Points /turnouts on my layout were initially operated manually using a wire-in-tube mechanism. There are currently 44 points on the layout and I started converting to servo control about half-way through.
The wire-in-tube (WIT) method I used worked very well and is shown to the right.
The mechanism is relatively easily fabricated and the cover is removable with one screw to allow easy adjustment of the point blades at the fascia.
It will handle a second wire to allow push/pull operation of 2 points in a crossover.
If there is any interest, contact me and I will add a section on the design and fabrication of the WIT method and the fascia mounted lever frames..
I changed to servo operation for the following reasons:
- with this type of mechanical operation, control panels would not be able to operate the points (there are 4 mini panels on the layout).
- the system selected allows precision adjustment of each point blade; variable speed of movement; position indication
- servos can be installed from the top of a 50mm (+) foam layout
- points can be controlled from a central position; a local panel; by a computer; as a route by changing many points at once and other options.
- the system I use is based on the UK MERG model. Circuits vary from simple to complex.
- Plus – I like working with electronics.
2019 UPDATE
(23/3/19)
I have had some of the servos become very noisy in operation which I believe may be due to their being relatively poor quality CLONES. This ARTICLE sheds some light on the differences between “counterfeit” and original MG90S servos.
I will report back on my findings.
The mounting slot in the foam is formed by drilling 12mm holes through 50mm foam to fit a micro servo … SEE DRILLING HOLES IN FOAM
The guide tube I use is a short piece of bicycle bowden cable outer – used for gear selection from memory. I just bought a metre or so length from the local bike shop.
Shown above is a “Micro 9g Metal Gear Servo For Futaba Hitec HS-55 GWS walkera RC HELICOPTER GA” as described on eBay.
Here is a LINK to the eBay site I used but check other sources for a possible better deal. The current cost is $4.87 (16 July 2016) with free postage to Australia. There are cheaper plastic gear models but I have found these ones to work more smoothly and to be much quieter. As you can see, they come with a variety of servo arms (aka servo horns) and any will work in this application.
That’s a little over 20c each. They were sold as “Durable 2mm Aircraft Stopper Servo Connectors Connector with Screws – Set of 20” and one eBay supplier I used was at this LINK . These things are TINY. The Allen Key grubscrew is 3mm.
Assembly order is shown for the quick-connect. It needs to be free to rotate in the servo arm and the nut is best secured using a tiny bit of thread locker. The grub screw allows positioning adjustment but the travel and end points need to be set by some electronics.
The right hand one is, in effect, a stand alone method of controlling one servo & its point with a switch. The 3 blue components are variable resistors used to control the speed of the servo and distance it moves Left & Right. I also use it for testing the servos.
MERG sells kits for the above 2 projects and they cost just £1.55ea +postage from the UK for MERG members. Almost all of the more sophisticated CBUS kits are based on professionally manufactured Printed Circuit Board (PCBs) and usually kits of the necessary parts are available or you can buy the parts locally.
There are other alternatives:
The device shown to the right is a ” MegaPoints Controller” by a UK company and could be very good for those people not confident in building PCBs themselves. I have not used it or seen it in operation but it comes ready to connect to 12 servos and has 12 corresponding switch inputs. Here is their Website and here is a YouTube Demo There are 2 videos in sequence. Cost is said to be £50 in the UK.
I also notice that DCC Concepts have an “above board” system that looks interesting for someone not interested in a DIY approach – Cobalt SS.