Controlling Turnouts with Servos

The next stage is to mounting these in place! My turnouts have a 1/2" holes drilled through the roadbed and underlying subbbase and directly centered under the turnout throwbar so with the old Switchmaster motor removed, I placed a strip of masking tape across the points and stock rails (but clear of the throwbar) to keep the throwbar equidistant from both stock rails. Then - with the servo disconnected and not getting power - I once again gently rotated the arm to 12:00 so the servo position was once again centered.

I also cut a thin strip of masking tape - say 3/16" wide x 3-4" long - and placed it across the mounting bracket in order to 'tack' it in place when i undertook the actual mounting as the whole assembly is of minimal weight. Then once the 0.032" steel throw rod was successfully threaded up through the turnout throwbar, I attached some forcep tweezers to the protruding 0.032" steel throw rod as a precaution to it dropping through and having to repeat the previous step!

From underneath the layout again, I oriented the servo assembly so that it was centered as much as possible before drilling and then attaching the first #6 x 5/8" mounting screw which should be one of the pair closest to the back of the servo. Gently tighten only...just enough to keep it in place but still allow some judicious twisting if required to adjust its position. Then remove the masking tape and if the points vs. stock rails relationship still looks good, then you can add the second mounting screw. I've found that installing two mounting screws kitty corner is more than sufficient to prevent any twisting or deflection.

The next step is to connect the servo to the QuadLN_S Servo Board and then undertake any final adjustment(s) for travel with the Remote Align Board. Optimally, you want sufficient pressure to keep the point tight to the stock rail but not so much as to stress any solder joint between the point and the throw bar. Once satisfied that this condition has been met, check that the 0.032" steel rod reaches it maximum height in mid-travel and then drops down a bit at each final position before trimming it off so that it doesn't protrude above the rails.

Troubleshooting: If you inadvertently miswire the servo to the QuadLN_S Servo Board, no biggie as the servo will just fail to respond but there is no damage to the board. And of course with the control cable from your SPDT or SPST switch, there is no backwards option as it's a simple on-off function. One thing to note is that when the Remote Alignment Board is connected to program a specific turnout that it can be controlled only by that until it is disengaged. One anomaly that I discovered was that when I had one poor (and intermittent) connection on a longer run due to a pin being partially pushed out (see previous comment) that it caused the affected servo to rotate to its maximum limit - which resulted in the 0.032" steel throw wire (which had been trimmed to top of rail height) dropping down far enough that it pulled right out of the throwbar hole. Arghh!! So there are two options to correct this (once of course, the balky connection has been identified). The first is after unplugging the cable to disconnect power to the servo, center the throw arm once again and then unscrew the servo arm from the servo shaft, being careful not to drop and lose the screw. Once again, place a strip of masking tape across the points to keep them in position equidistant from the stock rails and then feed the steel 0.032" throw rod up through the center hole on the Berrett Hill Shop's bracket and then through the hole in the throwbar once again. This is an admittedly fussy procedure at best but it does save having to trim off an extended steel 0.032" throw rod again so swearing is allowed and patience is required! Once done, place the servo arm back on to the servo shaft,making sure that it is in the same 12:00 position and reinsert the screw to retain it in place. The other option is to unscrew the entire mounted servo assembly (after centering the throw arm as noted above) and take it to your workbench, unscrew the servo arm and install a new longer steel 0.032" throw rod and then remount the servo arm back in the 12:00 position on the servo shaft and screw it back in place. Once done, it can then be taken back to the layout threading the steel 0.032" throw rod through the throwbar once again and remount it using the previous existing mounting holes. I've found that when powered up again that the previous programming for travel limits and speed remained intact so with any luck no additional adjustment will be required - other than of course, trimming the longer steel 0.032" throw rod down to top of rail height if you elected to do the latter option.

Addendum: I had one servo that for no apparent reason stopped responding to its toggle switch. Given my previous comments and experience, I suspected the culprit was a bad cable connection, either on the cabling to the servo or on the cabling to the SPDT switch. Determining which is quite simple: just plug in the Remote Alignment Board to QuadLN_S Servo Board and see if the servo responds to inputs from that; if it does, both the servo and the cabling from it to the QuadLN_S Servo Board are good which by process of elimination indicates that the issue is somewhere in the cabling between the QuadLN_S Servo Board and the toggle switch. I dutifully checked that cabling, adding one section at a time and all was good so I assumed that I may have just had a poor connection. However a few days later, the situation reoccuured...argh! It turned out that the issue appeared to be a cold solder joint with one of the cable pins attached to the SPDT switch so I must have jiggled it enough initially that the connection was partially restored before failing again; I resoldered the connections and all seemed fine...but...only a few days later, it started acting up again. I wiggled the switch and that seemed to restore operation which led me to the now inescapable conclusion that the root cause was an internally defective SPDT switch. So out it came and in went a new one and all seems fine now...(touching wood)!