Altimeter location question...

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PGerringer

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For those of you don't know I'm building an elDiablo scratch. :) Anyway, there is several inches of air space in the Motor Mount Adaptor that could easily house an altimeter. So I wonder, being outside the actual motor mount, could the altimeter get too hot to function?

http://www.cybergatetech.com/phpgraphy/?display=Rocketry/elDiablo/img_2191.jpg

The altimeter would go on some type of holding aparatus right behind the fore CR. In the above pic, you can see where there is plenty of room. I also vented this area to the outside world. So, I'm not worried about air. The area that would hold the altimeter is really at the fore end of a 38/720 casing. So what do you guys think? Too hot?
 

rstaff3

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I have seen people mount altimeters in hatches down by the motor mounts. In fact, I'm planning to do so on my upscale Big Brute. I plan to make sure there's a heat barrier (read this 'slab of plywood') in addition to the altimeter mount. Also good ventilation ( a problem since it will be near the butt-end and I want to keep the exhaust out).

I most electronics these days is pretty tough. Here's some ops temperature data from some component data sheets:

Motorola barometric sensor - 125 degC
TI LMX58X op amp - 70 - 125 degC (depends on package)
Linear Tech ACD - 70-85 degC (ditto)
PIC processor - 125 degC (one example, may vary?)

These should be the most sensitive components on a typical altimeter, so my guess is we're OK. Hope this helps.
 

PGerringer

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Thanks, I feel a little more comfortable about it now.

Although, here is a secret (don't tell Carl): I like your idea of making a masking tape extention to the casing for more BP. I think I am moving in that direction. :)

But, when I make a hybrid adaptor, God willing, that is exactly where I'm going to put my altimeter.

So, when are you going to start on your Big Brute?
 

rstaff3

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I was thinking more like a small piece of junk tubing, split lengthwise and wrapped/taped onto the motor casing. Prolly many possibilities of what to use.

I have most of the major components for the Big Brute. Body/motor tubing came for LOC as part of my Descon 9 prize. Have picked up a LOC long 5.5" NC and had some custom CRs made. It's gonna have 1 38mm mount, 2 29's and 2 24's. Still need to work out the altimeter/ejection design for both a main charge and the airstarts.
 
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