Cox Rocket Motor History
 

L.M. Cox Manufacturing Co., Inc. was sold to Leisure Dynamics in 1969.
Cox was in financial trouble as the company had invested heavily in the slot car craze of the 1960s and when that hobby had faded Cox was left with a large quantity of slot car parts which could not be sold.

Leisure Dynamics (LD) put money into Cox along with new management. The Space Race was still in the news and LD wanted model rockets as part of the Cox product line.

Cox would need to have their own motor making machines which was contracted to an outside company to develop, build and deliver.

The method by which Cox made rocket motors was a little different than other manufacturers.
While other hobby rocket motor makers of the time (Estes, Centuri, MPC) pressed loose black powder into paper casings Cox had an additional process.

Cox had two different motor making machines. The first machine would take black powder and compress it into pellets. These pellets would be placed in the hopper of a second machine which would press the nozzle followed by one to three BP pellets then the delay and ejection charge.

The number of black powder pellets used would be determined by the desired performance of the motor. One pellet would be an 'A' motor, two pellets a 'B' motor and four pellets a 'C' motor. (The D8 motor came later and was five pellets but this took up too much space in the casing so only -0 and -3 delay times were possible).

The motor machines were not powered by electricity to make the process safer but there was still the extra step of a person having to empty the first machine of the BP pellets and taking them to the second machine to make the motors. This added an extra element of risk to the process which would result in a tragic incident.

TBC...

Continued...

In the early 1970s Cox was busily pumping out model rocket motors from their custom built machines.

Black powder is an abrasive substance. As the second motor machine would ram/press the black powder pellets into the paper casing the ram would wear down a little. Over the course of producing thousands of motors the ram had worn down and little particles of BP had escaped due to the shrinking outside diameter of the ram.

BP dust particles levels were noted in the atmosphere in the building but no effort was made to replace the ram heads.

The process by which the BP pellets were transferred from the first machine to the second was done by a person. A tray of the BP pellets was carried to the second machine and dumped in a hopper. When everything was set the machine was turned on and started making rocket motors.

Everything worked fine until one day...

The later investigation never conclusively determined the initial source of the spark/fire but a tray of BP pellets suddenly ignited. This caused the BP saturated air in the room to flash off.
Two or three people were in the room at the time. One was killed and the other one/two received serious burns.

Cox was sued by the families of the deceased and injured individuals. Cox was found guilty and paid the families. After that, Cox ended their model rocket product line.

If only Martin would post on this forum.....

Thanks, Bob, for this interesting bit of history. Never knew that Cox had such a unique method of motor production. Sorry to hear that a life was lost and that severe injuries occurred in the process. Like you said, it was an unfortunate tragic accident for all involved. It's too bad that happened. Cox likely would have continued motor and model rocket production for some time longer, had the accident not occurred.

Kind regards,
Jeff Jenkins
aka: Faithwalker
NAR #46879 SR

Found a timeline for the L.M. Cox hobby products here including when Estes/Centuri acquired the company in 1996: https://www.mh-aerotools.de/airfoils/cox_frameset.htm

Kind regards,
Jeff Jenkins
aka: Faithwalker
NAR #46879 SR

AT the time this occurred, I don't believe there was any news about this published in the Model Rocketry Magazine.

who is Martin?

What year did the L.M. Cox factory explosion occur?

Kind regards,
Jeff Jenkins
aka: Faithwalker
NAR #46879 SR

Terry,

Thanks for posting the newspaper clippings.

well Bob, I was wondering if anybody was ever going to tell their story as to what happened that fateful day. And thanks to you we now know what happened and why it happened.