rocketboy242 Posted February 13 Posted February 13 Hey guys, can anyone suggest a cause/fix for a small fracture / chip of the fuel grain when the spindle is removed? The chip appears on the inside edge of the core for about 1/4 of the radius. It happens on both whistle and bp motors. The spindle is highly polished, waxed, with a continuous taper. I've tried different pressing pressures to no avail. Any help would be appreciated.
DavidF Posted February 13 Posted February 13 (edited) What size motors? How are you removing the motor, by twisting or by using a spindle puller? Have you tried waxing the spindle base as well as the tapered portion? Any pics? EDITED to add: Years ago a few of us had a similar problem, but I'd describe it more as radial cracking and crumbling of the first increment. We all had it at the same time of year- winter. I put it down to dry air. My solution was to press an increment of waxed BP propellant as the first increment. Perhaps a slightly moistened first increment would work just as well. Edited February 13 by DavidF Additional content
rocketboy242 Posted February 13 Author Posted February 13 Thanks for the reply DavidF, They are 1lb motors. I use a twist and pull motion by hand to remove the spindle. I did melt a small thin layer of wax on the spindle base and this didn't help. I agree to your hypotheses that it could be the humidity level. On close inspection of the main core length, it appears quite shiny and fracture free. Its that first pesky increment that is causing the trouble. All the motors seem to perform well, I'm just concerned that the increased irregular shaped surface area caused by the fracture will increase the burn rate and possibly cause cato's. I like your waxed bp. first increment fix. I will try it and get back with an update and pics. Cheers1
DavidF Posted February 15 Posted February 15 I just have to wonder about the spindle removal. Nozzled or nozzleless BP? I'm not super strong, but I don't think I've ever been able to twist and pull a 1 pound BP spindle by hand. How hard you pressing them?
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