Best Of Pennsy Position-Light Signal Head - Shapeways Project?

[nscaleSPF2]

Spent a couple of hours designing a Pennsy position-light signal head.  See images below.  According to the research documents that I could find, the dimensions pretty much correspond to the prototype:  the overall diameter is 54 inches (about 8.5mm), 18 inches between lights, the light holes are 6.7 inches diameter.  The visors for the bulbs look somewhat "stubby", but I want to be able to see the lights when my eyeball is higher than 2 inches above the rail.

The countersunk holes in the back are sized for 0603 LED's, which would be glued in place after the wires are soldered to them.  The bosses on the back are sized for a .0625 diameter vertical pole.

If you are still with me, you get the idea.

Because of some negative reports on this forum, I am wondering if it would be worth it to try to coerce a Shapeways maven to produce some of these for me.  Will this be worth the effort, or will I get an amorphous, unrecognizable blob of plastic?  Any opinions are welcome, so don't be bashful.  Hard facts are ok, too, but not necessary.

Before anyone tells me that Pennsy signals are commercially available, I would submit that the NJI units are way too expensive, and the TrainCat kits are way beyond my skill level.  (Sorry, Bob)

Here are the front and back images.





Jim

[peteski]

Spent a couple of hours designing a Pennsy position-light signal head.  See images below.  According to the research documents that I could find, the dimensions pretty much correspond to the prototype:  the overall diameter is 54 inches (about 8.5mm), 18 inches between lights, the light holes are 6.7 inches diameter.  The visors for the bulbs look somewhat "stubby", but I want to be able to see the lights when my eyeball is higher than 2 inches above the rail.

The countersunk holes in the back are sized for 0603 LED's, which would be glued in place after the wires are soldered to them.  The bosses on the back are sized for a .0625 diameter vertical pole.

If you are still with me, you get the idea.

Because of some negative reports on this forum, I am wondering if it would be worth it to try to coerce a Shapeways maven to produce some of these for me.  Will this be worth the effort, or will I get an amorphous, unrecognizable blob of plastic?  Any opinions are welcome, so don't be bashful.  Hard facts are ok, too, but not necessary.

Before anyone tells me that Pennsy signals are commercially available, I would submit that the NJI units are way too expensive, and the TrainCat kits are way beyond my skill level.  (Sorry, Bob)

Here are the front and back images.





Jim

One problem I see (assuming you use FUD resin) is that there might be light leakage through areas which have very thin layer of paint (like all the edges). I had problem with that whenever I tried to make clear or translucent objects fully light-tight.  Sometimes even with several layers of black paint, light still comes through at the edges.

[DKS]

Agree with Peteski on the light leak issue. Other observations: the hoods seem kind of short and too sharply angled. Also, if the recesses are for 0603s, why not make them rectangular to hold the LEDs more securely?

Reference image for hoods: http://www.flickr.com/photos/reivax/4958559673/

[Mark5]

Yeah the hoods don't look right.

(These targets or similar also used on N&W, Amtrak(NEC) and some LV (?))

[nscaleSPF2]

Yes, Peteski, I thought about the light leakage.  Would it help if the resin were opaque?

Making the recesses rectangular sounds like a good idea.

If the hoods are too long, I am afraid that you will only be able to see the LED's when you are directly in front of them.

Jim

[peteski]

Yes, Peteski, I thought about the light leakage.  Would it help if the resin were opaque?

Making the recesses rectangular sounds like a good idea.

If the hoods are too long, I am afraid that you will only be able to see the LED's when you are directly in front of them.

Jim

Black opaque resin would be ideal but I don't think that it is available from Shapeways.

I agree that the hoods need to be reworked. Other commercially available signals have more realistically shaped  hoods and I never heard anybody complaining that they can't see the lights.

Also, how thick is the target's face?  It looks a bit chunky.  I suppose that it might be a tradeoff so it is thick enough to hold the LEDs.

I agree about rectangular openings for the LEDs but I also worry about soldering the LED leads after they are placed in the openings. That might melt the resin.

[Ed Kapuscinski]

I hate to say it, but I think you should take a closer look at real PRR position light heads. They're a lot more complex than they seem.

The current offerings are about this same level of detail. If you're going to spend the time on making them, I'd argue that you should try to advance the state of the art.

[DKS]

I agree about rectangular openings for the LEDs but I also worry about soldering the LED leads after they are placed in the openings. That might melt the resin.

The countersunk holes in the back are sized for 0603 LED's, which would be glued in place after the wires are soldered to them.

