'JOHN HICK' Class, No 1549 "JOHN RENNIE"
The basis of this model is the London Road Models kit for the 'Greater Britain' 3-cylinder compound. The 'John Hick' class were basically 'Greater Britains' fitted with smaller driving wheels, the idea being to give them greater pulling power in exchange for a lower top speed - rather like changing down a gear in the car when you come to a hill. They were intended to be used on the steeper graded main line north of Crewe.
George Whale could not have considered them satisfactory machines as "John Rennie" was scrapped when it was only nine years old.
The difference in driving wheel diameter is 10 inches, but all is not that simple! The chassis, motion and cylinders all reduce in height above rail level by 5 inches but, in order to retain the standard buffer height, the footplate must remain at the same level. Nor does the boiler height decrease by the 5 inches one would expect. It decreases in level by only 2.25 inches. (I have no idea why and it must have led to a lot of redesign work.) The cab remains the same but the splashers and valances alter considerably.
The construction of the model was not straightforward but I do sometimes like a challenge. I had to make many alterations to the original kit, one of which was to get the cylinders into their correct location but, in the end, I was satisfied with the result.
It has the same drive arrangements as the "GB", an LH21 motor driving two gearboxes.
'John Hick' minus tender
And with tender
The works
The underside. If you look closely you can see that the rear pickup wires have slipped from the back of the wheels