Competing at his seventh straight Games, Van Dyk was locked in a late three-man sprint off the front of a large lead group in the closing stages of the H5 road race.
He crossed the line in 1:37:49, edging out silver medallist Alex Zanardi of Italy, a former Formula One racing driver, and Dutch athlete Jetze Plat who were awarded the same time in second and third.
Hamman, meanwhile, won gold in the men’s F38 final with a best heave of 50.96m, nearly two metres clear of Colombian athlete Luis Lucumi Villegas who earned silver with a 49.19m attempt. Justine Asher, meanwhile, finished 12th in the women’s H1-2-3-4 road race, completing the event more than 21 minutes behind German winner Christiane Reppe.
Elsewhere, on the track, 100m champion Charl du Toit won his 400m T37 heat in 55.28 to book his place in Friday’s final, while compatriot Louzanne Coetzee was disqualified from the women’s 1 500m T11 heats.
In the pool, Hendri Herbst finished third in his 100m freestyle S11 heat in 1:00.59 to reach the final, which was set to be held in the early hours of Friday morning (SA time). Going into the late session on day eight, the SA team had secured a total of 11 medals (five gold, three silver and three bronze).