[SML] S4 bench focus...

[e-mail frank.wood95]

Bi-metallic reactions take place only in the presence of an
electrolyte liquid. I like to think that such liquids woild be absent
from a lighting rig. The sacrificial magnesium anodes fitted to
sea-going craft provide a more attractive home for the electrons,
being eaten away in the process of protecting the steel, brass, and
bronze components immersed in sea-water.

What you should try is the copper-graphite gunge sold as anti-seize
compound for soldering iron bits. I have found this very effective on
shutters and iris diaphragms in vaious luminaires. Soldering irons get
much hotter (I hope!) than any part of a luminaire.

On 25 June 2015 at 14:44, Steven Hood via Stagecraft
<stagecraft at theatrical.net> wrote:
> 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
>> >
>> >
>> > ____________________________________________________________
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>> >
>> 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
>>
>>
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>
>
>
>
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-- 
Frank Wood