Nothing beats ground testing!

[Bruce R. Schaefer]

2-56
Clearance Hole = 3/32″
Tap Hole = 5/64″

4-40
Clearance Hole = 1/8″
Tap Hole = 3/32″

Thanks, guys. Great information. I was going to use (4) 2-56’s, but don’t want to take any chances, so I went up to (4) 4-40’s that most use at this level.

[Ken PlattnerParticipant]

For a 4/40:

Tap = #43 bit, or .089

[Bruce R. Schaefer]

Well, the online calculators say it will take 2.5 to 3 grams to sheer four 4-40’s with my volume, so I’ll start with 2 grams and no chute. Ken (xman) will give me a hand, and I promise, Ken, we won’t be standing in front of it, with its mass… not gonna happen. That nose cone will penetrate just about anything. We’ll figure something out. No hurry. I ordered another 8 Quickburst canisters… but it’s gettin’ about that time. After Oktoberfest most likely. I HOPE I don’t have videos to show any failures this time. 🙂 I really like Doug’s the best though. Man, what a setup!

[Anonymous]

….with my volume, so I’ll start with 2 grams and no chute.

Bruce, I have found **PROFOUND** differences in ground testing w/ and w/o the chute! In other words, if 2g works w/o the chute, that doesn’t mean it will work WITH the chute. I once ground tested a rocket 3-4 times and it was fine. I put a chute in, flew it, and it did not separate. I have always wondered if the chute absorbed or damapened the blast? Intuitively, I’d say the chute takes up volume which means the charge should be less. In practice, I recovered with a shovel. Note that the charges DID fire in that rocket, but it did not separate.

Be a lookin’ out!

J

[Bruce R. Schaefer]

Man, I’m so glad you said that, John! I’ve always tested with a chute, going with the premise that you MUST test the way the rocket will fly. I saw Doug’s video, and he didn’t use a chute. The chute does take up volume. Oh, man, now I gotta buy a chute that I may char. Isn’t this fun? 🙂

[Doug GerrardParticipant]

I saw Doug’s video, and he didn’t use a chute.

I did use a chute in the 2 gram test which was to deploy the main. I didn’t use the chute in the separation at apogee test.

Doug

[Bruce R. Schaefer]

Gotcha, Doug. Misunderstood. You DO have a VERY NICE setup. Very impressive.

[Author]

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