Cox model engine
Cox model engines are used to power small model airplanes, model cars and model boats. Cox engines were in production for more than 50 years between 1945 and 2006. The business gets its name from Leroy (Roy) M Cox, the founder. Roy Cox started L.M. Cox Manufacturing Co. Inc. who later became "Cox Hobbies Inc." and then "Cox Products" before being sold to Estes Industries when it became Cox Models. On February 7, 2009 Estes Industries stopped producing Cox engines and sold all of their remaining inventory i.e. mainly spare parts, to several private buyers from Canada and USA. One of the new owners of the remaining Cox engine and parts inventory has launched a website, Cox International with online store.
Millions of engines were produced and they became the most common 1/2A Class 0.049 cubic inch engine in the world and probably still are today. Although the production of the engines ceased some years ago now, engines made as far back as the 1950s are still sold "as new" and in abundance on ebay world wide.
The Cox range of model engines were the brain child of entrepreneur Leroy (Roy) M. Cox.
- Cox Manufacturing started out in Leroy's garage in 1945 where he made wooden pop guns for kids and employed local housewives to assemble them. Metal was scarce due to the war which is why the toy guns were made of wood.
- In 1946 metal became readily available again and competitors quickly moved into the market making their metal pop guns cheaper, so Roy moved to something else, making metal tether cars for kids.
- In August 1946 a fire in Cox's garage forced him to move to newer and larger premises at 730 Poinsettia Ave, Santa Ana, California.
- In 1947 Cox developed a racing car which used an engine manufactured by Cameron Brothers. The cars sold for $19.95 and generated $200,000 in sales in their first year of production.
- In 1949 Cox developed their own engine for their racing tether car which included some parts from Mel Anderson's Spitzy engine. This engine was called the "O Forty Five" as it was .045 cubic inch displacement.
- In 1950 with sales of the car proving to be a success Cox moved on to development of a model plane engine. Roy, felt the need for dependable, easy-to-start engines and spent the better part of the year 1950 in research. (actually 8 months) His three man engineering crew (himself, Mark Mier and Bill Fogler) spent 7 days a week, day and night, to develop the ‘.049 Space Bug’ contest engine. The end result was the Space Bug .049 Contest engine, Cox's first model plane engine which was completed in October 1951.
- In 1952 first name change was made to L.M. Cox Manufacturing Company Inc. The Space Bug engine sets the scene for all the Cox engines that followed and it went into full production in 1952. This engine was so popular that it caused problems for other model engine manufacturers.
- In 1953 Cox produced their first Ready To Fly (RTF) airplane the TD1 which was powered by the Space Bug engine.
- In 1953 Leroy Cox (L.M. Cox Manufacturing) is sued by Jim Walker (American Junior Aircraft Co.) for copyright infringement because Cox was using Walker's patented bellcrank system in the TD1 and secondly because Walker believed the Cox Skylon Reel was a copy of his U-Reely control handle. The court case lasted for 3 years.
- In 1955 Cox wins the court case against Jim Walker. Walker's patent on the bellcrank control system is ruled void and invalid because it was determined that the system had been designed before Walker's patent and by someone else - a man named Oba St.Clair, who was the first man to fly a control line airplane (in the USA) back in 1937 and the design was published in 1938. Oba St.Clair had shown his design to Jim Walker who took it upon himself to patent the design! The court also ruled that the Cox reel was not a copyright infringement.
- In 1956 Cox developed the Babe Bee 049, designed by William (Bill) Selzer, which had an extruded aluminum crankcase, not cast like the others, this engine sold for just $3.95 and stamped the final nail in the coffin of many competitors whose engines were selling for substantially more. The Babe Bee was a high quality high precision engine which started easily and was very reliable, unlike some of the competition.
- In 1957 Cox took over the Flying Circle at Disneyland which was a major coup for the company. The model planes were being flown each day in front of tens of thousands of people and they had a hobby shop right there full of Cox RTF planes. The Cox Flying Circle  remained in operation until 1965 when it was closed to make way for expansion of Tomorrowland.
- In 1960 Cox hired an engineer named Bill Atwood, (who had already build his own line of engines), to develop a new .010 cubic inch engine. Atwood was also responsible for the Tee Dee and Medallion line of engines. These engines put Cox on the map as a leading engine in the world for many years to come.
- In 1963 due to continuing growth the company moved to larger (225,000 square feet) facilities which were three times larger than the old site. Shortly thereafter Cox got into Slot Cars and focused attention on gearing up for this fad.
- 1965 Cox International is established in Hong Kong to meet the demands of the Slot Car craze.
- 1967 The Slot Car fad ends, leaving Cox with excess stock that cannot be sold resulting in financial cash flow problems.
- In 1969 Leroy's wife Myrtle died and Leroy was having health problems of his own so he retired and sold the company to Leisure Dynamics Inc. Leisure Dynamics continued to expand the range of Cox Model Aircraft as well as adding trains, boats, rockets, kites and radio control boosting sales to 25 million dollars per year. Roy Cox retired with the distinction of being the world's most successful model engine manufacturer.
- In 1970 William H. Selzer was appointed as President of L.M. Cox Manufacturing Inc. (a subsidiary of Leisure Dynamics).
- In 1971 Leisure Dynamics breaks the company in two and moves the model production to Minnesota and leaves the engine production in Santa Ana, California.
- In 1976 Leisure Dynamics changes the company name to "Cox Hobbies Inc."
- In 1980 Leisure Dynamics filed for bankruptcy, taking Cox Hobbies Inc. with them.
- In 1981 Leroy (Roy) M. Cox passed away Sept, 22. Age 75.
- In 1983 former Cox engineer and president Bill Selzer (whom Cox hired in 1952) purchased the company out of bankruptcy. All manufacturing was returned to Santa Ana. The company once again flourished into the 1990s with new products being added and another move to even bigger facilities.
- In 1990 Cox Hobbies moved to new facilities at Corona, California.
- In 1993 the company name changed again to "Cox Products". The Pee Wee, Babe Bee, and PT 19 Trainer still in production.
- In 1995 Cox celebrated 50 years and introduced some new engines and RTF models.
