Movable Switch Target In N-Scale

[narrowminded]

Rodney shows exactly what I meant earlier when I stated to use longer lever.  Heck, if using a servo, one could couple the switch target directly to the servo's output shaft and have it set to rotate 90 degrees.

Yes.  But if you're trying to run the stand from the switch throw bar, the .035" motion is all you get and the method to make that work (or not) is what I was referring to in my post.  The servo will work because the throw is whatever lever you choose.  If you have the option of using a separate source of travel like the servo, that's by far and away the easiest way to go as Rodney so beautifully executed and documented.   It does take the extra hardware, wiring, and space.

@rodsup9000 Since you found a working angle of about 60 degrees for your switch servo and because the spring wire projects past the attachments and sweeps a bigger arc the further out you go, you have plenty of action to adopt a linkage that uses a different lever ratio on the servo arm to the switch target arm, accomplishing your 90 degree travel at the target for the 60 degrees at the servo, and not fighting the tolerances required when the motion starts with such a small travel as the tie bar.  And those linkage pivots could be made with a small adjustment range to slide in and out on one of those arms to tweek the action as needed.  But this is all based on a motion source other than direct to the throw bar where the movement is so miniscule, the original problem being addressed.  I would consider that possibility if I already planned to use servos.  In fact, that might be an incentive to use servos.   Makes a complete package and the moving target is accomplished with a few extra trinkets.

[rodsup9000]

And those linkage pivots could be made with a small adjustment range to slide in and out on one of those arms to tweek the action as needed.  But this is all based on a motion source other than direct to the throw bar where the movement is so miniscule, the original problem being addressed.  I would consider that possibility if I already planned to use servos.  In fact, that might be an incentive to use servos.   Makes a complete package and the moving target is accomplished with a few extra trinkets.

 If you look at my mounts, they have adjustment slots in them. Another, is once you have everything mounted, you can make fine adjustments by changing the servo degrees in the sketch and re-flashing the Arduino too.

 To me, cost and time wise, this is the best way to throw turnouts (and now switchstand targets and/or lanterns)








 I guess now I need to get some switchstands drawn up and printed.

[narrowminded]

If you look at my mounts, they have adjustment slots in them. Another, is once you have everything mounted, you can make fine adjustments by changing the servo degrees in the sketch and re-flashing the Arduino too.

 To me, cost and time wise, this is the best way to throw turnouts (and now switchstand targets and/or lanterns)








 I guess now I need to get some switchstands drawn up and printed.

Go for it!

I see the second servo and all if its simplicity advantages.  That one didn't need remarking as it's well covered.   My remarks about adjustability were based on the idea of using just the one servo that drives the switch, getting it set, and then adding a linkage to drive the switch stand from the same servo action.  With the extra parts and room as an option your demonstarted example would certainly be straightforward, easier.   It'll be cool!

[kiwi_bnsf]

@Rodney — thanks for the great demo and lightning quick confirmation of how easy it is to use a second servo to handle the switch stand!

I already have Tortoise motors installed for turnout control, but from reading your Arduino notes, it sounds like I could use the aux contacts on the tortoise to ground the Arduino pin to have "chained" operation of a Tortoise and servo from the same control line (Digitrax SE8C in my case).

Did you write your own Arduino Sketches? or are there freely downloadable servo control examples for the Arduino Uno? (clearly I need to do some research into these).

One further question — is it possible to get the servos to run quietly with the Arduino? Is this more a property of the servo used or the control PWM used on the Arduino?



Another cool thing about using dedicated servos and Arduino controllers is that I'll be able to make my derail target stands operational too - which should make switching operations fun 

Now all we need is some fine scale Switch Stands and Derails with US targets and a centre shaft designed to connect straight to a servo shaft.

Happy days!

Cheers

[rodsup9000]

I already have Tortoise motors installed for turnout control, but from reading your Arduino notes, it sounds like I could use the aux contacts on the tortoise to ground the Arduino pin to have "chained" operation of a Tortoise and servo from the same control line (Digitrax SE8C in my case).

 That should work.

Did you write your own Arduino Sketches? or are there freely downloadable servo control examples for the Arduino Uno? (clearly I need to do some research into these).

 I modified the TrainServos8.ino sketch in this thread on the Arduino forum. If you want a copy of my sketch, send me a PM.

https://forum.arduino.cc/index.php?topic=315457.0

  There is this one that I want to try that lets you control the speed of the servo. If you go the post #6 in this thread, it has a sketch for that. For this sketch, you'll need to include the "<VarSpeedServo.h>" in your libary to make it work.

https://forum.arduino.cc/index.php?topic=419492.0


 I also have 4 Tam Valley Octopus III's that are super nice for controlling servos and have a very nice speed.

One further question — is it possible to get the servos to run quietly with the Arduino? Is this more a property of the servo used or the control PWM used on the Arduino?

 Mine are about as noisy as the tortoise with 5 volts running the servos. I think it's more the servo than the PWM.

Another cool thing about using dedicated servos and Arduino controllers is that I'll be able to make my derail target stands operational too - which should make switching operations fun 

Now all we need is some fine scale Switch Stands and Derails with US targets and a centre shaft designed to connect straight to a servo shaft.

 Post some pictures of what you have in mind and I'll see if I can get some drawn up and printed on the photon.
 

