Armstrong Siddeley 18hp & the early 20hp
Following the 1920 motor show it was quickly apparent that John Siddeley had found a winning formula in the new 30HP car. Also he was aware that there was substantial interest from would be purchasers who's pockets were not quite deep enough. So, only 12 months later the 18HP car was launched. Chassis priced at £575 while the complete Tourer was an attractive £670 which made it about the same price as the chassis only version of the larger car. Still not cheap, but of a quality which brought continuing Royal patronage. Prince Henry, Duke of Gloucester, acquired a 18HP saloon whilst Prince Albert purchased two 18HP cars, one an open sports and the other for state occasions.
Public awareness was further strengthened by a 10,000 mile day and night trial overseen by the RAC with an 18hp achieving an average 24.5mpg. Today some Club members would be happy with such a return using their later cars.
Technically the car was very much after the design of the larger 30 HP. The engine was a six cylinder bi-block of 2386cc capacity, whilst the wheelbase was 1foot 3inches shorter at 10feet.
As was common practice at the time braking was accomplished using the rear wheels only. Interestingly these drums contained two sets of shoes. The inner being operated by the foot pedal and the outer by the handbrake. Later cars were fitted with four wheel brakes which had aluminium shoes fitted with friction lining material and operated in large drums all round. These were unusual and certainly the latest technology of the day. Henri Perrot a French pioneer automobile engineer while working for the Argyle motor manufacturing company in Scotland had developed a system which allowed the brakes to be applied to all four wheels by use of either foot pedal or brake lever. This system was patented in America and would be more familiar to us as, Bendix 'servo' braking, not to be confused with modern servo power hydraulic braking. This was 1921 and it shows John Siddeley's awareness of the fast developing automotive engineering industry in that it would take till 1925 before some 50 makes of car had such braking
We should recall that the 18hp car had opened up a larger segment of the market to Armstrong Siddeley cars and consequently the increased feedback helped shape future policy. Over the next four years the company were busy expanding their range of cars, still maintaining quality, performance and value for money, into the medium size car
market. During this period much useful experience was gained from rallies and publicity events, along with customer and dealer feedback. It is also worth noting that almost half of the Mk1 cars produced were Tourers or Dropheads, this was now giving way to a marked customer preference for saloon cars, a trend which would continue into the 1930's.
So it was in July 1925 that the revamped 18hp Mk II was announced. Significant changes were made to the engine and in two stages to the chassis dimensions. First the engine: now a true monobloc having overhead valves and a removable head. Capacity was increased by 500 cc. to 2872cc. which gave an RAC rating of 20 hp.
Two different chassis lengths were available, the 10ft wheelbase chassis continued on from the MkI version and a new 10ft 9inch wheelbase version was introduced, these were to be known as the standard and short chassis respectively. On both options, the overall body length was increased by 3 inches. This arrangement gave the factory scope for the variety of body types which were to follow. Interestingly, by 1927 the standard chassis had become know as the long chassis, this is the naming custom that we have followed.
Whilst most customers purchased a complete motorcar with a body by the in-house coachbuilder Burlington, a rolling chassis was available for those who wished to have bespoke coachwork from an outside company.
From mid 1928 the Wilson 4 speed and reverse pre-select gearbox was available for an additional £35. This was a great improvement on the traditional “crash gearbox” in general use as it eliminated the need to double declutch to achieve a smooth gear change, something many motorists were unable to master. Eventually this type of gearbox became a standard fitting on all Armstrong Siddeley models
This model continued in production until August 1931 when it was replaced by the new 20hp model.
The following images are taken from Armstrong Siddeley's December 1927 brochure, they are all known as 20hp models rather than 18hp Mk II's, they are all produced by Burlington the in-house coachbuilders. It was around this time that Armstrong Siddeley started to give their cars model names, in this case, locations in the British isles. Prices for this model year ranged from £435 for the short chassis Arundel 2/3 seater through to £520 for the Conway Saloon.
1927 Mk II 18hp Stirling Saloon