- In 1996 Cox sold to Estes Industries / Centuri Corp. and moved to Penrose, Colorado. Things changed quite considerably from here on. Cox as the hobbyists of the world knew it had gone. The high reputation Cox engines had declined. One by one each product item was withdrawn from sale as stock ran out. Engine parts from different engines were mixed and matched making hybrid engines that performed very poorly compared to the Cox engines from previous years. Estes added new products to the Cox line using the Cox name, however these were electric radio control models. Some of which were known to explode resulting in a massive product recall by the company. 
- In 2005 an online company calling themselves Cox Hobby Distributors (owned by Estes Industries) appeared selling RC and electric products and some of the "classic" engines and RTF models. However as each item from the classic era sold out it wasn't replaced.
- In Feb. 2009 Estes Industries sold all of their remaining classic Cox stock to a private buyer from Canada. Bernie & Xena. In June 2009 they launched a website Cox International to sell the remaining stock online and also via eBay.
- In Jan. 2010 Estes-Cox Corporation purchased by Hobbico based in Champaign, Illinois.
Cox .049 Engine Specifications (All Cox .049 Engines) Bore: 0.406 inches (10.31 mm) Stroke: 0.386 inches (9.8 mm) Displacement: 0.04997 cubic inches (0.8189 cc) Bore/Stroke Ratio: 1.05:1 (Oversquare) Cox .051 Engine Specifications Bore: 0.41 inches (10.41 mm) Stroke: 0.386 inches (9.8 mm) Displacement: 0.0509 cubic inches (0.8341 cc) Bore/Stroke Ratio: 1.06:1 (Oversquare)
The Cox .049 Engine is a 2-stroke internal combustion glow plug engine. These engines use a glow plug to heat the fuel/air within the cylinder to start. Once running it is disconnected and operates in the same manner as a diesel engine. The self ignition is due to the heat produced from the compression of the air/fuel mix, and the catalytic reaction of the platinum element in the glow plug and the methanol in the fuel and does not depend in any way upon the continued use of the battery. Fuel intake to the engine is controlled by a simple needle valve and venturi system. Fuel/air mixture intake to the crankcase is controlled via a reed valve or rotary valve depending on the engine design.
In a reed valve engine the valve is drawn open by suction as the piston moves upward on the compression stroke. As the piston moves down on the power stoke, the pressure in the crankcase causes the reed valve to close. The fuel air mixture in the crankcase is then forced past the piston via the transfer/bypass ports in the cylinder. One characteristic of a reed valve is that the engine will run in either direction; an advantage for a "pusher" model but a disadvantage if the engine is finger started, as it may start in the wrong direction. (The Cox engines employed a starting spring which kept fingers free of the propellor and generally ensured correct rotational direction.)
On rotary valve engines the process is similar except instead of a reed, a rotary valve is used (incorporated in the crankshaft), which opens and closes as the piston moves up and down. The rotary valve is more efficient and adjustable (at design time) as there is a larger and clearer path to the crankcase than in the reed valve setup, but such engines can run in only one direction; pusher configurations require a special propellor, sometimes difficult to find.
The Cox line of reed valve engines designed prior to 1960 used a rear reed valve induction system. In the late 1950s they played around with rear rotary valve induction (as used in the RR1) before moving forward with front rotary valve induction for their Tee Dee and Medallion lines.
- 1949 O Forty Five Power Pak (Special Racer Car Engine #PP-45 - Manufactured 1949)
This engine was the first designed by Cox but included some major parts (i.e. piston and cylinder) of the Spitzy .045 engine designed by Mel Anderson. It employed a twin reed valve which was later used for the Space Bug. The engine was a major engineering achievement for its time, by incorporating reduction gears, fuel tank, flywheel and muffler all into one "Power Pak." The air intake was via one of the axles.
- 1949 O Sixty Power Pak (Special Racer Car Engine #???? - Manufactured 1949)
When slightly more power was needed for the Thimble Drome Special car to obtain more speed, a slightly larger version of the .045 was ordered with a bigger bore making the displacement .060 cubic inches.
- 1952 Space Bug (Cat#349 - Manufactured 1952-1958)
The Space Bug was the first engine built entirely by Cox. It was designed for Control Line flying use only and was marketed as a "Competition" engine and sold for $6.95. Back then there was no market for Radio Control and Free Flight hadn't been considered by Cox at this time. The piston and cylinder were made from mild steel bar stock and the crankcase and fuel tank were cast aluminum.
- 1953 Thermal Hopper (Cat#360 - Manufactured 1953-1958)
The Thermal Hopper is basically a Space Bug without the fuel tank. It has a needle valve and venturi mounted on an aluminum plate instead. These were designed for free flight and could also be used for control line flying. It allowed the user to put a fuel tank of their choosing on. The engine output was recorded at 0.066 bhp @ 17,000 rpm with a torque of 4.5 Oz.in at 10,000 rpm.
- 1953 Space Bug Jnr. (Cat#370 - Manufactured 1953-1958)
The Space Bug Junior is a Space Bug with a smaller plastic tank. This cheaper version also only had one intake bypass port and sold for $3.95.
- 1955 Strato Bug (Cat#380 - Manufactured 1955)
The same engine as a Space Bug but included a two piece fuel tank which was cheaper to make than the original space bug tank. The later Babe Bee tank was simply a further developed version of this tank. This engine was only produced during 1955 and sold as a mid range sport engine for $5.95. As such not many exist today which makes them very rare and collectible selling for over $300US in 2008.
- 1956 Babe Bee 049 (Cat#350 - Manufactured Nov 1956-Jan 1996)
The classic Babe Bee was the first engine Cox produced with an extruded machined anodized bar stock aluminum crankcase. This crankcase was machine made and was much cheaper and faster to make than the cast aluminum crankcase of the earlier models. This engine was also supplied in thousands of RTF (Ready to Fly) airplanes sold in department stores worldwide. It has an integrated 5cc fuel tank. Max output power was recorded around 0.057 bhp (42 watts) @ 13,500 rpm on 15% nitro.
- 1957 Pee Wee .020 (Cat#100 - Manufactured Feb 1957-Jan 1996)
Buoyed with excitement of the Babe Bee 049 Leroy wanted to make a half size version of the Babe Bee. So he did. And they called it a Pee Wee .020, just like a Babe Bee only half the size.
