ORBO Carabao

[Wildcat]

This build is mostly in theory at the moment, but I think it will work.
I have a fatbike I made up previously. It has a cowbell like the Carabao they use here for farming and transportation.

It will get a whole new rear portion of the frame to accomodate two rear wheels. The chainwheel will be on the left side of the frame so the drive wheel will be situated to the left of the frame. The rear wheel on the left will be the drive wheel, the wheel on the right will just roll freely. So it will be like an open differential on a car, with one wheel drive.
The rear frame has yet to be designed but will be as soon as I can lay it all out and make some measurements. The wheel on the right will be further outward to give some stability. I think 2 feet between the rear wheels will suffice.
The frame will be taken to the welding shop then returned home to see if everything lines up and works as hoped. I think there will be a few trips to the welder before it's done.
The springer needs redone also. I used scrap pieces of metal that can be replaced by one piece made to fit. I may use just one spring to get a softer ride. With two springs I can jump on it and there's almost no movement.

The three wheels are ready.

 

[Bike from the Dead]

The drivetrain idea you have in mind sounds similar to how some trike rear ends work. One of my trike axles uses a set of regular cruiser bike wheels, where the drive side is a standard 24" coaster brake wheel, and the opposite side is just the front wheel. The only difference is that the chainring isn't linked directly to the sprocket on the drive wheel. It links to an axle with a sprocket on one end, and a sprocket on the other side of the axle links to the sprocket on the drive wheel.

I'm curious to see how your bike will work with the drivetrain you have in mind, and how it'll all come together in the end. Best of luck to you!

 

[Wildcat]

I tore it apart and laid out the wheels to see if the idea had any merit. So far I don't see any major problems.

The wheels sit back farther so the drive wheel won't contact a foot on the pedal. That leaves plenty of room for a rack or box of some kind on the back. It will be about 90 inches long.

I was thinking of a way to widen the BB for the fat tire, but it isn't necessary with this configuration. The standard bb will work because the tire is outward from the cranks.

I spaced the wheels at 16 inches apart, making it 24 inches wide total. The drive wheel will sit a little farther inward to line up the chain line.
If it seems to narrow to ride smoothly, it'll go back to the welding shop to get wider. The shop only charges 10 to 12 bucks for hot work.

This is just a preliminary look, the height of the frame still needs to be assessed along with the design for the rear of the frame.

A radio flyer wagon would work great as a rear rack, if I could find one. And maybe a roof of some kind to keep the sun and rain off. They are very good at fabricating things over here.