Re: disc brake

I have my bike up and running. My problem is not making it go but making it whoa. Am attempting to make my own disc brake for the back wheel to suppliment regular brakes when riding in the mountains. Flat land no problem. Since I have run my gearing through bike gears ala sbc jackshaft, I machined a hub for the back wheel and am mounting the disc the same way as most would have there final sprocket. In fact am using the final gear with teeth ground off it as the disc. About to make bracket for brake. If it works I will need a source for bulk brake cable to lengthen. Any suggestions? Will try to upload picts if it works. Bob