[SML] S4 bench focus...

[Steven Hood]

The bimetal reaction was the other thing I thought of, but I was wondering 
why it was only happening in the 36 degree fixtures... my manufacturing 
professors warned me about that...

Steven R Hood
310.756.3555



On June 24, 2015 7:44:24 PM Dale Farmer via Stagecraft 
<stagecraft at theatrical.net> wrote:

> On 6/24/2015 6:21 PM, Steven Hood via Stagecraft wrote:
> > Lighting folks,
> >
> > Have any of you had an issue with the outer (XY) knob/nut seizing the
> > aluminum hub casting? We have... I've had to drill out 3 of them this
> > year - all from units that had been assigned 36 degree lenses. It seems
> > like that hub casting is heating up more from having to pull the Z
> > adjustment so far into the reflector and seizing on the outer nut as a
> > result. Is there some way to prevent that deformation?
> >
> > TIA,
> > Steven R. Hood
> >
> >
> > ____________________________________________________________
> > For list information see <http://stagecraft.theprices.net/>
> > Stagecraft mailing list
> > Stagecraft at theatrical.net
> > http://theatrical.net/mailman/listinfo/stagecraft_theatrical.net
> >
> It happens.  The only way to prevent it is to go in and unscrew the
> thing a couple of turns and retighten it every so often.  I've
> experimented with various high temp lube compounds, but haven't really
> gotten results yet.   My confidence is not high there is a reasonable
> solution.  It's bimetal corrosion between a steel nut and an aluminum (I
> think) casting.  So short of putting a magnesium sacrifical anode
> someplace on the light, that's not something you can stop.  (By the way,
> if anyone has a source of magnesium that is in the form of standard
> sized washers or nuts, I do have some gear that I do want to provide
> some sacrifical anodes on, but the only thing I have found is boat
> propeller nuts, which are way too large.  )
>
> If you have one that is seized up, and you have a couple of days, you
> can take a q-tip and apply some penetrating oil to the threads and let
> it sit and soak in, giving it a good hard attempt to unscrew it twice a
> day, and adding more penetrating oil after each failure.    Don't forget
> to degrease it well once you have it apart, or you are gonna get some
> nasty smells from it the first time it is used.
>
>    Or you can buy the replacement casting and a replacement plastic
> ring, because the plastic ring around the outside of the nut also gets
> broken when you put the big pliers on to unscrew it.  Which one depends
> on how much you are paying for parts and labor and how many spare lamp
> caps you have on hand.
>
> --Dale
>
>
> ____________________________________________________________
> For list information see <http://stagecraft.theprices.net/>
> Stagecraft mailing list
> Stagecraft at theatrical.net
> http://theatrical.net/mailman/listinfo/stagecraft_theatrical.net