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Madcow Torrent.

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Steven88

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Hello. I am wanting to launch my Madcow Torrent with chute release and discard the dual deploy for this flight. I am using the av bay as an open coupler and so have one long section of 48.5” from the top centering ring to nose cone. An ejection calculator calls for 4.21 grams of black powder. My charge well on my 38mm forward closure doesn’t even hold that much powder. Is that a sign that my rocket is too long for single ejection? I did extend it a couple feet from the stock kit.
 

Exactimator

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4.21 grams is a LOT of BP. I suggest ground testing and start with 2g, increasing 1/2 gram each test.
 

Nytrunner

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ya that was at 15 PSI
What led you to choose 15 psi?

The torrent is a 4" rocket last I checked. 15 psi will give you an ejection force of 175 lbs!

Try the calculation with ~8psi and see how much powder you need
 

Steven88

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The calculator recommends 10-15 psi and at the launch club they always say “blow it out or blow it up” so that’s the way I’ve been taught. 😂. Also, any time you have sheer pins you should aim higher than friction, fit. Am I correct?
 

Nytrunner

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If you're flying with single-break motor deployment, you can leave out the shear pins in the nose that you'd normally use for dual-deploy.

If you can pick up the nose and the rocket slowly slides off, your fit is fine for the flight. (And you don't need an overkill powder charge)

Rocket science works!
 

Rob702Martinez

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I learned the hard way about not using shear pins. Ruined 2 rockets in a weekend by the nose cone drag separating with interference/friction fitting. It works for some people, just wasn't working for me. I pin everything now. You are pressurizing a large volume. Would you he able to skip the payload tube?
 

Steven88

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Yes, that’s what I ended up doing. It made it a little short and less stable but flew ok.
 

Steven88

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So far I’ve never had trouble with friction fit but I’ve never flown over about 3,500’ and never over Mach. I do like to pin them if possible but it’s worked great for me not to so far on lower altitudes/slower speeds
 

timbucktoo

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I pretty much just use friction fit for motor deploy rockets only. The only time I would consider pins is if I had a really high acceleration motor. Regardless of the method you use, ground testing is always recommended.
 

rocketgeek101

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I am using the av bay as an open coupler and so have one long section of 48.5” from the top centering ring to nose cone.
Keep in mind that by doing this you will coat the inside of the coupler with ejection charge residue. Not great if you want to add electronics in it later on. I'd consider installing the bulkheads on the av-bay and just flying it with the bay empty, and having the rocket split in the middle to deploy the main (i.e. have the main chute in the lower section where the drogue would be on a dual deploy flight). This would also reduce the volume that needs to be pressurized substantially.
 

DaveRKP

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Keep in mind that by doing this you will coat the inside of the coupler with ejection charge residue. Not great if you want to add electronics in it later on. I'd consider installing the bulkheads on the av-bay and just flying it with the bay empty, and having the rocket split in the middle to deploy the main (i.e. have the main chute in the lower section where the drogue would be on a dual deploy flight). This would also reduce the volume that needs to be pressurized substantially.
Totally agree with rocketgeek101. I built my Torrent for my L1 cert flight and kept it single deploy with an empty av-bay with a Jolly Logic. Flying with the av-bay in place keeps the forward section clean from the ejection charges.

Torrent Level 1 Cert (2020-07-11).JPG
 

bclark989

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When I fly a DD rocket with motor eject instead, I still use the E-Bay bulkheads, so I'm only pressurizing the lower bay like you would for drogue deployment. Then you just rivet the upper airframe to the E-bay and the nosecone. Just make sure you don't put the parachute in the middle of that lower harness, otherwise its real easy for the two halves of the airframe to crash into each other during descent.

As for pins vs friction fit, just make sure you put static ports in all of your air frame sections. If you don't, the pressure differential on the way up will aid the drag separation. I have never pinned a single deploy rocket and never had a drag separation.
 
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