3D printed Sn2 turnout fixture

[JeffB]

Figured I'd share this...  They are 3D printed LH and RH HOn3 (Sn2) turnout fixtures for Code 70 rail.  The frog is a #6.5, halfway between a #6 and #7, which is what I wanted for these turnouts.  The slots for PC ties are dimensioned for Fast Tracks HOn3 PC tie stock.

3D_printed_turnout_fixture by jeffB, on Flickr

The fixtures (both LH and RH) are two piece because I couldn't fit the whole fixture on the build plate at a time.

They're screwed down to a laser cut 3/16" thick aluminum plate.  (I work with industrial laser cutters capable of cutting up to 1.25" thick Aluminum, steel and stainless steel).

I also have fixtures for holding the point and frog rails for machining the angles into them (I have a milling machine in my home shop) and a soldering fixture for soldering the frog rails prior to putting them in the turnout assembly fixture.

Jeff

[Chris333]

That is dynamite! And resin holds up well to a soldering iron, I'm made simple soldering jigs with it before.

[JeffB]

That is dynamite! And resin holds up well to a soldering iron, I'm made simple soldering jigs with it before.

Yes, the resin does hold up pretty well to a quick application of highish heat.  I've already experimented extensively with the frog soldering fixture, which works extremely well BTW.  Doesn't wick away heat like an aluminum fixture does.

Jeff

[C855B]

Outstanding! Nice work.

[timwatson]

Good for you Jeff!! Looks great. Show off your first turnout next.

[Mdrzycimski]

That is amazing.  Great work.

I have been trying to come up with a way to design and print a turnout fixture.  I could do it in PLA and keep the fixture flat but knew the heat would affect the jig.  Thought about resin but was concerned about the print warping.  The way you bolt it to the aluminum eliminates that issue.

Brilliant.

What kind of work did you have to do to the aluminum plate other than drill and tap the bolt holes?

[GaryHinshaw]

Gorgeous work.  I'm especially jealous of your laser cutter. 

Being able to bang out custom tools and jigs like this with 3d printing is a game changer.   I made a jig for soldering a throw-bar to a pair of points and it turned a tedious and error prone task into a simple and repeatable one.  And the resin is completely impervious to a soldering iron.

[JeffB]

Thanks guys!

Nice fixture Gary...  I may end up doing something similar.  I drill the throwbars to add hinges to the point/throwbar connection.  I don't like soldering the throwbars, especially for larger rail sizes (like Code 70).  Too much stress and it's too stiff a connection.  I'm using BluPoint's to throw these, so I want the points to be as easy to move as possible.

What kind of work did you have to do to the aluminum plate other than drill and tap the bolt holes?

Nothing other than just sanding the surface of the aluminum with some 320 grit emery paper on a sanding block.

Good for you Jeff!! Looks great. Show off your first turnout next.

I will...  It might be a few weeks, but I'll definitely take some photos.  I have to mill the rail parts first, then "practice" with them until I get a turnout I'm happy with.  It's a process as anyone who has used the Fast Tracks fixtures knows.  But once you get the steps down, it goes quickly after that.

Jeff

[Lemosteam]

I've cast molten lead in FUD and resin prints for a while now.  Wish I could figure out how to make a mini spin caster using them to make pewter castings.  I especially like them for specific handrail soldering fixtures.

@JeffB the prints look phenomenally accurate.  How do you like the DLP so far?

[JeffB]

I've cast molten lead in FUD and resin prints for a while now.  Wish I could figure out how to make a mini spin caster using them to make pewter castings.  I especially like them for specific handrail soldering fixtures.

@JeffB the prints look phenomenally accurate.  How do you like the DLP so far?

Good info John...  I have three locomotive projects that I'm working on where it'd be beneficial to pour molten Woods Alloy directly into resin cavities in the 3D prints.  Would make it a lot easier than 3D printing the weights in resin, then using those to make an RTV mold to cast them Woods Alloy.

