Graphite Nozzle
 
January 11, 2003
 
Project Parameters:

Where to Start:

My goal was to reproduce one of the Aerotech phenolic nozzles that I had purchased from RCS. I picked up some graphite rod from Aerocon Systems that looked great but at 1.5 inches in diameter was just not going to fit in the drill press!

It occured to me that I could make a shaft to mount the graphite on. I drilled a 3/8 inch hole in the top and forced a short piece of 3/8 inch aluminum rod into the hole. I wasted a fair amount of graphite to cracks before I discovered that a wipe of vaseline on the rod first somehow keeps it from cracking.


The ends can be made square with the same technique used with the 1/2 inch motors, a piece of sand paper on the bed of the drill press.

The graphite was cut with the same technique used on the 1/2 inch motors. Clamp the tool to the bed of the drill press and move the spinning part past it with the drill press handle. A bag underneath is handy for catching all the mess!

The convergent and divergent cones can be cut pretty easily. Here a cuttoff tool is clamped at the proper angle for a convergent cone.

 

Conclusion:

Objective acheived! After numerous test firings, the nozzles still show minimal erosion. I suspect that what minor scratches I see are caused when the igniter wire is pushed out during ignition. The O-ring that the nozzle fits into does take quite a bit of heat now since the graphite conducts the heat better. Probably would be a good idea to switch to silicon O-rings eventually but the standard ones function fine, as long as you don't mind the sweet smell of rubber cooking!

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