PS, the post#1 says the rider used a 200 cc engine that ran on 30 octane gas! (modern gasoline at the pump is 87-96) So it probably didn't have very high compression, and probably didn't have a really high RPM range. 1.5 hp sounds about like the bike motors of today. I bet 80lb felt like a LOT when riding tall road wheels (with wooden rims and old school tires too!).
I came across this thread by accident while trying to find if anyone had made a home-made drag brake for bicycling down long grades. I was thinking of things like the little wheel on old exercise bicycles that presses down on the tire, and has maybe a knob or nut to tension the washers against the wheel. I was thinking the device could double as a friction trainer for riding a bicycle on rollers (which don't usually have resistance units) or simulating hills on the flat roads here. :-)
Duck Brake, illustrated in old catalog (page 85) Hardware dealers' magazine - Google Books
drawing of brake in action