Although quite common in the U.S.A., bulk milk transport by road was rare in the U.K. in the early 1920's.
The difficulties with handling milk in bulk were numerous. It turned sour if warmed, to butter if allowed to surge and was easily prone to contamination.
The majority of dairymen therefore relied on the railways to transport their milk, usually in churns. Only the larger dairies had experimented with road tankers.
Viner and Long of Frome, Somerset turned to Scammell Lorries to transport their milk to London. Before using road transport, Viner's milk travelled to London by rail and in churns. It had to be first taken by road to a station within 100 miles of London to gain a one penny per churn discount on the cost. It then required taking by road from the London station to the distribution depot.
Scammell supplied two bulk tankers coupled to their standard 12-ton motive unit. The frameless trailers were based on an 18ft x 6ft diameter tank made from 8swg steel in 3 sections, bolted together with steel flanges. Within this shell were 3 aluminium, single piece tanks built by the Aluminium Plant and Vessel Company (APV).
Each tank rested on a bed of 3 inch oak slats and were secured with tensioning straps. The resultant gap between inner tanks and outer shell was filled with cork to provide insulation. Access to each tank for filling and cleaning was through a top mounted hatch. Discharge was through a bottom mounted, lockable stopcock.
The unladen weight of 8 tons 4cwt allowed for 2,620 gallons of milk, weighing 12 tons. This compared to the 2,100 gallons possible with a heavier glass lined tank. The two lorries left Frome on alternate days, returning the next and thereby a daily delivery schedule was maintained.
Loading took 3 hours and the lorries left Frome at 11.30am. Each tank was filled to absolute maximum to prevent surging of the milk.
Using the A4 trunk road, the average speed for the 110 mile journey was 11mph and the lorries arrived in London, probably Park Royal, at 9.30pm on the same day. After delivery to the distribution depot, each tank was scrubbed and then steam cleaned. The following day's return journey was completed with the stopcocks open to allow ventilation and the steaming process repeated on arrival at Viner & Long's dairy.
With innovative tank design solving the practicalities of bulk milk transport by road and two lorries providing a reliable daily service, the cost benefits of road transport over rail could be calculated. Viner & Long estimated an annual saving of £6,000 in rail charges. The saving in cost and upkeep of the 1000 churns needed for the same quantity of milk was more than the initial cost and annual maintenance of the two lorries.
The saving in fuel costs from the fleet of small lorries transporting the milk to a station within the 100 miles of London was enough for the fuel for each tanker to get half way to London.
An unforeseen benefit was that the insulated tanks meant that only a one degree rise in milk temperature occurred during the journey. This compared to a ten degree rise for the rail journey. This effectively added an extra day's life to the milk.
From my original article in Vintage Roadscene, Vol 7, 28 (September-November 1991)