NFFS Special Cox .051 Medallion - A truly rare motor!
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Cox Medallion .051 NFFS Special

NFFS Special Cox .051 Medallion


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NFFS Special Cox .051 Medallion - A truly rare motor!
Cox Medallion .051 NFFS Special

This page is dedicated to the history of the Cox Medallion .051 engine. Manufactured in 1996 at my request on behalf of the National Free Flight Society, there were 258 engines made in total, maybe the shortest production run of any Cox engine ever. The order was for 300 motors, however when it came time to make them, Cox (now Estes) found they only had parts for 258 of the small (049) Medallion size motors. They manufactured 258 very unique .051 cylinders.  They were to match the .049 Medallion specifications except for the larger bore, but they had a little fun with them unbeknownst to NFFS at the time (See Martin's article and photos below).  These were assembled into these very few, rare, and special Class A Medallion .051's.

Your stories about the motor are welcome, and I'll incorporate them best I can. Suggestions, corrections, and constructive criticisms most welcome.



Left: Look closely, you can see the serial number on the bottom of the case. This is Medallion .051 number 5258. The LAST serial number in the very short run of these quite special engines.

From Martin Hepperle's Web site:  (

Medallion .051 (0.8 cm³)

Manufactured in 1996

In 1996 NFFS president Bob Beecroft approached Cox to produce 300 Medallions for the NFFS (National Free Flight Society). The idea was to allow for easy swapping from ½-A to A for Nostalgia Free Flight events.

To make the illegal usage of Tee Dee .051 cylinders impossible, these Medallions were to have dual slot exhausts. The transfer system of the untapered cylinder consists of two bypass flutes each having a single boost channel (the Tee Dee hast two boost channels). The later Killer Bee .051 has exhaust slits of different size. The piston shows an added grove to indicate the .051 displacement.

Just at the same time Estes took over the reigns at Cox and they were not much interested in such a small and not very profitable production run. Finally, 258 engines were produced and shipped in December 1996. The small production run makes the Medallion .051 a quite rare engine - the much touted Venom was made in about 1000 samples.

In contrast to the standard production engines these engines bear engraved serial numbers ranging from 1 to 258 - a leading 5 was added to indicate the unusual displacement. All engines were sold through the NFFS to individual free flight enthusiasts.  A complete record of the engines and their numbers exists. The pictures sample is #5238.

Thanks to Robert Beecroft for supplying the background story about this engine.

Right: Close up of the hand engraved serial number found on each of the 258 .051 Medallions.

Plain brown wrapper.

There was no insert made for the .051's, so they came plain Jane.  Each did come with a pair of wrenches, an 049 Medallion instruction sheet, and a pair of Cox stickers.

Each was date stamped inside...the date it was assembled and boxed I believe.

Left: The information sheet that was with each box shipped out.
This is what the note packaged with each of the Medallion .051's shipped says:
"At Last!!
The long-awaited special run of Cox Medallion 051 engines are here.This engine is special and distinct from other engines in the Cox line and is NOT simply the Killer Bee 051 piston and cylinder on a Medallion case. They are different in the same manner that the (NOS legal, slit exhaust) .049 Medallions are different from the Killer Bee's:
- the Killer Bee has a lighter weight, tapered piston
- the Killer Bee has a tapered cylinder similar to the Tee Dee
- the Killer Bee has sub piston induction similar to the Tee Dee
- The Medallion 051 has the familiar ID groove in the piston skirt
(And, it should be added (2008) that the Medallion .051 cylinder has a single boostport and dual bypasses, but the exhaust timing slits are different from the Killer Bee engines, making it unique from any other Cox ever manufactured.) 
The engines came without serialization, however each has been numbered so that a record exists indicating who ordered each engine. Engines were numbered in the order pulled from the pallet and shipping in order of the postmarked date of the order wherever possible. The delays were numerous, and with Cox being taken over by Estes, it looked as if the original agreement would not be met... we can be thankful these were produced at all - we received 258 of 300 engines ordered and at a higher price than initially agreed. There were not enough parts available to produce 300 .049s (cases, etc.-RKB)... so what they had (258) were produced as these special order .051s. There will probably never be more new Medallions"