[SML] S4 bench focus...

[Richard John Archer]

They make various sizes of magnesium anodes for boats…..maybe there's something there that would work or could be easily adapted.

DickA
TD, cornell U
On Jun 24, 2015, at 10:44 PM, Dale Farmer via Stagecraft 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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