A number of couriers in NYC use `fixies' -- fixed-gear bikes with no brakes.

A U235 bomb would therefore need to incorporate a gun weighing ten tons. Then there was the question of initiating or triggering the bomb.

[p162] Eastleigh Locomotive Works: Layout and functions of shops … Boiler Shop: Overhaul and testing of boilers, manufacture of light plate details, tender plating. [p162] It may seem incongruous that a locomotive works should build landing craft and refuelling barges, but this type of work did not prove so difficult for a well-equipped boiler shop. [p163] The boiler shop welders, whose skill is of an extremely high standard, are trained … at the welding school close by the laboratory in the main works building.

Juan made seven attempts to pervert the auton. One involved twelve hundred years of careful observation, timing the failure of various subsystems, maneuvering the auton into a position where he might take control and get transportation to resources in near space.