well as far as the T1 & S1 are concerned,they had a history of slipping on the tracks especially when the weather was bad and trying to start a heavy train up steep grades,and part of the problem which resulted in their demise was weight on either the first set of drivers and/or the second set,had they added more weight to the front end of the locomotives,the chances of slipping would have been reduced and the performace could have been better compaired to the diesels that replaced the steam locomotives that were in service at that time the steam to diesel replacement was in effect!