Release mechanism

Im not sure if this is in the right section as its to with mechanical things but is used in aerial photography and atmospheric circles.

You have your platform attached to its balloon and you release them into the heavens but you have no predetermined release mechanism so it thing will go up and up and up and then more than likely plummit, tumble, breakup and splat. Poor platform it was only young.

Ive gone through some high altitude balloon setups only to find the release mechanism is non existant or unexplained. Here people are recommending servo driven systems but no one gives any details, pictures or diagrams. Rocketry us explosive bolts or CO2 which is a little OTT (apart from being really cool). I have found a blokes website that give some arduino based triggers using nichrome wire and some watch batteries which seems to be a pretty pimping idea given mass restrictions but I cannot be the only one thinking about this sort of thing.

What is your release mechanism?

If you do not have one, what would yours be if you did?

I'm looking for any idea really. A repository of ideas for this so myslef and others can expand upon this for future schemes

We're (czanso.com, I promise to put up a decent homepage before the launch :D) using a resistive wire (Manganine alloy, probably like Nichrome) as a hotwire cutter to slice through the nylon load line and release the payload. Its advantages are simplicity (it's really just a wire), weight (zilch), and reliability over a wide temperature range. Its major disadvantage is that it needs some juice to operate - for example our czANSO Cutdown Device needs 750 mA at 9 V for a successful cutdown. Not that much, but it might pose a problem especially when the cutdown might be needed - at the end of flight, when batteries are running dry.

A pyro cutter mitigates this issue by storing the heat energy in a small chemical charge instead of the battery - then only a very small impulse is needed to initiate it - 1 A at 9 V for about 5 ms, which can be easily provided by a capacitor. It's fatal flaw is that the compound we used (the only one I know how to cook :) is not exactly willing to burn at -60 °C, so instead of dealing with plasticized thermites we went all electric.

We have a bunch of pictures and videos from our cutdown device research session over here (in czech though, if you feel up for some google translatese, then here). The last picture shows a "CAD" drawing of the cutter, if you're interested.

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Jason Short July 30, 2010 at 6:26pm

A lot of people just put a piano wire through a pair of loops connected to a servo.
Overwatch July 30, 2010 at 4:48pm

We're (czanso.com, I promise to put up a decent homepage before the launch :D) using a resistive wire (Manganine alloy, probably like Nichrome) as a hotwire cutter to slice through the nylon load line and release the payload. Its advantages are simplicity (it's really just a wire), weight (zilch), and reliability over a wide temperature range. Its major disadvantage is that it needs some juice to operate - for example our czANSO Cutdown Device needs 750 mA at 9 V for a successful cutdown. Not that much, but it might pose a problem especially when the cutdown might be needed - at the end of flight, when batteries are running dry.

A pyro cutter mitigates this issue by storing the heat energy in a small chemical charge instead of the battery - then only a very small impulse is needed to initiate it - 1 A at 9 V for about 5 ms, which can be easily provided by a capacitor. It's fatal flaw is that the compound we used (the only one I know how to cook :) is not exactly willing to burn at -60 °C, so instead of dealing with plasticized thermites we went all electric.

We have a bunch of pictures and videos from our cutdown device research session over here (in czech though, if you feel up for some google translatese, then here). The last picture shows a "CAD" drawing of the cutter, if you're interested.

Home - czANSO! We are going to near-space...

czanso
James F. July 30, 2010 at 3:55pm

Hobbyking sells a servo driven system with everything you need.

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Release mechanism

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