- 1958 Golden Bee (Cat#120 - Manufactured Oct 1957-Jan 1980)
The Golden Bee is a Baby Bee that has a larger (8cc), stunt vented fuel tank and has been anodized gold. The larger tank allowed the planes to fly longer while the stunt vents allowed the airplanes to fly inverted without fuel running out or the engine cutting out. The first versions of the Golden Bee had a single bypass intake port but later versions had two bypass ports making them slightly more powerful.
- 1966 QZ (Cat#450 - Manufactured 1966-1996)
QZ stands for Quiet Zone. It is a Babe Bee with a muffler, twin bypass port cylinder with no sub piston induction and a high compression (#1702) glow head. An attempt to regain the power loss caused by the muffler. Very similar to the later QRC engine which reportedly worked better. Cox also sold the muffler, cylinder and high comp. glow head components of the QZ as a Muffler Conversion Kit (Cat#495) for $2.98.
- 1976 QRC (Cat#450-1 - Manufactured 1976-1996)
The QRC was a modified Babe Bee engine that had a muffler and larger (8cc) fuel tank. In the 1970s noise became an issue and the Cox engineers discovered that when adding a muffler the engine would lose significant power. This problem was alleviated by installing a cylinder with no sub piston induction. The engine was designed for power launching Radio Controlled Gliders and had a red tank with a blue spinner.
- 1976 RC Bee (Cat#360 - Manufactured 1976-1996)
This engine was designed for small Radio Controlled model planes. It has a plastic clunk tank and an unusual cast crankcase. The Leisure Dynamics team thought that cast crankcases would be cheaper to produce, however they discovered that there were many manufacturing defects and they were difficult to machine, resulting in a high failure rate, so they returned to the tried and proven machined aluminum bar stock crankcase.
- 1982 Dragon Fly (Cat#4505 - Manufactured 1982-1996)
This engine was designed for the Radio Controlled model planes. It is basically a Baby Bee with a clunk tank and a muffler throttle.
- 1989 Texaco (Cat#4506 - Manufactured 1989-1996)
The is engine was designed for 1/2A Texaco RC duration competition. The engine has an additional fin on the larger glow plug which dissipates heat better allowing the engine to swing a larger propeller. i.e. 7 or 8 inches. This engine has a red 8cc fuel tank and a black crankcase. Original 1989 engines did not come out with 5 fin glow plug. The 5 fin glow plug came later in the 1992 Catalog.
- 1995 Texaco Jnr (Cat#4507 - Manufactured 1995-1996)
The same engine as the Texaco above except that it has a smaller 5cc fuel tank which is also red. First appeared in 1995 Cox Catalog.
- 1956 RR1 (Cat#390 - Manufactured 1956-1965)
The RR1 uses a rear rotary valve intake rather than a reed valve in an attempt to achieve more power. The engine came after the Babe Bee and looks very similar with its anodized, machined extruded aluminum crank case and fuel tank. The power improvement was negligible so Cox reverted to the cheaper easier to build Babe Bee. The engine was made for quite a few years and sold for $6.95. It has become a collectors item due to its uniqueness and pretty colors and is worth around $300–500US in 2008.
- 1959 Space Hopper (Cat#150 - Manufactured Nov 1958-1961)
The Space Hopper was Cox's first attempt at a beam mount engine plus the first steps towards their greatest engine, the Tee Dee. The engine was basically like the Thermal Hopper was to a Space Bug. That is a Babe Bee without a tank, but a venturi and needle valve relying on and external fuel tank. It is claimed it has as much power as a Tee Dee but how can this be if the Tee Dee was the most powerful engine? Anyway, this engine was short lived and made way for the Tee Dee in 1960. They look very retro and due to their apparent rareness are worth around $200US in 2008
- 1973 Black Widow (Cat#150 - Manufactured May 1973-Jan 1996)
During the 70s a couple of Cox engineers were playing around with different colored Babe Bee and Golden Bee parts and came up with an all black engine with a red spinner. They hopped it up a bit with a dual bypass cylinder from a Medallion, a black Golden Bee tank and a slightly larger (0.062") venturi intake. The Black Widow was born. These engines were marketed as a High Powered Combat Engine. On later Black Widows the red rubber spinner was replaced by a red anodized aluminum Tee Dee style spinner. In the late 1990s some Black Widows were produced with the a dual bypass slit exhaust cylinder. The slit exhaust was to prevent fires. According to an Aeromodeller engine test done in August 1974 the Black Widow on 25% Nitro output power was 0.08 bhp (60 watts) at 15,000 rpm with a max. torque of 6 oz.in at 9,000 rpm.
- 1995 Killer Bee 049 (Cat#340 - Manufactured 1995-1996)
The Killer Bee was a real good attempt at making a fast reed valve 049 engine from information that had been learned over the years of racing and competition. It had a tapered cylinder with SPI and lighter piston similar to the Tee Dee, a stronger balanced crankshaft and a new reed valve shape. They had a Yellow plastic needle valve. Later in 2002 Estes produced a Killer Bee that had none of these features but looked like the original Killer Bee except for the needle valve.
- 1996 Killer Bee 051 (Cat#360 - Manufactured 1996)
The Killer Bee 051 existed so that modelers could fly the same plane in two competition classes (i.e. A and 1/2A) simply by changing the engine. This engine has the same performance features as the 049 and the piston has two thin lines (or grooves) in the skirt for positive identification.
- 1996 Venom (Cat#140 - Manufactured 1996)
The Venom was Cox's last attempt at making a really fast 049 mouse racing engine. Again taken from ideas learned from years of competition, this engine put all those ideas into an off the shelf product. It used the Killer Bee crank shaft loosely fitted into the crankcase, and a cylinder with porting very similar Tee Dee cylinder and tapered like the Tee Dee and with a lightened piston like the Tee Dee. The rest of it was like a Black Widow. The problem was that the production engine was not the same as the prototype. A mistake had been made in manufacturing and the piston was lightened too much. This made the engine fast but the piston weak and they would blow the top off the piston after a few runs at high speed. As such only 1000 were made and they never bothered to make any more. They are now worth a lot of money (around $300US in 2008) in the box.
