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Double-throttled TeeDeeReedie049

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Double-throttled TeeDeeReedie049

Post  balogh on Thu Feb 11, 2016 3:54 pm

Good day CEF.

I guess what I am about to show here is probably not new to many of you. I equipped my TeeDeeReedie (a reedie with Killer Bee crankshaft+backplate, and a TeeDee049 piston cylinder combo) with the throttle carb conversion unit of Bernie. As with all throttled carb COX engines without a muffler, the throttled idle means very rich air/fuel mixture entering the cylinder that occassionaly overcools the glowplug and the idle becomes erratic and unstable, and the engine may even stop.

So I decided to add an exhaust throttle barrel as well, just to check if the heat retained by the exhaust throttle will make the idle more stable.

I am yet to test and tach it in the weekend, but here is a picture of how I combined the 2 throttles with a common pushrod mechanism.

Not a big deal - and will probably not win the award of Most Elegant Adaptation of a Pushrod Mechanism, it is actually a kitchen-table tuning project -  but some of you may want to do the same just for fun and experiment. I would love to read anyone's experience with such a combo throttle. (I just refurbished an old Medallion 049 RC with a double throttle operating on the same principle as this one, and I found the idle very stable.)


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Tee Dee Reedie Double Throttle

Post  VUgearhead on Thu Feb 11, 2016 9:22 pm

This is about as close to the 1960's throttle muffler assembly as you can make with readily available parts. The only thing that might make it better would be if you could fit one of the medallion throttle muffler assemblies on there in place of the exhaust restrictor style throttle sleeve. At least that fully encloses the piston housing (better heat retention), but at the cost of the SPI pulling in exhaust fumes (a little lost top end?)
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Re: Double-throttled TeeDeeReedie049

Post  balogh on Thu Feb 11, 2016 11:51 pm

Thanks VUgearhead the SPI still enabled by this throttle combo is why I believe this is what you can get as best in throttle control.

But I will see how it idles and post a video in the weekend.

Thank you for the comments.
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Re: Double-throttled TeeDeeReedie049

Post  batjac on Fri Feb 12, 2016 12:39 am

An incredibly clever idea. It should be interesting to see how it works after you get the linkage tweaked properly for the best idle.

The Impressed Mark
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Re: Double-throttled TeeDeeReedie049

Post  balogh on Fri Feb 12, 2016 1:10 am

Thanks Mark. For the time being it is set to be fully proportional I. E. Both throttles fully open and close together.

With my Medallion I noted though the carb throttle is closed somewhere halfway only when the exhaust is fully closed for a smooth low idle.

Because of the shared carb throttle arm for the mechanism the only meaningful tweaking is with the position of the holes relative to each other drilled on this arm.


Last edited by balogh on Fri Feb 12, 2016 2:07 am; edited 2 times in total
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Re: Double-throttled TeeDeeReedie049

Post  Surfer_kris on Fri Feb 12, 2016 1:29 am

The problem is not heat to the plug, the problem is that the "throttle carb conversion", as you call it is, that is not a carburator at all, it is simply a cold start choke. Once you understand how a cold start works, the running of the engine will also make sense.

The medallion on the other hand has proper carb on it, there is a rotating plate that regulates both the air and fuel supply. The design is not as good as the rotating barrel ones though, and the linked exhaust throttle then also helps to throttle the engine speed.

So for a properly throttling reed engine one just have to put a proper carb in the backplate, like they did with the Queen Bee.
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Re: Double-throttled TeeDeeReedie049

Post  balogh on Fri Feb 12, 2016 2:02 am

Thanks Kris, you are right this "carb throttle conversion" is just a cold start choke, I used the name as it appears on Bernie's website http://coxengines.ca/throttle-conversion-for-cox-049-engine.html
I had couple of scooters when a highscool kid in the 70-s and they had the same chokes.

But because the throttle carb conversion works well in itself as it is, with the only shortcoming of sometimes erratic idle that I attribute to the rich fuel/air mixture and the overcooled glow filament, I think the addition of the exhaust throttle barrel will ideally not make it worse but may even slghtly improve it with the heat it partially retains in the cylinder at idle runs..

Anyways the "proof of the pudding is in the eating" as the British say, so lets see how it idles and tachs this weekend. I will keep you posted no matter if this combo works or fails.

At the end of the day at least I had some fun fiddling with my COX engine even if my combo throttle fails Very Happy
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Re: Double-throttled TeeDeeReedie049

Post  Surfer_kris on Fri Feb 12, 2016 7:06 am

Yes, fiddling around with a hobby is all part of the fun, no objection there. Smile

I just get a little sad when I see all these new inferior products being made for cox engines. Cox were once ahead of the bunch, leading both in terms of developments and power levels, and delivering well thought through and tested products. To then now go some 50 years back in time and put on intake chokes and regular glow plugs (to deal with the rich settings) on these engines, just doesn't feel right somehow...

Back on topic, you could possibly get some better running by using a hot glow plug rather than the stock one. Not the regular glow plug adapters, they loose to much power, but one that uses Turbo plugs. OS has some really nice "hot" glow plugs that worked well in the TD .05RC for me. The hotter plug helps at reduced throttle settings and gives both a smoother run and pickup from idle. I'm not sure where to get Turbo heads from now though, but they might pop up on ebay.
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Re: Double-throttled TeeDeeReedie049

Post  balogh on Fri Feb 12, 2016 7:55 am

Sic transit gloria mundi...this is how the glory of the World is fading away....


I am not evaluating these add-on products from the perspective of what COX once was. That was a fully fledged factory with product development teams and a long line of select sub-vendors, .. .

