Accessories 049/051 rpm control

balogh wrote:Mauricio,

the throttle ring can be applied on reed valve engines as well as rotary valve shaft (TD) engines both. Simple and non-expensive, the idle speed is somewhat higher than with the R/C carburetor, and the rpm control range is narrow.. It helps retain heat in the cylinder in idle runs without the engine unexpectedly stopping.

The R/C carb is mainly for TeeDee engines. A bit more "elegant"  and costly than the throttle ring and provides lower  idle speed , but also needs a muffler for stable low idles, in lack of which the engine may  idle erratically because of the rich air/fuel mixture that overcools the glow filament.

This is my experience but other will weigh in certainly with more detailed explanation.

Hello !, thank you very much for your clear explanation, I'll remember his comment when riding a model, thanks! Mauricio.-

Some engines used a combination of exhaust throttle and carburetor, maybe using both would be a solution? It would of course require a linkage between the two and also some adjustment for sure.

Here is an example of my double-throttled Tee Dee Reedie....although not with the subject R/C carb for TeeDee-s, but with an intake throttle, the throttle ring is in combination with it.

I have just put this DTTD =Double-Throttled Tee Dee together and will test how the exhaust and intake throttles combined help keep the idle low...will post results once done...

i'd think that would work well, early larger bore R/C engines used a exhaust baffle before mufflers became common.

Voila...:



Amazing....I need to fine tune the air-bleed a bit on the R/C carb and will have the COX 051 DTTD :  COX Double-Throttled Tee Dee (my trademark     ) ready to fly.

Wow that's great! It would make a nice setup for boat use too. The idle is steady and low and the response is amazing... How was the mid-range if you accelerate, say, from 2/3 to full throttle?

Kari it gives an immediate response without a lag no matter if accelerating from midrange or idle. I need to finetune the air bleed to stabilize the idle. The response is much better than on my COX TD050 RC engines. This is probably because of the better heat retainment by the throttle ring than with muffler.

Way to go!

A muffler with back pressure will help with a lower idle when using a RC carb.
How low can you go without it dying? Each time it would drop off and start to die
then you would throttle back up. I want to audio tach a steady idle. = )

I have had good luck with the carb without a muffler. I usually use a few extra head gaskets and a merlin type hot glow plug insert. As much as I know the prop selection shoud be based on the plane and type of flying, if you want a lower idle then use a more highly loaded prop. Just make sure your prop selection matches your intended flying application.

balogh wrote:Voila...:



Amazing....I need to fine tune the air-bleed a bit on the R/C carb and will have the COX 051 DTTD :  COX Double-Throttled Tee Dee (my trademark     ) ready to fly.

Impressive Sir Andras!!! "DTTD"... I remember your working toward this a few months back. Nice running engine BTW...! Sounded like no-lag at all with the engine-speed transitions. I enjoyed your repeated "quick-blips" of the throttle to demonstrate that! Just to clarify adjustment between the two throttles.. (I've never used an exhaust throttle sleeve) I assume that the sleeve's clip-ring is used to radially adjust the exhaust-port's index-position? That seems like how it would work.. and if so; a brilliant design by Cox's engineer(s). I had thought about placing a v-bend in the link-rod between the two throttles for fine-adjustment.. but your engine seems to be dialed-in perfectly!  

I have been a proponent for throttled small displacement IC engines... because of their history of only being able to perform at W.O.T operation; given the "period-available" building-materials and the early airborne-RC components. All that has changed drastically.. especially where batteries are concerned. Add to that; the currently available nano-servos/receivers... and you can build tiny R.O.G. scale-models that are capable of touch-and-go landings.. as well as throttling-back/soaring to experience increased fuel-economy! Aside from noise-restrictions.. the power-to weight ratio of IC vs. EP still favors IC power.. real engines burning fuel.. like "real" airplanes.

