Opinions Wanted on a Narrow Gauge 3-Way Turnout

[Ed Kapuscinski]

But a 3-way?  The challeng with a 3-way is unique...getting the center position perfect every time.

I think so.

Also, sack up and do it right!

Don't "Ed out" on it.

[Dave V]

Reached out via e-mail to Tam Valley.  While I prefer manual turnout control for such an old-timey style railroad, if the cam system they sell can assure perfect alignment then I'll go ahead and bite the bullet. 

The RGS posse on Facebook predictably (and correctly) overwhelmingly advised in favor of putting the 3-way on the main given how iconically RGS it was.  Theoretically I should have two 3-ways at Rico (one leading to the enginehouse as well) but practicality, cost, and risk assessment led me to use only one.

[davefoxx]

Rico must have been an exciting place to live, considering all of those three-ways going on. 

DFF

[Dave V]

Rico must have been an exciting place to live, considering all of those three-ways going on. 

DFF

Was thinking the same thing.  Dolores had a few too. 

[DKS]

If it were me, I'd tinker up a DIY solution. My thoughts aren't complex or esoteric, but they would require a degree of ability to fabricate some relatively simple parts. Ordinarily I'd just build one for you, but I'm not in a position to do much fabrication of this sort at the moment. Perhaps someone else on TRW would be willing to participate?

https://www.ebay.com/itm/3-Position-Switch-Rotary-Lever-Wafer-New-Phenolic/183242930442?hash=item2aaa21390a:g:MtUAAOSw-W9bCFQF

I'd start with a 3-way lever-style rotary switch, readily available on the 'bay. The mechanism to build consists of a single lever: one end has a stiff steel wire attached that would engage the throw bar, and the other has a series of holes for a metal rod. The rod would connect the lever to the rotary switch, and the multiple holes would permit fine-tuning the amount of throw. The only other part is a right-angle bracket to hold the lever. The only overarching requirement here is that moving joints all be as tight as possible to maintain registration.

Assembly would require that the switch be in the precise center position, and the parts assembled in situ such that the rotary switch is in its middle position. (Alternatively, the connecting rod could have a coupling that would permit final adjustment.) Once this is set, then the connecting rod would be adjusted to create the proper amount of throw by choosing the hole that works best. The bonus of using a rotary switch is that it provides built-in current control as needed.



I kinda rushed on the drawing and didn't label it, so here are the parts: turnout throwbar, top left. Lever middle left, with fulcrum screw in the center of the lever (attaching it to the right angle bracket, behind it), and music wire attached to the top of the lever (could be simply soldered on). Connecting rod at the bottom, which engages a hole drilled in the rotating disc within the rotary switch, far right.

BTW, you can also turn the whole shebang on its side for a nearly flat system that might be easier to install.

 

[Point353]

This looks quite similar to the Tam Valley system.  I may give them a call and find out more about whether it'll work for my setup through 4" of foam.

Have you considered mounting the turnout and actuating mechanism as a sub-assembly on a thin piece of plywood?
Then make a recess from the top side of the 4" foam base to clear the actuator and allow the turnout to be installed level with the rest of your trackwork.

[DKS]

Have you considered mounting the turnout and actuating mechanism as a sub-assembly on a thin piece of plywood?
Then make a recess from the top side of the 4" foam base to clear the actuator and allow the turnout to be installed level with the rest of your trackwork.

I'd definitely do something like this. Putting 4" of foam between the turnout and any kind of mechanism is automatically inviting problems.

[davefoxx]

Have you considered mounting the turnout and actuating mechanism as a sub-assembly on a thin piece of plywood?
Then make a recess from the top side of the 4" foam base to clear the actuator and allow the turnout to be installed level with the rest of your trackwork.

^This.  Or, do what I do for under-the-table switch machine mounts.  Considering your 4" foam subroadbed, cut a large hole in the plywood base and the bottom sheet of 2" foam.  On the upper layer of 2" foam, glue a scrap of plywood to the bottom side, which you can use to mount your switch machine of choice.  I have found on the one Tortoise that I have on my layout, it had no problem with the throw through at least 2" of foam.  I was pleasantly surprised when this worked.  You may need to use a stiffer wire actuator, but that shouldn't be a problem.

Hope this helps,
DFF

[Dave V]

Have you considered mounting the turnout and actuating mechanism as a sub-assembly on a thin piece of plywood?
Then make a recess from the top side of the 4" foam base to clear the actuator and allow the turnout to be installed level with the rest of your trackwork.

I have actually considered that and am leaning toward doing precisely that. 

[DKS]

You may need to use a stiffer wire actuator, but that shouldn't be a problem.

It could be something of a problem. The longer that wire is, the more difficult accuracy becomes. It also means leverage is working against you because of the small amount of throwbar travel relative to the length of the wire that's moving it.

[davefoxx]

It could be something of a problem. The longer that wire is, the more difficult accuracy becomes. It also means leverage is working against you because of the small amount of throwbar travel relative to the length of the wire that's moving it.

You're probably right, considering the concerns over the center position of the three-way turnout.

DFF

[Dave V]

It could be something of a problem. The longer that wire is, the more difficult accuracy becomes. It also means leverage is working against you because of the small amount of throwbar travel relative to the length of the wire that's moving it.

Hoping to hear from Tam Valley as I explained my exact situation to them.  But yeah, if I need to get some of that foam out of the way, it's not a problem.  Even if I need to build the whole turnout as a plywood "lift out" and then dig an access hole beneath it, I'm willing to do that.  I think the layout has more than sufficient structural integrity for that sort of thing.

[nkalanaga]

If you want more 3-ways, and are comfortable building point-style turnouts, a 3-way stub is actually simpler.  No points to file!  As long as everything is in gauge it will work. 

I built one years ago, but can't help with a control method.  Mine was just to see if I could make it work, and was thrown with a Caboose Industries ground throw.  Put the handle in the center vertical position for the middle track, and eyeball the alignment!  Frog polarity was controlled by two microswitches, one at each end of the throwbar.  To make it even cheaper, they came off a microfiche processor at work, after the spring arms broke...  It was ugly, but the turnout works, and worked the first time, with no fiddling, usually required on my points.

[narrowminded]

Without direct experience with a servo in this application but in others, I would be inclined to use a miniature servo.  They are pretty capable at repeating or holding a position.  With that said I'm also sure a straight mechanical device could be made that would work very reliably.  It would include a spring loaded device, loading against positive stops to assure repeatability with such small travel.  It might also be easiest to make it a sub-assembly.  I have a general idea in mind but nothing detailed.  If I should get to work I would need dimensions, travel and such.

[nkalanaga]

It also helps if you file an angle on the ends of the rails.  Not a long angle, like a frog point, but maybe 45 degrees., halfway across the head.  That will eliminate the chance of having a blunt rail end catching a flange, while not giving enough room for the wheels to turn and derail.

The same trick works for turntables.