Searchlight signal build?

This forum is dedicated to Riding Scale Railroading with propulsion using other than steam (Hydraulics, diesel engines, gas engines, electric motors, hybrid etc.)

Moderators: Harold_V, WJH

rkcarguy
Posts: 475
Joined: Tue Aug 22, 2017 10:33 am

Searchlight signal build?

Post by rkcarguy » Fri Sep 15, 2017 12:07 pm

I'm going to build a few searchlight signals similar to this one below. As always, building in quantity makes it worth it for having parts laser cut and machined instead of doing the one-two off builds on my own from scrap bin finds by hand. Chime in if you'd be interested. I'll certainly build one first so everyone would see what they are getting.
These would be fabricated steel of which I would shot blast the bases to give a cast appearance, and contain 10mm R-Y-G 12 volt LED's in the head. I'll probably simulate hinges on the door but screws will hold it in place. Target and sunshade would be ABS plastic.
As for scale, a 1-1/2" scale fabrication of this signal is only about 24" tall with a 4" target and 1" lens, and in 2" scale(mine), about 32" tall with a 5" target and 1-1/4" lens. Being there are giant people riding on these trains, would we want to upsize them a little more?

http://www.redoveryellow.com/signals/mi ... _davis.jpg

User avatar
BigDumbDinosaur
Posts: 583
Joined: Tue Jun 28, 2011 9:19 pm
Location: Midwestern United States

Re: Searchlight signal build?

Post by BigDumbDinosaur » Fri Sep 15, 2017 6:16 pm

rkcarguy wrote:...contain 10mm R-Y-G 12 volt LED's in the head.
I question the use of a 10mm LED in this application. Even the super-bright ones don't produce all that much output, and are not likely to be clearly visible in bright sunlight without sophisticated optics to shape and focus the beam.

The (full size) searchlight signals I worked on in the distant past had a rotating lens array in between the incandescent light source and the objective lens. The latter is what shaped and focused the beam, whereas the rotating lens array had the three colors. These contraptions would sometimes get stuck between positions in cold weather, causing a dark signal and mainline tie-ups. When I designed the signal system at the Illinois Live Steamers I did not even consider using a searchlight design due to the mechanical components. I did concoct a design that used three colored LEDs and a set of prisms to direct their light to the objective lens. However, I nixed the idead due to the increasing complexity and went with the three-indicator design that is most common in modern practice.
Target and sunshade would be ABS plastic.
That material doesn't hold up well in this sort of application—been there, done that. When I fabricated the signals at the Illinois Live Steamers I used steel for the faceplate and shades. The shades are welded to the faceplates and the assembly was blasted and painted with a flat black epoxy finish for durability The signal heads and masts are silver grey, like the prototype). They've now been in service for more than 10 years and still look good.
As for scale, a 1-1/2" scale fabrication of this signal is only about 24" tall with a 4" target and 1" lens, and in 2" scale(mine), about 32" tall with a 5" target and 1-1/4" lens. Being there are giant people riding on these trains, would we want to upsize them a little more?
The 24 inch height is okay—that's what we used at the ILS, and the indicators we used are 1 inch high intensity LED panel lamps, which are easily visible at several hundred feet in bright sunlight. The one change that I suggest is you oversize the target to make the signal more discernible at a distance—human vision doesn't scale.
Science makes it known. Engineering makes it work.

rkcarguy
Posts: 475
Joined: Tue Aug 22, 2017 10:33 am

Re: Searchlight signal build?

Post by rkcarguy » Fri Sep 15, 2017 6:37 pm

Thanks, feedback noted!
I'm thinking these would be more for a smaller operation like mine where I'll have 800-1000' of track and maybe 4-5 blocks at the most, where visibility wouldn't be much more than ~80' due to terrain and tree's anyway. I also failed to mention that I'd planned on using 2-3 of each color LED for increased output and "backup" so if one burns out the color still operates, just limited to how many I can fit behind a prototypical size lens.
I was considering the ABS for it's ability to jig and router the funny shaped sunshade, and then scuff and paint to prevent UV issues with the plastic, but steel is an option for sure. I think my main issue is our laser cutters are busy and several weeks out which has me looking for more DIY options.
I do want to put them behind a lens, which is proving hard to find. I've been looking at some glass 1/2 ball rounds and such trying to figure out a direction there without getting too custom.

User avatar
neanderman
Posts: 570
Joined: Mon Jan 09, 2012 7:15 pm
Location: Cincinnati, Ohio, USA

Re: Searchlight signal build?

Post by neanderman » Sat Sep 16, 2017 12:35 am

What size lens are you thinking?
Ed

Le Blond Dual Drive
US-Burke Millrite MVI
Atlas 618
Files, snips and cold chisels

Proud denizen of the former "Machine Tool Capitol of the World"

rkcarguy
Posts: 475
Joined: Tue Aug 22, 2017 10:33 am

Re: Searchlight signal build?

Post by rkcarguy » Sat Sep 16, 2017 1:50 am

I'm thinking of going with about a 1-1/2" lens and a 6-7" target diameter. USS&S's specs are still online, they say it's a 10" lens and a 30" diameter target in full scale.