[robert3985]

I hate to say it, but I think you should take a closer look at real PRR position light heads. They're a lot more complex than they seem.

The current offerings are about this same level of detail. If you're going to spend the time on making them, I'd argue that you should try to advance the state of the art.

I agree 100%

[Dave V]

I hate to say it, but I think you should take a closer look at real PRR position light heads. They're a lot more complex than they seem.

The current offerings are about this same level of detail. If you're going to spend the time on making them, I'd argue that you should try to advance the state of the art.

http://www.railroadsignals.us/signals/pl/pl.htm

http://www.trainsarefun.com/lirr/lirrdiagrams/PRRpositionlightsignalplans.gif

http://farm5.static.flickr.com/4130/4958559673_56e5eb05ce.jpg

I have no experience with Shapeways, but since the real signals are made of sheet metal I'm inclined to believe brass still remains the best medium for making them in N scale.  Brass can be intimidating at first, but remember that good CA glue can hold it.  I used medium-viscosity CA for brass, or a 15W pencil-tip soldering iron.

I waited for many years before braving Alkem's brass signals, and in the end assembling the brass masts were not as bad as I thought they would be.  In fact, I decided to solder them.  I suspect Bob's PLs assemble in an equally straightforward way.

I just feel like the designs you've posted won't gain you much over a proper brass kit which could look much more prototypical in size/depth.

[nscaleSPF2]

Thanks, guys, for all of your comments.  Seriously, I can count on you for your honest opinions.  And thanks especially to Dave Vollmer for the Drawing of the PRR signal.  That is the drawing that I tried to find, but could not.

I incorporated as many of your suggestions into a revised design, shown below.  Except for Ed Kapuscinski's, because there is a limit to how much detail you can add (without a microscope) to a part that is only 8.5mm across.  Ed, if you have any specific suggestions, I would like to hear them.  The signal heads will be supported by TrainCat's pole with the attached ladders and platforms.  This will add a little more detail, at least.

This project will proceed.  That's because, although I could probably assemble one of TrainCat's brass signal heads on a good day, the layout will require about 12 of them.  Then installing the LED's into these would require the skill level of someone like Peteski.  This forumer is not up to that task.

Will report back, with any meaningful results.

Thanks again,
Jim





The grid in the bottom image consists of 1mm squares, for comparison.

[djconway]

Having seen the PRR signals up close - one of the things I want to include in making them is that the main disk is thin sheet metal.  A resin representation of the signal head if sean head on may be ok, but if you get to the side of it it looks THIN. 

I'm new to Traincat's kits but have been making steady progress on 3 caboose kits, and have a signal bridge on the bench.  The instructions are some times a bit hard to understand just what you should be doing - but read, reread, print them in color and they do make sense.  They are well engineered kits, take your time and  they do come out.  Brass sheet parts glued with CA can be unglued with a cotton swab of acetone and a little scrubbing.     

[jereising]

You are assuming Traincat will be around to buy his kits, and given the current state of affairs that is unfortunately NOT a sure thing.

I have a pending article on creating signals that just may go down the tubes because of unavailability of parts.

Don't take this as a slam at Bob; I love his stuff and want more.

[Alwyn Cutmore]

Jim,
I think most understand your point and we are all right there behind Bob. I do not think anyone would slam Bob and if they do then there are more than enough to take them on.  Unfortunately I have a very negative view on Shapeways so I will not comment any further.
Regards
Al

[nscaleSPF2]

Finally have some results to report.  There were a couple of false starts; Shapeways does an automated check of the design model as soon as it is submitted, but they also do a "final check" about a week and a half later, just before the part is about to be printed.  It was at this point that I discovered that I violated their design guidelines - twice.

The result was that the hoods had to be printed solid, and I had to drill them through from the back.

Anyway, here is a picture of the result:



OK, before you ask me why I don't just throw it away, see what happened when I removed the wax from the surface of the part.  This is something that one learns from various forums, not necessarily from the Shapeways website.  I tried several solvents to remove the wax, but hot soapy water and a toothbrush worked just as well.

Here is the part with the wax removed and a very light wash of flat black:



A view of the back:



A couple of other views:





The hoods look a little lumpy, as you can see, they are about a scale 3 inches thick.  I think that overall the signal head will be an acceptable placeholder on my layout until something better comes along, after the LEDs are installed and the part is properly airbrushed.  Keep in mind that the entire head is only 8.5 mm across.

If anyone is interested, I can post some further in-process photos as work continues.

Jim