- 1961 Tee Dee 049 (Cat#170 - Manufactured Nov 1960-Jan 1996)
This is without a doubt, Cox's greatest and most famous engine. This engine was "THE" engine to use in competition for many years. It was designed by Bill Atwood who had been hired by Cox specifically to produce the Tee Dee line of competition engines. The important features of the Tee Dee are as follows:
- Tapered cylinder and a lightened and tapered piston
- Result: tighter piston fit at TDC and less piston mass = more performance.
- Two deep bypass ports with two bypass booster grooves on each bypass port, extending slightly above the main bypass groove
- Result: significantly better air fuel mixture induction = more performance
- True peripheral venturi
- Result: more efficient fuel intake, fuel draw and induction = more performance
- Precision balanced and milled crankshaft
- Result: better fuel intake, better balanced engine = more performance
The Tee Dee was tested by Aeromodeller Magazine in 1962 and the output power was recorded to be .105 bhp (78 watts) @ 22,000 rpm with a max torque of 5.5 oz.in. at 18,000 rpm on 25% Nitro. (Note: The modern Norvel AME 049 engine which has a ceramic coated aluminum piston outputs .2 bhp (150 watts)@ 17,000 rpm). In 1973 the bypass porting, crank shaft timing and venturi were modified slightly and a mesh screen was added to the venturi to keep out dirt. This resulted in a minor performance improvement over the earlier versions.
- 1961 Tee Dee 051 (Cat#200 - Manufactured Oct 1961-Jan 1996)
The 051 was simply a Class A version of the engine, physically the same on the outside only the bore was different and the piston had a small groove in the skirt to differentiate it from the 049. The 051 also had a RED carb body.
- 1994 Tee Dee .05 RC (Cat#201 - Manufactured 1994)
This engine had a proper RC carby and a full sized standard muffler and was designed specifically for RC flying. It had no Sub Piston Induction. Only two production runs of 1000 each were done so there are only 2000 of these in existence, making them the second rarest production engine next to the Venom. Note: Although the box said Tee Dee .05 the engine is actually .051
An .09 RC version also exists (Cat# 211 - Manufactured 1994 also)
- 1961 Tee Dee .010, .020, .09 & .15
Cox also built Tee Dee's in .010 (Cat#130), .020 (Cat#160), .09 (Cat#210) and .15 (Cat#180) size. All these engines were very successful.
A little known fact was also this: One of the things Cox wanted Atwood to do was make him a .010 engine. Cox had already tried to halve the size of the Pee Wee .020 but couldn't get it to run for some reason. The suspicion surrounded a problem with the tiny reed valve. Atwood found that the front rotary valve worked well on the .010 size hence the .010 was born. Why? Because Leroy Cox wanted one. 
- 1961 Medallion 049 (Cat#240 - Manufactured Nov 1961-Jan 1996)
Also known as the "Poor man's Tee Dee" these were similar to the Tee Dee in appearance but had cheaper parts on them, making them cheaper to buy. The cylinder was a non tapered twin bypass with no boost ports (like the one used on the Black Widow), the crank shaft was drilled out rather than milled like the Tee Dee, and the carb body was a one piece unit with a conventional needle valve and spray bar. These engines were marketed as a Sport / Stunt engine as they were much tamer and much less cantankerous than the Tee Dee. These are a great reliable easy to use little engine even today. They can be purchased for under $100US in 2008. R/C versions of this engine were also produced with exhaust throttle. ie 1968 Cat#240-1 and the 1988 Cat#2501 with muffler/throttle.
- 1961 Medallion .09 & .15
The Medallion engine was also produced in (Cat#230).09 and (Cat#220) .15 cubic inch size. There were also R/C versions of these ie Cat#230-1 Medallion .09 RC and Cat#220-1 Medallion .15 RC.
- 1995 Medallion 051 (Manufactured 1995)
The .051 came about when a special order for 300 Medallions was placed on Cox by the National Free Flight Society in the USA. It was a gentleman's agreement done on a handshake and it nearly didn't happen when Cox was sold to Estes. But the determination of the NFFS resulted in the deal happening, however Cox only came through with 258 engines. The NFFS engraved each engine with a serial number and kept a record of who purchased each engine. These are probably the rarest of all Cox Engines due to the small size of the production run. These engines have a unique piston and cylinder setup that occurs on no other Cox engine, before or after. The cylinder has a straight bore (0.41 inches), slit exhaust, no sub piston induction.
These are all variations of the Baby Bee with different back-plates and other parts designed for different RTF aircraft, cars and boats. There were literally hundreds of different models with subtle differences. Listed below are just a few of the more common ones.
- 1959 Super Bee (Cat# 350-1)
Babe Bee with twin bypass cylinder to give more power for the P40 Warhawk RTF model. Early version had 'P40' stamped on the cylinder. It had a standard Babe Bee tank.
- 1964 Silver Bee (Cat# 350-6)
Similar to the Super Bee but it had a larger 8cc non-vented fuel tank. It did not have P40 stamped on the cylinder but it did have the twin bypass ports. This engine came with the Spitfire RTF airplane.
- 1962 Series 190 Product Engine (Cat#190)
Babe Bee with plastic backplate and brass needle valve. Various shapes were used depending on the model they were fitted to. Some had dual bypass port cylinders while others had single, it depended on the airplane.
- 1963 Series 290 / Spook Product Engine (Cat#290)
Came on a blister pack as a "Two Ninety" replacement engine. Basically a replacement 190 engine. An aluminum back plate was used for the "Spook" flying wing combat model kit engine (290-1).
- 2000 Surestart (Cat#191)
Another variation of the modern Babe Bee. These were pretty good because they have a choke tube attached to the grey plastic backplate. The choke tube makes the engine even easier to start. They were fitted to the very last RTFs (e.g. PT19 and Hyper Viper) before they went out of production.
Original Equipment Manufacturer (OEM) Engines
Over the years some Cox model engines were sold to other companies for use in their products and sold under the other companies names. Examples of these companies were, Testor Corporation, Sanwa & Kyosho of Japan, Johannes Graupner of Germany, Jerobee Industries trading as JoMac Products, Lite Machine Corporation and Tissan Haifa in Israel. Of all of the above mentioned companies, only Tissan Haifa assembled their own engines called the Banana .049. All the rest used motor manufactured by Cox themselves.
