Homemade tool to check/set .049/.051 Cox cylinder deck-height

Great job Roddie!! …. The tool will give you a little more feel for how an engine is “set”….Will be interesting to try on some of your engines and track down differences…. I made one for .020’s …. Need to take the time and make some shims…

roddie wrote:

rdw777 wrote:Great job Roddie!! …. The tool will give you a little more feel for how an engine is “set”….Will be interesting to try on some of your engines and track down differences…. I made one for .020’s …. Need to take the time and make some shims…

After reading Joe Klause's explanation of timing adjustment.. it just seemed "worth it" to make a tool for measurement. I had bought .049/.051 timing-shims a while ago.. when they were available from our CEF/Cox vendors. I don't know if they're still available though.

Matt had these..





as received; with some other parts..





How would you go about making timing-shims Robert?

I just bought timing shims from Burnie (Cox International) for C.T.'s(boats) engines and there were "four" in the pack.
Burnie has "eleven" in stock.
Cylinder shims

They worked out very well.
One I had to use a sanding "flat" block (with 320 grit sandpaper) to sand it down to .006" (0.153mm)

If you're measuring for the .020 engines, then you'll have to make them yourself?

If you purchased a custom-built engine from Joe Klause (Kustom Kraftsanship) the timing was done on that hand built engine.
But of course, the cost of those engines was more than a "stock" Cox engine.

I find it interesting that everyone is interested in the deck height now?

Mike Mac

Just to let you know, I did a "tutorial" back in 2020 on how I did my Texaco engines which also covers most Cox engines as well.

Shimming Cox Cylinder for Transfer and Exhaust Timing

Click on the link above.


And here are "FIVE" of the shim kits that Joe Klause (Kustom Kraftsmanship) sold.



These kits were very helpful to reproduce the shims that I needed to rebuild many of my Cox engines.

roddie wrote: How would you go about making timing-shims Robert?

Well, I could tell it wouldn’t be nearly as elegant as Mike’s methods and tools ….Would consist of very simple tools along with trial and error…. My focus would be on .020’s…. I’ll give it a try soon and share what happens

Yes, deck height makes a difference, hard core engine runners shim .010's
Down wind passes thus far:
.010 / 42k unloaded stock black prop
.020 / 38.6k U 3x3 full carbon prop
.049 / 33.1k U 4x4.5 carbon blend

The TD .020 really benefits from checking deck height and performs well with a sealed turbo plug adapter.
Oil the threads, run it up check for snug while it's hot able to cold pop with after run oil.
1 ball socket reset will be enough for many flights - oil in the loose socket before resetting.
A hot TD .20 will really jam in a sport plane with 15cc to 20cc of fuel.

Like KK Pro Mods this man below was keen on setting up TD .020's for solid premium running.

The Great Bob Mattes Custom Rework - Cox TD .020 / APC 4.2x2
He had a passion to produce the best possible power for popular .020 FF competitions.
Solid radial mounts he made sealed well compared to plastic.

He made adapters for the small Nelson insert plugs, offering superior potential.
Deck height was set, element height from deck was set with the adapter.
Kamtechnik makes aluminum mounts / turbo plug adapters to improve power.
https://kamtechnik.com/shop/

Results,


Sep 29, 2018
Nano TD.020  Nelson Flat Coil Plug / HQ Carbon 3.6 x 4.5N Prop
Static: 24,870 rpm / 106 mph Pitch Speed / .083 hp / 62w
Static Peak: 25,113 rpm /107 mph Pitch Speed / .086 hp / 64w
4.6oz thrust. Bob Mattes Plug Adapter / 30% Nitro / 20% oil
Thanks to the pressure tap the tank was bone dry when the engine
stopped providing steady rpm throughout the run. Kamtechnik
1 off custom muffler allowed good breathing. KK 128 tpi NV was
special made for the TD .020 very rare part and worth having
for all TD .020 projects.

Pure scream mode open exhaust / no comparison to stock engines.
Static: 3.6x4.5 @ 30,604 rpm so much power can be allowed to run a bit rich at 28k
This condition will help soak more oil setting the stage for a long use performance engine.

For new folks note Kamtechnik makes aluminum mounts / turbo plug adapters to improve power.
Low weight APC prop centering hubs / low mass spinners to sus out more rpm!
https://kamtechnik.com/shop/

     

That Bob Mattes .020TD run was Screaming and and and nice . most people want pay much for the .020TD engines as the .010TD alot more 128TPI needle for the .020 just makes it i see he was still using a piece of hose for a seal , those are not available to replace are they ?

