When the Construction and Use Regulations were revised in 1950, the major bus and coach chassis manufacturers produced underfloor-engined two-axle single deck chassis to the new 30ft x 8ft dimensions. Previously, there had been 27ft 6in x 7ft 6in chassis such as the AEC 'Q' with a vertical side-mounted engine between the axles. The London Transport 'TF' which had a Leyland chassis with the engine mounted horizontally between the axles but, perhaps surprisingly, with the front axle still in the then conventional position well forward and a half cab. Also, Beadles had produced the Sentinel-Beadle chassis-less single decker in what was about to become the conventional layout for an underfloor-engined single deck bus or coach.
Dennis Bros Ltd exhibited three examples of their Dominant underfloor-engined chassis at the 1950 Commercial Motor Show. Probably the most well known of these was HOU 900 - Aldershot & District Fleet No. 174 - which was displayed on the Strachans Coachbuilder's stand. An un-bodied chassis, which probably never moved under its own power, was on the Dennis stand, whilst in the demonstration park was the third chassis with a front entrance Strachan body.
A significant feature of the Dominant was the use of a Hobbs Semi-automatic gearbox and the prediction in the 1950 Show booklet that a fully automatic version could perhaps become available later. Dennis was at last offering a post war, full-size bus or coach chassis, which did not have their 'O' type crash gearbox with the overdrive fifth gear. However, Lancets such as the 'J3' had a reputation for speed because of that overdrive gear, which gave a theoretical maximum speed of just below 50 mph at 1800 engine rpm. Just what the maximum speed of HOU 900 would have been with the Hobbs gearbox, I do not know, but it did have a two-speed axle and I suspect that many drivers either left it in high ratio and used all gears in the Hobbs box, or, if they needed low ratio and bottom gear in the Hobbs box, changed up through the Hobbs box and then changed to the high axle ratio.
The Dominant demonstrator was based on an export specification chassis, which differed to HOU 900 in that the engine had a supercharger - not a turbocharger - mounted at the front. As a result, the output at 1800 rpm was 130 bhp, against the 100 bhp of the un-blown engine. It also had air brakes whereas HOU 900 had a triple servo vacuum system.
The third chassis was for display only and was a left hand drive, export specification model. Compared to a forward engined chassis, the change from right to left hand drive would have been relatively simple, but in this case almost irrelevant as the chassis never ran, and possibly the only design work completed would have been the re-positioning of the steering system, the driver's seat, pedals and handbrake.
After the show, testing continued and the "Commercial Motor" published a road test report of a run they made with the demonstrator vehicle. Also, in due course, HOU 900 entered service with Aldershot & District - probably on the 19 Service to Bognor.
However, it would appear that the Hobbs gearbox was less satisfactory than had been hoped and both HOU 900 and the demonstrator were ultimately fitted with Dennis twin plate clutches and 'O' type gearboxes. In the demonstrator, a display panel high up at the front of the saloon was removed - this held large dials showing engine speed and road speed together with columns of lights which showed which gear and which axle ratio were in use - and the vehicle sold to Trimdon Motor Services, where I believe it had an unfortunately short life.
I had started my apprenticeship with Dennis's in August 1950 and it was some time before I worked in the Fitting Shops, but I often spent my dinner hour there, and saw the Dominant chassis on the line. In view of the need to get them to Strachans in time to be bodied for the Show, I suspect that there was little time to spare for extensive testing before the bodies were fitted.
Midland Red apparently were also interested in the Hobbs gearbox and I believe I may have seen one of their horizontal engines with a Hobbs box coupled to a dynamometer in Dennis's Engine Test Shop.
Like several other chassis manufacturers, Dennis sought a lighter chassis to replace their initial underfloor-engined model. AEC brought out the Reliance; Leyland, the Tiger Cub; and Dennis, the Lancet U/F. Although Aldershot & District had a demonstrator on loan, they chose to switch to the Reliance with a syncromesh gearbox. Consequently, East Kent became the largest operator of the LU.2 model, taking a batch of 30 with Duple 41-seat coach bodies which were nicknamed "Spaceships". Other operators included Cooke's of Guildford, Whites of Camberley, Hutchings & Cornelius and Glenton Tours.
The LU.2 chassis had a drop extension at the front which gave the driver a fairly low position and also a low passenger entrance, if a front entrance body was fitted. Behind this dropped section, the major section of both side-members was flat whereas the Dominant had a hump in the right hand side-member to pass over the engine. The engine was the horizontal '06' as in HOU 900, with the Dennis twin plate clutch and 'O' type crash gearbox with overdrive. A Lockheed braking system with hydraulic accumulators was used - rather similar to that used on Routemasters.
Between August 1955 and August 1958, I was in the Forces and consequently lost track of events at Dennis's - I didn't see the introduction of Lolines - but I was back before the first front entrance one (Walsall 845) was built. The Lancet U/F was still being produced, but was now the LU.4 model. Just what the LU.3 was, I do not know, but I do know that the last Lancet U/F chassis built were 2 LU.4's for Glenton Tours. As far as I am aware, there were only two differences between the LU.2 and the LU.4. Firstly the 8-litre engine had replaced the '06' (108 mm bore against the earlier 105 mm) and secondly, a Meadows gearbox had replaced the Dennis 'O' type. The Meadows gearbox had been used on the previous batch for Glenton and the nature of the lengthy linkage from the gear lever to the gearbox had been criticised.
As a Draughtsman, I had the job of designing a revised linkage which I hope overcame the problem, and also modifying the exhaust system to add an Ashanco exhaust brake unit. One of these vehicles attended the 1959 Brighton Coach Rally.
Further to Ted Gamblin's article, below is a reproduction from the contemporary trade magazine, Bus & Coach. Members of the editorial staff rode on HOU 900 during a visit to the factory. A full road test was published in a later issue where they were critical of a number of features; in particular the uneven top to the chassis frame which they suggested would make body building more difficult. This was rectified with the Lancet UF design. In retrospect it can be seen that the Dominant was in the same class as the Heavyweights such as the Royal Tiger and Regal IV from Leyland and AEC. Unlike these two, it did not go into production and Dennis quickly switched to the Lancet UF as an alternative offering for would be purchasers of Reliance and Tiger Cub.
OUT OF THE ORDINARY
On a recent visit to the Dennis works, Mr. V. W. Pilkington, the company's engineering director, gave me a short run on the Dominant, which made its first public appearance at the 1950 Earls Court show. The Dominant is a flat engine job, but what makes it different is the adoption of the Hobbs semi-automatic hydraulically controlled gear box, and the choice of a supercharged engine and a two-speed Eaton axle. At present two Dominants are on the road. One is in the service of the Aldershot and District Traction Company and is fitted with the un-supercharged Dennis 7.6 litre oil engine and a Strachan 41-seated body with central entrance and exit. The second machine, being used by the makers for demonstration purposes, has a supercharged engine, Eaton axle and a Strachan 44-seated body with front entrance and exit.
My run was on the latter vehicle, which is fitted with a rev counter and an illuminated panel showing the gear being used and whether on the high or low axle ratio. Though the trip was but a short one on the Guildford by-pass at a time of little traffic, it did indicate the value of eight speeds in enabling the engine to be kept at a fairly constant speed-one missed the ups and downs of engine revs- and the ease of driving resulting from the elimination of the clutch pedal. Although the engine had plenty of power it was quiet, and I am looking forward to hearing what our technical people think of it after a proper test. A detailed point noticed is the grouping of the driver's controls, electrical switches and instruments on a pedestal surrounding the steering column and bolted to the floor structure.