Mike,
Only the tenon is square. It fits into a plastic/nylon cup in the square hole in the other axle half. That insulates the axles. The gear does have a square hole larger than the tenon that fits onto a corresponding square surface on the axle half with the 2mm tenon. It's a lousy weak system. I don't know what they were thinking!
The real early Porters used an entirely different axle arrangement, equally bad. they had a solid axle that was pressed into plastic wheel centers. It did that just fine but the wheels would get loose in the wheel center and fall off. Again another bad design. Hope this helps you decide to retire the old Porter and get a newer one in 1:20.3 scale. I have and converted to battery/RC. It's a solid design. Finally!
Only the tenon is square. It fits into a plastic/nylon cup in the square hole in the other axle half. That insulates the axles. The gear does have a square hole larger than the tenon that fits onto a corresponding square surface on the axle half with the 2mm tenon. It's a lousy weak system. I don't know what they were thinking!
The real early Porters used an entirely different axle arrangement, equally bad. they had a solid axle that was pressed into plastic wheel centers. It did that just fine but the wheels would get loose in the wheel center and fall off. Again another bad design. Hope this helps you decide to retire the old Porter and get a newer one in 1:20.3 scale. I have and converted to battery/RC. It's a solid design. Finally!