Summary Bachmann 35-945SF OO Gauge Class 13 Shunter D4502 BR Green With Wasp Stripes DCC Sound Fitted. To aid the forming of new trains the yard employed hump shunting which allowed wagons to roll into the siding where their train was being assembled, however, to move these trains and propel the wagons up the hump for gravity to take effect, a new locomotive was required.