Another of C.T. engines cleaned ---- Cox Tee Dee .09 --- Just today (3/26/2024) more Cox parts

rdw777 wrote:Looks like throttled Tee Dee .09’s are getting a lot of attention lately!…. Beautiful job on the restoration Mike …. With the cleaning/servicing/repairs and checking spec timing it will be a fine runner!!

I forgot to add that I also reset the socket joint on the connecting rod as it was really loose.

sosam117 wrote:I forgot to add that I also reset the socket joint on the connecting rod as it was really loose.

With your attention to detail that is a given

Speaking of timing, A few months ago I made up the brass disc with a hole in it and an old glow head drilled out as described in one of Kirn’s letters to check deck height on my .020’s …. Some spot on,…. Others never touch… And one would not pass the disc…. I think it may explain why some run better with two head gaskets and others with one using the same 24% fuel…

rdw777 wrote:Looks like throttled Tee Dee .09’s are getting a lot of attention lately!…. Beautiful job on the restoration Mike …. With the cleaning/servicing/repairs and checking spec timing it will be a fine runner!!

I forgot to add that I also reset the socket joint on the connecting rod as it was really loose.

rdw777 wrote:

sosam117 wrote:I forgot to add that I also reset the socket joint on the connecting rod as it was really loose.

With your attention to detail that is a given

Speaking of timing, A few months ago I made up the brass disc with a hole in it and an old glow head drilled out as described in one of Kirn’s letters to check deck height on my .020’s …. Some spot on,…. Others never touch… And one would not pass the disc…. I think it may explain why some run better with two head gaskets and others with one using the same 24% fuel…

I always like to check the deck height to make sure that it is even, that way each engine will run about the same.
It will have about the same compression ratio and if I add more head shims, that will decrease the compression ratio (if I need to).

I had thought, when I found my engines out in the weather out on the edge of our carport, that they were not salvageable. I am amazed they are looking this great! THANK YOU, MIKE! I have plans for the the TD r/c .05. Comet P-40. The TD .09 has been a mainstay for me for far too many aircraft. An obscure rubber model blown up to 150% will be its next aerial home.The TeeDee .049 was in a Bebe Jodel rubber conversion. Don't have a home for it, yet.

Thanks, again, Mike,

Thanks to all that have made me feel so welcome, here,

CT

Beautiful restoration, Mike. Your post made me want to check deck height in some of my red postage stamp reedies that work different than others..one would think that with the heyday precision of COX setting the deck height fixed to design should have been simple by keeping the linear dimensions of cylinder bottom (where it sits on the crankcase) to top and crankcase centerline to crankcase top constant.....

Hi Mike and Andras
Mike, your cleanup and recon of the engines is excellent I noted your comments on checking the top of the piston to the top landing of the cylynder where the gasket sits. I was wondering how best to check this? I have always done it by eye when turning the engine over without a glowplug. doesnt seem to be a very accurate method I use and wondered how you go about it? I do have some sets of timing shims if needed. any help or thoughts greaty appreciated.

Yabby.
I posted a couple of years ago a posting on how to do the timing on the Cox engines.

Below is where it is at:
Timing and SPI shimming of the Cylinder


I have instructions that I also gave to Jacob to post in the "INFO" section under the Documents and Manuals.
The instructions originally came from Kustom Kraftsmanship.

I have "FIVE" Kustom Kraftsmanship shimming kits for timing still new in their packages along with thousands of KK parts that I have purchased over the years when they were in business along with many Kk engines.

That is a very nice “how to” write up Mike, I saved it for reference ….. I Made up the test rig but haven’t tried to make shims yet… Interesting just see where they are at….Another visual….

Being a Quality Engineer, as a percentage of the assembled parts to be spot on will be at best 1%.

If you look at the prints of the cylinder sleeve, it will have machining tolerances of plus and minus.
The glow head shoulder inside the bore has a +/-, then the bottom of the cylinder that threads into the crankcase has a +/- tolerance.

