Got my Norvel 049 running

Rusty, Mark, Kris and others,
thanks, I am not pretending to be an expert - simply a Coxaholic - but I gauged the phone app with the Hobbyco minitach and they show the same readings.

I do not necessarily want to convince anyone, these are my continued observations with many of my old-stock TEE Dee-s be it a 010, 020, 049, or 051 and I am quite happy with that. Unfortunately but understandably the non-SPI 050 with the silencer is a bit tamer.

I did not want to stir controversy but i am convinced TeeDee-s are one of their best if not the best in their class, and even though the design is 50+ years old, the pre-Estes quality is unsurpassable...


How on earth a piston-cylinder set with no rings can maintain such a close fit after so many hot runs, let alone the conrod balljoint that I reset only once, can only be explained by the sheer fact it was made by COX in the good old days.

The engines I have on benchmark are all lower in quality and longevity: Moki (the old-school Hungarian made ones), MK, Webra, OS Max, and of course the NV.

Mark Boesen wrote:Guys, couple things...

-The prop in question is not a Cox Competition prop, its a re-pop of the early 5x3 Thimble-Drone prop, not nearly as efficient and nowhere near the load as the Competition version, so its gonna turn more RPM.

Place of commercial here :http://coxengines.ca/cox-.049-propeller-5-x-4.html

(Bernie, how about some sales commission for me? :-) )

Being that I got an entry level smart phone with a Windows 8 OS, I can find no audio app to tach an engine, Next September when my contract is up I will get a more widely used Droid so I can get such an app and get some readings on my in flight RPMs.I've always been curious, so for now I can just add 15% to the launch RPM.

Hi Guys. Thank you for all the info.

Balogh and Surfer_Kris. Thanks for the figures and advice. You guys have some serious fast engines.

I will try and have a look at the screw and see while running if it makes a difference to turn it.

I must mention that I am using 20% nitro. But the biggest issue is my altitude. We are 1967meters (6454feet) above sea level, so that is already taking a big bite out of the performance of my engines.

Thanks for the info on the prop Rusty. When I saw how mine run with the master airscrew, I was also sure it is to much prop for it. I will cut it down to a 5x3 and see what it does.

Thanks again guys, I will report back once I have checked and tested a few things that you guys have proposed.

Theo

https://play.google.com/store/apps/details?id=com.javiery.rpmgauge

This RPM App works

Yeah for Android. I have yet to find one for my Windows phone. maybe I should look for one for my PC desktop.
Rusty

Theo Kleynhans wrote:Hi Guys. Thank you for all the info.

Balogh and Surfer_Kris. Thanks for the figures and advice. You guys have some serious fast engines.

I will try and have a look at the screw and see while running if it makes a difference to turn it.

I  must mention that I am using 20% nitro. But the biggest issue is my altitude. We are 1967meters (6454feet) above sea level, so that is already taking a big bite out of the performance of my engines.

Thanks for the info on the prop Rusty. When I saw how mine run with the master airscrew, I was also sure it is to much prop for it. I will cut it down to a 5x3 and see what it does.

Thanks again guys, I will report back once I have checked and tested a few things that you guys have proposed.

Theo

Theo, you can compensate a little by opening up the venturi to allow it to breath better. Higher nitro should help as it brings it's own oxygen. 4 pitch props will probably be your go to for the Cox engines.

Ron

1/2A Nut wrote:


https://play.google.com/store/apps/details?id=com.javiery.rpmgauge

This RPM App works

Pree-tty cool! I had this on my last phone and didn't really use it much as it didn't seem to work very well, just down loaded it on my S5 and its seems to work pretty well, at least taching speakers! I do wonder how an audio tach is affected by the "doppler effect" of sound coming and going?

Exactly the same gear on my side: Samsung S5 and Hobbyco minitach, with identical reading results...I hope this lends me and my TeeDee051 rpm accoustic readings some confidence....

I think it does as far as "bench" readings go, but I'm not sure of unloaded inflight readings and if the "doppler effect" has any effect on the readings since its the audio the tach is picking up?

Also remember the prop your using doesn't have near the load as the Competition 5x3 prop has and because of that it should have higher readings.

That's what I like about the Tach Race, all engines are run with the same prop, same fuel and same temp on the same day.

Here is a reading I made on a  tach measurement on youtube:


I agree the Doppler effect may falsify accoustic readings. But if you go back to my vid yesterday when I tached my TD051 based on its sound recorded on a keychain camera mounted on the plane, the Doppler effect is not there because the camera recording the sound and the plane fly together. And on that vid I measured 24k with the acoustic tach of my Samsung S5 which is now proven to be measuring the same as a Hobbico minitach.

(The Doppler efffect is only there if you stand with the acoustic tach in your hands and the plane flies towards/away from you.)

Ergo, the engine spins 24k and the measurement is exact.

I also agree the commercially available 5x4 prop may not require such a torque as a competition prop of the same nominal dimensions. BTW, where do you guys buy competition nprops?

RknRusty wrote:Run Cox Run!
I'd like to know what my Tee Dee .049 is turning with Microflitedude flying it on 25% Beta test Cox Super Power Fuel this past Sunday. Of course you'd have to average due to doppler effect. That's an MA 5.25x3 prop.

https://youtu.be/EKV9cDuHLJM

Rusty,

I tached 22k on your 049 when the plane flew nearest to the camera i.e. neither approaching nor departing from it i.e when the Doppler effect was minimal.

Sometimes even 23k...

lol, I got low 22's as well!

http://coxengines.ca/cox-.049-propeller-grey-5-x-3.html

I am afraid that while we were debating enthusiastically defending our beliefs, we have just invented the warm water...but it was a good debate, I liked it and hope not to have offended anyone with my notorious promotion of the COX TD051 merits...

Next time I am in the US I will make sure to have a couple beers with you guys...just meet me in a place with authentic live blues music, instrumental, with as much nerve-ripping  harmonica in it as possible...and I will have my 051 with me  just to further tease you all with its brute performance

[quote="Cribbs74
Theo, you can compensate a little by opening up the venturi to allow it to breath better. Higher nitro should help as it brings it's own oxygen. 4 pitch props will probably be your go to for the Cox engines.

Ron[/quote]

I was always wondering if the charge of the engines like TD-s and NV-s with their venturi inclined towards (but not pointing fully into) the prop could be enhanced by mounting a funnel extension on the venturi, pointing right into the plan of the prop? Kinda compressor-charging?

Anyone has seen/done something like that?

Look in the Reed Speed discussions. I think Jim and/or Roddie made a forward facing ram air scoop, but that's a reedy, not a rotary valve, so I wonder if too much ram air could conceivably float the reed.
Rusty