How to rebuild a Scalextric Johnson motor

 
When you buy an old 1970s or 1980s Scalextric car from a swap meet, such as my Back From The Dead BMW that we are working on today, most will come with a long can ‘Johnson’ style motor that came standard in the cars at the time.

As great as these motors are they can come with issues. Many are 30-40 years old now and as such dirt can build up between the brushes and armature, bits of dirt and get into the can of the motor itself and, ultimately, smaller parts of the motor can begin to deteriorate and break apart. Thankfully, they are super easy to strip down!

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These motors are normally press fitted into the cars and so removing it is just a case of pushing it out of the holder. The wires and connections popped out of the guide as I pushed the motor out. Normally I would suggest taking the guide out and removing as one piece so you don’t get confused with what way around the wires go. If the wires do pop out, just make a note of which way up the motor goes back in. There is text on both ends of the motor to help you with that.

To remove the armature from the can you will need to pull back the two little metal tabs that hold it in place. I normally use one of the little flathead screwdrivers you get from a Christmas cracker or phone screen repair kit as they are small enough to get under the groove.

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Bend the tab so it’s pretty much flush with the rest of the can. Don’t bend it to far back or you risk snapping it.

Once those tabs have been bent back give the black end of the motor a pull and the armature should slide out of the can.

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There should be a tiny little washer on the can end of the armature. If it is not there then have a look inside the can and you should be able to see it. This photo is appalling and you can’t really see it, but it was sitting just to the right of the hole the armature passes through.

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Pull the washer out of the can with a pair of tweezers and  slip back over the end of the armature like so:

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Now for the fun part! Taking out the brushes!

On the assembly at the gear end of the armature you’ll see a little coiled bit of metal. One end is hooked under a metal shield and the other rests against a metal block under the shield. The metal block is called a brush and it’s what allows electricity to pass through the armature and allows the motor to spin. Over time the gap between the brush and armature gets dirty and then the current can’t get through effectively.

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The way to remove them is to push the end of the metal clip that’s tucked under the hook in the shield towards the centre of the motor and them up and over it’s retaining hook. Again use a tiny flat head screwdriver. The whole coil of metal will now be able to turn and release the brush. If you remove the coil just make sure that you remember the straight end goes to the hook and the curved end goes onto the brush.

If it’s been in there a long while the brush may want persuading to come out with the flathead screwdriver.

This is what the brush looks like when out. The curved ‘C’ shaped part goes onto the armature and the flat end with the groove goes towards the outside of the motor.

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Rub over and around the brush with a cloth to remove any carbon build up and dirt. It should go from being black to a copper colour.

The armature end of the connection will want cleaning too. Spray some electrical contact cleaner down the shield and onto the armature. I then put a small, old paintbrush down the shield so the hairs make contact with the armature and then turn the armature via the gear to displace any dirt.

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The rebuild is pretty much the reverse. Slide the brush back into it’s holder and fold the retaining clip back into place and then slide the armature back into the can, making sure that washer is in place first!! Press the tabs back down with your screwdriver and voila! You have a nice clean motor!

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