"How to" Series

Electrically isolating the motor: Steps 5 - 6


Original channel in chassis motor cradle


Step 5 - Create a chaseway for the bottom motor wire by extending the channel along the full length of the chassis motor cradle and insulate the channel with Kapton or electrical tape.  (Actually, the only spot you really need to insulate is directly underneath the bottom motor contact.  That's what you don't want shorting to the frame.)

Channel extended using 3/16" OD endmill


HELPFUL TIP: I had access to (and experience with) a milling machine so I used a 3/16" OD endmill to extend the 1/16" deep channel.  This makes for a nice smooth machined surface.  If a milling maching is not available to you, a Dremel tool could work in a pinch.  A drill press and drill bit could also be an option, as long as you have a stop for keeping the drilling depths consistent.  You would also need to hold the chassis in a vise and brace the vice so that it doesn't move while you drill.  (Neither of the latter two will do as good and as clean a job as a dedicated milling machine.)


However, don't be afraid to ask around.  Someone you know may know someone else who knows a machinist.  You might also go to your local yellow pages and give one a call.  With the economy the way it is, you might be surprised that their might be folks clamouring to do any job - however small - just to bring in a few bucks.  And this is very easy machining job so it wouldn't take them long at all to complete.

Channel isolated with Kapton tape
Top and Bottom motor contact


Step 6 - Solder a 3" long piece of gray flexible 28/30 ga wire to the top contact of the motor. Solder an identical orange wire for the bottom contact*.


NOTE: The Sagami can motor that comes with the SW1 is actually installed upside down. This was prusumably done so that the pretuding motor contact could make electrical contact with the chassis. (The other motor contact is recessed.) This is not a problem if you operate in DC. However, it IS a problem if you want to convert the unit to DCC. The motor must be electrically isolated from the chassis for you run the risk of cooking your decoder.


HELPFUL TIP: With the motor being upside down, I found out near the completion of the installation that the SW1 ran backwards. If you prefer, you could swap the motor wires so that the orange wire is on the top contact and the gray wire on the bottom contact. Once you hardwrie the motor wires to your decoder, your SW1 will then run in the correction direction.


Rotating the motor 180 degrees axially would have been one solution. However, the protruding motor contact presses up against the light board, raising it slightly. Since there isn't much leeway under the hood with space at a premium, leaving the motor orientation as is and swapping the motor wires is the better choice.