COX today remains, I believe, the toy of guys like we on CEF who fiddle with them partly from nostalgia and partly for fun and experiment. The main thing is we cause harm to neither the engines nor to third parties while fiddling and having fun with them.

These simple and economical add-on products sold by Bernie may not all bring the ultimate performance and efficiency but I appreciate the great versatility these add-ons provide the COX engines with. With ready-made ultimate-efficiency gadgetry COX would be less of an entertainment, we would be left with less desire to experiment...
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Re: Double-throttled TeeDeeReedie049

Post  Surfer_kris on Fri Feb 12, 2016 12:41 pm

balogh wrote:
These simple and economical add-on products sold by Bernie may not all bring the ultimate performance and efficiency but I appreciate the great versatility  these add-ons provide the COX engines with. With ready-made ultimate-efficiency gadgetry  COX would be less of an entertainment, we would be left with less desire to experiment...

Well, we simply have very different views of these things then...

To me it is the constant improvement of things over the years that keeps my interest up. With the improvement on the RC equipment side and the batteries, plus the development of performance engines with proper RC carbs and mufflers etc, the 1/2a class has never been as performant as it is today. We can now have full-house controls in very small and lightweight planes, something we could only dream about when I first got into this hobby.
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Re: Double-throttled TeeDeeReedie049

Post  balogh on Fri Feb 12, 2016 1:06 pm

Sure Kris,

I am also thrilled by the latest developments, while I do this hobby for adding my own - quite often backhanded and amateurish -
part in fashioning the equipment (in my not at all equipped shop i.e. the kitchen) that  I fly.

I could afford buying the most sophisticated engines, RF planes, electronics currently available on the market, but then I would have to give up messing with balsa, scorning CA glue every time I use it and it sticks my thumb and forefinger instead of the wood, blending my own fuel, and hand-cranking old COX engines and sometimes putting bandage on my severed fingers.

Test flying, test running and fine tuning what I put together with home made efforts and ideas of my own is what drives my COX hobby. I like to see my efforts materialize in a functioning plane more than just flying laid back something industrially perfect. (This is what I see most of electric R/C flyers in my area do, with due respect)

But I agree and respect we all may have different motives to do this.
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Re: Double-throttled TeeDeeReedie049

Post  getback on Fri Feb 12, 2016 5:22 pm

WELL I HAD A POST and it went away and I am not to reduce it tonite sooooooo  Cold Popcorn Popcorn Popcorn  Keep us posted  http://www.superbowlcommercials2016.org/budweiser/  Yea the 1/2A break , getback bounce
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Re: Double-throttled TeeDeeReedie049

Post  roddie on Fri Feb 12, 2016 8:52 pm

Hi Andras, I like these experiments! You seem to have the length of the linkage between the two, optimized for where your cylinder indexes. You could try cutting another rod.. long enough to include a "V-bend" for trimming. This would allow you to tweak the length to absolute optimal. It might be easier than adjusting the c-clip on the sleeve?

Actually.. it would be an interesting experiment to run the two independent of each other. The choke-throttle would then serve as a remote mixture adjustment. Maybe that sounds crazy.. Huh... You'd need an extra servo/channel to do it. Your killer-bee backplate flows some serious mix at WOT! BTW.. how does the orifice size in the choke barrel compare to the size of the air-intake on the backplate? I would hope it to be as big.. or you're not getting enough flow.

The "Ace-style" kit for the Bee works really well.. but is tough to make mounting provisions for using it in an airplane. It actually meters some fuel.. because the plunger-needle passes by the spray-hole in the backplate when it enters the venturi. Performance is limited by the stock 1.6mm venturi though.. and a muffler is recommended.. which negates using an SPI cylinder. The hotter plug that SurferKris spoke of, would be good to try. Maybe going less nitro would keep the mix hotter for a better low-idle?

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Re: Double-throttled TeeDeeReedie049

Post  balogh on Sat Feb 13, 2016 3:19 pm

Thanks Roddie

Having 2 separate channels for the 2 throttles sounds interesting but would probably require more manual ability for mid-air hand control than what I have.

I tached the combo throttle today and it is pretty stable but I messed up the video with the headcam set too high and the tachometer and engine are not visible so I will re-vid and post it tomorrow.
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Re: Double-throttled TeeDeeReedie049

Post  balogh on Sun Feb 14, 2016 8:17 am

This is the final setup. I have bent the pushrod to allow a wider exhaust barrel travel, and added a ballpoint-pen spring to eliminate unwanted "play" of the pushrod in the oversized holes on the circlip and the air throttle arm, as well as to reduce vibration.



And here is how it works:



The fuel is 20% castor + 20% nitro + 60% methanol. The prop is a 3 bladed 5x3 COX Thimble drome.
The full throttle rpm was around 17400 max, the minimum idle was around 9900, but very stable. I could lower it more by further closing the air-intake throttle (it was about 2/3 closed) when the exhaust throttle is fully closed.
Disregard the mess in the farthest corner of my garage where the leander and other delicate garden flowers are stored in winter.



I also shot a short vid in the field but my fuel line was clogged and had to land early:
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Re: Double-throttled TeeDeeReedie049

Post  1/2A Nut on Sun Feb 14, 2016 1:15 pm

Way to go Balogh,

I see on the first Canary video you are starting to fly closer passes by the cam
very good, now you just need to do some circle laps around your car!
The plane lands very nice great glide ratio. You can throttle down and do
some slow passes by the camera too. Thumbs Up

Beer Cheers
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Re: Double-throttled TeeDeeReedie049

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