 Following experience of occasional cracks appearing near the spring brackets had one or more further batches of Class 7 Standard Pacifics been built to complete the intended 91 engines the chassis would have been rearranged to be similar to that used on the solitary BR Standard Class 8 Duke of Gloucester and that drawn up by Derby Drawing Office for the 2nd batch of Class 6 Standard Pacifics . This would have resulted in the locomotive riding on cast steel " sub @-@ frames " carrying the spring brackets . Unlike the smaller BR Standards the exhaust steam manifold within the smokebox saddle ( along with the BR Standard Class 6 engines ) was an intricate steel casting . 
