Cox model engine

Cox model engines are used to power small model airplanes, model cars and model boats. They were in production for more than 60 years between 1945 and 2006. The business is named for founder Leroy (Roy) M. Cox. He started L.M. Cox Manufacturing Co. Inc, which later became Cox Hobbies Inc., 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 – mainly spare parts – to several private buyers from Canada and the US. One of the new owners of the remaining Cox engine and parts inventory has launched a website with an online store. 
Millions of engines were produced. 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, engines made as far back as the 1950s are still sold "as new" and are in abundance on eBay worldwide.
Cox history.
The Cox range of model engines were the brainchild of entrepreneur Leroy (Roy) M. Cox.
The engines.
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 stroke, 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 propeller, sometimes difficult to find.
The fuel used to power the engine is called Model Engine Fuel, a mixture of methanol (70–40%), castor oil (20%) and nitromethane (10–40%).
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.
Early engines.
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. 
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. 
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.
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.
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.
Basically 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 tank itself is turned aluminium while the tank back is red, yellow or blue plastic from the Space Bug Junior but is modified to include an aluminium pick-up tube and a larger hole to expose the venturi that is integral to the aluminium 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 and $1000+ in 2012. Beware of fakes! Some unscrupulous sellers have been selling fake Strato Bugs that have a CNC machined tank and a Space Bug Junior back-plate.
Standard Bees.
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.
Buoyed with excitement from the Babe Bee 049, Cox wanted to make a half-size version of the Babe Bee. It was a Pee Wee .020, just like a Babe Bee but half the size.
The original Golden Bee was 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 and same size backplate venturi opening (0.0625") as the Babe Bee but later versions had a 0.082" venturi opening to 11/64" at the reed valve while the Babe Bee was 9/64". This was the secret to its slightly higher power output. The 1969 and later RC version with throttle sleeve had two bypass #1 cylinder making them slightly more powerful again to make up for power losses due to the exhaust throttle sleeve.
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.
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.
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. 
This engine was designed for the radio controlled model planes. It is basically a Baby Bee with a clunk tank and a muffler throttle.
The engine was designed for the 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. This engine also has the smaller 0.062" venturi opening of the Babe-bee to provide a longer engine run. 
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. 
High-performance Bees.
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. A left and right hand rotary valve were made, as were left hand 6×2 glass-filled nylon props for the RR-1. Some versions have a blue tank, others have a clear anodized tank. There were two versions of the tank back as well, to fit the corresponding tank. It has become a collectors item due to its uniqueness and pretty colors and is worth around $300 in 2008.
The Space Hopper was Cox's first attempt at a beam mount high performance reed valve engine plus the first steps towards their greatest engine, the Tee Dee series. 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 an external fuel tank. The engine looks similar to the Sportsman engine with a machined aluminium crankcase and rear induction via a reed valve with the needle valve assembly and venturi similar in appearance to the later Tee Dee series. This engine was short lived and made way for the Tee Dee in 1960. Due to their similarities to the Tee Dee that followed some of the parts crossed over from this engine to the Tee Dee. They look very retro and due to their apparent rareness are worth around $200US in 2008
During the 70s a couple of Cox engineers were playing around with different coloured 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 Super Bee (#1), a black Golden Bee tank and a slightly larger (0.082") 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. 
The Killer Bee was an 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. Beware of fakes! Some unscrupulous people are producing fakes and selling them. Check to make sure the engine is the "real deal" before purchasing.
The Killer Bee 051 existed so that modellers could fly the same plane in two competition classes (i.e. A and 1/2A) simply by changing the engine. This engine has exactly the same performance as the 049. There is a legend that two thin lines (or grooves) in the piston skirt are for positive identification but this is incorrect. The grooves were intentionally designed to bleed off just enough power so that the 4% increase in displacement does not necessitate trim changes to a free flight model when switching the model from an 049 to the 051 to fly in the higher "A" class. The benefit of the grooves as a visual identifier was accidental.
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 crankshaft 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. Because of that, and all the fakes, they are not worth a lot of money. Beware of fakes! Some unscrupulous people are producing fakes and selling them. Check to make sure the engine is the "real deal" before purchasing.
Tee Dees.
The Tee Dee is Cox's most famous engine. This engine was dominant 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:
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 an aluminum piston running in a ceramic coated cylinder, outputs .14 bhp (100 watts)@ 20,000 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.
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 bleed off just enough power to exactly equal an 049 so no trim changes would be required to free flight models ["citation required] (this groove also visually differentiates the 051 from the 049 but this was of secondary importance). The 051 also had a RED carb body.
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).
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. The original Tee Dee 15 immediately became the engine to use in FAI FF with vastly higher performance than the Olympic, which had supplanted the European diesels used at the time. They proved fragile, particularly the thin-wall cylinder, and ball-and-socket connecting rod, and were replaced by beefed-up versions (as noted below).
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.
Medallions.
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 crankshaft 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 $20US in 2008. R/C versions of this engine were also produced with exhaust throttle. i.e. 1968 Cat#240-1 and the 1988 Cat#2501 with muffler/throttle.