- 1989 Cox Banana .049 (Cat#250)
This engine looked like a standard product engine with plastic backplate. It also had a spring starter, red aluminium spinner, and the fuel intake tube was extended below the plastic backplate. Cox also supplied a specially printed "Banana .049" box insert to fit their standard box.
Other Cox engines
Other engines made by Cox are:
- 1959 Sportsman .15 (Cat# 110 Manufactured 1958-1961)
Rear reed valve .15 sized version of the Space Hopper
- 1959 Olympic .15 (Cat# 140 Manufactured 1959-1961)
Sportsman with twin ball races - designed for FAI Power FF event.
- 1961 Special .15 (Cat# 260 Manufactured 1962-1964)
Second version of Tee Dee 15 with thicker cylinder and wrist pin conrod instead of ball socket.
- 1964 Special .15 MkII (Cat# 270 Manufactured 1964-1968)
Third version of the Tee Dee .15 Single exhaust port Schnürle port intake system and gold crankcase.
- 1965 Olympic .15 Drum Valve
Prototyped only (50 made by Bill Atwood)
- 1968 Concept II .35 Front Rotary R/C (Cat# 2500 1968)
Prototyped only - Bill Atwood - Pictured in 1969 Dealer Catalog
- 1968 Concept II .35 Front Rotary Sport Engine (Cat# 2510 1968)
Prototyped only - Bill Atwood - Pictured in 1969 Dealer Catalog
- 1968 Concept II .40 Front Rotary R/C (Cat# 2520 1968)
Prototyped only - Bill Atwood - Pictured in 1969 Dealer Catalog
- 1968 Concept II .40 Rear Rotary R/C (Cat# 2530 1968)
Prototyped only - Bill Atwood - Pictured in 1969 Dealer Catalog
- 1976 Cox Conquest .15 (Cat# 2800 Manufactured 1976-1978)
This engine took over from the Tee Dee .15 as "THE" engine for FAI racing, combat and free flight for many more years until the Russian AAC Engines came along. This engine was patterned on the Australian designed 1973 Taipan 2.5cc Twin Ball Race engine by Gordon Burford. The entire top end of the Cox Conquest and the Taipan TBR are interchangeable. Also came in R/C version Cat# 2810.
- 1976 Cox Conquest .40 - prototyped only
- 1987 Queen Bee .074 RC(Cat# 3701 Manufactured 1987)
Rear reed valve RC engine. Uses a standard glow plug. Power output is similar to Tee Dee .051. Came out Mid 1987 and is listed in Cox 1987 Catalog.
There were a wide range of cylinders produced with three different wall thicknesses. Most are interchangeable between all engine types which can create problems when buying a used engine. All early cylinders had a thin wall which was later found to need improvement because they bent easily in a crash or when trying to undo with a Cox wrench. Some people refer to these as Mk1 cylinders. The next type was thickened at the exhaust ports and are also known by some people as Mk2. The third type was thick wall the way down from the cooling fins to the bottom. This one facilitated the exhaust throttle ring and some people refer to this as a Mk3 although Cox never referred to them like this.
Referring to the Cylinder Cross-sections above:
- depicts a thin wall Tee Dee .049 cylinder with dual booster ports on the bypass port.
- is a late model thick wall cylinder with slit exhaust and a single bypass booster.
- is a Black Widow #1 cylinder with no bypass booster with a stepped wall.
- is a pre-1955 cylinder used on early Space Bug, Space Bug Jr, Thermal Hopper and Strato Bug. Note how the thread diameter for the glow head is much smaller. No engines produced after 1955 used this cylinder.
The most powerful cylinder piston combination without a doubt is the number 4 Tee Dee 049 cylinder. This cylinder has a tapered grind and tapered and lightened piston so the piston fit gets tighter as the piston reaches top dead center (TDC). The intake or bypass porting is 2 deep ports with 2 bypass booster ports on each bypass. This setup causes a swirling of the intake fuel air mixture which promotes better combustion. The Tee Dee cylinder was the basis for the design of the Venom and Killer Bee Cylinders.
Engine Exhaust Ports Bypass Ports Bypass Boosters SPI Tapered Grind Number on cyl. Space Bug Open 2 0 Yes No None Thermal Hopper Open 2 0 Yes No None Space Bug Jnr Open 1 0 Yes No None Space Hopper Open 2 0 Yes No None Strato Bug Open 2 0 Yes No None Product Engine Open 1 0 Yes No 2 SureStart Slit 2 1 No No None Babe Bee Open 1 0 Yes No 2 Golden Bee Open 1 0 Yes No 2 Black Widow pre 96 Open 2 0 Yes No 1 Black Widow post 96 Slit 2 1 No No None Texaco Slit 2 1 No No None QRC pre 96 Open 2 0 No No 6 QRC post 96 Slit 2 0 No No None Killer Bee ‘96 Slit 2 1 Yes Yes1 None Killer Bee ‘02 Slit 2 1 No No None Venom Open 2 1 Yes Yes1 None Medallion pre 96 Open 2 0 Yes No 1 Medallion post 96 Slit 2 0 No No None Medallion 051 Slit 2 1 No No 7 Tee Dee 049 Open 2 2 Yes Yes2 4 Tee Dee 051 Open 2 2 Yes Yes 5
SPI = Sub Piston Induction
1 The Killer Bee and Venom had a special competition lightweight piston and a heavy duty crank shaft for speeds above 22K rpm.
2 The Tee Dee also had a lightweight tapered piston and the crank was stronger and ported different to the Medallion crank.
The early engines that were produced before 1957 had a light alloy piston rod which is retained in its socket by a slotted steel retaining cup which in turn is held in place by a steel circlip located in a shallow groove in the interior piston wall. This arrangement (known as a three piece piston) was abandoned as of 1957 in favour of a hardened steel rod which was swaged into a bearing cup formed integrally in the piston interior. The advantage of this latter set-up was that it simplified assembly and the bearing could be re-set to take up play using a suitable "reset" tool to re-swage the cup.
