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Les Kramer's L-3 Certification Project
 
NOSE CONE ASSEMBLY
The following parts make up the Nose Cone Assembly:
• (1) Custom Made PML Fiberglass Nose Cone PIC
• (1) Bulk Plate PIC
• (1) 3/8" U-Bolt
• (1) ½” wide piece of 8” Sono Tube PIC
• (3) #2 Nylon Screws (Shear Pins)
• (6) Mini Washers
All parts are assembled with West Systems epoxy (105 resin / 205 hardener / 404 filler) where required. PIC
Overview
Besides the obvious function of providing an aerodynamic shape to the rocket, the nose cone also acts as the forward attachment point for the main parachute shock cord. The main concept is to keep the nose cone attached to the rocket until it is time for the main deployment charge. This assembly will use 3 shear pins to hold the nose cone in place until the main charge "shears" the pins and allows the nose cone to separate from the parachute body tube.
Install U-Bolt & Bulk Plate
The nose cone U-bolt will be the forward anchor point for the 1" tubular nylon shock cord. The first step in the process was to drill (2) 3/8" holes in the bulk plate for the "legs" of the U-bolt. The U-bolt was installed, the excess threaded stock was cut off and epoxy applied to the nuts to lock them in place. The bulk plate must then be secured in the nose. To ensure that the bulk plate does not pull out of the nose cone base, a ½” wide band of Sono Tube is used as a retainer. First the bulk plate is inserted into the nose cone, and then the Sono Tube is epoxied in place. Next the plate is pulled tight against the Sono Tube retainer ring and secured with fiberglass cloth and epoxy. PIC 1, PIC 2, PIC 3
Locating and Drilling the Shear Pin Holes
The forward end of the payload tube was marked at 3 locations 120 degrees apart. A fin guide was used to locate the marks. A line was drawn down the tube from each mark approximately 6" long. The shoulder of the PML nose cone is 5" wide so I made a mark on the payload tube 2 1/2" from the forward end. This will locate the shear pin holes about 1/2 down the nose cone shoulder.
Once the holes were marked, I placed the nose cone back in the payload tube and drilled (3) 5/64" holes through the tube and nose cone.
Creating the Shear Point
The #2 nylon screws will be screwed through the body tube and through the nose cone. At the point where the screw goes through the nose cone, a sharp edge will help shear the screws and free the nose cone from the payload section. A small metal washer with a hole diameter slightly larger than the #2 screw will be used as the shear point.
I removed the nose cone from the payload section and located the shear pin holes. Using a large drill bit, I carefully cut around each hole in the nose cone to make a recessed location for the washer. Next, the washer was placed in the nose cone and a small amount of epoxy was used to secure it in place.
Testing the Nose Fit
The nose cone was placed back on the payload section tube and (3) #2 nylon screws were screwed through the body tube and nose cone. The nose cone was checked for a proper and secure fit.
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