Most people are so weak from driving cars most of their lives that they can't even think about hauling more than 40lbs with a bicycle. Yet I haul 80lbs at least once a week.
I am a third degree backyard engineer so don't ask foolish questions about "how do I know if these bikes are strong enough".
For a long nose bike I recommend no more than 2.3" trail, with a steer angle less than 60 degrees. But for a short bike more than 70 degrees with 1.3" to 1.7" trail is best.
If you’re working with a BMX fork you have to make compromises.
A steer angle 68 degrees with a 1.5" rake is 2.4" trail. But a steer angle of 70.2 degrees will do a trail of 2", so 69.7 degrees will do a 2.1" trail, close enough. It would work better with more rake. Like maybe 2".
The reason these long bikes are so popular is that trailers can yank your bike around when full of heavy cargo.
How to motorize a heavy bike:
Forget about adding a disc brake to an old BMX fork
The only way is to use post mounts, and even then it is very difficult.
Tools to think about, but Not all these tools are needed:
Head tubes, steer tubes and a disc brake tab jig .
Construction of Utility bike (the prototype)
A simple jig to hold the drop-outs should be mounted on 1/2" steel flat bar.
|or build a large jig that will hold it all|
Some bikes will need new Heavy Duty drop outs (these also need a derailleur hanger) with disc tabs built in on the rear. Disc brakes will allow you to use a smaller rear wheel for an effectively lower gear.
a protractor square is essentieal for determining the head tube angle
|This is a frame alignment guage|
fork alignment tools