Bob retired from it all, lucky for us Kamtechnik has a good backplate design, turbo plug adapter and
low weight prop plate drive hub to center vibration free APC props. The APC 4.6x3 can be cut to 4x3N
4.3x3E works better proper blade thickness for thrust with and a bit of speed. Can use back cut on
the blades to maintain thrust while gaining rpm. The APC 4.1x4.1 can be back cut for speed 3.6x4.1N

Bob set up the engines with the APC 4.2x2 req. FF prop. He had a bit of fuel line over a stock NV.
Mattes adds gasket goo to seal before mounting his aluminum backplate. Kamtechnik uses an O ring.
It's possible the .049 head gasket can be used as a cylinder shim for the .020 engines. I recall, using a
.09 head gasket on a .049 cylinder and it fits as a shim.

On a side note for 1/2A engine projects in general,
Having sub 250g / 8.82oz 1/2A projects to fly RC is a must these days to enjoy IC freely. Possible to fly a TD.09
sleeved 3ch at or under 250g less fuel. 144mph down wind with 106sq. in. TD .09 @ 11oz / sub 9oz RTF with a
redesign is possible or sport fly with throttle projects at 120sq. in. for sub 250g design with careful planning.
3ch 6.19oz Lil Speedy TD .049 has been done 66sq. in. wing, more reasonable 80-110 for sport flying.  

I always appreciate your data and statistics Brad, Thanks for sharing those…. I’ve taken a few notes!!! ….. TeeDee .020’s are one my favorites and I have a few…..Amazing power for their size and weight….. Need to make something for them to fly!….. Yes, A sub 250g TeeDee .020 design would be a hoot!…..When I was still working I had access to a lab with 3-D printers…. I drew up and printed a false tank in Nylon to mimic the normal tank footprint ….Photo below….. …. Allows the use of the Kamtechnik backplate…..Might help to streamline the front of a nose section with remote tank…..

Very nice engine Robert, great photo with a vintage thin wall cylinder.
A solid ridged mount helps to keep the prop singing.

.020 and .049 turbo plug adapters can be used to lock down disk plates.
It is to note thin carbon plate will not be anything but flat by nature.
-soft metal warps during the cutting out phase. No doubt any protrusion
above the natural piston crown from the piston or plate will skew the results.

If anyone tries to set the deck height on a TD .010 / .020 please share the
before and after results!

1/2A Nut wrote:If anyone tries to set the deck height on a TD .010 / .020 please share the
before and after results!

Yes, I'm curious. I've never seen a before/after. Obviously if the cylinder is low, port durations are low so power may be down. Weather is finally turning this week. Maybe I'll play with this some, assuming a have a combo of components that needs shimming.

I made a couple  from .002” copper to correct an .020 that would not rotate thru the test disc….. A little crude but workable…. Cut with a sharpened piece of .032 music wire….Has that slight “bump” now at TDC ….Will live test when I get some time….

rdw777 wrote:I made a couple  from .002” copper to correct an .020 that would not rotate thru the test disc….. A little crude but workable…. Cut with a sharpened piece of .032 music wire….Has that slight “bump” now at TDC ….Will live test when I get some time….

Hey, What ever works and gets the job done!

WTG this looks promising, look forward to your results.
Pee Wizzers can make some good power. My first Cox engine was the red tanked .020

1/2A Nut wrote:WTG this looks promising, look forward to your results

Thanks Brad!… Working on a couple of P-Wizzers on this deck height thing to see what the results/changes may be…. Interesting to fiddle with!

sosam117 wrote:Hey, What ever works and gets the job done!

Mike, Do you ever run across situations where the piston does not touch the test disc at TDC?…. I suppose then it’s a simple matter to mill (fine sandpaper on glass) the crankcase a bit to cause cylinder to sit a little lower?….. To get some kind of visual I have on one like this I used a little ball of modeling clay then rotate thru to squish it….I flipped the disc and tried both sides for similar results….The disc is .005” for reference…

This sounds interesting and to see some RPM results would bee a hoot Making it worth while . You sharpened a piece of .032 music wire ! Well you still got it !

Thanks Mike!! I appreciate your tutorial and insight on the engines and sharing the know how!! ….CEF is like a custom encyclopedia for Cox Engines

Robert