[time-nuts] WG mounting h/w (3)

J. Forster jfor at quik.com
Thu Sep 23 02:41:49 UTC 2010


WG flanges are brass or aluminum. Dowel pins are case hardened steel. For
all practical purposes, they do not wear.

-John

================


> Robert,
>
>
> Many apologies for giving you the "big snip" (!) - replying to TN postings
> when receiving via "Digest mode" leaves room for such mishaps.
>
> I'm not familiar with 5/32" dowels or how well they fit in WG mounting
> holes. One major problem is European IEC & US-MIL spec'd flanges have
> varying size holes!  5/32 is 0.156 - this dowel may/may not fit WR75
> (0.144 or 0.161) but will be "loose" on WR90 (0.169).  Then there's metric
> & imperial variations ...
>
> What I can say with confidence that if you're building a WG run with 20-30
> flanges (ie an HPA hybrid combiner) using disparate makes of hardware and
> don't take anal care with tapered pins on each and every joint, you <will>
> end up with dB's of ppk ripple when the assembly is swept end-end.  This
> is well-nigh impossible to reduce without re-aligning every flange.  If
> the system has only a few mating flanges, other methods may be OK.
>
> I can appreciate how shoulder screws reduce the degree of craft assembly
> skill and assembly time required - certainly less messy than pins !  Thick
> flanges don't seem to be in common use in satellite earth stations.   (BTW
> - do dowels wear with use?)
>
> Rgds,
>
>
> Kit
> VK2LL
>
> *****************
>
> Message: 4
> Date: Mon, 20 Sep 2010 18:44:37 +0000 (GMT)
> From: Robert Atkinson <robert8rpi at yahoo.co.uk>
> Subject: Re: [time-nuts] WG mounting h/w (2)
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Message-ID: <750194.71696.qm at web27108.mail.ukl.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> I think you are a snip too soon. My original post said "If you have to use
> screws, at least align two diagonal holes with 5/32" dowels while nipping
> up the ?first two screws". Taper pins are also OK of the taper is slight
> and flanges are not too thick. Don't tighten the first two screws too
> tight at first to aviod warping the flange.?In aircraft installations I've
> designed have used shoulder screws because they were specified by the
> equipment manufacturer.
> ?
> Robert G8RPI.
>
>
> --- On Mon, 20/9/10, Kit Scally <kScally at BYTECAN.com.au> wrote:
>
>
> From: Kit Scally <kScally at BYTECAN.com.au>
> Subject: [time-nuts] WG mounting h/w (2)
> To: "time-nuts at febo.com" <time-nuts at febo.com>
> Date: Monday, 20 September, 2010, 9:19
>
>
>
> Hi,
>
>
> Well, still not strictly, strictly true !?
> In Ku & K? band earth stations I've worked in, I've never seen shoulder
> screws used, although the equipment used was mainnly from the USA.?
> Next to you precision adaptors, SMA torque wrenches etc in your personal
> goodie box are sets of tapered pins, about 35-40mm long - that fit various
> diameter WG mounting holes (the old metric vvs Imperial issue again).
>
> You insert a pair of pins on diagonal corners then add bog-standard SS
> hardware to the opposite diagonals & tighten.? The tapered pins are then
> removed and replaced with another pair of screws/nuts.? This ensures
> absolute (?) internal WG slot alignment.? There are a few variations on
> this theme if you must have absolutely minimum RL within that section of
> guide or if one guide face is threaded.? Hex-headed bolts are usually
> used.
>
> That may explain why shouldered bolts are seldom seen.
>
> Tapered WG pins fall into the 99.9999% unobtainium class of materials.
>
>
> Kit
> VK2LL
>
> Message: 2
> Date: Mon, 20 Sep 2010 14:58:41 +0000 (UTC)
> From: k6rtm at comcast.net
> Subject: Re: [time-nuts] WG mounting h/w (2)
> To: time-nuts at febo.com
> Message-ID:
> 	<324993853.1018422.1284994721127.JavaMail.root at sz0110a.emeryville.ca.mail.comcast.net>
>
> Content-Type: text/plain; charset=utf-8
>
> Another mystery solved!
>
> My (late) father-in-law spent most of his career at Varian-Eimac, mostly
> working on TWTs, BWOs, and the occasional magnetron. In one batch of his
> goodies, along with the H&S SMA torque wrench, was a little box with some
> tapered metal pins! I've wondered what those were for, and now I know!
>
> He was very happy when his daughter brought home someone who knew what
> vacuum tubes were, even if he did think that the RF work I did as a ham,
> even the 144 and 440 MHz stuff, was still practically DC...
>
> Bob K6RTM
> ------------------------------
>>>snip
> ------------------------------
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