Last week’s post was all about converting Wrenn OO locomotives with horizontal motors to DCC; you can find the post here.  This week I’m going to share with you how to convert the vertical motors.

The vertical motors were used in the City & Duchess 4-6-2s, A4 4-6-2s, 0-6-2 tank engines, Royal Scott 4-6-0s and Bullied Pacific 4-6-2s.  The two engines I’m converting are the ‘City of Birmingham’ and ‘Sir Nigel Gresley’.

To remove the all-metal shell simply remove the screw located at the front and it will come away from the chassis.

As with the horizontal motored locomotives the wiring is very simple.  The black wire goes to the right side pickups and connects to the isolated motor brush at the front of the motor.  The brown disc is the capacitor which acts as a suppressor to prevent interference with televisions etc.  The other wire from the capacitor connects to the chassis and the left side pickup.

All the wires are removed except the black feed from the right side pickup.  The brush at the rear of the motor is not isolated from the chassis and, as with the horizontal motor, it’s this one which gives us a problem.

The steel cap covering the brush simply pulls out to reveal a spring and a brush as below.

The cap fits into a brass sleeve which guides the brush and spring to the armature.  In order to isolate the brush from the chassis this sleeve will have to be removed and replaced.

It’s very unlikely the sleeve will push out; you may be lucky but chances are it will need to be drilled.  Before you do this the armature will need to be removed to prevent damage and metal filings getting where you don’t want them.  In the picture above you can see I’ve removed the magnet and side plates: this is done by removing the main bolt through the motor.  The front brush should also be removed by pulling the end cap out.  Then the top nut above the armature can be loosened and unscrewed.  Note there is a small ball bearing in the cap. The grease should hold it there but be prepared for it to fall out. Then the armature can be removed, normally from the right hand side.  There’s also a small ball bearing in the fitting at the bottom of the armature. Again, it should stay in place but be ready just in case.  The chassis should then look like this.

Using a 5mm drill the old sleeve can be drilled out and the hole made ready for the new 3D printed sleeve; you can see the new sleeve in the bottom right of the image above.  Once the hole has been drilled, clean and remove any burrs from the hole and remove any metal fillings from the chassis.  Before you fit the new sleeve make sure the brush fits through without any resistance.  It should be able to fall through if tipped up.  If it sticks there may be some 3D printing residue inside which can be removed with a drill bit or round file.  The new sleeve can now be fitted and, if necessary, held in place with a little glue.

Then simply reassemble the motor.  Before you put the armature back in check to make sure the ball bearing is still there.  The top nut should be screwed down so the armature spins freely but has no vertical movement; only then should the nut be tightened.  With the brushes refitted, a continuity test should be done with a volt meter to double-check that both brushes are isolated from the chassis.  Then the wires can be added for your DCC decoder.  The red goes to the black wire, the black goes to the chassis, the orange goes to the front motor brush and the gray goes to the rear as below.

Once a DCC test has been performed the shell can be refitted and the loco is good to go.

So where can you get these 3D printed isolating brush holders? They’re available here:

Two Wrenn horizontal motor isolating sleeves.

Four Wrenn horizontal motor isolating sleeves.

Two Wrenn Vertical motor isolating sleeves.

Four Wrenn Vertical motor isolating sleeves.

Two Wrenn Vertical & two horizontal motor isolating sleeves.

I will also keep a few in stock so please drop me an email or message me through the contact page.  If you have a different locomotive which needs a special part to isolate the motor for a DCC conversion I’d be happy to look into it for you.