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Plarail: Percy, The Engine That Couldn’t

After scouring recycling shops in Japan and finding some Pla-rail 300-series Shinkansen... I did a little more investigation (aka. purchasing) of tracks and other relevant equipment to set up a test layout. As with any hobby, this small intial effort then kept expanding once I'd realised that Tomy released Plarail in Australia under the Thomas brand.

Trash and Treasure is a usual haunt on Sunday mornings and I have been happening across more and more Plarail equipment. Sure, it's for 2-4 year-olds, but some of it is just so simple and easy, that it can actually be rewarding. You then look at the components available from Japan and start to realise what can actually be built! I reckon, with a little bit of further modification and automation, you could create some seriously crazy layouts.

The design and equipment is also rugged and resilient. As that it's made to be run on carpet (by children), the tracks are easy to connect and hold together after being kicked and beaten. The locomotives also are built to cop a beating, with internal gearing to allow the axles to be held whilst the train is trying to move. You can even wrench them backwards when they want to go forwards. Of course, with age, any fail-safe equipment can also fail.

I've only learnt all this recently. I picked up a Percy The Small Engine from Trash recently and found it to be defective. With zero loading, the loco could move around... but as soon as you gave it something to haul it just sat still. The engine was still rotating... you could even see the gear on the driving axle spinning. It seemed to have quite a 'click' on every rotation.

The cause turned out to be a split final gear on the driving axle. It was still on the axle, but due to a split between two teeth, it had very minimal grip. This meant that it'd keep contact with the axle on light load, but spin incessantly on anything else.

The gears are held onto the axle by friction. The axle is roughed-up where the gear is finally meant to sit, but the diameter of the hole in the gear is smaller than the diameter of the axle to ensure a proper fit. This meant that, any attempts to glue the gear shut would fail; the pressure would snap the gear back open as soon as I tried to slide it back on.

From here, I tried to widen the hole in the gear, to allow it to slide on easier. This worked, and I then attempted to also glue it to the axle. Unfortunately, I had no type of glue that would correctly bond to both substances.

Not even Araldyte worked! The next step was to scour eBay for gears. Turns out they're dirt cheap.. when purchased from China. Of course, that means 4++ weeks of waiting. So.. 4 weeks later, the following arrived.

Included was a total assortment of gears. Around 6 of them were in the right ballpark. The blue ones fit way too easy and I'd have to work out a method for securing them to the axle. I tried the hot-glue-gun... but I was just making a mess.

The next effort was with one of the white gears. They were the right diameter, but too wide. Their hole diameter was also too small. Firstly I widened this with a ~2.0mm drill bit in the dremel. Make sure that you drill perfectly perpendicular and centered!

Once on I then used a grinding stone chomp the gear in half. I filed it down afterwards to clean it all up. It actually worked!

Based on the note above, the first one I did actually failed to run smoothly... Percy had a huge limp! Turns out I drilled out the center hole completely off-center. The gear actually 'wobbled' around the axle badly and pushed the innards of the gearbox up into the chassis! Be really careful. The second one worked perfectly and Percy was grinding along again once more!