here are some details on making a wide rear coaster hub like the one i used on this bike.
Step 1: This Is What You Need
you need two hub shells for a coaster brake, the complete guts for at least one of them and an additional cone nut/pad ramp thingy for another.
then go to grainger.com and buy a 3/8 24 threaded rod in three feet made of G7 alloy.
bang the spoke flange off the wide side of one hub
cut the narrow side off the other, you don't want the inside part where the coaster brake cone acts to move forward , use a level to trim the wide open side cut until it is lathe straight, got it?
Step 2: Make a Wide Hub Shell
Now if you lay them side to side there is an extra wide hub with the narrow side and braking surface unchanged and the wide side from the other hub next door with the bearing surface unchanged. if you had left both hubs alone, the braking cone could not be inserted into the hub because of the duplicate narrow area
now add a section of steel pipe into the center gap to make the hub as wide as needed, mine was 6 inches added.
Weld all that together , keeping them square by laying them into a piece of angle iron and lots of checking. finished hub pictured
Step 3: Magic Happens Here
The last thing to do is weld together the left side bearing nuts with a spacer made from ½ inch steel pipe, use the threaded axle rod to make sure they are aligned properly. Grind the bearing surface off the inner one if you plan to use the caged wheel bearings, I didn't do that and laid in loose bearings.
Confused? You should now have a stack that looks like this= inner nut will now only act as the brake pad retainer, welded to ½ inch pipe spacer, then to outer nut that will now only be the bearing carrier and action arm mount.
Step 4: Finish Assembly
Reassemble the coaster hub, it may be difficult to lay in the brake pads but use sticky grease and a small screwdriver. Substitute the threaded rod for the original axle. All you have really changed is to split the function of the left side axle nut ! And a 12 inch wide hub is born.
I have actually built one and it works, but please point out anything I may have missed because it is my only brake and i'd rather not crash.
I'm thinking of doing a 3 speed hub next, does anyone want to see an extra wide 3 speed hub? also would be built on a car spare tire or maybe a motorcycle tire.