I was wrong. 125mm wheels do exist in 3 dimensions, but only sporadically. The rest of the time, they exist in 2 and a half. Through some research, I found out that some competitive inline skaters use these 125mm wheels, so they are generic enough and not just confined to some specialized part from one company.
The wheel style in use on the ElectricX2 from Sharper Image, as well as the most common replacement, is a 12-spoke design with plastic fake chrome accents. I detest fake chrome anything, but what’s worse is that the wheels have no real hub or solid mass of plastic with which to mount a hub to. It was more or less designed from the start as an idler.
In a moment of madness, however, I discovered that a 3/16″ pin fits snugly in hub corner, like an emo. Thus, an easy drive solution was discovered… Just drive a bunch of thick steel pins through the pulley and the wheel slides right on. It certainly beat the other idea, which was using a spare wheel from a nonrelated, strange-looking vehicle that was slightly out of spec.
Here’s a drawing of “pinhubdrive”. Yes, I meticulously took to the front wheel on the thing with digital calipers and duplicated most major dimensions in Inventor. It’s alot shinier in 3D.
The pins are(will be?) pressed into the aluminum pulley, which hopefully isn’t shitluminumâ„¢ like the rest of the scooter frame. The wheel just sits between the pins, and the whole assembly runs on some regular skate bearings, held together axially by the bolt that is the rear axle. Essentially a trade-out of the stock assembly with the same mounting dimensions.
According to McMaster, each 3/16″ hardened dowel pin has a shear strength of 3,600 pounds, so with six on there, I hope there won’t be a problem with broken pins. Only 13,000 in-lb of torque separates me from disaster. Cool, huh?