Here's a question that may have been previously answered.
The easiest way to test a motor is verticle with nozzle up. You could simply
dig a hole, and drop in a load cell with the rocket on top.The problem with
that is you are also measuring the changing mass of the propellant as the motor
is thrusting at the same time.Another problem with sugar motors is the
accumulation of KCO3 slag on the bulkhead that doesn't get blown out of the
nozzle...We had nearly 4" of hot molten slag on our bulkhead after our 12"
motor tests.
Testing horizontally does not measure the weight of the rocket, only thrust but
also has the issue of slag build up on the bottom side of the motor. Not an
issue provided your liner is able to take the heat. We have in the past
experienced burn-throughs when doing horizontal testing and nearly always on
the bottom side of the motor where slag accumulates. Also, Tripoli does not
like horizontal testing because the motor can fly cruise missle style is
something does wrong as shown in the video:
Eric Beckner 4 17 21 APCP CATO
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Eric Beckner 4 17 21 APCP CATO
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I try to do all my testing of motors (solid, liquid, and hybrids) in-flight
orientation vertically with the nozzle down. For sugar motors, this also helps
blow out the slag that would otherwise accumulate in the motor case. In such an
orientation, the motor would not move until enough thrust overcomes the weight
of the motor. We have thought about 'hanging' the motor on a
tension/compression load cell and thus seeing the amount of thrust used to
overcome the weight of the motor. After the burn the reading would return to
the weight of the motor minus the weight of the load cell.
We had not yet tried that method for recent testing and were simply using a
vertically mounted single BATES grain J-impuse sugar motor with a 65/20/15
KNO3/SB/SU formula nozzle down against a top mounted load cell. After a dozen
or so successful tests with various propellant formulas this one CATOed. The
load cell was mounted on a 1/2" thick angle iron support bolted to an Ibeam.
About two feet above that was a 1/4" angle iron support botted to the I-beam
used for testing hybrid motors. The nozzle blew out shearing off the bolts to
both supports.
The steel nozzle was found 7 feet away from the test stand after striking the
deflector shield and the concrete foundation. The 1/2" angle iron support was
found 40' away and the 1/4" angle iron support about 20 feet in the opposite
direction. The motor case took flight after taking out the angle iron supports
and was found about 200 feet away. The load cell has still not been found.
I'm including this as a precaution when testing motors of how much power a CATO
contains. Any of the four large pieces striking a person could easily have
caused injury or...and I've seen some people in videos testing motors in back
yards or even in the front yard with traffic driving by. Please exercise
caution and in a safe place when doing motor testing.
