Who knew designing rocket motors from scratch would take so long? But..I finally think I am ready for a compression test next week with the full load cell test stand. I was originally using Elmer's Glue as a binder, but further tests revealed the Elmer's glue actually substantially inhibited the combustion and ignition (motors took forever to ignite, and then burn at a low rate for a minute or so...way too long when I want a burn of at max 2 seconds). I speculate that since Elmer's glue is water-based, it is somehow degrading the propellant.
I thus moved to an organic binder, a nasty smelling contact cement I bought at the local hardware store that is used to apply linoleum to floors. The movie below shows a mixture of 25 g pyrodex, 3/4 ounce of the binder, and 10 g sodium bicarbonate (baking soda). After baking in the oven at 200 degrees for about a week, it was sufficiently dry to do a burn test. It took 5/6 of a second to burn (measured via the video time), which may be short enough to provide a good level of thrust for the rocket but long enough that the risk of overpressurization is low. Last night I gave myself a headache making some more motors (that binder glue is nasty), but stayed tuned for next week when fellow gearhead and garage guru Dr. Mark Lehmkuhle comes to Ann Arbor for a week! We'll finally get that static test up and running with the new motors!
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