0 Members and 1 Guest are viewing this topic.
@Mark W 's proof-of-concept here demonstrated surprisingly good results in modeling 3-color vertical signal heads with the Photon 3D printer. It's a great start, much improved over SW versions due to the minimum thicknesses of SW output.Like I said in the other thread, I'm no expert especially with dimensions other than the couple I have in my 1:1 collection, so any and all correction or enlightenment is encouraged.Random signal modeling notes, in no particular order:Three popular target widths, 24", 30" and 35" (36"?). 24" is mostly modern.Top and bottom target radii are centered on the top and bottom roundels. One significant exception is a "slim" 24" type seen on ex-SOU lines (and probably others), where the radius "clips" the bottom of the lamp housing, and the bottom lens has maybe a couple of inches of target below the lens ring. I hoped to have photos of local versions, but I didn't move fast enough when the PTC Vader-izing crew came through town two years ago.Consider 2, 3 and 4-color variants. Lens center-to-center is 12"Outer doublet (lens) is 8-3/8", the retainer ring is about 1-1/4" wide and 3/8" thick.Visors - there are several shapes of visors, but by and large they amount to short, medium and long. Modern long in the picture below.Hoods - two major distinct versions, modern, and not-modern ; the profiles are different. There are some variations in the older style including things like a top baffle. The older style is still found on UP mostly on intermediate signals. UP, GN and I believe the Canadian roads used the old-style hoods as intended for snow defense.Shop-built hoods exist, with rounded square corners rather than the radius top. Very rare in the US... unless it's the RR you're modeling. Seem to be common in Europe.Hoods and visors are not mutually-exclusive. I have seen photos of old-style hoods with a short visor over the bottom roundel.Backs, as mentioned previously, can be lumped into three styles - cast "one piece" (housing with a single door), modular square aluminum (early Safetrans and other makers), and Safetrans plastic modular (round-ish with mounting ears).The most vexing problem (to me) in modeling is building heads with SMD LEDs in quantity. Proofs-of-concept, OK, but multiply the effort by 50 or 100 or more and it becomes a task of diminishing returns.We'll need mounting brackets and bases. @Wutter has a good Safetrans base on SW, the relay cases and different base from Showcase Miniatures solve the mounts, but pole brackets will need to be developed. Modern pole brackets (photo below) with wire feed-through may be a challenge; old-style typically has external conduit making the job a lot easier.By sheer coincidence, last night I was dinking around with PCB software trying to create a micro-PCB with three 0402 LEDs that would slip into a 3D-printed back. 0201 LEDs aren't necessary in this case as there's plenty of real estate for the easier-to-handle 0402 size. My design concept was a 0.012" two-sided substrate, component placement on front, with vias (connections between the front and back layers) bringing the connections - R-Y-G and common - to pads on the back for wires. This, I think, works well with Mark's hollow-back concept. I would expect the board to be commercially-produced as a populated fret with multiples of RYG micro-boards in 1/16" strips you would cut off as needed. I would also populate the fret with a small handful of less-common configurations such as R-Y, R-G, R-Lunar, and R-Lunar-Y. Maybe also a R-Lunar-Y-G or two, not as rare as one would think, as here are two on UP at Kearney, NE (two left lower heads), and the 4-indication heads were standard practice on Soo Line.The PCB software I was trying to make work was awful and there was not, for instance, a way to plot a small plated-through via, nor was there a convenient tool for routing (as in machining cutouts, versus circuit paths). If somebody here was handy with a CAD package that exported finished Gerber files, we might be able to do this. None of my handful of CAD apps will do Gerber.I'm hoping this to be a community effort. @Mark W has certainly taken the feasibility lead, now we need proto references ( @robert3985 and @draskouasshat , I'm calling you) and somebody with Gerber file capability. I'll do what I can in finding additional photos and maybe blueprints, the latter has proven challenging. With Gerber files in-hand I can certainly front finding a reasonable PCB assembly house to do the LED frets.Don't everybody jump on me all at once.
These are just the raw print. I hope a coat or two of metallic silver will help the opacity, and I could turn down the brightness a bit too.
@Mark W That looks like a winner. You've proven it can be made to work. If you want or if it would help I can drill those holes in that tube very precisely and very on size. No wobble marks on entry, just the hole. To that end, what size is the tube and the hole? Or maybe more precisely, what would you want it to be?
Black is on the way, but I 'm sure they'll need a masking coat. @narrowminded yes, that would be awesome! Right now I'm just using the smallest K&S tube I could find. @C855B mentioned a few smaller options may be out there too.
Pete, after doing parts research I think the end game with LEDs is probably going to be hand-soldered 0603s. Board or no board, we're still going to be hand-soldering wires. I like the Kingbright "domed" APTD1608 series in 60° for this project for several reasons. First, 0603 is about the smallest we can reasonably expect to do in hand-soldered. You and I have done 0402s, but a cough, sneeze or even a heavy <...sigh...> has sent more than one 0402 flying off my microscope stage never to be seen again. Second, 0603 are 1/16" x 1/32". That's about right for the chip to fit horizontally relative to the target and back. Then there's the lensed chip for focus, rather than spraying light everywhere. Also, Kingbright domes are available in the "correct" yellow (590nm) and "correct" green (525nm), and there's even a cool white for the lunar indication I want in several locations. Finally, the domed chip should make it easier to build a soldering jig out of, say, a small bit of aluminum with drilled holes for the domes.
... I held a soldering iron set to 600 deg.F to the gray resin and it did not have any effect on it. So if you design the signal head to cradle the LEDs, it will safely hold the LED while being soldered. ...
Excellent. Makes life much easier. I can deal with that.
A couple of suggestions for making these. First, if you're going to try to use 3/64"x .005" wall tubing the ID will only be .036", just over 1/32". So what size hole can you realistically have? 1/32"? That hole will have to accept a spigot from the resin printed head with at least 4 wires passing through it. And those wires will have to be turned at entry and fed down the tube. Am I the only one seeing the proverbial 10# of something in a 5# bag?
Author
Topic: 3D-Printed Signal Heads (Read 6463 times)