Throttle sleeve on my TD .010 worked well reduced 16,400 rpm off of  peak.

https://www.youtube.com/watch?v=PIzrCJxmJXk





Check out the custom machine work on this TD .010
absolute awesomeness. Full boat RC Carb and Muffler
with a pressure tap.

https://www.youtube.com/watch?v=NP5ptRXy87g




He did the same thing to a TD .020 this time it is exposed
we can take a better look at the mojo

https://www.youtube.com/watch?v=hkxDK3FN1us



He must be a machinist he made his own .096 RC engine



And then a micro RC twin with the same cc per cylinder amazing!!!!!!!!!!!!!!!!

roddie wrote:

Impressive Sir Andras!!! "DTTD"... I remember your working toward this a few months back. Nice running engine BTW...! Sounded like no-lag at all with the engine-speed transitions. I enjoyed your repeated "quick-blips" of the throttle to demonstrate that! Just to clarify adjustment between the two throttles.. (I've never used an exhaust throttle sleeve) I assume that the sleeve's clip-ring is used to radially adjust the exhaust-port's index-position? That seems like how it would work.. and if so; a brilliant design by Cox's engineer(s). I had thought about placing a v-bend in the link-rod between the two throttles for fine-adjustment.. but your engine seems to be dialed-in perfectly!  

I have been a proponent for throttled small displacement IC engines... because of their history of only being able to perform at W.O.T operation; given the "period-available" building-materials and the early airborne-RC components. All that has changed drastically.. especially where batteries are concerned. Add to that; the currently available nano-servos/receivers... and you can build tiny R.O.G. scale-models that are capable of touch-and-go landings.. as well as throttling-back/soaring to experience increased fuel-economy! Aside from noise-restrictions.. the power-to weight ratio of IC vs. EP still favors IC power.. real engines burning fuel.. like "real" airplanes.

Thank you Roddie, this is my seasoned old 051 which already shows the signs of impaired compression when nearing to its 300 hours runtime...but it still swings the 5x4 prop of COX Int'l like crazy...I did not tach it when the vid was made but I assume the rpm was well over 21k..

In fact the clip on the throttle ring can be rotated if the ring clip grip is released, so the relative position of the clip and the exhaust slots on the ring can be adjusted. Hence the length of interconnecting rod between the throttle  clip and the R/C carb arm need not be cut super accurate....you do the fine adjustment by rotating the clip on the sleeve.

I am on the road for a 2 weeks vacation and business trip combo and will not be able to fine tune the air-bleed and throttle ring setting. Currently the throttle ring totally covers the exhaust ports on the cylinder when the R/C carb is also almost fully closed. In fact the exhaust throttle need not close completely, just to ensure some heat retention in the cylinder when throttled. If the ring is closed too much, with the overly rich fuel air mixture the glow filament may blow easily.

More to come when I hit home again.

Mark Boesen wrote:i'd think that would work well, early larger bore R/C engines used a exhaust baffle before mufflers became common.

My 1965 version OS Max 10R/C with mufflerless exhaust baffle ganged to throttle horn throttles very smoothly. Had a blast with it on a 39" (991mm) Top Flite School Master.



Same era Enya .09-III TV has a similar exhaust baffle system, very effective.



I found the ring exhaust throttle on Cox reed valves to work every effectively. In the 1970's & '80s, I used the Ace throttle sleeve, which closely resembles EX Engine's one. I imagine Bernie's Cox International's one is equally effective.

On a Black Widow, I was able to obtain good Hi-Med-Lo sequential throttle response using a KRD quick blip sequential servo on my Ace Pulse Commander. Making a custom measured hole in the servo wheel to get the right throw. High was wide open. Low was closed except for a slight crack. (Ace had a small round notch cut in one end of a slot in the sleeve to provide relief during idle.) Medium pushed past to the other side until I had about 1/3rd of the slot exposed.

Did the same using an R/C Bee, a decent throttling predecessor of the Dragon Fly with ample tank. It had an odd silicone cover over the throttle ring for muffling, worked quite well. Didn't have a tach so can't give numbers, but got decent idle from the exhaust throttled .049's.

