Why is tee dee a better engine?

Hmmmm ... so I thought the rotating part under the carb ( or in the back ... found a video where someone it looks like tried to put a rotary valve on the back of a standard reed engine) is a pump?

I thought this was just an on / off valve, my guess would be it would be open when the piston is at TDC so there would be a slight vacuum in the case and then close so the fuel air mixture is not pushed back out the carb.

Is it somehow pumping air / fuel in ... more like a super charger????

I am hoping to find my engines as I unpack in the next few weeks ... I carefully packed them away before moving so I would not loose parts. I do have 6 engines I just bought a couple of weeks off craigs list. The seller said they were his as a kid. Mine all had single slot cylinders but these all have two slots. One has a silver tank .... one a small black tank .... one a large black tank ... three with plastic backs. Two have black bodies and the other 4 silver. They were all frozen when I got them. Soaked them in carburetor cleaner and they all freed up. Not bad for $20! Even got two plastic glow clips, a wrench and a glow head still in the package.

Thanks .... Mike

It helps to draw in fuel air acting like a pump somewhat, there are RR Cox engines with a incorporated
Rear Rotary valve using the crank pin to rotate it unlike a reed that lifts / seats / lifts / seats the rotary
valve has no cycling limits for max possible rpm.

Reed engines can not turn as high of RPM as a rotary valve design, at high RPM the reed will 'float' not open and close properly limiting the power the engine could develop
, much like valve float on a car engine.

Welcome to the forum, you won't finder a better group of people!

xtal_01 wrote:Hmmmm  ... so I thought the rotating part under the carb ( or in the back ... found a video where someone it looks like tried to put a rotary valve on the back of a standard reed engine) is a pump?

I thought this was just an on / off valve, my guess would be it would be open when the piston is at TDC so there would be a slight vacuum in the case and then close so the fuel air mixture is not pushed back out the carb.

Is it somehow pumping air / fuel in ... more like a super charger????

I am hoping to find my engines as I unpack in the next few weeks  ... I carefully packed them away before moving so I would not loose parts.  I do have 6 engines I just bought a couple of weeks off craigs list.  The seller said they were his as a kid.  Mine all had single slot cylinders but these all have two slots.  One has a silver tank .... one a small black tank .... one a large black tank ... three with plastic backs.  Two have black bodies and the other 4 silver.  They were all frozen when I got them.  Soaked them in carburetor cleaner and they all freed up.  Not bad for $20!  Even got two plastic glow clips, a wrench and a glow head still in the package.

Thanks .... Mike

Welcome to CEF Mike...as others already summarized, TD-s are more efficient in drawing fuel, mixing it with air, and charging the cylinder. As a comparison, a good reedie (possibly with at least a No 1 cylinder that has 2 bypasses) will turn a 5x4 COX prop at around 16-17k, a TD will do 21k+ on the same prop.

The carburetor of the TD allows the mixing of fuel with air with better atomization and distribution of the fuel, and the fuel droplets also travel longer before they reach the crankcase and hence mix better with the air than in a reedie.

The dual bypass in the cylinder, especially when 2 booster grooves are also added (then it is a No 4 or No 5 cylinder) allows for a quicker charge and more efficient scavanging of the cylinder...so a different concept than a reedie..

I like both reedies and TeeDee-s but if I want real brute COX performance I usually go with the TeeDee .

You will find some useful COX engine performance comparison charts in the "Performance " chapter of this site:
http://www.mh-aerotools.de/airfoils/cox_frameset.htm

The power diference between the two probably has a lot to do with port timing as well. A reed valve opens when exposed to a vacuum (from the piston going up) and it closes when exposed to pressure (piston going down). It's only timed by the current atmospheric pressure. In a rotary valve engine the opening and closing of the valve can be accurately timed for optimal gas transfer at just the right time.
Reed valve Cox engines can be made to pull some pretty high numbers, but as Mark said, the reed becomes unreliable at those speeds. They also have a tendency to break crankshafts at high speed, wheras the Tee Dee has a much stronger shaft as it was designed and built to run faster than the reed valve engines.

Rod.

One of the other advantages, besides the power, is that Tee Dee and Medallions, with their external fuel tanks, make it easier vary the amount of fuel you can pack aboard your plane.  The 'Perfect' and Brodak brand tanks will also feed fuel to these engines when the plane is inverted, which can be done tanked engines, but with a bunch more time to fly.

Here's photo of Ron, fueling the 'Traveling Engine' on his 'Flying Clown', which has a bladder fuel system:  A pressurized way to feed fuel to the Tee Dee for a constant engine run.



