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Occasionally, during the course of discussions, members of the NMRA's DCC Working Committee explored new applications made possible by this leap forward in technology. One item often reappearing was the ability of the operator to uncouple whenever and wherever he desired, as can be done with the prototype.

Electrical uncoupling is possible with proprietary systems but to my knowledge it hadn't been done with the most accepted coupler - the Kadee. Members of the Committee had experimented with Kadees using cotton, solenoids and memory wire. Whatever method used we all agreed that to uncouple reliably with Kadees required the operation of both couplers. When DCC decoder chips fall out of Weeties packets this will not be a problem, we will just put one in every carriage! Until this occurs experiments with Kadees were abandoned.

While at Melbourne's Model Rail Expo last December I came across Steam Era Models' Auto Couplers II. This coupler mates perfectly with a Kadee but has no annoying springs to lose. The coupler itself is in two parts, the top part is the knuckle and the bottom the guide. They both pivot around the centre bolt in the draught gear housing and being made of acetal their springs are integrally moulded.

Immediately after assembling my first SEM coupler came the obligatory attempt with a piece of cotton. Tied to the magnetically sensitive brake hose of one coupler and pulled lightly sideways, and yes, these SEM couplers uncoupled! Pages of drawings were made to determine the best way to move the brake hose or the top half of the coupler sideways using solenoids and levers.

With serious experimentation about to commence more SEM couplers were required so I proceeded to cut them off their sprues. I was about to cut off the ejector sprue on the rear of the knuckle half, the part that has to move to uncouple, when I realised this sprue could not be in a better place. This extra piece of superfluous plastic provided a perfect point where a lever could connect to the coupler behind the box and out of sight under the chassis! Thus this simple and effective uncoupler was born.

What follows is a description of my conversion of a Powerline ‘G’ Class to DCC uncoupling. Yes, I know that this locomotive has more internal space than most, but we all have to start somewhere!

A DCC compatible Decoder with at least 2 function outputs
2 x Steam Era Models couplers
2 x 12Volt miniature relays
2 x 1N4148 Diodes
Spring steel 0.38mm(.015") guitar string

Construction

Remove the bogies, cut off the old couplers flush to the bogie and fit the Kadee mounting brackets onto the pilots. Assemble the couplers. When cutting parts off the sprue do not remove the all important sprue on the rear of the knuckle half. Cut the rear off both parts of the coupler box so that the sprue can swing freely. I found it easier to glue the coupler draught gear housing and when set drill the #70 hole vertically through the sprue. Mount the coupler in its normal location. checking for clearance around the actuating sprue., removing material from the coupler mount or chassis as required.

Prise the relays from their cases, remove the contacts and trim the solder tabs and excess plastic until it fits in the chassis above the coupler. Ease the tension on the relay spring by carefully stretching the spring a little at a time. The aim is to have the spring provide as light a load as possible so that it just holds the armature in place. (The armature is the part that moves when the relay operates).

Refer to diagrams 1 & 2 and establish the best place for the relays. The actuating lever is on the right when looking out of the cab and the best place is usually slightly left of centre. Drill an 8mm hole through the chassis floor for the actuator wire to go through.

Solder the actuating wire to the relay armature and place the relay in position. Note that the spring steel wire will have to be bent approximately 45 degrees about 2mm below the relay and in the direction of the front centre of the relay. From the point level with the front centre the wire is bent down vertically to go through the hole in the sprue. Some trial and error will be necessary for your first one. Keep placing the relay in position with the wire through the sprue. When the relay is not operated the coupler should flick from side to side without being fouled by any of the mechanism. When the relay is closed the coupler should be held firmly to the side but still able to be moved to the opposite side against the resistance of the spring steel.

It is surprising how rough the adjustment can be without affecting operation. Once you feel that the system is performing well solder some temporary wires, one to each ‘terminal’, and connect to 12volts. If the system is operating correctly the loco should wag its tail every time power is applied. Repeat the operation for the other end of the loco then superglue the relays in place and find something else to do for a few hours.

Refer to the notes that came with your decoder and install the decoder as per instructions. Identify the wires required for the uncoupler. The two function wires should be green and violet. If your decoder has a separate accessory power wire it will be blue, if it doesn't have this wire connect a separate wire to the red wire (the right hand rail pickup) to use as the accessory power wire. Refer to diagram 3 for the wiring details and note the location and orientation of the 1N4148 diodes which are soldered between the relay tags. The accessory power wire must be soldered to the end of the diode that has the band around it.

Putting it simply you can now uncouple whenever and wherever you like with only one restriction - the couplers will only uncouple when slack. Slack occurs when decelerating while in forward motion or by stopping slowly in reverse so the carriage does not jerk back keeping the couplers tight with its own momentum. When shunting just back up a little, uncouple and move forward. Weighting to NMRA Recommended Practice improves performance. Uncoupling can even occur when travelling on the mainline at speed due to slack occurring as the carriages bounce along behind the loco, but only when the uncouple function is activated! This introduces the possibility of broadcasting a random "runaway" to add excitement to any serious operating session.

My son Andrew and I had some fun fly shunting by weighting a wagon to increase its inertia. (I remember seeing a fly wheel in a box car once). Proceeding at a reasonable speed on a 2% downhill grade toward a turnout which Andrew had manned I operated the uncouple function, dropped the throttle down a notch or two to slacken and thus release the couplings, then accelerated through the turnout and away from the wagon. Andrew threw the turnout just as my loco cleared it and the heavy wagon rolled into the siding. Sound like the real thing? Well, it felt like it!

ÓADCC

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