Next is the tolerance of the connecting rod which has its own +/- tolerances.
And the crankcase, centerline to the top of the crankcase that the cylinder sleeve threads into has its own +/- tolerances.

So, what do you get?
Crankcase at a minus / con rod a plus / and a cylinder at a minus equals a piston that will be pass the glow plug shoulder height.
Now "if" the crankcase was -0- /con rod a minus / and the cylinder a plus equals a piston that will be below the glow plug shoulder.

As a simple of an explanation as above, engineers call these +/- tolerances on each part when assembled as "Bonus Tolerances".
The bonus tolerances are tolerated as the product will work (but not at the best performance) and "if" the bonus tolerances are too much (another 1% or so) the product will not work altogether.

So, you have at either end of the scale of a product that is designed as it was supposed to and another at the other end of the scale that will not work.

That is why, some model engine mfg. tested their engines before leaving the factory.
At Cat (where I worked in the Fuel Systems Division), when the injectors were assembled on the assembly line, at the end of the assembly line there were test stands to run the injectors through its paces (High RPM/Low RPM/Mid range and idle as well as fuel rate at the different speeds)

If/when it failed the test stand, there was a printout for the failure, and went to rework to change the part that gave the injector too high discharge or too low discharge fuel rate.(changing out the shim spacer for the check lift height --- just like a Cox engine!)

My job for a couple of years was to check and verify the calibrations of the test stands with "working" injector masters at the start of the shift.
Then, once a week use the "silver" masters in the test stands to verify the "working masters" (plus/minus tolerances here too)
Then go to the "Gage Lab" and with the "silver masters" and verify them against the "Gold Master" (which never leave the lab)
every 3 months.
By the way --- The Gage Lab is a temperature controlled/positive air flow room. ( temperature at 68°+/- 2° and humidity at 47%+/- 3°)

Thank you very much for the link, and the "how to" along with the explanation of the tolerances. I will make up a test jig as described and test and adjust my TD 049 engines as described. I have a suspicion that the piston going just past the correct height may be why I am having trouble with glowheads always coming loose on some engines but not others. It will take me some time to setup a jig and sort out, but, I am keen to try and set the deck height on my engines correctly. My engines are all home assembled from crankcase assemblies I bought from Matt and cylinders from Bernie. So the tolerances could be anywhere dependant on which parts I choose to combine. could be great, could be bad. Now with the "How to" and the jig I can measure, swap parts, use shims to get it as right as I can.

I have had some 049 TDs I built that were just absolutely great, high revving, easy start, just a joy to use and fly. And then others I assembled that just were problems. note. the cause of this is my assembly method NOT the engines.

Im glad I asked. I think this will definately help with my Engines I build.

This is a great forum I learn so much from it which helps make my flying time more enjoyable

Yabby wrote:Thank you very much for the link, and the "how to" along with the explanation of the tolerances. I will make up a test jig as described and test and adjust my TD 049 engines as described. I have a suspicion that the piston going just past the correct height may be why I am having trouble with glowheads always coming loose on some engines but not others. It will take me some time to setup a jig and sort out, but, I am keen to try and set the deck height on my engines correctly. My engines are all home assembled from crankcase assemblies I bought from Matt and cylinders from Bernie. So the tolerances could be anywhere dependant on which parts I choose to combine. could be great, could be bad. Now with the "How to" and the jig I can measure, swap parts, use shims to get it as right as I can.

I have had some 049 TDs I built that were just absolutely great, high revving, easy start, just a joy to use and fly. And then others I assembled that just were problems. note. the cause of this is my assembly method NOT the engines.

Im glad I asked. I think this will definately help with my Engines I build.

