The cast cranks were replaced with forged versions providing running for 20,000 hours .
Initially cast cranks suffered from low surface hardness ; this problem was solved by nitriding the surface , and by locally heating the surface with a CO laser ( see annealing ) .
The cast cranks were replaced with forged versions providing running for 20,000 hours , but initially they suffered from low surface hardness ; this problem was solved by nitriding the surface , and by locally heating the surface with a CO laser ( see annealing ) .