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Date: Thu, 26 May 2005 12:26:59 -0600
From: Bob White <bob@bob-white.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] D-sub connectors - Prewired cables
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On Thu, 26 May 2005 09:20:32 -0700
"Al Gietzen" <ALVentures@cox.net> wrote:

>  
> 
> One thing to consider is that with a canard pusher you can't get a prewired
> 
> harness installed easily because the plugs won't go down the electrical
> 
> conduit. A harness could be installed during the fuselage construction, but
> 
> once the fuselage is built you either have to run the harness another way,
> 
> add a connector, or snip and resolder all the wires.
> 
>  
> 
> One easy solution is to use the gold plated, machined crimp-on d-sub pins.
> Put all the pins on, but pull the wire bundle to where it goes before
> snapping the pins into the connector. 
> 
>  
> 
> After doing all my avionics and EFIS plugs with the gold plated crimp-on
> D-subs, I got to love them.  Quick easy, and with the special D-sub crimp
> tool; very secure connections. Snap them into the connector after making and
> checking the crimp.
> 
>  
> 
> I'm recommending that Tracy go that route.  Yeah, it takes a good tool ($44
> t Aeroelectric
> http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?9X358218#RCT-3)  I
> believe in soldered connections for all critical leads that carry much
> current, but the risks involved in soldering those little solder-socket
> d-subs that are already in the connector - I don't think so. 
> 
>  
> 
>  It is especially important on the EM2 P-1 connector because the TC wire
> does not solder well.  Tinned copper works OK, but the TC wires do not form
> a eutectic at the joint, and you only get a 'mechanical' connection anyway.
> I found I had to use additional acid to get the solder to wet out on these
> wires - risk of corrosion in the future. If I were doing that one over, I'd
> toss that connector and get a new one with the plated crimp-on pins.
> 
>  
> 
> Any seconds to that motion (Tracy needs a little more pressure; don't ya
> think :)
> 
>  
> 
> Al
Hi Al,

I looked at the crimp connectors when I started thinking about how to
do this.  The only problem with them is expense.  The pins are about
26 cents each.  Total cost for each connector is 3 or 4 times what a
gold plated solder cup connector goes for.  I have the tool and can make
them if needed.  Not too bad for each, but when looking to buy 20 or 30
connectors at a time, it's noticable.

If you want to connect the thermocouple wire to a solder cup, I think
it would be better to make a mechanical transition first so that you
have a copper wire to solder.  What you're really doing in either case
is making a second reference thermocouple joint at the point of
transition.  It won't be a very good thermocouple either. Fortunately
the measured temperatures are high enough that the poor reference
doesn't make a lot of difference.

Bob W.

-- 
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