[robert3985]

Speaking of "fine scale switchstands"... I was browsing through a totally unrelated Google search and happened upon these:

Photo (1) - Mainline U.P. high and low switchstands plan views:


Photo (2) - Switch Lamp Fork, which fits on top of target mast:


Photo (3) - Another type of low switch stand with a good view of the switch lamp:


I've noticed that some switch stands had lamps and some didn't.  I found this which explains what the AT@SF's rules were as to whether to put a lamp on a switchstand, or not...

Photo (4) - Switchstand lamps, rules from the AT&SF about it:


I'll be printing these in a month after I get my Anycubic Photon...or the new one maybe, but I'll be printing castable resin to make hard brass masters, then making a vulcanized rubber mold for injecting wax masters for lost-wax brass investment castings for durability's sake.

Anyway, I thought this might save some time getting a "fine scale" switchstand...maybe both tall and low stands...up and going for someone else who doesn't have a portable layout where non-brass, resin models would be okay.

Seems like I remember that I've got plan views for more modern switchstands and several types of derails somewhere on my computer.  I'll post 'em if anyone is interested and if I can find 'em.  However, these stands here look a lot like the stands I'm seeing in my transition era photos...which is the era that I'm most interested in.  Also, I can verify that the tall stands were in use when I started documenting Weber and Echo Canyons in the late '80's. I didn't look closely at the low stands.

Cheerio!
Bob Gilmore

[MK]

Quick!  Someone 3D print these parts!   

[robert3985]

Quick!  Someone 3D print these parts!   

That's what I put 'em here for...

Cheerio!
Bob Gilmore

[peteski]

These switch stands will be so delicate (if modeled close to scale) that I think even on a permanent layout, 3D printed switch stands will be too fragile to be viable.  Lost-wax brass castings would be much better alternative. Or at least some of the parts (like the vertical posts) should be made from metal.

[C855B]

Here is a photo corresponding to Bob's (THANK YOU! - saves me much time) drawings for the high stand.



Probably not a good candidate for 3D printing as the frame flanges are 3/8" thick. However, it might be worth considering for an etched metal version in 0.010" without looking too clunky. Let me dwell on the how-to for a bit.

[MK]

Someone just put that in their yard???   

[C855B]

Someone just put that in their yard???   

Yeah. Somebody did.



    

[MK]

Ah!  Now that's cool! 

[robert3985]

Truth is, I don't think that printing these stands at prototype metal thicknesses would be practical, even lost-wax casting them at a scale 3/8" thickness is going to be impractical.

And, of course the understanding that I have is that only the body, base and locking mechanism would be 3D printed...the target would be much better represented by being half-etched with bolt-head detail for centering it on a piano wire or springy bronze "target rod".  Even brass is going to be too soft for the "rod" and would always be bent after a bit of layout operation, unless you are better at keeping your hands off the layout than I am!

The handle on the locking mechanism would also be metal.  Brass rod you get at your LHS would be just right, but even better would be stainless wire.  I'll be using .007" stainless wire for mine. 

If the locking mechanism is modeled without the matching portions that fit into the switchstand's round top where there are grooves machined to hold the rotation of the switch stand in place, then the 3D printed locking mechanism would rotate with the shaft.

So...the target would be etched brass,  and the locking mechanism handle would be brass rod, and the the target rod would be steel piano wire.  The rest would be an appropriate UV resin...or, in my case...investment cast brass.

Actuation would be accomplished from either servos, or hooking it up to the throw-rod on the turnout. 

If you have hand-laid turnouts, it is easy to standardize the amount they need to throw, which in my case is slightly less than what the NMRA recommends.  The L-shaped lever on the bottom of the target rod, will be easy to make out of brass... .010" with properly etched hole in it so the turning distance actuation of the target will be standardized on the switchstand...if not at the switch's throw rod. Maybe 3 or 4 etched L-shaped levers with differently spaced throw-rod holes would be a good idea to etch simultaneously if you haven't standardized your layout's turnouts, and to compensate for manufacturing differences on those you have.

I think that doubling the thickness of the switch stand's "plating" would be a good place to start, and wouldn't be noticeable after the model is painted, weathered and installed.

Cheerio!
Bob Gilmore

[narrowminded]

For my prototype that I made several years ago that was this approximate style.  It was fabricated from styrene.  It was also too large as I didn't have dimensions at the time and just winged it.  It is strong enough in the oversize but not sure it would be if made to scale. 

The most recent I did, to be used as a manual operator, was based on several I've seen and took dimensions from'  It's more of a floorstand style, tapered tubular.  That stand could be printed reasonably to scale and would be strong enough.  The operating crank and shaft should be metal and I planned on machined brass, drilled to receive .010" to .015" wire.  The 010" is decent for scale but if it is to be used as a manual operator too, the .015" will probably be the better choice and still doesn't look too out of scale, especially in person.  For the crazy magnification of closeup photographs the .010" would probably be better.

 I was considering making the stand's throw lever integral with the top flange, that flange actually turning with the lever, although made to look like part of the stand, which it is.  That way the latching notch could be modelled as well and the additional engagement of the flange with the shaft would add friction enough to keep it turning with the shaft.  I would hold it in place with just the friction so in the event of an errant move that knocked it out of position it could easily be reoriented without breaking it or if it did get broken it could be replaced.