Fast Freddy Markham in the Gold Rush did 60.35 km on the Major Taylor Velodrome in Indianapolis back in 1984 but that's the last one I can say was definitely set on a velodrome. He subsequently did 67.01 km in Vancouver BC but I don't know what the track was for that one. All subsequent hour records have been done on car test track ovals, with the current record being 92.43 km by Francesco Russo on the DEKRA track in 2016.
A 250m track isn’t really designed for that sort of thing so the speed attainable is limited as much by the amount of common sense possessed by the rider as it is by their power output. Well I recall Vinz Burgherr decking his brand-new and impossibly shiny Birk Comet on the Ghent-Blaarmeersen track when the front tyre lost interest in gripping the track at about 70 km/h. Did about half a lap on its side. Lovely shiny paintwork all scratched. Rider philosophical: it's a bike, not an artwork.