This is a great forum I learn so much from it which helps make my flying time more enjoyable

Yabby,
The engines that don't go past the shoulder (lower) where the glow head stops will have a lower compression and less of a gap for SPI (sub-port induction) which gives the Cox engines that extra power.
Now with the ones that go past the shoulder, those have then two problems.
1st is the piston hammering into the bottom of the glow head (like you have noticed the glow head loosening).
2nd is the SPI is larger than it should be and with that larger "air" gap, you are losing a little of your fuel/air mixture.
Now with that 2nd problem.
You could just add 3 of more shims under the glow head but that really is the right way to fix the problem because the SPI is still more than it should be -- though the engine will run without the glow head backing out.

Kustom Kraftsmanship knew of the problem and how to resolve it by them selling a timing shim kit for the Cox engines.
It would be nice to have them available these days?

Thanks for the additional information. It matches what I have experienced with the odd engine I have built. the ones with the glow plug coming loose all the time also tend to blow fuel back out the venturi as ive added glow gaskets increased the spi window and spi air is going in when a fuel charge is still coming in through the crank.

Bernie sells timing shims and I think Matt does also.

I am definately going to put some effort into this to tryand get my engines right. Glow plugs not coming loose and the correct fuel charge entering the crankcase without spi blowback. definatey worth the effort.

thanks for explaining so cleary. Im in with half a chaceow.

Yabby wrote:Thanks for the additional information. It matches what I have experienced with the odd engine I have built. the ones with the glow plug coming loose all the time also tend to blow fuel back out the venturi as ive added glow gaskets increased the spi window and spi air is going in when a fuel charge is still coming in through the crank.

Bernie sells timing shims and I think Matt does also.

I am definately going to put some effort into this to tryand get my engines right. Glow plugs not coming loose and the correct fuel charge entering the crankcase without spi blowback. definatey worth the effort.

thanks for explaining so cleary. Im in with half a chaceow.

The shims Burnie/Matt sells is to eliminate the SPI so that you can use a sleeve throttle on the outside of the cylinder.
It is not really for timing.
But it will shim up your cylinder (maybe more than you would like)

This is straight from Cox International about the "Cox .049 / .051 Timing Shims"

Set of four (4)

Features:
Raises exhaust port to delete SPI (Sub Port Induction)
Counteracts RPM loss when using a muffler or throttle ring on engines with SPI
Installs between crankcase and base of cylinder
Two (2) Shims .27mm (.010")
Two (2) Shims .39mm (.015")
Brand new Current Production items

Hi, yes, that was the purpose I bought the shims for and is a story of its own. Anyway these are the only shims i have, and one 10though shim doesnt remove the SPI, although it reduces it. As i dont have access to any other shims, my thought is to see if one of these shims will correct the deck height on one of my TDs which for now prior to measuring, I believe may be wrong. I can always use extra glow gaskets but its possible this may work better. It will be easy enough to Tach the two approaches using the shim and head gaskets available to me.

Using the jig, I can also try mixing and matching different engine components, but, a shim would probaby be easier. At least the jig will confirm if the height is wrong or not. Then it enters the solution space and the pros and cons of the solutions If any, I can apply.

Thanks for all the info. I am going to buy the tools and shimstock to make the shims from
. I think this is extremely worthwhile. bad luck cant get the shim holder anymore. but once the tools and shim stock are purchased can make more shims.

thank you greatly. awesome info.

Yabby wrote:Thanks for all the info. I am going to buy the tools and shimstock to make the shims from
. I think this is extremely worthwhile. bad luck cant get the shim holder anymore. but once the tools and shim stock are purchased can make more shims.

thank you greatly. awesome info.

Another thing you can do (and I do it) have 400grit sandpaper on a flat surface (I have "T" bar sanders) and using your "fattest finger, (the thumb?) place the shim between the thumb and the sandpaper and sand the shim down (if it is too thick?)

yes, very good idea. This will all take me a while but thanks to your info and explanations I have a way ahead to try and resolve what may be problems caused by mismatch of tolerances. I will go at it slowly, I understand the technical side of it, my problem is Im not particularly good with my hands, which isnt great in the hobby of aircraft modelling but, im going to give it a good go as it makes sense, and if i sort out an engine this way I will be especially pleased.