The engines that used the early style three piece piston are any engines produed prior to 1957. i.e. Space Bug, Space Bug Jnr, Thermal Hopper and Strato Bug. Since the Space Bug, Space Bug Jr and Thermal Hopper where produced up until 1958 you will find versions of these early engines around with the later style pistons. (and cylinders)
The post 1957 piston is coated with copper on the inside and top. This was done to prevent the nitrile hardening process from hardening the ball socket joint area. The outside wall of the piston was then finely machined and polished to produce a chromed appearance. The piston is not coated with chrome. To prove this point, if you can clean a Cox piston up with alcohol then place it in water overnight - it will rust.
Piston / Conrod ball socket joint free play
Sometimes, especially with engines that have had a lot of use, the piston / conrod ball socket joint is very loose and will adversely affect performance. A Cox “reset” tool, available for the 020, 049/051 and the 09 series engines, is used to tighten the ball joint back up again. The correct free play is .001 to .003 inches. The .15 engines use a wrist pin so a socket reset tool is not required for these.
On the Bee engines there were 2 types of crankshaft produced. (and they are interchangeable)
- All Bees with the exception of the Killer Bee and Venom had the same crankshaft that was only good for about 20,000 rpm before the conrod pin would break off.
- The Killer Bees and Venom had a heavy duty balanced and lightened crankshaft that improved performance and could withstand speeds in excess of 22,000 rpm.
A company named Davis Diesel Development in the USA also make a similar crankshaft called a Killer crank for their diesel conversions. They found under the heavier torque loads caused by running diesel fuel, that the pins would break also; hence they produced their own killer crank. The same Killer cranks are now being produced again by Cox International.
On the Tee Dees and Medallions the cranks are also interchangeable but quite different. The Tee Dee has a large square hole at the intake end of the crank whereas the Medallion has a smaller round hole. The timing is also different. On the later TD RC versions, the crankshaft is lightened and strengthened similar to the Killer Bee crank. i.e. ground away and hole in conrod pin.
Cox Glow Heads
There were 5 main types of Cox Glow Heads produced for the Cox 049:
- #302 Pre 1955 Standard Head - Hemispherical shape - Low Compression - Smaller dia. threads - used on Space Bug, Thermal Hopper, Space Bug Jnr and Strato Bug Only.
- #302-1 Post 1955 Standard Head - Hemispherical shape - Low Compression - Larger dia. threads - used on all engines produced post 1955 until the #325 head was produced in 1979.
- #325 Standard Head - Hemispherical shape - Low Compression - Larger dia. threads - used on all post 1956 engines except Tee Dees, QZ, Killer Bees, Venom and Texaco. Replaced 302-1 head in 1979.<ref.Cox Product Catalog 1979</ref>
- #1702 Hi Compression Head - Trumpet shaped - High Compression - knurled top - 3 fins on early, 2 fins on later - used on Tee Dees, Killer Bees, QZ and Venom 
- #315 Texaco Head - Hemispherical shape - Low Compression - 5 fins - used on Texaco Engine only. Supposedly allows greater cooling for engine when swinging larger propellers. 
There are some minor variations to the above mentioned heads including different thickness cooling fins and thicker centre electrodes on later model OEM glow plugs however the internal shape and glow plug filament remained the same. 
Special glow heads
Along the way there were also some special heads made:
- #302RH 1953 Racing Head - Hemispherical shape - High Compression - Smaller dia. threads as used on Space Bug, Thermal Hopper, Space Bug Jnr and Strato Bug Only.
- #??? "W" element Standard Head - Hemispherical shape - Low Compression - Larger dia. threads. The concept was borrowed from either Atwood or Holland engines and Cox lost the ensuing patent fight therefore the production run was very short due to the legal situation.
- #331 & #335 Special 1 fin car head. This head was built for the 1992 Cox GTP Nissan, Stocker and Indy Car engines. The engine used a purpose built heat sink assembly with cooling fins Cat#1972
Aftermarket glow heads
- Standard glow plug head—uses standard conventional glow plug—low compression—standard performance
- Turbo glow plug head—low compression—medium performance
- Norvel Freedom Glow Plug—high compression—high performance—rare and hard to get.
- Galbreath Head with Nelson Plug Combo—high compression—high performance—most popular, gives the engine an immediate performance boost by up to 2,500 rpm depending on the engine.
- Cox International Insert Style glow head—Available in both Standard and Texaco style
There were three main types of reed valve produced:
- Early engines—Space Bug, Thermal Hopper, Strato Bug—circular twin copper reeds
- Bee Engines prior to 1989—star shaped single beryllium copper reed held in place by a circlip reed retainer. (see image on left)
- Later Bees, Killer Bees, Venom (post 1989) —oval shaped stainless steel reed which is held in place by a plastic reed retainer. (see image on right)
Later variants of the star and oval reeds were made of Mylar and Teflon. Some say Mylar is the best while others prefer the stainless steel and then others prefer the Teflon. Claims are that Mylar and Teflon are lighter and make the engine easier to start and go faster, but they do not last as long as the stainless ones.
049 engines run well on a 5x3 to 6x3 prop. A 5.7x3 APC works well. To get any suitable speed for mouse racing a 4 inch pitch prop is required at high revs but to do this plenty of nitro-methane is also required, for example, a 4.75 X 4 prop with 40% Nitro. Texaco engines are designed to use bigger props. e.g. 7x4
The highest performance is achieved with fuel of 30% or more nitro content. At least 20% oil (50/50 castor/synthetic) is required. With high Nitromethane (nitro) fuel it may be necessary to lower the compression by installing up to six or more additional head gaskets.
When using Castor Oil it is advisable to clean the engine cylinder wall with a Scotch-Brite pad to remove castor oil varnish buildup that will occur, especially after lean running. This buildup of varnish will cause the engine to run inconsistently.
To avoid this problem, it is advised to use a Synthetic oil or synthetic and castor oil blend. Synthetic oil contains detergents that will keep the cylinder wall clean, however these small engines do rely on some castor oil buildup to maintain high compression at higher running temperatures.
Using clean fuel and keeping everything clean and free from dust and dirt particles is also very important for consistent running in an engine of such small size as these.