But, of course, they're ALL great little engines!!!

Welcome to CEF !!!!

Kim

Hi Mike, and welcome to the forum.

Matt of EX Engines and Bernie of Cox International both supply new and sometimes used engines, parts are also available at MECOA all easily found on the net. Buy a "Cox Engine Powered" Tee shirt here to help support this forum and wear it to events.

As you probably know while the main theme here is Cox engine related many other topics are discussed which brings me to your once owned Suzuki dirt bike with the reed valve engine. Do you remember the year and model?

Bob

Wow ... thanks for all the information!

Just before I forget ... it was a Suzuki RM125B ...about 1976

Also had a Polaris snow mobile in the 80's but it was about a 1972 vintage 250 cc ... two cylinder, 2 stroke.

The tee shirts are awesome!

Thanks for the information on the difference in the engines .... makes a lot of sense now.

My wife says I like "living history" .... I don't want things just to look at ... I want them to work the way there were intended to.  I have a couple of old hit and miss engines that I keep running .... a vertical steam engine ... a  bunch of old toys from my childhood (trains, slot cars, meccano and erector sets, ....I even had my old tricycle and metal pedal fire engine, I just reworked my old tube tester, I built (tested ... almost finished) an elevator out of a forklift, ......, I don't own a smart phone and even my home phone is an old 60's rotary dial unit.

I wanted to get all these old engines running.  I miss my days of u-control flying (though when I showed my wife a youtube video she asked so you only go around and round and round and ...?).

I will take an inventory and see what I need to get on order to get these in good shape.  Mine were fine and only needed a mild cleaning.  The ones I bought were really stuck!  No rust but what ever type of fuel the guy used left a blue almost hard layer.  I could not even turn the with a wrench ... probably why the guy sold them all to me fore $20, thought they were junk.  But as I said ... carburetor/choke cleaner freed them up after a couple hours of soaking ... they look good, rotate free and have decent compression. I think the black tanks should be on the black bodied engines but I put them back together the way I got them.



New question .... why the two ports on the cylinders?  All mine had a single opening on each side of the cylinder ... these have two slots on each side?

Thanks again ..... Mike

Nice looking set of engines there. As mentioned above, the TD series engines are known for more efficiency and power but does that make them "better" for the masses. Not necessarily! I run and fly Cox engines of many sizes and styles, enjoying the unique merits that each has to offer(and sometimes suffering the downfalls ). RPMs and high power aren't always the main objective, depending on the application. Those reedie .049s have provided many hours of flying fun for many people and I still enjoy them today. When it comes to bang for the buck, they are often the winner when operating on a budget or flying something that doesn't require a whole lot of whizz-bang up front. And welcome to the forum!

Wow ... as I said, I just remember all of my old engines (circa 1970 - 1974) had a single large port ... I think they were all baby bee engines. Also, all had a brass (copper) cross for the reed.

The engines shown that I got, I am betting are a bit newer. Some had a standard reed and some had the newer style that is shown available now.

Two have the large ports I am familiar with but four have what I will call double slits on each side of the cylinder.

I am guessing if I do some searching, someone has a list of all the possible parts and the pros / cons of each?

Thanks again .... Mike

I don't know your location, but if you're within possible travel distance of Little Rock Arkansas, you can immerse yourself in more types of Cox and other small engines or rockets or electrics, bolted to the noses and tails of some of the coolest airframes ever at the annual Small Model Airplane Lovers League (S.M.A.L.L.) Fly-In.

You WILL be warmly welcomed and parked among friends as a fellow fanatic admirer of these castor-slingers! I bought two more lawn chairs for my collection of those!!! If not this year, perhaps something that can eventually be planned

This year's Fly-In is May 31st-June 3rd, just outside of Little Rock.

https://www.rcgroups.com/forums/showthread.php?3015954-SMALL-2018-May-31-June-3-2018-%28Thr-Sun%29-Mayflower-Arkansas#post38958319

Here's some of the great stuff that goes on!



https://www.youtube.com/watch?v=dbwIBHQfBks&t=8s



https://www.youtube.com/watch?v=y4exoiGbuGU

Found it .... interesting out of the 4 engines I have with slits, 2 do not have the top fin milled!

This actually baffled me when I took them apart as I wondered how to get the cylinder off.

I ended up wrapping it with a rag and using channel locks but I did not think this was correct.

I don't see any slit cylinders listed without a milled top fin.

Any idea what I have?

Thanks .... Mike

I will have to add this to my list!

After 5 years building a house my wife and I are talking about traveling again.

My wife (we have been together 10 years) was paralyzed from the shoulders down in a diving accident when she was 12.  Because she need care every 4 hours she had never traveled.  When we met, I got an old RV, built a wheelchair lift, a lift inside and installed a couple of hospital beds.  Now we just get up and go when every we want.  Did a lot of traveling for the first few years while I sold my house in SC (she was here in VT ... I am originally from Canada ... with her job and health insurance here, I just sold everything and moved north again) but only short trips to see family since ... well and one trip to Disney in FL (needed a break between framing and finishing).  To save money, we spend three years in the RV (not easy with -30 winter temps) on site.  I am just finishing up all those 200 little things before we move from the unfinished part of the house to the finished living area.  That leaves only one real job ... the workshop.  I have the pad poured and will start on it when the weather breaks.  I am a machinist by trade and have been dying with out the use of my lathes and mills  .... got desperate and dragged the welder from the storage trailer and used it in the house.

Here is a link to the RV project:

mcsele.shutterfly.com/2299

We wanted an two story house but they quoted $40K for an elevator (long story ... started at $15k with a $10K grant so only $5K out of pocket).  Anyway, I ended up getting a forklift for $850 and using the mast and hydraulics to build one ... about a $2k project.

Thanks .... Mike

Wow! With a mechanical resume' like that, your Cox engines will no doubt run just fine!

Hi Mike, Welcome to CEF! So.. you and your wife are living in Vermont. That would technically make "me" the nearest regularly-active forum member to you geographically. I live in Northern Rhode Island with my wife of also 10 years.

I really enjoyed reading about you through this thread. We're all "good buddies" here. In short-order; you'll get to know people who live half-way around the world.. and wish you could meet them face to face someday. Travelling-distance is the only thing that really separates us.

Your "question" (topic of this thread) intrigued me.. and I'm glad that you posed it. Until fairly recently (2-3 years).. my Cox engines were all of the "reed-valve" type. I now have a couple of Tee Dee's and a Medallion. I don't have much experience with them though (or spare-parts).

Regarding your recent 6-engine score for $20..    You done good!



The previous owner swapped some parts between engines.. but many of us do this. I would say that those two "black" 8cc fuel-tanks were originally paired with those two "black" crankcases.. making them "Black Widow" engines. The Cox "Black-Widow" paperwork shown, would confirm this. As for the engine-cylinders mounted to those black crankcases;.. you'd need to check their intake-porting to know if any of them are of a Black-Widow spec. but most likely two of them would be. The Cox "Black-Widow" is a high-performance reed-valve engine. The venturi/air-intake is of a larger diameter (.082" compared to .063" for the Babe Bee and Golden Bee engines) therefore; swapping certain Cox integral tanks onto a different crankcase having a different cylinder.. can have a profoundly different performance.  

It's been questioned "why" Cox would have later produced their popular .049 engine cylinder with no provision for removal using a Cox wrench.   There’s a “Cox handbook” that might reveal the answer to that question.. but I don’t own one. You asked why the change to the thinner “dual-slit” exhaust-ports on the cylinder.. to which Fred provided the answer. Here lies a clue. I would guess that Cox didn’t immediately realize that this design-change would prohibit the previous-use of their wrench to remove the cylinder from the crankcase via the larger port.. which their wrench would engage to remove it. Maintaining the "cheaper" reed-valve/product-engine… Cox may have figured; didn’t generally involve removing the cylinder from the crankcase for the novice.. but piston/rod reset tools were being offered.. and cylinder-removal is needed to use that tool. "Cost" was a factor.. unfortunately.. and Cox was competing with "Testors" around that time.

The plastic reed-valve backplates designed to use an external fuel-tank.. in my opinion “all” flow more air/fuel to the reed-valve, than any of Cox’s integral-tanks do. This is why many of us use more aggressively-ported (as in “Tee Dee”) cylinders with them, if higher-performance is desired.

Three of those six engines shown in your pic. have plastic backplates. These were “carbs” (for all intents and purposes) which mated-up to the crankcase, having a rear air-intake, reed-valve induction, needle-valve assembly and a barb for a fuel-line. Cox designed their RTR/RTF models with this “modular” engine which was referred to as their “190 engine”. It was much cheaper to produce.. than putting a beautiful spun-aluminum “integral” fuel-tank on an engine that might be thrown-away when and if the model got broken. The “red one” is the earlier of the three.. and is referred to as a “postage-stamp” backplate. These earlier backplates had higher-quality fine-thread needle-valve assemblies of 120/128 TPI compared to the later 80 TPI NVA’s produced later. These NVA’s can be pressed-out and reinstalled in the later "horseshoe" backplate (which has provisions for a radial/firewall-mounting) if desired. One advantage to having a fine-thread NVA is when running a pressure-bladder fuel-feed. The fine-thread needle has a much finer "resolution" when it comes to dialing-in the optimal fuel-air ratio. Nothing I’ve needed to do.. but something I’d like to try in the future.