Exhaust throttle ring gives a non-linear response, but with today's programmable transmitters, one could fix that by tweaking exponential rates, IMO. A caveat on the Tee Dee may be that if it uses sub piston induction might cause some issues with idle. I didn't have any problems with the Black Widow even though it uses sub piston induction. It may not be a problem, just something to be aware of.

how much information to share, very interesting !!!!, greetings, Mauricio.

GallopingGhostler wrote: A caveat on the Tee Dee may be that if it uses sub piston induction might cause some issues with idle. I didn't have any problems with the Black Widow even though it uses sub piston induction. It may not be a problem, just something to be aware of.

If the exhaust throttle ring is fully open, the SPI will inhale fresh air under the piston, unlike with the static muffler whose volume is filled with exhaust gas, and the SPI engine will not work well because of inhaling flue gas. I found unfortunately this is also true with the simple mufflers that were applied on the  Quiet R/C COX engines,  though..http://coxengines.ca/cox-.049-muffler.html

If you throttle an SPI engine with the throttle ring,  the more you close it, the more exhaust may be inhaled by the engine and this may also impair the engine output...but you close the throttle to reduce engine speed, anyway....

I also have had very good experience with the throttle ring and because I favor SPI engines for their higher performance, this is the throttle I used most frequently.

When a COX TD 050 R/C carb is also combined with the COX exhaust throttle, I find them to respond even more smoothly.

Yes as you mention balogh, there is another caveat. An open unmuffled exhaust throttle ring works well. It allows the engine at full throttle to induce a fresh air charge under the piston skirt to increase fuel charge density and improve maximum horsepower. Muffling prevents this, reintroducing exhaust gases, which has the opposite effect of diluting that fuel charge density.

Solution for muffler use would be for a piston cylinder combination without SPI. I'd think there would be some loss in maximum horsepower as SPI is high performance, but the latest non-SPI cylinders are ported sufficiently that the loss would be slight or so I gather compared with SPI and exhaust gas dilution.

When I used Cox's new non-SPI ported R/C Bee with muffled exhaust throttle ring when it first came out, it was more than sufficient power for my Sterling Minnie Mambo. It definitely wasn't underpowered. I loved flying that plane so much that I wore out the cylinder and piston, replaced those parts. (Then, one could drop by the local hobby store or even Sears or Montgomery Ward and get the parts.)

The Minnie lives on in its 3rd crash rebuild.

balogh wrote:I have just put this DTTD =Double-Throttled Tee Dee together and will test how the exhaust and intake throttles combined help keep the idle low...will post results once done...

Here I am doing my homework! ...
I am using a propeller 6 x 4
I low rpm range would be appropriate ??

I guess a 6x4 will a bit overprop a TeeDee051and you will not be able to enjoy the peak power this lil critter can deliver. My best experience is with 5x4 on TD051 that allows the 21k plus rpm where the power curve peaks out.

balogh wrote:I have just put this DTTD =Double-Throttled Tee Dee together and will test how the exhaust and intake throttles combined help keep the idle low...will post results once done...

Looks like you have a candidate for the next Cox Engine of the Month winner!

Yes I may want to enter it but have reasons to believe it won't draw any more attention than my previous entries that all lost. Anyway building it and experimenting were already worth it

in practice:

balogh wrote:Yes I may want to enter it but have reasons to believe it won't draw any more attention than my previous entries that all lost. Anyway building it and experimenting were already worth it

Balogh, I've entered my engine pictures in and they have never been the best, the brightest or the most unique picture of a Cox Engine. Didn't receive many votes either. But by the sheer number of my entries I was entered into the "participants " drawing at the end of the year.  Quote from the rules:
"
DON'T WORRY if you entered an engine in the Cox Engine of the Month and it didn't get chosen. Everyone who has entered an engine in the Cox Engine of the Month will have a chance to win a Black Lynx .049 engine at the end of the year! So it does pay to enter! *Winners of previous Black Lynx engines will be exempt from this drawing. "

So, if you do have pictures please enter them in the contest. I have been lucky enough to have entered a picture in most of the monthly contests, and one time  I deleted my entry in favor of another who missed the "first ten" submitted. I'd gladly do this again if it would entice you to submit your entry.