Cox Fuel Formula
Fuel Name Methanol Nitro-methane Castor Oil Klotz Oil Glow Power 70% 10% 18% 2% Flight Power 65% 15% 18% 2% Race Power 50% 30% 18% 2%
Davis Diesel Development  manufactures and sells heavy duty Bee cranks (Killer cranks) and diesel conversion heads. These can be purchased direct from their web site or from eBay. The DD cranks are similar to the original Cox Killer Bee crank.
Use in Radio Controlled Models
At the time Cox developed the first Cox engines, they were used in Control line and Free flight model planes as there was no market for throttled Radio Control engines back then. Radio Control, although first developed in the 1890s it was not available for model airplanes until the 1950's and did not become economically viable for small model planes until the mid-1970s and even then was for the modelers who could afford it. It was certainly out of reach of the hands of most children.
From the mid-1960s Cox produced throttle control devices for some of their engines, however these were not as effective as throttles on other brand engines as the Cox throttle worked by restricting exhaust flow. Exhaust throttles were produced for most Bee and all Medallion engines but not Tee Dee.
It wasn't until 1988 that Cox produced an engine with a true R/C carburetor and that engine was the Queen Bee .074. Then in 1994 Cox finally produced the Tee Dee .05 and .09 which both had a conventional R/C carburetor, with adjustable airbleed, and a full muffler.
In 2010, an after market R/C throttle/choke has been developed for the .049 reed valve engines. This throttle is attached to the choke tube on Sure Start .049 engines and can also be adapted to fit .049 reed valve engines with an integral tank. The throttle was developed by Saras Associates and is being marketed through Cox International.
Cox Ready to Fly Model Airplanes
Over the years, as well as producing millions of model engines Cox also produced a similar number of Ready To Fly (RTF) airplanes, as well as boats, cars, helicopters, trains, etc.
The following is a list of the RTF airplanes produced by Cox between 1953 and 1978:
Year Model Cat. # Engine Notes 1953 TD1 400 Space Bug .049 Cox's first RTF 1954 TD3 600 Space Bug Jnr .049 1956 TD4 Trainer B51, 5100 350 Babe Bee .049 1957 Super Cub 105 C52, 5200 350 Babe Bee .049 Replaced by the Super Cub 150 1958 Lil Stinker D53, 5300 100 Pee Wee .020 First 020 powered plane 1958 Super Sabre E54, 5400 100 Pee Wee 0.020 1959 P40 Warhawk 5500 350-1 Super Bee .049 Dual bypass port Babe Bee 1960 Commanche 5600 110-1 0.15 Sportsman Larger 2.5cc engine for Dads 1960 PT-19 Trainer 5700 350 Babe Bee .049 Also came out in 5710, 5761, 5900 and 6300 1960 Curtiss Pusher (Kit) 5800 350-2 Babe Bee .049 First kit form RTF 1961 Avion Shinn 2150-A 6200 190 Product Engine 1962 Ju87D Stuka 6400 190-1 Product Engine 190-1 has a dual bypass cylinder - drops bomb 1962 Avion P51B Bendix Trophy Racer 6600 190-2 Product Engine Special backplate and needle valve 1962 Super Cub 150 5200 190-4 Product Engine Updated version of earlier Super Cub 105 1963 Curtiss SB2C Helldiver 7000 190-3 Product Engine 190-3 also has dual bypass - pilot bails out 1963 L-4 Grasshopper 7200 190-4 Product Engine 1963 Spook 7420 290 Spook Engine Flying wing (kit form) 1963 Avion P51B Mustang 7600 190-2 Product Engine Special backplate and needle valve 1964 P40 Kittyhawk 8400 350-1 Super Bee .049 RAF version of P40 Warhawk 1964 Spitfire 7800 350-6 Silver Bee .049 First version of Spitfire replaced in 1966 1965 Curtiss A-25 Bomber 7100 190-3 Product Engine Dive bomber - drops bombs in flight 1966 RAF Spitfire 7800 350-6 Silver Bee .049 2nd version with RAF colour scheme 1966 T-28 7900 290 Product Engine 1966 QZ PT-19 Trainer 5900 450 QZ .049 PT-19 with QZ engine 1967 AD-6 Skyraider 9700 190-6 Product Engine 1968 F2G-1 Corsair 7500 290 Product Engine #7562 with flying accessories 1968 Pitts Special 5300, 8200 100 Pee Wee 020 Variation of the lil Stinker 1969 Thompson Trophy Corsair 27 2900 290 Product Engine 1969 Red Baron 5300 100 Pee Wee 020 Also released as "Red Knight" 1969 Mini Stunt Biplane 7300 100 Pee Wee 020 Another version of the lil Stinker 1969 Ryan ST-3 Super Sport 6200 (&6200-80) 90-1 Pee Wee 020 also available in trottled version 6200-80 1969 Ryan PT Army Trainer 6300 (&6300-80) 100 Pee Wee 020 same as 6200 & 6200-80 but in Army colors 1970 Corsair II 3900 290 Product Engine Chrome plated - left hand prop. 1971 Acro Cub 4600 190-4 Product Engine variant of the Super Cub 1971 Rivets 6800 350-9 Product Engine popular design sought by collectors 1971 P51D Miss America Mustang 6900 190-7 Product Engine Stars and stripes color scheme 1971 P51D Mustang 7600 190-6 Product Engine bubble canopy 1972 Sopwith Camel 8000 191-0 Product Engine 1972 Fokker DVII 8100 191-2 Product Engine 1972 Fokker DR1 Triplane 8300 191-0 Product Engine 1973 Super Sport Trainer 8600 191-3 Product Engine Pink aerobatics trainer 1973 Bushmaster 8700 190-4 Product Engine convertible with floats and skis 1974 Super Stunter 5400 191-2 Product Engine First design with foam wings 1975 Sky-Copter 7100 100 Pee Wee 020 First helicopter (free flight) 1975 Cessna 150 4000 191-8 Product Engine Sure Flyer with autopilot 1975 Piper Comanche 4100 191-8 Product Engine Sure Flyer with autopilot 1975 Combat Mustang 7700 191-x Product Engine 2 speed throttle control 1975 Super Chipmunk 9300 191-x Product Engine Foam wing stunter 1976 Skymaster 4200 191-8 Product Engine Sure Flyer with autopilot 1976 P-39 Airacobra 4300 191-8 Product Engine Sure Flyer with autopilot 1976 Crusader Stunt Trainer 9000 191-9 Product Engine Foam wing stunter 1977 Wings F-15 Eagle 3310 192-3 Product Engine One piece beginner plane 1977 Wings Hustler 3315 192 Product Engine One piece beginner plane 1977 Wings F-15 Falcon 3320 192-3 Product Engine One piece beginner plane 1977 Wings Mantis 3325 192 Product Engine One piece beginner plane 1978 Star Cruiser UFO 7200 049 Product Engine Free Flight
Part numbers appear to skip and jump, however cars and boats produced around same times had numbers similar to the airplanes, therefore causing gaps. (see "Other Cox Toys" below)
Other Cox Toys
Over the years, Cox also produced a range of model cars and boats.
