Introduction

This guide is intended to assist folk who are intending to purchase Cox model aircraft engines.

History

Cox engines started out as Leroy M Cox Manufacturing in 1945.  The company enjoyed a long period of strong growth until 1969 when Mrs Cox passed away and the company was sold to Leisure Dynamics. The Cox line continued to flourish until in 1983 Leisure Dynamics were declared bankrupt and the company was sold to a former Cox Engineer named Bill Selzer. In 1995 the company celebrated it's 50th anniversary and some new engines including the rare and very much sought after Venom were introduced. In 1996 the company was sold again to Estes Rockets / Centuri Corp. Quality and standards changed dramatically from this point on. In 2005 Cox moved back to the hobby market and are still available today, however the line of products now are nothing like what they used to be and are mainly RC electric park fliers.  The 049 engines and gas power RTF planes are no longer available.

The Engines

There is a wide range of Cox engines available on eBay as a lot of the engines were purchased by collectors and never run.  These range from the 010 cubic inch Tee Dee (ci) through to the .15 ci Conquest.  There is a very good web site on the internet that goes into a lot of detail about the different engines at www dot mh-aerotools dot de slash airfoils then go to the Cox Engines Link or simply search for 'Cox Engines' on Google.

To describe the engines I have broken them up in 6 main categories. Early Engines, Bees, Medallions,  Tee Dees, Product Engines and Special Engines. (Note: The ebay Guides feature only allows me to post 10 pictures otherwise I would post them all.)

Early Engines covers years 1949 to 1960 and includes the Thimble Drome Space Bug, Space Bug Junior, Space Hopper, Thermal Hopper and Strato Bug all of which were .049 cubic inch engines or 0.8 cc and utilized a rear reed valve induction system and most included and integrated fuel tank. These engines are distinguised by their cast crankcase. The Strato Bug is the rarest of all Cox engines and therfore worth the most money.  The early engines used a narrow thread cylinder and glow plug up to about 1955, so you will find these engines with both the early and modern style cylinders because they were produced with both types of cylinders.  Some other engines that were produced in the late 50s were the Olympic and the Sportsman which were all rear induction reed valve engines. The RR1 was an early engine that looked very similar to a Bee, but it had a rear rotary valve intake system rather than a reed valve. This model is also very much sought after by collectors and pull very high prices on ebay.

  < Thermal Hopper

Bees The Bees were the backbone of Cox engine production and included the ever popular Pee Wee .020 Babe Bee .049, Golden Bee .049 and Black Widow .049 engines. These engines feature a crankcase machined from bar-stock aluminium. This allowed Cox to build machines to produce the crankcases and as a result the engines could be made for much less cost and labour than a cast crankcase engine. The Black Widow came along in the earlt 70's and although a much better performer than the Golden Bee, it doesn't bring as high a price as the Golden Bee's do on eBay. This must be because of the gold anodizing fooling people into thinking the Golden Bee must be better. The Black Widow has two fuel transfer ports instead of the one that the Babe Bee and original Golden Bee have, plus it also has a larger venturi hole in the backplate. All of these engines included an integrated fuel tank setup for control line flying and reed valve intake system. Other variations were the QZ (Quiet Zone) and QRC Quiet RC engines which were both supplied with mufflers, and the Texaco and Texaco Jnr, RC Bee and Dragon Fly. The Texaco has a 5 fin Glow head which allows it to run cooler with a larger prop and is used for RC Texaco competition.

  < Golden Bee  < Black Widow

In 1995 and 1996 came the Killer Bees (049 & 051) and the Venom 049, both of which were high performance engines with strengthened crankshaft, improved reed valve intake system and different fuel transfer and exhaust porting, all of which contributed to these engine doing speeds of over 22,000 rpm and still holding together. The Venom engine has a manufacturing fault in the piston and as such only 1000 were ever produced. This makes them a very much sought after item for collectors. They bring around $250 US and buyer need to be very aware as there are a lot of fakes out there.  It is important that you check with the seller to ensure that you are getting the 'real deal' before bidding on a Venom.  With the Killer Bee there were two versions produced. The first one was in 1996 which was advertised as a high performance competition engine and it lived up to it's name, and the second was a 2002 version (produced by Estes) with the same looks and name but it was no more than a standard Bee. As with the Tee Dee 049 and 051 the two models can be distinguised by a black back plate on the 049 and a red back plate on the 051. The back plates are interchangable so the only way to be sure is a groove on the 051 piston. ie. If it has a thin line about 1 mm up from the bottom of the piston it is an 051.

