New brass Milwaukee Bipolar EP-2 clinic- part 2

[peteski]

Couldn't you encapsulate the back of the assembly with epoxy, then paint it white first (to make it reflective), then black until the light leaks were sealed?  I have done this several times on various light assemblies and it works really well.

[u18b]

I'm not sure I follow you.

You mean fill this with epoxy?

[peteski]

Sure, that one. You could have even done that with the first disk you made.  On that disk you could have made an epoxy dome which would have covered the back of it.  Then paint that white, then black (before installing it in the headlight housing).

You could also do that with the brass tube.  I would first paint the front of it whatever color it is supposed to be. Then install the LEDs (hopefully not wired in parallel  ).  Then fill the back of the tube with epoxy. That will nicely insulate the LEDs and the wiring from the metal tube. Then paint the filled back with white, then black paint.  Actually with the brass tube you don't even need to paint it white first, since the LEDs are sitting so close to the triple openings that there is no need for the back of the assembly to be reflective.

[u18b]

OK.
You've given me more to think about.

However, whatever I do, it will have to be at the end.

This was just experimentation.
But I learned from the last one that it is best to install the LEDs AFTER the loco is painted.

I think I see some possibilities.

Better write this down while it is percolating.

1.  finish painting loco
2.  Solder 2 LEDs.


3.  That heat shrink makes a plug that protects the wire going through the housing hole in the nose- but it also would make a plug for epoxy to keep it from leaking into the shell.


4.  Paint the back of the housing black.  Makes for easy simple initial insulation.
5.  Install LEDs.



6.  Put a little epoxy behind the LEDs and then add more to about cover the LEDs.   Let it harden. 
7.  Paint the outer rim black since this is where the light leaks out.
8.  Make my tube as before.  Solder to thin brass as before.  (might try superglue)


9.  Shape smooth, and drill holes.  Make them a little farther apart than before.  Closer to the out edge.


10.  Now UN-solder that little brass cap.  Sand it smooth.  This is the step that is really different.  You're right.  I don't need the barrel.

11.  Paint the outside of the disc silver.
12.  Mount in housing on top of the epoxy.
13. Put the glass over it.  Done

That is still a lot of work for three little holes.  But I can see that it would work.

Like you said, I might be able to use styrene instead of brass

[u18b]

OK.   I'm thinking some more.

Given the epoxy trick that Pete suggested.  That helps solve the light leakage.

The hardest part of this is making that tiny tiny disc.

To be honest, it's kind of depressing thinking I need like 16 of these.  Yikes.

If I could make one good one out of styrene, the I might be able to make an RTV mold.  It would be a Flat, so it would be easy.

This disc did not turn out perfectly circular because I did not beat the tool hard enough.  Family was asleep and it was late.
But using that tool on a hard surface would cut that styrene more cleanly.



Then, I could pour some copies with Alumilite.

In fact, if I get a good master and a good mold, then I could make a new mold with about 6 of these and pour six at a time.
It would be a little work up front, but would save a lot of time later.

So it would save a ton of time if I could just make poured castings of a bunch of these.

[u18b]

With renewed efforts... I tried again.

I cut a much cleaner disc.
Blackened it.
And did not use fiber optics at all.
Made the holes bigger.




With the exposure cranked down, you can see three lights.




This is more what it looks like to the naked eye.
Better.

[peteski]

Photo etched brass disk would have solved the problem of making lots of them (but it is not realistic to have just 16 photo-etched commercially).
I often use black sheet styrene for this type of application (0.010" is the thinnest black sheet available from Evergreen).

[nkalanaga]

I don't know that you'd have to paint it silver.  Polished brass is a good reflector, better than most silver paint, and if it's covered with epoxy it shouldn't tarnish.  It would also give a nice yellowish tint to the reflected light, more like an incandescent bulb.

[peteski]

I don't know that you'd have to paint it silver.  Polished brass is a good reflector, better than most silver paint, and if it's covered with epoxy it shouldn't tarnish.  It would also give a nice yellowish tint to the reflected light, more like an incandescent bulb.

I agree what you said about brass. I don't recall anybody mentioning painting anything silver.  Ron did mention Alumiite casting resin.  I mentioned white paint on the outside of the encapsulating epoxy before painting it with light-tight black.

