[Collins] John Bowers <k9utk at one-eleven.net> Subject: Help
Jerry Boman
mdg11fbf at gmail.com
Thu Jan 6 15:31:17 EST 2011
JB weld quickset (5min set), quality masking tape, files, sandpaper (wet/dry
400, 600, 1200), plastic polishing compound, patients and elbow grease. 73's
Jerry
On Thu, Jan 6, 2011 at 12:00 PM, <collins-request at mailman.qth.net> wrote:
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> 1. Help (John Bowers)
> 2. Re: Help (Dr. Gerald N. Johnson)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Wed, 05 Jan 2011 15:17:50 -0600
> From: John Bowers <k9utk at one-eleven.net>
> Subject: [Collins] Help
> To: collins at mailman.qth.net
> Message-ID: <4D24DFFE.8030607 at one-eleven.net>
> Content-Type: text/plain; charset="iso-8859-1"
>
> We are building up a 51S-1 from parts we have collected over
> the last couple years. However, we have a weighted main
> tuning knob that is damaged. We have been unable to locate
> another knob and so are looking for info on how to repair
> the plastic crown part of the knob. The knob has the finger
> tip hole feature and the outside half of that hole feature
> is chipped off and missing. Otherwise it is complete. Our
> first thoughts are to look for something like black bondo
> used to repair auto bodies. Sure would like some advice or
> to be referred to an expert in these matters. This weighted
> knob has a nice feel to it when compared to the unweighted
> version.
>
> Thanks for you help in advance
>
> John, K9UTK
>
> ------------------------------
>
> Message: 2
> Date: Wed, 05 Jan 2011 20:17:16 -0600
> From: "Dr. Gerald N. Johnson" <geraldj at weather.net>
> Subject: Re: [Collins] Help
> To: collins at mailman.qth.net
> Message-ID: <4D25262C.8070505 at weather.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Weighting an unweighted knob isn't difficult. Forming a new finger tip
> hole from bondo would seem to be difficult. At best Bondo type products
> take several applications to build up thickness, else they warp and
> typically they give you three minutes to mix, apply and smooth. After
> that you smooth by sanding or grinding. You'd want something that would
> polish too otherwise you'd have to try to get a shine by glossy paint.
>
> It might be easier to find some solid black plastic and carve (with a
> lathe) a new finger piece, after using a milling cutter to remove the
> whole finger hole leaving a space for a nearly symmetrical replacement.
> You might want to mount the knob off center in the lathe spinning on the
> axis of the finger hole so you could carve the remains away with some
> shape, not just straight back.
>
> To weight an unweighted knob, you need some lead shot (BBs at a
> Wallyworld sports counter), some slow setting pourable epoxy, and some
> tubing to protect the set screw holes. Probably have to drill from the
> outside and a little bit into the hub at each set screw to take brass or
> plastic tubing. Nice if its a press fit. Then you fill with lead shot
> and anchor it by pouring in the liquid epoxy, though with a slow seeting
> epoxy, it might be better to mix the lead shot into the epoxy and then
> work the combination into the back of the knob. Or likely you could pour
> some very lot temperature melting point metal after protecting the set
> screws. Look at McMaster-Carr for lumps of those metals www.mcmaster.com
>
> I don't know how Arnie Spielbauer got the first one of those knobs made,
> probably made a drawing and sent it to the model shop and waited for it
> to appear a few days. I'd have turned a finger piece and then machined
> part of the original know away to all epoxying the new finger piece into
> place. Or I'd have started with a big enough lump of bakelite to have
> carved the whole thing with lathe, mill, files and polisher.
>
> 73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.
>
> On 1/5/2011 3:17 PM, John Bowers wrote:
> > We are building up a 51S-1 from parts we have collected over the last
> > couple years. However, we have a weighted main tuning knob that is
> > damaged. We have been unable to locate another knob and so are looking
> > for info on how to repair the plastic crown part of the knob. The knob
> > has the finger tip hole feature and the outside half of that hole
> > feature is chipped off and missing. Otherwise it is complete. Our first
> > thoughts are to look for something like black bondo used to repair auto
> > bodies. Sure would like some advice or to be referred to an expert in
> > these matters. This weighted knob has a nice feel to it when compared to
> > the unweighted version.
> >
> > Thanks for you help in advance
> >
> > John, K9UTK
> >
> >
>
>
> ------------------------------
>
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> End of Collins Digest, Vol 81, Issue 2
> **************************************
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