< Killer Bee 049   < Venom

Medallions -  In the early 60s Bill Atwood was hired by Leroy Cox to produce a new more powerful line of competition engines. Cox discovered there was only so much you could achieve with a rear intake reed valve. Leroy Cox also wanted to make an 010 sized engine but could not get it to run with a reed valve.  Bill is responsible for designing the new line of engines that caused Cox to continue to be "the force" in 1/2A engines.   A precursor to the Tee Dee the Medallion engines were released as a Sport engine and employ a front rotary valve fuel intake much more like a conventional model air plane engine.  These are available in sizes 049, 09 and 15 ci in both Control Line and R/C versions although the throttle is rather crude and is derived by limiting the flow of the exhaust gasses, almost as though this were an after thought.  A special run of 286 Medallion .051's were produced by Cox exclusively for the NFFS in 1996. These engines are all individually serial numbered and are rare as rocking horse poo. I have never seen one for sale on eBay.

< Medallion 049 Std  

Tee Dees -  These are the high performance contest range of engines that in their time pretty much out performed everything that came before. A peripheral port venturi replaced the conventional needle valve and spray bar of the Medallion, plus it has triple fluted transfer ports and a heavy duty crankshaft. Available in sizes .010, .020, .049, .051, .09 and .15 ci. The physical size of the 049 and 051 are very similar so to distinguish them apart the Tee Dee 049 has a black carb body and the Tee Dee 051 has a Red Carb body. The 051 also has a small groove on the bottom of the piston so you can be sure it is an 051 if the engine has one of these. There are also some special versions with RC throttle and different exhaust port configurations as in the Tee Dee 15 Special and Special MkII.

< Tee Dee 049    < TD 15 MkII Special

Product Engines - These are pretty much standard Bees and range from the 020 to the modern day Surestart 049. These engines are supplied in the Cox RTF model planes, helicopters, boats and cars and had different backplate configurations to match the toy they were fitted to.  The Surestart Engine is a great little engine and can still be purchased new on eBay. These start so very easily if you follow the instructions provided. The main reason for this is the choke tube fitted to the engine which make priming very easy. I have personally started them 1st flick straight out of the box.  Thats how good they are. Beware when buying these on eBay as there are a lot of sellers out there starting them at $20US and up. See my eBay guide to hotting one of these up.

< SureStart .049 Engine

Cylinder & Piston Types

Update: 26/10/2007 - Many people have asked me about the porting and configuration of the cylinder and piston between the different .049 models.  There are more than 10 different .049 cylinder head types and all are interchangeable between models.  So you can see why it can be confusing as to which head belongs to which engine, especially when people can easily change things around. 

There are 3 different thickness cylinder walls.  The early cylinders has thin cylinder walls and were lightweight buy weak and would warp if over tightened when trying to undo with the cox wrench. They could also bend out of shape in a hard crash. To combat this problem a cylinder with a thicker wall around the exhaust ports was produced. This one stepped down to a thin cylinder wall below the exhaust ports because keeping the engines lightweight was important. After this the mufflers and throttle sleeves were coming out so it was was decided to make them thick all the way down to the bottom to help the throttles seal better and operate more smoothly. This thick wall cylinder also had the top fins milled so the cylinder could be removed using the Cox wrench without damaging or warping the cylinder at the exhaust ports.

Make sure you check with the Seller before buying that the engine has the correct cylinder and piston. See the table below.

.049 Engine       Exhaust    Bypass Ports   Bypass Boosters   Sub Piston Induction   Tapered Grind 

Space Bug                Open              2                       0                               Yes                        No
Space Bug Jnr          Open               1                       0                               Yes                       No
Thermal Hopper       Open               2                       0                               Yes                       No
Space Hopper          Open              2                        0                               Yes                       No
Product Engine         Open               1                       0                                No                        No
SureStart                  Slit                  2                       1                                No                        No
Babe Bee pre 96     Open              1                       0                               Yes                        No
Babe Bee >96          Slit                  2                       0                               No                         No
Super Bee (P40)       Open              2                       0                               Yes                        No      
Golden Bee              Open              1                       0                               Yes                        No
Black Widow           Open              2                       0                               Yes                        No
Texaco                     Slit                 2                        1                                No                        No
QRC                        Open              2                        0                                No                        No
Killer Bee                 Slit                 2                        1                               Yes                       Yes*
Venom                     Open              2                        1                               Yes                       Yes*
Medallion  pre 96     Open              2                        0                                Yes                       No
Medallion  >96         Slit                 2                        1                                 No                       No
Tee Dee                   Open              2                        2                                Yes                       Yes

* the Killer Bee and Venom also has a special competition lightweight piston and a heavy duty crank shaft for speeds above 22K rpm.

Cylinder Numbering

Another way to identify the different cylinders is by a number stamped on the outside of the cylinder, or inside one of the exhaust ports. However, this is not conclusive because sometimes the number wasn't stamped on at all and at other times the number meaning changed. But anyway here's what I do know:

• No.1. A two bypass cylinder with a large exhaust port that permitted sub-piston induction. It was originally made for the 290 and 291 series engines that were used in plastic cars. Later, it was used in the first Black Widow engines. At that time the top cylinder fin was not milled to accommodate a Cox wrench. Later, the Black Widow cylinder had two narrow slits for each exhaust, and the top fin was milled but the cylinder was not numbered in this configuration.
  
