing a follow up on the TD .15 mount I put a muffler on to reduce noise and
did a bench test to see how well the engine vibrations translated to the radial
mount. I used two screws to hold it down and rotated the cylinder to snug up
the mount to the crank case. Vibrations to the board was low seemed like a
solid setup to a very powerful TD .15 Special (aluminum piston / with pin)
The needled was set to steady top end no effort to max out the rpm with a
APC 7x5 / 25% nitro / 20% castor. I had the spring steel band closed off to
reduce noise, was surprised it made this much power quite the beast!
Checked two reviews on this one claimed peak .47 hp

The muffler was still in the package before I slapped it on, the fit was not so good
loose enough to rotate around per pic while the engine was running and leaking black
aluminum / oil out the seat.

Needs a quality manifold / header to control the goo with a good seal, paid $25.40
on a ebay bid good enough for bench testing but not worth using with a project.

That's good to hear about the mount not so about the muffler ! I wonder what it would have did with the restriter opened up ? Was the review with the same prop Pitch / style , seeing you gained some HP ?

Thank you Eric, reviews where done using older prop designs vs modern APC prop and
glow plug adapter with a med heat plug.

I have done a test with a throttle sleeve but did not mess with the NV ran out of time.
The entire board was moving forward, I had to lay an arm down on it to keep in place aborted mission
after sub 15 seconds. The new test the muffler was bearable on the ears and I had a weight on the board.
I now have a slide throttle installed.

Recap current 2nd round testing Cox 4.5x2:

- TD .020 / 17.72k / 5.65oz thrust (looking for 18k +)

- G Mark .030 / 21,237 rpm / 8.5oz thrust (looking for same or better)
The .03 adapter was modified on my end and hit 21.24k
Amazing power, blows away a TD .020 truly fitting between
a .049 and .02 displacements. Perfect if you have a .020
size plane needing more power.

Prepping for round 3 for the .03 and .02 displacements.
The 3rd generation turbo plug adapters are in / will use the
same engines / same props and fuel. Note some changes
the wrench slots have doubled in case you mare one set
or if the wrench is best fit base on your position to the
engine or turbo plug seating. Both have good compression
after assembly will have to see how they hold up once
heated up.

Will fire them up this week and get some power data!




A side note while waiting for the 3rd gen plug adapters:
I reworked a APC 4.2x2 added some backcut to the blades and feathered in a new trailing edge.
Here are the results a whooping 6.73oz of thrust using a G-Mark .03 carb it is quite the beast.
Tested with the 2nd gen modified turbo plug adapter.

Benched the .020 / 4.5x2

2nd gen adapter untouched
best peak: 16,795 rpm / 4.93 oz thrust

+ 566 rpm
3rd gen adapter untouched
best peak: 17,361 / 5.3 oz thrust

Close to the mod version missed it by 359 rpm.
2nd gen modified:
- TD .020 / 17.72k / 5.65oz thrust (ground down)

Same OS RP4 plug - just placed a order for some OS P3 plugs the hottest plug OS makes.

Pretty Good numbers Brad , So i take it ya'll are getting close to the release of some them ? Is it the combustion camber that it casing the diff. rpms or something else ?

Thank you Eric!  

The shape and distance to the glow element effects how well
the fuel/air charge is used during the combustion cycle. The
raw values are Greg's intellectual property I have not requested
to know.

A cold engine flips with plenty of compression it's when heated
up that counts, the oil is thinner compression is reduced finding
the best compression during it's thermal balance with the stock
prop is the goal.

This new adapter beats out the 2nd gen unmodified so we are
heading in the right direction. The 18k goal is based on:

New never run Cox TD .020 with aluminum backplate / 4.5 x 2
Static Peak: 18.33k / 6.3oz thrust /  35 mph prop pitch speed
-15.87% more thrust than the gen 3 plug adapter with a used engine.

Needs around 14% more compression yet / careful steps to increase without
going to far and creating pre ignition. For folks that can only obtain low nitro
fuels the extra effort now will go along ways as methanol burns hotter than nitro.
Can always add a extra shim if need be, goal is 1 shim with the stock prop.

Update with the G-Mark .030
Tested with the 4D x 2.5P race prop
Best peak was 21,218 rpm
Average read was 20,914 rpm
OS RP4 used this adapter has passed the test!
25% nitro 18% castor / 2% synthetic oil
Recommend 22% all castor with this engine.
Static Average: 20,914rpm / 5oz / .042hp - 31.33w / 50 mph.
Static Peak: 21.22k / .044hp - 33w

The modified Gen 2 hit a peak of 21.4k so this Gen 3 stock version
is perfect if anyone wants to up the compression they can. I use 2k
grit on a flat surface.

During warm up it hit 21,963 rpm / 5.3 oz thrust / 52 mph pitch speed / .048hp
P3 plug and 22% all castor should hold this number easy enough.

So I try the APC 4.2x2:
Static went over 25k settled in 24,547 what a Lil screamer for a GM .030
8.5oz of screaming thrust / 47 mph prop pitch speed.
Compression is good when hot. It flips like a TD .049 with less compression
compared for it's displacement I would say perfect, way better then the stock
plug by miles. RPM Gauge was set at 7k so could not read the low idle - well under 7k.
APC 4.2 x 2

G-Mark .03 Gen 3 plug adapter is a go!


Typical rpm with the Cox 4D x 2.5P prop

Update for the Cox TD .020
The engine has ran many prop tests and flights it
has finally busted 18k with a modified G3 adapter
and a OS P3 plug. The engine needs a aluminum
carb body to help combat heat. It should also improve
a better leak free venturi and NV body. I have not
improved the engine as it has to remain the same
for each plug adapter. I have better running .02's
that can hit 18k it's good to see what is possible
with the improvements they should translate well
to any TD / Pee Wee .02


Tested Cox 4.5x2 / OS P3 with modified G3 adapter:
18,168 rpm / 6oz thrust / .035 - 26w / 34.4 mph PS

Also for this first time put the APC 4.2x2 prop with some back cut on this older engine
with the plastic carb body results are good.

Tested TD .020 with plastic carb body and venturi / OS P3 turbo plug:
APC 4.2x2 / 21,721 rpm / 6.7 oz thrust / .045hp - 33.6w / 41 mph prop pitch speed.

Update with modified Gen 3 adapter:



Published on Jul 1, 2019
Static 26,808 rpm / 6.7  oz thrust / 114 mph prop pitch speed
Est. unload to 33k / 140 PS / 25% nitro / 20% oil

 

Published on Jul 7, 2019
Build date: June 3, 1997 Real Cox Killer Bee .049 Engine Break In APC 4.2x4
Ran it rich controlled by the needle valve bringing the rpm up just lean enough to nearly sing.
SPI engine does not typically  perform well with mufflers. It ran just fine for this break in period
the goal was to keep the noise down. All the same will require open exhaust to reach it's full potential.
Engine needs at least two rich 1 oz tank runs / first run completed. This new old stock engine was in it's
factory box never touched / stored and sealed for 22yrs. Finally it has it's chance to see's the light of day!
See link for full review per the link with engine break down and parts review showing what makes this a
Real Cox Killer Bee .049:
https://www.rcgroups.com/forums/showpost.php?p=42239893&postcount=1100

Update open exhaust 1st run APC 4.2x4
23,498 rpm / 89 mph pitch speed / 7.83oz thrust / .116hp - 87w / 25% nitro / 20% castor / 74F
Very loud had to keep it very brief, great project engine.



Typical .049 piston weight is 3.2g