[u18b]

Yes, I was the one who mentioned silver..

But that is for a prototypical look.

When you see this...




... you don't see black, but rather a mirrored surface.

But I think all black will be fine (in fact, that is how they do it in HO brass).
Remember, the model still will have a lens over the outside as the last step.

[victor miranda]

3 tiny led will not fit?

[u18b]

Victor,
Good question.

I have actually thought of that.

I even drew a circuit board.

But, space is indeed tight.

I'm going thru a sort of evolution on micro-LEDs. --otherwise known as SMD  (surface mount device) LEDs.

The smallest I have ever worked with are the Nano Super-Incandescent LED that N-gineering sells.

http://www.ngineering.com/lightng.htm

You could definitely get three of those in there- but to be honest...
1.  They are REALLY expensive - about 3 bucks each.
2.  They are so small, it is really hard to work with them- they are tiny.  My success rate was about 50% (or worse    ).  Meaning if I needed two for ditch lights, I would probably destroy or lose 2- so it took 4 (12 bucks plus shipping- or more!).

So then I tried the LEDs from TCS.
I really like these.
http://www.tcsdcc.com/Customer_Content/Products/Supplies/ToolsAndSupplies/LEDs/SMLEDs.htm

I like the ones already mounted on a circuit board- much easier to handle- but they are also about 3 bucks each.
http://tcsdcc.com/Zen/index.php?main_page=product_info&cPath=20_32_75_81&products_id=303

A TCS LED is in here.
It looks good and worked well.  I had to file and round the edges of the mounting board just a little.



The difficulty with the TCS LEDs (for the current 3-light EP-2 project) is that they are fat.

So recently, I was searching ebay and saw some pretty cheap SMD LEDs direct from China.
So I tried them.

These have about the same footprint as the TCS LEDs- but with no tiny circuit board.  And they are much thinner.  Which is good for getting the 3-hole disc on top of it in this project.
And they are CHEAP.
They were so cheap, I ordered 500 more.  I figured at that price (less than 2 cents each) I could burn thru them and not even worry about the offerings to the carpet gods.

(At that price.....quality?  Failure rate?  Don't know.  I did wire up a pair and just left it in the layout for several hours to see if it would burn out/fail.  But I saw no problem).

In my latest application, here is two of them mounted in parallel.



So as you can see, with a little filing, I MIGHT be able to get three in there.
But it would be hard.
And....  I'm thinking it would be so blindingly bright that the effect would be diminished.  You would not see three lights-- just one REALLY big and bright light.

What I would have to do is a lot of experimentation to find just the right resistor to lower the brightness of three- so that you could actually see three lights.


Edited:  Besides, that does not even consider the FOUR headlight version!   That will be when I make E-2. 

LOL.
http://earthseaimagery.com/images/bipolar_oly_hiawatha_in_puyallup_valley_1953_fbt.jpg

[u18b]

Todd at Streamstyle graphics already makes what I need- but only in HO.



 

[victor miranda]

Hi u18b

I should know better than to ask,
sometimes what I see as obvious is a novel idea.

this is what I found from digikey.

Rohm Semiconductor SMLP13WBC8W1
1mm by .5 mm
corners are clipped
the specifications are pretty good.

http://www.digikey.com/product-detail/en/SMLP13WBC8W1/846-1098-1-ND/3079581


41 cents each if you get 25  is a bit more than your find.

I have some osrams from a while ago that I have not burnt or lost... yet.

what I had in my mind was a 90 degree (a side shooter)
LED and have the PCB in the center. two on top and one below.
the package sizes do not lend themselves to that idea however.

they shoot from the wide side and are the next size up.

carry on!

victor

[u18b]

Hmmm.  That might be interesting.

My tiny round circuit board has about 2.2 mm diameter of usable space.
So it might work with 4 shoe-horned in there.

Once again, if the resistor was big enough then brightness could be reduced to where you see 4 lights instead of 1.

The really cheap ones I described above might fit 3, but certainly not 4.

The color on the small ones you listed is described simply as white.

But obviously, a slight blue-ish "white" would not be good for 1950.

warm white would be better.

I might buy some and do some testing in the future.
Thanks.


EDIT:  Have you actually used these?
Can you clarify the shade of white?