Ok. I want to run internal cables on a custom bike I am building. I want basically no visible cables around the bars at all.
I know, it's a waste of time, but I happen to HAVE time and a engineering workshop at hand.
So here is some background.... It's an old 1930's steel frame. It's a road bike.

Cable 1. Goes from the inside of the right handlebar (reverse levers) and down to a cable operated disc brake on the front wheel.
Cable 2. Goes from inside the left handlebar end and to the rear disc brake on the left side of the rear axle.
Cable 3. Goes from a thumb lever on the right bar, into the handle bar and ends at the left side of the rear axle. (7 speed rear hub.)

In the frame I can do. In the fork leg I can do. In the handle bars I can do.
It's getting from inside the bars to the frame for cables 2 and 3 and at the bottom of the stem for cable 1 that I am having to think long and hard about....

But I have an idea.....