A working RPO in N-Scale

[randgust]

Years ago I attempted an auto-reversing loop by placing a magnet under a caboose, putting reed switches between the rails, and having that throw the DPDT relay that reversed the main line while the train was in the loop.

Conceptually, and even in practice, it worked.  What I didn't account for was the current hit that any given solenoid is capable of generating.  It hit enough of a current spark in the reed switch to rapidly damage the switch.   Current is not your friend on what's essentially a resistor; so the 'pickups' or 'switches' are being asked to do a lot here.

Capacitor discharge systems work wonderfully to reduce that sparking; just saying.  But you only get one blast for a second or so until it recharges.

Any kind of servo-motor, or even a micro gearhead motor, has a lot less draw and can run off of track power.   The 'trick' is to have some kind of latching-relay-switch that's magnetically controlled - Rapido pretty much perfected that on their lighting boards for N with the 'wand' feature to turn it on and off.  Or you control it via a DCC function you're otherwise not using.

I still think this is very doable, I'm just struggling with the solenoid concept to do it.   Here's my candidate for the lowest-current, highest-torque little motor I've ever worked with:  http://www.robotshop.com/ca/en/solarbotics-gm15-gear-motor.html.  I use these to run my Climax models and recommend them highly, just with a 100-ohm resistor in series if you are off of track power.

That's also what I used to power my rotary snowplow head from track power.   That's duck soup to control if you're DCC, only DC is tricky.  They just have a ton of torque for such a tiny little package.

[peteski]

I still say that for this type of linear motion device, memory wire type of mechanism would be most suited (and by far, the simplest).

[randgust]

Same guys that sell the gearhead motors sell a TON of memory wire, they just call it by another name..... 'muscle wire'....

http://www.robotshop.com/en/flexinol-en.html

Wow.   I was looking for a distributor and various parts suppliers, this may be it.   I've had good results with this dealer.

The 'silent' part sure sounds (pun intended) good.

[peteski]

Same guys that sell the gearhead motors sell a TON of memory wire, they just call it by another name..... 'muscle wire'....

http://www.robotshop.com/en/flexinol-en.html

Wow.   I was looking for a distributor and various parts suppliers, this may be it.   I've had good results with this dealer.

The 'silent' part sure sounds (pun intended) good.

Yes, muscle wire is silent in operation.

I was incorrectly using the term "memory wire".  I did mean "muscle wire" all along. Brain fart!  Thanks for the correction Randy!

[nkalanaga]

"A mail pole would never be next to water pans"  But it would be next to a station platform, and if there are two or more tracks, the platform often continued across the tracks.  Just put a section of platform between the rails.  You could use pieces of rail as the contact strips, with paving between them, as was done at some grade crossings.

[VonRyan]

"A mail pole would never be next to water pans"  But it would be next to a station platform, and if there are two or more tracks, the platform often continued across the tracks.  Just put a section of platform between the rails.  You could use pieces of rail as the contact strips, with paving between them, as was done at some grade crossings.

Well the pole is going beside the red-line on my N-Trak module. The only station is a small GWR branchline station on the 10" line.


-Cody F.

[nkalanaga]

OK, so platforms wouldn't work.  Who hangs out the mail for the train?

[VonRyan]

OK, so platforms wouldn't work.  Who hangs out the mail for the train?

Model wise, there is a dirt path leading to the mail pole.
In reality, I hang the mail bags. 

[nkalanaga]

That would work.  No station building, as the town is too small to warrant a stop, but there is a post office, off the edge of the layout.  A station sign on a post would make a nice finishing touch, as railroads name EVERYTHING, and give viewers a sense of place.

[VonRyan]

After many a test and with much fussing about, I've completed some spring tests with the old Arnold solenoid, and with a slightly larger solenoid made by Kurtz-Kraft Models Company.

Neither solenoid could overcome any of the springs, even when 13.75v DC was applied. As such, it would seem that either a function-only decoder on the solenoid, or some other control method, will need to be utilized.

Further contemplation has made me come to realize that the water-pans idea was not feasible as the two contact wipers would be susceptible to shorting across diverging rails in turnouts.

At this point, it may be a good idea to also consider other possibilities for making a "grab and drop" mechanism that can operate as reliably as the American Flyer RPO car, but is more in tune with modernity, and that I can build into this Micro-Trains RPO car.

[towl1996]

Since this thread has been brought back from the dead, @VonRyan how's the FM coming along? 

[VonRyan]

Since this thread has been brought back from the dead, @VonRyan how's the FM coming along? 

All I can say about the FM Flatcars, as far as Camden & Amboy Models is concerned, unforeseen circumstances have resulted in us halting all work on the project and as such we are looking at pursuing other possibilities.
But with that being said, our next project will still be a class of PRR rolling stock.

[peteski]

I still think that memory wire might be a better actuator option than solenoid. Or maybe one of the nano-servos used in radio-control hobbies.

[VonRyan]

I still think that memory wire might be a better actuator option than solenoid. Or maybe one of the nano-servos used in radio-control hobbies.

My beef with the memory wire and the servos is the speed. The solenoid is nearly instantaneous, but the servo takes time and while I'm not 100% sure on the speed of the memory wire in its change of length it also doesn't make much sense to me as to how it works.

[chicken45]

All I can say about the FM Flatcars, as far as Camden & Amboy Models is concerned, unforeseen circumstances have resulted in us halting all work on the project and as such we are looking at pursuing other possibilities.
But with that being said, our next project will still be a class of PRR rolling stock.

What were the unforeseen circumstances?