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 i.e. Cat#230-1 Medallion .09 RC and Cat#220-1 Medallion .15 RC.
This particular .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, Estes-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.
Product engines.
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. 
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.
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.
Babe Bee type engine with "postage stamp" type Delrin backplate and brass needle valve instead of the integral Babe Bee fuel tank. Various shapes were used depending on the model they were fitted to. Each time they made a modification for a new model that was built a new Cat number was produced. (e.g. 190-8) Some had dual bypass port cylinders while others had single, it depended on the airplane. e.g. JU-87D Stuka, P-51 Bendix Racer, P-51 Mustang & Miss America models.
Babe Bee type engine with "horseshoe" type Delrin backplate and brass needle valve. The horseshoe backplate had additional mounting holes drilled in the plate allowed fitting to after market and kit aircraft. Various shapes and colours were produced depending on the model they were fitted to. Some had dual bypass port cylinders while others had single, it depended on the airplane. e.g. Sopwith Camel, Fokker DVII, ME-109, Super Stunter, PT-19 Trainer and others produced in the mid 1970s.
Similar in appearance to the 191 series engine, produced for the 1977 Wings series of air craft. i.e. Hustler, Mantis, F-15 Eagle and F-15 Falcon air planes. 
Came on a blister pack as a "Two Ninety" replacement engine. Basically a replacement 190 engine. An aluminium back plate was used for the "Spook" flying wing combat model kit engine (290-1). 
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, Kenbrite Corp. Australia 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 motors manufactured by Cox themselves.
The 1989 Cox Banana .049 (Cat#250) engine looked like a standard product engine with plastic backplate. It also had a spring starter and 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:
Rear reed valve .15 sized version of the Space Hopper 
Sportsman with twin ball races - designed for FAI Power FF event
Second version of Tee Dee 15 with thicker cylinder and wrist pin conrod instead of ball socket.
Third version of the Tee Dee .15 Single exhaust port Schnüerle port transfer system and gold anodized crankcase.
Prototyped only (50 made by Bill Atwood) They were handed out to various people to try out and as such a few still exist today and appear from time to time for sale at swap meets and on eBay.
Prototyped only - Bill Atwood - pictured in 1969 Dealer Catalog
Prototyped only - Bill Atwood - pictured in 1969 Dealer Catalog
Prototyped only - Bill Atwood - pictured in 1969 Dealer Catalog
Prototyped only - Bill Atwood - pictured in 1969 Dealer Catalog
This engine took over from the Tee Dee .15 as "THE" Cox 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. The Taipan TBR was based on the Rossi MkII so the top end is also interchangeable with a Rossi MkII. Also came in R/C version Cat# 2810. As a result of reorganisation within Leisure Dynamics who owned Cox and K&B at the time, production of this engine was handed over to K&B and it became known as the K&B Conquest after 1978. Production continued for a number of years when the engine was sold to MECOA owned by "Randy Linsalato" where it continued on as the RJL Conquest for some time.
Samples do exist and the Conquest .40 was a grown up version of the Conquest .15 however due to reorganisation with Leisure Dynamics who owned Cox and K&B at the time it was decided not to commence production as K&B already had a .40 sized engine in the market.
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.
Cylinders.
There was 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 in this way.
Note: The chart does not differentiate between specific modifications and changes made over the years as the company changed hands.
Referring to the Cylinder Cross-sections above:
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. 
Pistons.
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 that 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 produced 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 were 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.
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 .010, 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.
Crankshafts.
On the Bee engines there were 3 types of crankshaft produced. (and 2 are interchangeable).
The normal babe bee & Killer bee crankshafts are interchangeable. A third 'Car' crankshaft
will only fit into a car crankcase with wide neck.
A company named Davis Diesel Development in the USA also made 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.
Glow heads.
Cox glow heads.
Five main types of Cox glow heads were produced for the Cox 049:
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:
Reed valves.
There were three main types of reed valve produced:
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.
Propellers.
049 engines run well on a 5×3 to 6×3 prop. A 5.7×3 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 × 4 prop with 40% Nitro. Texaco engines are designed to use bigger props, e.g. 7×4.
Fuel.
The highest performance is achieved with fuel of 30% or more nitro content. At least 20% oil (50/50 castor/synthetic) is recommended. Acceptable performance can be had without nitromethane, although the engine will be very sensitive to needle adjustments making it more difficult to operate. 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 a 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:
Diesel conversion.
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.
Other conversion heads are made by MECOA RJL, and include .049, .074 and .09 engines. These use an o-ring seal rather than a Teflon disk.
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 1950s 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.
In 1988, Cox produced an engine with a true throttle-able R/C carburetor and that engine was the Queen Bee .074. In 1994, Cox produced the Tee Dee .05 and .09 both of which had a conventional R/C carburetor with adjustable airbleed and a full muffler.
In 2010, an after market R/C throttle/choke was developed for the .049 reed valve engines. The throttle attached to the choke tube on Sure Start .049 engines and acted like a cold-start choke on regular engines. The throttle was developed by Saras Associates and was 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, and trains.
The following is a list of the RTF airplanes produced by Cox between 1953 and 1980:
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: