My first customer bike 5 years ago. Trike from Beijing, China. I found this out by finding an identical one in a book calling "Chasing Rickshaws". It came to me in need of brakes, which contsist of a cable woven around the headtube gusset going down to a brake that actuated like an oil filter tool. You either tugged up or tugged down on it to stop, using your hand or foot. The gear were operated by placing the chain on the desired sprocket by hand, which meant stopping and moving it to 1 of the 3 rear freewheels, or 1 of the 2 front chainwheels, which could be done on the fly, sometimes.
The idea behind the modifications I was making was to make it appear is if it were done in the Third World, with no welding, from whatever parts were on hand. So the first thing I had to deal with was a completely non-standard bottom-bracket size, smaller than Amercian (OPC) , but larger than threaded. The only other place I've run into it is on very cheap 16" kid's bikes. I got a bottom bracket shell from Sacha White, and found out there was still about 1/16" to take up on the radius. I got a piece of muffler tubing and sanded it to fit. Then it was tapped together with a hammer everything a fairly tight sliding fit. I drilled through all three tubes, tapped two holes m8 x 1.25 and put a short bolt through them.
Then I added a "modern" drivetrain form an inexpensive mountain bike. I had to modify the rear cluster, taking out "2nd" gear and having a spacer there, so that "1st" could be used to drive one of the rear axle freewheels. The wheelbase is adjustable, but the plate that holds the hub (now an intermediate shaft, if you will) is slotted so it can be moved fore and aft. The front and rear derailleur mount conventionally, and the bb is now threaded so better parts can be bolted up.
The band brake is now operated by a footbrake, and this one is similar to how it would be done in China. The lever itself was cut out with a jigsaw while bolted down to my bench, and then shaped with a big ol' bastard file. The foot pad it just a bolt with rubber hose over it. The rest of the hardware is just from Ace Hardware. The brake pad itself was replaced with a chunk of bald motorscooter tire, and now it will lock up one wheel, as one wheel spins on its own hub, enable the trike to turn without needing a differential.
This is the easiest way to work on one, just tip it up.
I also added a front brake, and regreased what I could. It works much better with these modern conveniences and safety features but it loses a little but of it's soul and simplicity. I guess that's the trade-off when a life is on the line other than your own.