I'm starting to make some progress.Tonight I discovered a Sears riding lawnmower blade arbor in the garage. It is smaller than the several others I recovered from the Sears repair shop dumpster. Ya gotta love those guys. They get someone's mower in the shop and replace most everything and throw the used good stuff away. This one has a 4-1/4" "A" pulley and a 4-hole flange. I ground off the weld at the blade holder and drove the 5/8" shaft out. I took about 1" off on the lathe and re-seated the bearing. I have decided to use a 18-T coaster brake sprocket for the brake. By putting a few links in the chain it will have several teeth in contact sitting on top of the bottom run of chain with the idler sprocket on the bottom in front of it making the "S curve. The bottom 2 flange holes fall in line with the lower fork. I will weld 2 studs for it on a piece of 3/16 X 2" plate and mount to the lower frame tube with 3/4" "U"-bolts. The pulley will be 2/3 toward the tire from the axle and the whole assembly from sprocket to outer pulley surface ~2-1/2". A strut will be welded rearward at about 45 deg. to the top frame fork tube with another "U"-bolt securing it to prohibit twisting. Since the shaft has a securing bolt thread in it for the blade, I will find a steel something with a keyway slot in it and mount the sprocket to it and mill a Woodruff slot in the shaft. The bolt will retain it on the shaft in addition to a setscrew, and the length just right to not crowd the bearing with end loading. The upper flange holes will retain a plate to secure the idler sprocket mounting plate from rotating. I will mill enough of the flange base so there is room for the rotating plate sandwiched between the flange and it's mount to the lower frame tube. The braking belt I will play by ear after I get the rest of this mess configured.brno