The following is a list of cars and boats produced by Cox between 1954 and 1976:
Year Model Cat. # Engine Notes 1954 Prop Rod 900 Space Bug Jnr .049 Cox's first air propelled car. 1956 Prop Rod 900 350 Babe Bee .049 engine changed to Babe Bee 1956 Water Wizard Hydroplane A50, 5000 350 Babe Bee .049 Cox's first boat. 1960 Mercedes-Benz W-196 6000 350-3 Babe Bee .049 First Babe Bee car engine 1964 Buick Riviera 8240 350-4 Babe Bee .049 1964 Corvette Sting Ray 8640 350-5 Babe Bee .049 1964 Ford GT Le Mans MkII 8940 350-5 Babe Bee .049 1965 Chaparral 9340 350-7 Babe Bee .049 Authorized by Jim Hall 1967 American Eagle Indy Racer 9640 350-8 Babe Bee .049 Authorized by Dan Gurney 1968 Shrike 9100 350-P Baby Bee .049 Inverted engine 1969 Dune Buggy 3700 350-4 Babe Bee .049 Pull Starter 1969 Group 7 Road Racer 9340 350-7 Babe Bee .049 Same as Chaparral 1969 Eagle Indy Car (Blue) 9640 190-6 Product Engine .049 plastic back plate 1969 Eagle Indy Car (Red) 4500 190-6 Product Engine .049 1969 Sea Bee Boat 2800 350-3 Babe Bee .049 Pull starter 1969 VW Baja Bug 6000 350-4 Babe Bee .049 Pull Starter 1969 AA/Fueler Dragster 6100 190-8 Product Engine .049 1970 Chopper 6700 350-8 Babe Bee .049 Pull Starter 1972 Pinto Funny Car 6500 190-5 Product Engine .049 1972 Vega Funny Car 6600 190-5 Product Engine .049 1972 Sandblaster 8400 190-5 Product Engine .049 1972 Ski Doo Snow Mobile 8500 190-9 Product Engine .049 1972 Command Jeep 8800 191-4 Product Engine .049 1972 Chopper II 4400 350-8 Babe Bee .049 1973 Action Van 4500 191-6 Product Engine .049 1974 Matador Stocker 4500 Product Engine .049 Pneumatic Control 1974 Adam 12 Patrol Car 9400 Product Engine .049 1975 Stinger Funny Car 7900 190-2 Product Engine .049 1976 Vanblaster 8410 Product Engine .049 Quick Start System 1976 Magblaster 8420 Product Engine .049 Quick Start System
- ^ The Engine Collectors Journal, Issue 105, May 1993, History of the Cox Engines Part 1 by Dan Sitter
- ^ West Coast Model News. L.M.Cox Company. Howard G. Puckett. Editor and Publisher. December, 1958. Page 22.
- ^ Playthings. The L. M. Cox Story. April, 1957. Page 153.
- ^ Mier, Mark F. Interview with author. Brian L. Winney. Bonner, Montana. 28 November, 1995
- ^ American Modeler Annual. How Roy Cox Turns Out World’s Smallest Engine…plus other fascinating facts on America’s biggest non-modeling model maker. Downie D. 1962 Edition. Pages 29-32.
- ^ L.M.Cox Manufacturing Co., Inc. Unpublished company biography. December, 1960
- ^ Biography of Oba St.Clair - AMA National Aviation Museum
- ^ Biography of William E. Atwood - AMA National Aviation Museum
- ^ General consensus of aeromodellers, hobbyists, engine collectors and hobby retailers who sold Cox products
- ^ U.S. Consumer Product Safety Commission Recall notice.
- ^ Model Aircraft Magazine, August 1955
- ^ Aeromodeller Magazine, May 1961
- ^ 049 Collectors Forum, Larry Renger, Former Cox Engineer, Designer of the Black Widow and QRC engines.
- ^ Aeromodeller Magazine, August 1974, UK, Engine Test by Peter Chinn
- ^ Aeromodeller Magazine, November 1962, Engine Analysis 101 by R.H. Warring
- ^ The Atwood Story by Dr TC O'Meara Model Airplane News. January, 1979
- ^ Cox Model Engine Handbook by Dan Sitter & Tim Dannels
- ^ Engine Collectors Journal, Issue 127, May 1997, Cox Product Engines Parts Breakdown by Dan Sitter
- ^ Keilkraft Cobra 049 and the British 1/2A Revolution by Adrian Duncan
- ^ 049 Collectors Forum, Larry Renger, Former Cox Engineer, Designer of the Black Widow and QRC engines.
- ^ Cox Dealer Catalogue Feb 1962
- ^ Cox Dealer Catalogue Feb 1962
- ^ Cox Dealer Catalog 1961
- ^ Cox Dealer Catalog 1993
- ^ Cox Model Engine Handbook by Dan Sitter and Tim Dannels
- ^ Cox 1955 Catalog
- ^ Cox 1989 Dealer Catalog and Parts List
- ^ Original Cox Fuel Formula Drawings 4/12/1977
- ^ Cox 1966 dealer catalog
- ^ Cox 1988 dealer price list.
- ^ Cox 1994 dealer catalog
- Biography of Leroy M Cox
- The Cox Engines Museum
- Model Engine Collectors Journal
- American Model Engines Encyclopedia
- Yahoo 049 Collectors Forum
- Model Engineering and Model IC Engine Projects
- The Internet Craftmanship Museum - Cox
- Original Author: Warren Leadbeatter - Model Engine Collector - AUS-14782
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