7S-005-009 O Gauge Sentinel Y1/Y3 NE 8154The Y1 Y3 sentinel was based on the road going lorry, utilising a similar centrally mounted steam tube boiler and chain drive system to the wheels. Whilst not having the greatest turn of speed (approximately 36mph top speed) these small locos proved capable of pulling a constant draw weight and were considered ideal for shunting in yards and providing motive power along smaller branch lines. These quirky little locos were used by all of the big four