Detecting Motor Burnout

Hi there,

Has anybody experimented with using a microswitch or similar at the top of a motor to detect burnout, or does pretty much everyone stick with accelerometers?

wetmelon said:

Hi there,

Has anybody experimented with using a microswitch or similar at the top of a motor to detect burnout, or does pretty much everyone stick with accelerometers?

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For what? Staging? Airstarts?

I'd just use accelerometers. You get fun data that way.

UhClem said:

https://adeptrocketry.com/ES231MLHds.htm

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Hmm. That's more clever than mine. This uses an inertial rod to press the microswitch... I was just going to have the motor slide slightly in the tube.

wetmelon said:

Hmm. That's more clever than mine. This uses an inertial rod to press the microswitch... I was just going to have the motor slide slightly in the tube.

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Which motor? The booster motor will always be trying to go forward: during boost for obvious reasons, and during coast because the rocket is experiencing drag and the motor is not.

CarVac said:

Which motor? The booster motor will always be trying to go forward: during boost for obvious reasons, and during coast because the rocket is experiencing drag and the motor is not.

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I... right. I always underestimate the drag forces on the rockets. They are certainly significant, aren't they?

Some rockets will see almost as much deceleration on burnout as they saw in boost depending on airframe diameter and speed, almost all of that is drag. I've had 80G decelerations on smaller rockets when the motor burns out.