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PVC AARD type device

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edwardw

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So I was in Home Depot and I saw some 3/4 PVC end plugs and some 3/4 couplers. Lightbulb came on. If I glue one plug into the coupler, then leave the other free, it could be pushed out by a charge. To keep it from moving though I need shear pins. So I bought two couplers and four plugs. Got home and glued a plug into the coupler. Then I sanded the other plug until it was a very nice and smooth fit. Then I drilled four hole for 1/16" Styrene rod to act as a shear pin. I've used this rod before on rockets for nose cones. Then I needed a way to attach the whole assembly to my bulkhead on my e-bay. I went and drilled a 1/4" hole through the end where the plug was glued. Then I ran a 1/4-20 bolt through the bulkhead and secured it. At the top I needed a connection point to secure the drogue to the rocket. I found a 1/4 cable crimper - a mini u-bolt. I put that in the other plug that is free to go where it wants. I assembled the unit and tested with 1/2g of 3F. BANG. That little piece sure gets going quick! I had it tied town and it went zooming into a tree and I had to pull it down. This was with all 4 shear pins in place. I'm hoping to static load it later, but I have to go get a bigger water jug to fill up.

Now for the obligatory picture....


Edward
 

Missileman

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Now that looks like a very effective and simple design.
I like it alot.
You should patent that idea before someone else steals it.
 

aksarben10

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How much weight/force will the shear pins take? I like the idea very simple and neat but it appears that it could be a bit touchy. You need to know what the deployment forces are going to be on the drouge and know what your shear pins will take.

I like it, I also like your other version with the plastic bolt. I have looked for bolts like that to try it but have not had luck finding them. This one is much easier to come up with the parts.

Thanks for sharing.

Scott
 

edwardw

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The shear pins took 50 lbs before they snapped. Not to bad for 1/16" styrene. I'm making another that will you 4-40 nylon screws. I'm sure that with the proper sized shear pins I can achieve what I want. Also, the rocket that this is going in weighs 5# loaded, so it's not a massive beast.


Edward
 

GL-P

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nice!!! I was thinking of something similiar but your design is much better (any probably easier to build) than mine. I gotta try that!!!
 

BlueNinja

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*raises hand*


do you have a diagram of how this will work?
 

edwardw

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I'll explain it first. This device is screwed down to my bulkhead on my electronics bay, which is secured to the rocket using some 6-32 well nuts (expansion type plugs). The effect I'm going after is dual deployment out of a single compartment. I can't do that with this rocket - not enough room. So I took the AARD device and made one out of PVC.

At apogee, the nosecone and a small drogue chute will come out. I'm using a charge that is placed above the main, but the main is protected by a d-bag and lots of dog barf. The other end of the drogue is connected to the small u-bolt on this device. That keeps it from pulling away. Another line is connected from the top of the main's d-bag to the u-bolt. At 900', the altitude I chose, the charge inside the device goes off. This lets the u-bolt and top come free and the drogue pulls out the d-bag and the main also. I'm using a 'freebag' technique so the nosecone and drogue come down by themselves and the main and rocket come down by themselves. I hope this makes a little clearer - if needed I can sketch something up.

Edward
 
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