Cox Engine Tests/reviews ONLY

Mr. Chinn's take on a "Factory Modified Holland Hornet" from the July 1960 issue of Model Airplane News.

Also, Mark's Original Owner's Manual and his explanation of the "Timer Tank" feature on some of these engines.







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Mark Boesen wrote:here's the early Hornet manual:

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Here's how the timer tank worked: Fire up the bad boy, set needle, just prior to launching your plane, you'd move the wire spring (held in place by small groove) another sping around the top of tube, inside the tank (see photos) would push the tube down sealing the top half of tank off, the bottom would be full and you'd have a premeasured, predictable run time.

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Mr. Chinn from Model Airplane News...December, 1964.







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Listing of Thimbledrome engine part numbers

RknRusty wrote:Once the thread gets started, we can sticky it, no problem.

Please Sir, can we have a sticky now ?

Stickyed.

RknRusty wrote:Stickyed.

Thank you, kind Sir!

Peter Chinn TD .09 Test, Model Aircraft December 1962

You will find tons of tests of COX and others here:

http://sceptreflight.net/Model%20Engine%20Tests/Index.html

Posted by  Kim on Fri Apr 27, 2012 5:04 am, there is no option here to store as PDF. Here's a link (until it disappears). Suggest someone with admin privileges to download, and if there is a place in the forum to store it for others to access. If you give me a link on your server, I will update below:

George's Google Drive: McCoy 049 Engine Test Jan70MAN.pdf (2.6mb)

Some great information in the posts.

Welcome to the forum.

You will find plenty of great reads on tests here:http://www.sceptreflight.com/Model%20Engine%20Tests/

Kustom Kraftmanship - example of a genuine modified TD .051
KK (Kustom Kraftsmanship) Joe Klause 1990's





 

I wonder how the compression was set.....it can only be reduced by any intervention, but not increased?  Even by lapping that removes material, compression will not increase...He may have meant compression ratio setting by head gaskets or shims under the cylinder, instead of compression setting?? How does one add taper to a stock piston without reducing compression?

Just would like to understand the background, not doubting that overall the performance was increased..

Andras, I’m not completely sure but I’m guessing compression was “set” would be to bring it to Cox factory specifications by setting ideal deck height (max compression) and then the user could adjust using head shims for fuel and weather…..  I’m sure you’ve seen the instructions for setting deck height from Kustom Kraftsmanship that’s been posted a few times…. I decided to play with it on .020’s a little just out of curiosity and made the brass disc and bored out a burned out head…. Some of the PeeWee’s I have will not rotate past the disc due to interference….. Some will not touch it at all…. I adjusted Pageboy’s engine crankcase to barely touch it with a piece of .001” copper foil on top of the piston …Maybe that leaves a little room for ball/socket set?….

Another thing I found interesting in the KK instructions was to look for a SPI gap of about .012” on a .049….Best guess to figure it on a .020 was a percentage of stroke which puts it at about .009”…. Getting the deck level brings SPI very close to that figure…

With the adjustments I’m still using two head gaskets on 25% Nitro ….Just my thoughts on compression to be taken lightly

Yes ,Robert, this is what I meant, that it was the compression ratio, and not the compression, which was set by shims, head gaskets etc..the shim will also help set the SPI and change timing..so most probably the ratio was set..

Cox #5 TD .051 cylinder has a tapper fit, Joe lapped the cylinder in for more power.

The engine is in a time lock, untouched after Joe's pro setup.
This state of condition is very rare for 2023 and needed to be documented.

At some point will run the engine to document the performance of a fully
reworked TD .051 with the supplied prop and KK bushing for the APC 5.7x3

See list of services:







 

Another Kustom Kraftsmanship Tee Dee .051 example sourced and can be compared.
Confirmed has the piston marked with a single ring etched into the lower part of the skirt.





Review for all to enjoy- lesson / instructions for breaking in the engine and a 1 way pressure valve.
Simple aluminum tube crimped in a way to seal with a small steel ball, the other end is pinched to
stop the ball from escaping the tube. Later down the road KK had a built in valve with the backplate.