Issus
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- Aug 27, 2012
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I've been trying to think of a better way to setup an AV bay than how I've been doing it with the two threaded rod rails running down the AV bay. I don't have a problem with it on 4" and larger rockets, but getting down to 54mm airframes with redundant dual deployment seems to be overly heavy for me.
I use centrifuge vials with grain of wheat bulbs in them as deployment charges. My track record is pretty bad, with a 10% failure rate, but its so cheap I don't care. I just use two altimeters and two sets of charges - easy and I've still maintained a 100% recovery rate.
I'm working on an idea for a rocket at the moment which i'm going to launch a prototype in bluetube using a 38mm motor before going carbon/glass and 54mm motor. As I'm going for performance, I'm trying to cut down weight where I can. To that end - this is what I've come up with.
Rather than using rails, I'm using a 1/4" eye bolt down one end, the sled plate will be epoxied to the AV bay end plate, and the nut for the eye bolt is embedded in the sled - the nut/eye-bolt assembly will also be epoxied in place. At the other end, I have two 1/4" bolts going to nuts embedded in the sled. The nuts in the sled will be epoxied in place however the bolts will be removable to facilitate access. The eye bolt on this end will be secured with a nut that is epoxied to the centring ring but will not touch the AV Bay sled.
In the past I've used "Eurostyle barrier terminal block"s before, however have had some difficulties with ensuring the tiny grain of wheat bulb wires are hit by the screw coming down inside the cylindrical assembly inside. To that end, I've gone with a two row 3 position barrier block - unfortunately I can't get a finer pitch than this off the shelf. Dual row is simply to make life easier when switching out vials - the altimeters always stay connected so there is no worry of a connection not being made properly on one wire in a group stuffed under one screw. The barrier blocks will be screwed in and sitting on a bed of hot glue "just to make sure"
I've mounted a voltage selection switch in the sled which will be JB welded in place. This keeps it out of the way and gives it plenty of clearance to the altimeters.
Bottom:
Blue box at the left is a 180mAh 2S lipo - 25-40C nanotech from HobbyKing, more than enough to light my globes up.
The bottom has an Entacore AIM-USB. I'm not a huge fan of either of these altimeters but they do the job well enough.
The battery will get Velcro and zip ties.
Given the 150+ G's this is simulated to pull with a J motor, the 6mm plywood sled will get a couple of layers of glass on it just to be sure everything stays together.
I use centrifuge vials with grain of wheat bulbs in them as deployment charges. My track record is pretty bad, with a 10% failure rate, but its so cheap I don't care. I just use two altimeters and two sets of charges - easy and I've still maintained a 100% recovery rate.
I'm working on an idea for a rocket at the moment which i'm going to launch a prototype in bluetube using a 38mm motor before going carbon/glass and 54mm motor. As I'm going for performance, I'm trying to cut down weight where I can. To that end - this is what I've come up with.
Rather than using rails, I'm using a 1/4" eye bolt down one end, the sled plate will be epoxied to the AV bay end plate, and the nut for the eye bolt is embedded in the sled - the nut/eye-bolt assembly will also be epoxied in place. At the other end, I have two 1/4" bolts going to nuts embedded in the sled. The nuts in the sled will be epoxied in place however the bolts will be removable to facilitate access. The eye bolt on this end will be secured with a nut that is epoxied to the centring ring but will not touch the AV Bay sled.
In the past I've used "Eurostyle barrier terminal block"s before, however have had some difficulties with ensuring the tiny grain of wheat bulb wires are hit by the screw coming down inside the cylindrical assembly inside. To that end, I've gone with a two row 3 position barrier block - unfortunately I can't get a finer pitch than this off the shelf. Dual row is simply to make life easier when switching out vials - the altimeters always stay connected so there is no worry of a connection not being made properly on one wire in a group stuffed under one screw. The barrier blocks will be screwed in and sitting on a bed of hot glue "just to make sure"
I've mounted a voltage selection switch in the sled which will be JB welded in place. This keeps it out of the way and gives it plenty of clearance to the altimeters.
Bottom:
Blue box at the left is a 180mAh 2S lipo - 25-40C nanotech from HobbyKing, more than enough to light my globes up.
The bottom has an Entacore AIM-USB. I'm not a huge fan of either of these altimeters but they do the job well enough.
The battery will get Velcro and zip ties.
Given the 150+ G's this is simulated to pull with a J motor, the 6mm plywood sled will get a couple of layers of glass on it just to be sure everything stays together.