[roc-chat] Re: roc-chat Digest V1 #141
- From: John Kennedy <john@xxxxxxxxxxx>
- To: roc-chat@xxxxxxxxxxxxx
- Date: Wed, 24 Aug 2011 16:05:55 -0700 (PDT)
I'm not too familiar with the electronics used in rockets (yet) but I expect
most of it to be DC current (to set off a charge etc.). If it is the case that
DC is of most interest then there is no skin effect, which is why the NASA page
I sent out earlier shows larger current ratings for solid over stranded. If it
is really A/C, then skin effect is there, but unless we're talking MHz or GHz
then even then the skin effect is negligible.
I certainly would agree though that stranded is easier to work with if you
don't
mind the weight increase for needing a larger AWG.
I'm happy to be corrected on the use of A/C in rocketry, one of the reasons I
subscribe is so that I can learn more about the sport.
John
----- Original Message ----
From: "veronica@xxxxxxxxxxxxxxxxxxxx" <veronica@xxxxxxxxxxxxxxxxxxxx>
To: roc-chat@xxxxxxxxxxxxx
Sent: Wed, August 24, 2011 3:43:33 PM
Subject: [roc-chat] Re: roc-chat Digest V1 #141
Hi Richard,
You are right for choosing stranded wire as it typically will carry more
current
for a given gauge since there is more surface area (electrons like to flow on
the surface).
I look at the temp concern as follows: the motor tubes (mounts) are typically
classified as class 'A' materials (cardboard) which means they have a flash
temp
around 400 deg F. So, if you don't see charring in the motor tube (and I
haven't) then the outside temp is far less than that. Cardboard (and similar
materials are a descent insulator, so, I would have great confidence at a
rating
of 90 C.
I hope this helps. - Veronica
Sent via BlackBerry from T-Mobile
-----Original Message-----
From: FreeLists Mailing List Manager <ecartis@xxxxxxxxxxxxx>
Date: Wed, 24 Aug 2011 11:52:54
To: roc-chat digest users<ecartis@xxxxxxxxxxxxx>
Reply-to: roc-chat@xxxxxxxxxxxxx
Subject: roc-chat Digest V1 #141
roc-chat Digest Wed, 24 Aug 2011 Volume: 01 Issue: 141
In This Issue:
[roc-chat] Wire for High-Powered Rockets
----------------------------------------------------------------------
From: Richard Dierking <redierking@xxxxxxxxxxx>
Subject: [roc-chat] Wire for High-Powered Rockets
Date: Wed, 24 Aug 2011 15:52:41 +0000
When I started wiring electronics for rockets, I purchased wire from Radio
Shack. I know a little about household wiring, but not much about low
voltage/DC stuff. Previously, I heard that shorter distances or much larger
gauge wire must be used for DC vs. AC. Also, it seemed logical to use stranded
wire instead of solid. I think that all wiring in vehicles is stranded. I just
kind of fell into using 20 ga stranded wire because it seemed heavy enough to
put up with some abuse but small enough for the hook-ups to the terminal blocks
on PC electronics. Now, because I need many different colors of wire, I'm
purchasing at a local electronics business that receives small rolls (25' and
100') of respooled wire. I'm assuming they're getting the respooled stuff from
businesses that just didn't need that 10,000' or whatever they had. There's
lots
of different types of wire at this place, and I'm wondering if I should be more
careful about the wire I purchase. For example, I just
bought some 20 ga stranded that has PVC coating, and another that listed the
temp on the roll as 90 degrees C. The PVC coated wire was a little expensive,
and the 90 C stuff seems a little low on the temp. Also, they have some
"Aircraft grade" stuff that's really expensive. I have some other wire that's
listed as 105 C. Should wire passing by the engine case for air-starts be
further insulated? What's the size and best grade for high-power rockets? Your
thoughts on this would be greatly appreciated. Thank you,Richard Dierking
------------------------------
End of roc-chat Digest V1 #141
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