I really like having the 3D printers I have (all DLP's)...  The turnout fixtures are printed on my Sonic Mini-4K, which has been great for detail and dimensionally accurate prints.  Printed a few test gearboxes a while back and they worked very well.  I've also been printing up a lot of detail parts, so much so that I don't feel the loss of Grandt Line any more!

I printed a test rivet panel on my Mini-8K a few weeks back (yes Chris333 I FINALLY used it!!) to evaluate how small I could print rivets on it (0.2mm diameter x 0.15mm tall printed well enough that I'll be setting that as my minimum rivet size).

I'd previously printed a hood for a Davenport diesel mechanical on the Mini-4K that had some raised lettering on the radiator (a Caterpillar D13000 radiator, with "Caterpillar" written across the front of it), where the lettering was about 0.3mm high and 0.15mm proud of the surface) and it printed almost legibly enough.  Looking forward to seeing how well it prints on the 8K.

Jeff

[Mdrzycimski]

Hey JeffB,
I was curious if you drew this template out in your CAD software entirely from scratch using known turnout dimensions or did you start with an image such as the FastTracks printed templates?

I attempted my own version today using Onshape and importing the FT template as a jpg.  I had a bugger of a time getting the image sized correctly to accurately draw the rail locations.

Please note: I am pretty much a beginner with CAD software so there may be easier ways of doing it that I haven’t learned yet.  Any words of wisdom would be appreciated.

[JeffB]

Hey JeffB,
I was curious if you drew this template out in your CAD software entirely from scratch using known turnout dimensions or did you start with an image such as the FastTracks printed templates?

I attempted my own version today using Onshape and importing the FT template as a jpg.  I had a bugger of a time getting the image sized correctly to accurately draw the rail locations.

Please note: I am pretty much a beginner with CAD software so there may be easier ways of doing it that I haven’t learned yet.  Any words of wisdom would be appreciated.

Hi,

Yes, I drew it from scratch in Solid Works.  You have to know your frog angle and the angle that your points are (generally, 2° is the default for point angle).  You start by estimating the lead of the turnout, which is the distance from the end of the points to the crossing point of the frog rails at the frog itself.   I think the NMRA has a chart with some of this information.

From there, you manipulate the sketch until you get the geometry you want.  I used an intermediate frog angle (8.75°, which is more or less a #6.5 frog), so I had to make things up as I went along.

My goal was to have the largest diverging route radius I could, while still having a short length of straight rail in the diverging route, just before the bend for the frog wing rail, at the frog.  Not sure if that makes sense though.

Ideally...  You don't want your curved rail leading up to the frog (called the closure rail), to be curved through the frog.  It's also advisable to not have that tangency point land in the gap before the frog point.  Mostly for smooth tracking purposes.  Honestly, I'm not sure it matters for model train trackage, but that's the way I've always designed my turnouts, starting in the early days where I came up with my own HOn2 (7mm gauge) #7 turnouts.

Also...  You want to have the point rail of closure rail, straight for a good distance before transitioning into the curve.  I try to make this as close to 8 scale feet as possible, only because somewhere I read that point rails on prototype turnouts are usually half, or one quarter the length of a full length of rail (which at one time was 32' or 33' IIRC).  For narrow gauge turnouts, I use 1/4 of a full length of rail, which is about 8'.

Hope that helps...

Jeff

[JeffB]

Here's a 2D CAD drawing of the LH version of the final turnout.  I did this so that I had something for track planning in CAD.

Sn2_number_6.5 by jeffB, on Flickr

Jeff

[Mdrzycimski]

Thanks Jeff.  That’s helpful.

[JeffB]

I know it's been a while, but I finally got around to building and installing a few turnouts out of the 3D printed fixtures.  Here's a few photos...

turnout_1 by jeffB, on Flickr

turnout_2 by jeffB, on Flickr

Jeff