Tuesday, August 10, 2010
Sugar Motor Testing [not all sweet]
Black crescent at bottom of guage
window is probable damage.
Instant On! Ignitor wires inflight,
Guage needle is still on zero.
Burnout. Foreground smoke
came out of guage face
Expelling a bit of casting tube.
Blackened guage guts hanging out.
In order to evaluate possible changes to sugar motor recipes, I developed a new shorter motor that would be more economical to operate. It helps that I was given a damaged reload case [Thanks Ray!]. My long motors use two 6 1/8" fuel slugs, unfortunately the short motor, after repair, only fits 5 1/4" of fuel. An even 50% would've been nice, but this is close enough, and it was a free motor.
Late last year I made 4 pairs of reloads, all physically the same, but each pair has a somewhat different formula. All are moonburners since they burn twice as long. Eventually some will go to a thrust stand, but IMO, chamber pressure tests are initially more important. It's good to know what even works before tieing up [or risking] a high dollar digital thrust stand.
I made a new nozzle with a 3/16" throat that would be used with some of the new grains, especially the baseline formula. Being virgin territory, none of these reload kits have the
nozzles listed on the labels like I do with the larger mature reloads. On Feb, 20 2010, the morning of the test, I picked the new 3/16" nozzle and installed it with reload #1 rather
than with reload the mildest. Reload #1 was a hotty and should've been tested first with a 1/4" or even 5/16" nozzle. The motor survived the test but barely. Probably only because it trashed the guage and was blowing out both ends. As it is, it severely belled the nozzle washer and crumbled the corners of the nozzle where it was pressed into said newly angled washer. Despite the short foliage and limited dipersal angle, we never did find the polycarbonate guage window. There is evidence that the pressure guage was damaged previous to this test attempt.
The hydraulic test stand has been cleaned and is getting rebuilt. Besides the new & better guage, it's getting a grease fitting and a brake bleeder valve. Instead of filling the stand with brake fluid as before, I'm going to use grease. This will allow for easier transport of the stand and with a good grease gun I should be able to use the stand to pressure test motor case materials and other components.