[lincpimp]

I wish I still had my f103, I could make you a disk brake that would fit the bill just fine. The only problem i can see is that the shaft that the brake and pinion are on would have to be supported with 2 ball bearings. You could use the ctr bulkheads from a 1/8 buggy to hold the bearings and turn one inside out to but the brake assy between the bulks. The you just need a shaft that has the correct interface for the disk and machined down to 1/8" for the pinion. Or you could make the required bulks and shaft from scratch and use whatever brake disk that would fit in the space. Would be no bigger than 35mm, same size as a 540 motor.