I hope I haven’t confused you mike. Like you; I have some machining background.. so I’m pretty sure you understood most of what I wrote here. I look forward to more communication.

Stock sucks. Hybrid mutts are waaay better.

Thanks so much for the warm welcome!

As I said, my wife figures I am re-living my childhood ... my family just says that I never grew up.

I can just see lots of projects in my future. As I said, I definitely what to try u-control again. I have a small river running along the side of my property. Maybe an air boat or even a hover craft .... hmmmmm.

I will need to take a good inventory of everything I have, including my engines and see what I can put together. For the little planes I remember flying, even a simple baby bee performed well. Probably because anything I built was still half the weight of a cox RTF plane.

Being a machinist, I am amazed at how well these engines are built. In my mind, it is much easier to machine larger parts. The fit and finish of a motor that can fit in the palm of my hand is quite something.

Once I get my shop set back up, lots of ideas .... building a rotary valve for the back or maybe one of the two cylinder set-ups I have seen. I was amazed at what people had done with little marvel. I will need to practice up on my micro machining skills.

I have never used an 049 with a separate tank ... well not in anything I built. My introduction to Cox was a Stuka my parents bought for me ... I may have been 8 or 10. I would never had guessed there was different thread on different needs ... for that matter, till I got this batch, I didn't know there were different plastic backs ... I thought they were all just for cox plastic planes.

This sounds like an awesome group! I sure I will have a million questions as time goes on.

Heck, even while writing this, I noticed that some of the engines have an aluminum plate behind the prop and some have brass .... must be dozens of small changes thought the years ... some good, some bad.

Mike

Goodaye Mike,

One of the things I like about the TD as compared to the Reed based engines is the mechanical simplicity, no reed valves, no crankcase gasket to leak, no built in fuel tank limitations, nice sane carby setup, stronger crank, easy to mount in any aircraft you build, you don't have to purchase firewalls and such. You can make them perform like all buggery if you want, but you can mix and match a bit to get the engine that suits you. I don't really need the TEE DEE horsepower most of the time, but I do have an issue with noise as I fly on School grounds ovals and Ozzy Rules Ovals when no one is on them. But neighbors don't like all the noise. So I muffle it with a muffler that both Matt and Bernie sell. Seeing as I decided to muffle it, I figure the TEE DEE cylinder isn't worth using due to the SPI issues, So I just use a standard Sure-start Cylinder with one of the heads that takes a normal 1/4 inch thread glow-plug. (hot). I run pressure from the muffler. Just fitted a pop rivet head into the muffler and connected to the tank. Works fantastic.

This way my TEE DEE acts as the base for me to build an engine that is absolutely perfect for my needs and uses. Easy mount, easy needle, constant revs in flight from pressure, uses standard Engine glow plugs no Cox ones, uses a spring for easy start, is quiet enough, provides the power and reliability I need, is really simple to start and maintain.

And then, you can build the brother of the motor I described above that is a complete hand-grenade motor that can always run within half a bees pube of blowing to pieces.

Thats what makes them soo much fun for me, and why I so enjoy reading all the different experiences and ways people do things with them, nothings right or wrong, different needs for everyone, I take little bits from here and there and can experiment to get the engine I want. And then you can even go and buy fancy custom heads, back-plates, cranks all kinds of stuff. Or if you are lucky to have equipment and skills like yours make up parts yourself.

Take it easy.
Cheers,
Gary

Ok let me help u save time mony at same time ok mis match engine black crankcase make sure piston conecting rod stay in track inside crankcase if bind wit top casing it have To toutch back plate Not the track inside crankcase take al the cylinder of the engine place top dead center push conecting rod on the read valve body section turn crank if lock Not correct gap wit back plate crankcase its normal litle loos y sugest put back the black tank wit black crankcase make sure Not swap piston wit difrent cylinder To mutch its posible tapered cylinder non tapered cylinder look for the correct cylinder on the black widow engine use correct cylinder wit back plate neadle parts black widow its the larger one it hapen To lots of engine after clean multiple engine at same time Most tink engine al the same Not exact lots of difrence is meny difrent engines piston cylinder back plate size tank ventury size Reed valve seat size

Is tee dee powered bugy plus upgrade Reed valve rc wit tuned pipe black widow texaco crank very powerful modified engines
Is lots of possibility wit them y like cox engine