User avatar
BigDumbDinosaur
Posts: 583
Joined: Tue Jun 28, 2011 9:19 pm
Location: Midwestern United States

Re: Searchlight signal build?

Post by BigDumbDinosaur » Sat Sep 16, 2017 9:24 pm

rkcarguy wrote:I'd planned on using 2-3 of each color LED for increased output and "backup" so if one burns out the color still operates, just limited to how many I can fit behind a prototypical size lens.
Unless driven beyond their recommended ratings, most LEDs will not fail in their rated lifetime, which is 50,000 to 75,000 continuous hours. More likely, the ballast resistor used to control the LED current will go south, which is avoidable by using carbon film or metal film resistors.

A 10mm LED is ~0.400 inches in diameter, so I don't know how you plan to get two to three of them in each color behind a 1-1/2 inch lens. Also, how do you plan to reconcile the disparate light sources for each color into a single, focused beam?
I was considering the ABS for it's ability to jig and router the funny shaped sunshade, and then scuff and paint to prevent UV issues with the plastic, but steel is an option for sure. I think my main issue is our laser cutters are busy and several weeks out which has me looking for more DIY options.
ABS will last in the short-term, but its main enemy will be heat absorption from the sun. In a steel design, the target is easy enough and could be made with a hole saw for the center opening and some patient sawing and sanding for the periphery.

As for the shade, the ones I did for the ILS were made from 1-1/2 inch exhaust pipe tubing gotten from a local muffler shop. I attached the drawing so you can get some ideas on how to make it. These shades were made to work with 1 inch diameter LED indicators.
shade_faceplate.gif
Faceplate Shade
I do want to put them behind a lens, which is proving hard to find. I've been looking at some glass 1/2 ball rounds and such trying to figure out a direction there without getting too custom.
Edmund Optics might be a possible source for a lens.
Science makes it known. Engineering makes it work.

User avatar
neanderman
Posts: 570
Joined: Mon Jan 09, 2012 7:15 pm
Location: Cincinnati, Ohio, USA

Re: Searchlight signal build?

Post by neanderman » Sat Sep 16, 2017 10:45 pm

I thought of Edmund, as well, but upon looking I don't see what I think you'd want, which is a Fresnel. They have some, but nothing in the 40mm diameter -- lots of plano-convex, but not even any concave-convex.
Ed

Le Blond Dual Drive
US-Burke Millrite MVI
Atlas 618
Files, snips and cold chisels

Proud denizen of the former "Machine Tool Capitol of the World"

rkcarguy
Posts: 475
Joined: Tue Aug 22, 2017 10:33 am

Re: Searchlight signal build?

Post by rkcarguy » Sun Sep 17, 2017 12:05 am

I pulled out an old miniature band saw today and revived it with a new blade and guides, and it cuts aluminum very accurately and I can turn about a 2" radius before things start to whine. I think these heads will be aluminum. I should be able to jig up a chunk of 1-1/2 aluminum pipe for the sun shade(the real profile is actually a radius cut into the pipe from the end), and then just saw the outside edge and hole saw the center.
I've got some convex "lenses" on the way, we'll see how they look when they get here.
The LED's are cheap enough, I'm going to play with a few different kinds behind the lens and see how they perform. Once dialed in, I want to create a round "LED sheet" that will fit into the back of the pipe and then either bed them and the wiring in epoxy or black silicone.

User avatar
Erskine Tramway
Posts: 191
Joined: Wed Sep 10, 2014 4:13 pm
Location: South Dakota
Contact:

Re: Searchlight signal build?

Post by Erskine Tramway » Sun Sep 17, 2017 1:14 am

rkcarguy wrote:I do want to put them behind a lens, which is proving hard to find. I've been looking at some glass 1/2 ball rounds and such trying to figure out a direction there without getting too custom.
At Sandley's, we used to get our 1-1/2" diameter Fresnel lenses for class lamps, markers and signals from Kopp Glass Company. Can't say if they're still in business or not.....or how many you'd have to buy at once :shock:

Mike
Former Locomotive Engineer and Designer, Sandley Light Railway Equipment Works, Inc. and Riverside & Great Northern Railway 1962-77
BN RR Locomotive Engineer 1977-2014, Retired

User avatar
Atkinson_Railroad
Posts: 159
Joined: Mon Jun 08, 2015 6:27 pm
Location: Michigan
Contact:

Re: Searchlight signal build?

Post by Atkinson_Railroad » Sun Sep 17, 2017 2:38 pm

Here’s the upper half of PLATE B-2800 from an old US&S catalog that may be helpful.
The single instrument case searchlight shown at "B" looks to match the reference photo
at the beginning of the thread fairly close.

John
Attachments
PLATE B-2800.jpg

rkcarguy
Posts: 475
Joined: Tue Aug 22, 2017 10:33 am

Re: Searchlight signal build?

Post by rkcarguy » Mon Sep 18, 2017 12:21 am

Wow thank you for the drawing!

rkcarguy
Posts: 475
Joined: Tue Aug 22, 2017 10:33 am

Re: Searchlight signal build?

Post by rkcarguy » Mon Sep 18, 2017 1:41 pm

The signal on the left has that mini-light about 1/2 way up, what were the color options of that and what was it supposed to indicate?

Post Reply