Saturday, December 31, 2011

Changing Directions

In one of my earlier posts I mentioned that I scratchbuilt my point motors :

using a method shown to me by Allan G., whilst I have been reasonably pleased with the end result, they do have some shortcoming - the main one is that they are not adjustable in their movement - it's all or nothing, and they do not have any DCC functionality, sure I could get a DCC stationary/accessory decoder but that would not have fixed their other limitation of no flexibility in their movement range, and whilst in the main they function OK, there are a few which are noisy, and others which just do not move far enough, leaving a small gap between the point blade and the stock rail which can lead to some rolling stock derailing, so I have been toying with the idea of replacing them with something better for a while now.

I've always been impressed by the servo motor (from the RC hobby) point motors
9G servo mounted in a bracket and actuator fitted ready for under point deployment

they are a very small and compact unit , compare the size of the scratchbuilt unit to the servo based unit in the photo below :

but have thought them to be a bit dear, then whilst at one of the CCWN meeting held at Rowan place (Main South) I noticed that Rowan had some servo motors acting as point motors, when I asked Rowan how he found them he said that the original decoders he got where a bit 'chatty' and figured out close to $100 per four, to me $25 per point is a bit on the dear side, he then mentioned that he had just got a set of decoder/drivers from Tam Valley in the States and found these to be quite good, and reasonably priced (Rowan was using the 'Singlets' at the time).

 Upon investigating the costs I figured out that if I bought the Quad Pic boards and the servo motors in quantity it would figure out to about $10 per point, that includes DCC capability, compared to the $7-$8 it was costing me to scratch build the point motors (with no DCC capabilities) I figured that out to be a good deal, pretty well a no brainer.

A Pair of Quad Pic servo drivers/decoders, these control up to 4 individual servos (or more if paired as crossovers)
I found a good article in the 3rd Quarter, 2009 edition of the free Model Railroad Hobbist EZine  which describes the Tam Valley decoders and how to connect the servos to the layout, whilst I did not follow their method to the letter(they recommend using double sided tape to fix the servos to the layout, I prefer to use screws as I think that gives a better fix), it certainly has some good ideas which I have used.

Seeing I had a requirement for more point motors I figured out that I would be better getting these rather than continuing along the scratch building path because they give me flexibility in their movement range, they have DCC inbuilt let alone that fact that it save me time in not having to scratch build any more point motors, I would still have to make the mounting brackets, but that is a fairly quick task which took all of about 2 hours to make sufficient brackets to mount 36 servos. I have made two types of mounting brackets, one is made from a 25mm Plastic angle (about $9.00 for a 2.4M length) which will be used where the point motor is not directly underneath the point as it has slightly more clearance than the other style of bracket :

the other is made from a 'U' shaped piece of plastic moulding  sold at Bunnings as a plastic floor covering cap for about $3 per 2.4M length, this will be used where the point motor is directly below the point,

the 'U' type bracket has a channel of about 13mm in width into which a servo fits quite nicely, an end on shot of both types of brackets is below:

You may have noticed that the actuating wire is 'threaded' through the plastic lever, this is quite easy to do as shown in the photo below:

So far I've replaced about a dozen point motors and am very happy with the result to date. As for the scratch built point motors I currently have on the workbench and those currectly in place in the layout that will be replaced with the servo motors, I will probably end up using these replaced point motors to drive the lower quadrant signals I have.

I hope Santa was kind to all (Looks like the Jolly Gent has put down for a set of Euruka BSV's for me:-) and that the New Year is a prosperous and good one.

Well that wraps this little session up, now back to fitting more point motors.