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Railroaders' Nostalgia > Signal mast finials


Date: 09/09/18 09:54
Signal mast finials
Author: mile250

TO has a section for railFAN technology. I wish it had one for railROAD technology.
So, for all you signal maintainers out there: What was the purpose of finials on signal masts?
I thought the answer would be straightforward until I checked some seemingly reliable sources and found these claims:
  • To give the top a classy appearance
  • To prevent birds from perching and fouling
  • To serve as the initial contact point for a lightning strike




Date: 09/09/18 10:25
Re: Signal mast finials
Author: PHall

I'll believe the first two, but to serve as a "lightning rod"? Believe me a lightning strike is going to fry everything electrical in that signal. Lamps, motors, relays and all.



Date: 09/10/18 08:49
Re: Signal mast finials
Author: ButteStBrakeman

Glen,
I would have to agree with  P. The first two are plausible, but not the lightning rod.


Butte St Brakeman
 



Date: 09/10/18 10:25
Re: Signal mast finials
Author: jtwlunch

Keeping water, snow, ice out of the pole itself too.



Date: 09/15/18 19:21
Re: Signal mast finials
Author: rrman6

jtwlunch Wrote:
-------------------------------------------------------
> Keeping water, snow, ice out of the pole itself
> too.

And not just the pole (mast), but the flexible conduit leading the wiring to the motor housing, but most of all, keep these natures products from entering the relay cabinets below the mast as well.

These finials once fitted over the mast usually had a single bolt to lock it to the mast.  Most had some slack between the finial and the mast so they weren't entirely sealed as water tight.  I have one AT&SF that for some reason was made water tight by an appliction of asphalt sealant to the joint that was later painted over with the aluiminum paint.



Date: 09/15/18 21:35
Re: Signal mast finials
Author: PHall

When talking about electrical stuff, nothing is really "water proof". Water will find a way in. It always will.



Date: 09/22/18 09:23
Re: Signal mast finials
Author: GBW309

The finial usually overlaps the pole by 3-4 inches.  Unless you are in a hurricane, it's going to do a pretty good job of keeping water out of the pole. 

Dave



Date: 09/22/18 11:43
Re: Signal mast finials
Author: LarryDoyle

GBW309 Wrote:
-------------------------------------------------------
> The finial usually overlaps the pole by 3-4
> inches.  Unless you are in a hurricane, it's
> going to do a pretty good job of keeping water out
> of the pole. 

Wooden poles had their tops sawn or adzed at an angle, or peaked, or pointed so that rainwater would run off.  Very important to prevent water from standing on top of the pole causing rot.  This was especially true for utility lines, communications lines and streecar/interurban overhead.  The Milwaukees electrification used wooden poles right up to the end

Early railroad signals also used wooden poles, but metal quickly became standard construction.  The finial placed on top to kieep water out imitated the top of wooden poles.

The finial sat atop the pole, slipping over the outside of the pole, as illustrated below.

I've also included a drawing of a streetcar pole showing a cap (finial) that is insulated and has a screw-eye to support the trolley span wire.

-Larry Doyle






Date: 09/23/18 14:02
Re: Signal mast finials
Author: PHall

GBW309 Wrote:
-------------------------------------------------------
> The finial usually overlaps the pole by 3-4
> inches.  Unless you are in a hurricane, it's
> going to do a pretty good job of keeping water out
> of the pole. 
>
> Dave

You would be amazed how easily water can get in.  Fog or even condensation will get water inside. Maybe not fast or in large quantities, but it only takes a little moisture to do it's thing.
Moisture + copper + electricity = corrosion (aka wire cancer)



Date: 09/25/18 12:35
Re: Signal mast finials
Author: spnudge

Try birds, etc.

The finial would not let birds sit and crap all over or set up house keeping. There was just one or two set screws holding the tops on. Also, didn't want other critters making a home inside where it could jam the gears or block the rods from moving.  

Lightning would just melt and blow everything. There were "protectors" that kept high voltage from traveling down to the next signal but have no idea what their success was. I know if AC or high voltage was introduced on low voltage wires, it could weld the relay contacts together, making a signal stick in a green or yellow indication, even with an H-Head.



Nudge



Date: 09/25/18 19:51
Re: Signal mast finials
Author: PHall

spnudge Wrote:
-------------------------------------------------------
> Try birds, etc.
>
> The finial would not let birds sit and crap all
> over or set up house keeping. There was just one
> or two set screws holding the tops on. Also,
> didn't want other critters making a home inside
> where it could jam the gears or block the rods
> from moving.  
>
> Lightning would just melt and blow everything.
> There were "protectors" that kept high voltage
> from traveling down to the next signal but have no
> idea what their success was. I know if AC or high
> voltage was introduced on low voltage wires, it
> could weld the relay contacts together, making a
> signal stick in a green or yellow indication, even
> with an H-Head.
>
>
>
> Nudge

The protectors did their job by vaporizing and opening the circuit during a lightning strike.
Have replaced more then a few on telephone lines.



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