DIY Network

Manual Equipment Manual Equipment From "Trade School" episode DTRS-110

In this episode of Trade School, we follow the education of precision machinist Carl Battles (figure A). An amateur rocketry enthusiast, Carl plays the part of engineer and machinist by designing and building a custom rocket motor test stand (figure B). The stand allows Carl perform a static fire to analyze the stages of thrust and pressure of various rocket motors before rigging them in expensive rocket shells ....

Figure A

Figure B

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	Figure C
	Figure D

The stand works by measuring the vertical thrust and outward pressure of a rocket motor. A rocket motor is placed upside-down in the vertical steel tube called a boot. When ignited, the motor forces down the thrust arm which presses upon presses upon a modified brake cylinder called a load cell. This action forces brake fluid through a hose to a transducer. (figure C). Meanwhile, a hose coming out of the center of the motor sends pressure information to a separate transducer. Both transducers convert this energy information into computer data. The data is then fed into a laptop computer where Carl analyzes the information to determine if the motor type is suitable for a given rocket shell.

In this segment, Carl demonstrates his skill in using manual equipment to form several components of the stand.

Basic Tools:

Centre lathe
Cobalt steel cutting tool
Cutting oil
Knurling tool
Micrometer
Horizontal band saw
Sand blaster
Vertical mill
CNC vertical mill
CNC lathe
MIG welder
C-clamps

Using a manual centre lathe (figure D), Carl creates a large custom bolt that secures the thrust arm to the base beam. The lathe works by spinning the part at a high rate of speed while engaging it with extremely hard cutting tools. After setting the aluminum stock in the lathe, he begins creating threads on one end.

Carl first reduces the diameter at the end of the stock to match the desired thread diameter. By manually traversing a cobalt steel cutter along the side of the piece, he slowly removes material (figure E). He checks the width frequently with a micrometer (figure F).

Figure E

Figure F

For the threads, he sets the lathe to an automatic traverse, which moves the cutter across at a steady rate. As the cutter traverses, he constantly applies cutting oil to keep the surface cool (figure G). Before removing the stock from the lathe, he tests-fits the threads with the corresponding nut (figure H).

Figure G

Figure H

To finish the bolt, Carl creates a gripping surface on the opposite end to enable hand-tightening in the field (figure I). After turning the bolt around in the lathe, he positions a knurling tool over the bolt end. Instead of cutting, this tool compresses and deforms the metal, which creates a diamond crosshatch pattern (figure J). As the bolt rotates, Carl keeps the knurling tool cool using cutting oil (figure K).

Figure I

Figure J

Figure K

Carl also uses the manual lathe to square up the cylindrical boot that fits on top of the stand. The boot is stabilized on the lathe with an implement called a steady vest (figure L). Before trimming the edges of the boot, Carl attaches two dial indicators, which measure tiny variances in movement (figure M).

Figure L

Figure M

If the dial indicators do not detect movement, than the rotation of the boot is true. He uses a cobalt cutter to square the edges (figure N). Then he secures it in the vertical mill and cuts a channel for a pressure hose (figure O).

Figure N

Figure O

Next, Carl begins to form the stand’s thrust arm and support base. He cuts sections of rectangular aluminum tubing to length on a horizontal saw (figure P) and strips off the rust using a sand blaster (figure Q). Then, for the thrust arm and base beam, he clamps two sections of tube together, and uses a vertical mill to square the ends (figure R).

In the next segment, Carl continues manufacturing the parts for his rocket motor test stand.

Figure P

Figure Q

Figure R