• No.2. This denoted a single bypass. sub-piston induction cylinder. The top fin was not milled. This type was used on the Golden Bee, however, the cylinders were not always numbered.
  
• No.3. A two bypass cylinder that initially did not have the bottom of the exhaust ports milled low enough to provide sub-piston induction. Later, the exhaust milling permitted sub-piston induction, and the outside was ground for use with an exhaust-restrictor type throttle, and the top fin was milled.
  
• No.4. This was made for T.D. .049 engine. There are two bypasses, each with three separate milling cuts, and the bore is tapered. The exhausts allow sub- piston induction and the top fin is milled.
  
• No.5. This has the same features as number 4, however. the bore is .410 inches. It is used on the T.D. .051
  
• No.6. Twin bypass, no sub-piston induction. and milled top fin. Some were externally ground for restrictor throttles.This was used on the QRC.  Later some of the SureStart engines were stamped with this number. This cylinder had a twin slit exhaust, no SPI, and twin bypass ports with a single boost port on each bypass.  Known to work quite well.
  
• No.7. The same as number 2, but with a milled top fin. Also seen on some of the SureStart Engines, and known to be similar to or the same as, the number 6 version above.
  
• No.8. Single bypass. narrow exhaust. no sub-piston induction. Top fin not milled. Used in cars.
  
• No.9. Known to exist but very rare and limited.
  
• No.0. Known to be similar to number 6.

As mentioned earlier, a lot of cylinders had no numbers on the outside, so the only way to tell for sure, is to have a look inside. Most of the twin slit cylinders had no numbers stamped on them at all, because the makers had either found another way to identify them or more likely cost cutting caused them to cease this practice. 

Glow Head Types

There are 4 types of Cox Glow Head available for the .049s  but there are also others as well.

1) The early engines pre 1955 (e.g Space Bug and Thermal Hopper) had a smaller diameter thread on the Glow Head.
2)  Standard Low Compression Head - designed for all post 1955 engines (except 3 & 4 below).
3) High Compression Head - designed for Tee Dee, Killer Bee & Venom
4) Five Fin Low Comp. Head for Texaco - allows better cooling for larger props on Texaco models.

After Market Heads.

1) Standard Glow Plug Heads - allows a Std Short Plug to be used - not as good as a Std Cox Head
2) Turbo Glow Plug Head - uses Turbo Glow Plug - about the same as a Std Cox Head
3) Norvel Freedom Glowplug - straight from a Norvel AME or Big Mig - becomming rare but good.
4) Galbreath Head and Nelson Plug combo. - Recommended - This will give you up to 2,500 rpm increase for very low price. Don't waste your money on other Cox heads. Google them.

How Fast?

On a 5x3 Tornado Prop, a good Tee Dee 049 should be able to do 24,000 rpm + on 30% nitro
A really good Black Widow should be able to do 18 to 20,000 rpm.  A Killer Bee should do around 22,000 with a Cox 5x3 competition prop on 30% Nitro. Engine test results can be found in old Aeromodeller magazines. e.g. Nov 1962 for the first TD .049 test.

Special Engines -The Conquest .15 is a high performance engine capable of around 23,000 + rpms and was introduced to compete in the market with the Rossi .15 which dominated the scene at the time. These are also highly sought after and have undergone a couple name changes as the ownership of the Cox company changed of the years. e.g. it is also known as a K&B 15 when the company was owned by Leisure Dynamics. The Conquest has a conventional cast crankcase and is available in control line and RC versions.  There are a few other Special Engines, some that never made it to production due to the demise of the company.

Buyer Beware

Which brings me to the part where I warn you about what to watch out for.  As briefly mentioned earlier, due to changes of ownership and management, the company went through some rough times quality and standards wise and as most of the engine parts are interchangable between models, you will see a large variation in models, colours, and hybrids out there.  It's a case of Buyer (and Seller) Beware. 

If you are in the market for a Cox engine, I advise you to use the web site I have mentioned in this guide and join the Yahoo 049Collectors forum to bring yourself up to speed with exactly what you are after and ask lots and lots of questions of the seller to ensure that they know actually what they are selling and you know exactly what you will be getting. Because I can tell you, just because the box says, Killer Bee, you will more than likely not be getting a genuine 1996 Killer Bee with the genuine Killer crank shaft.  Many sellers are actually selling off motors from a collection they have inherited from an estate and therefore have no idea what they are selling either. Be especially aware of sellers who say this because it gives them the opportunity to say they didnt know that the engine was a fake or whatever.

I hope you find this information of use, before purchasing your Cox Model Engine, and not after. :-) 

Now, If you didn't learn something from this guide then I want to know. Contact me on eBay "warrenlead69"  If you did then please provide feedback by clicking below.

Submitted by: Warren Leadbeatter
Cox Model Engine Collector
Port Stephens, NSW, Australia

P.S. Most of this information comes from knowledge I have gathered from my own collection and experiences with Cox engines. However some infromation has been obtained from other sources like former Cox employees, other Cox collectors and internet forums.