Tilling-Stevens

 

Tilling-Stevens was a British manufacturer of buses and commercial vehicles, based in Maidstone, Kent. Originally established in 1897, by William Arthur Stevens, it became a specialist in petrol-electric vehicles. It continued as an independent manufacturer until 1950, when it was acquired by the Rootes Group.

 

The Stevens family members were timber merchants, but William Arthur Stevens developed a fascination for electric power. Stevens and Barker, Electrical and Mechanical Engineers was a company he jointly established in Maidstone, in 1897. The partnership ended in 1902 and W A Stevens carried on the existing business, until 1906, when it became W A Stevens Ltd. The company’s principal business was the production of electric motors and dynamos.

William experimented with a petrol-electric drivetrain in his ‘Old Grey Car’, a modified Clement-Talbot, coupling its 20bhp, four-cylinder petrol engine to an electric dynamo (where a mechanical transmission would have normally gone), wired to an electric motor on the back axle. Operation was done by a four-armed controller that provided neutral, two forward speeds and one reverse.

At the time, its selling points were a high degree of flexibility and ease of operation, back at a time when transmissions were siding-mesh (crash boxes), so a high degree of skill was needed to time clutch action, engine revolutions and gear shifting.

That car was used as a company demonstrator and attracted the interest of bus operator, Thomas Tilling, whose chief engineer was Percy Frost Smith. Thos Tilling was interested in the potential for an easy-to-operate chassis for its bus fleet.

 

 

A patent for a heavier-duty electric-drive worm axle was shared by Stevens, Frost Smith and gear-maker Francis Brown, according to a company history, penned by Chris Newman and Richard Rosa. This design employed two electric motors, driving two worm gear sets, with ‘differential’ action done electrically, by varying the speeds of the two motors.

The first Thos Tilling petrol-electric bus was built by Stevens, Tilling and J & E Hall, of Dartford, under the brand name, ‘Hallford-Stevens’.

After successful operation for more than 100,000 miles that bus was joined by seven more that also proved successful, so Thos Tilling later adopted the petrol-electric powertrain as standard in its fleet that was largely built in-house. 

During the development years of the electric drivetrain, W A Stevens maintained its production of dynamos and motors, to keep the company afloat, but it was never very profitable.

It’s important to note that the Stevens electric drive system was not a petrol-hybrid-electric type, because there was no storage battery incorporated; it was purely an electric drivetrain. However, there were some experimental Hallford-Stevens battery buses produced and W A Stevens retro-fitted its electric drivetrain to several in-service, petrol-powered buses.

 

Melbourne Metropolitan Tramways Board Tilling-Stevens petrol-electric bus

 

For 1911, W A Stevens took more manufacturing responsibility and the patented drive axle arrangement was changed from a two-motor type to a single-motor, coupled to a Dennis axle. The petrol engine was a 36bhp White & Poppe, replacing the Hallford engine. The orders flowed in, from the UK and export markets, including Australia, for buses, trucks and for tram powertrain conversions.

The company also produced some mechanical-transmission vehicles (B-types) for its own use, but these were later offered to buyers, including the French Army, which bought 75 of them during WWI.

W A Stevens’ unique petrol-electric drivetrain afforded it a particular advantage as a searchlight-carrying truck and as a fire-fighting pumper, because the engine could be operated with the controller in neutral and the dynamo powering the electric equipment.

By 1912, Thos Tilling had significant financial investment in W A Stevens, described in the W A Stevens’ company records as a ‘preponderating interest’. 

Alongside Stevens’ Maidstone production, Thos Tilling had been building its own buses in-house, using Stevens drivetrains and these had been designated ‘TT’ (Thomas Tilling) models. By 1913 the nomenclature changed to ‘TS’ (Tilling-Stevens), so the writing was on the wall for William Arthur Stevens.

(Incidentally, the most popular bus chassis was designated ‘TS3’ and that nomenclature reappeared after WWII, on the famous Commer’ ‘Knocker’ engine that was manufactured by Tilling-Stevens, after its 1950 absorption into the Rootes Group.)

Because of their electric drivelines, Stevens’ trucks and buses were not bought by the War Department during WWI and production was seriously affected by diverted raw materials and staff enlistments required for the War effort.

Out of the blue, at the February 1915 W A Stevens board meeting, William Stevens resigned. He left the company he’d founded and saw it renamed Tilling-Stevens Ltd.

However, William retained the intellectual rights to his petrol-electric designs and entered an agreement with Dennis Bros. Stevens’ electric transmissions were supplied to Dennis Bros and these vehicles were named ‘Dennis-Stevens’. After production of mainly searchlight-carrying vehicles the agreement was terminated at the end of WWI and Dennis concentrated on mechanical-transmission vehicles.

 

 

Tilling-Stevens

 

 

Elizabeth I is reported as saying: “I dislike wars; they have uncertain outcomes”. An unforeseen outcome of WWI was that truck and bus usage increased disproportionately. Within four years, a conflict supplied largely by horse-drawn transport morphed into an automobile-supplied, modern war.

Trucks and buses became better performing and easier to drive, as power outputs improved and transmissions became easier-shifting. Newer gearboxes still needed double-de clutching, but many men were trained to drive during the War, so there was no shortage of capable drivers.

Also, the relative refinement of the post-War mechanical driveline meant that the principal ease-of-operation of the petrol-electric powertrain was largely negated. The mechanical-driveline vehicle was also lighter, cheaper and more reliable.

 

1914 Tilling-Stevens TSB3 tipper – SV1ambo

 

By 1920, Tilling-Stevens was producing more mechanical-driveline 2.4-4.0-ton trucks alongside its petrol-electric truck and bus chassis. There were around 1000 workers employed and the order book was healthy. Then the 1921 recession arrived, profits collapsed and much of the management team resigned.

Profits returned in the following years and the company added trolley buses to its range, but in October 1925 Thomas Tilling severed all manufacturing involvement with the company.

 

NZ fire appliance – Howard Pettigrew

 

In the late 1920s Tilling-Stevens introduced a Ricardo-designed six-cylinder, side-valve petrol engine; the company name was changed to T S Motors Ltd…and then the Great Depression hit. 

In 1931, the Gardner 4L2 diesel engine was made optional in the Express bus chassis.

In 1932 a proposed merger with Karrier tore the management team apart; followed by a collapse in sales and financial difficulties. Mainly bus chassis sales kept the company afloat and the name reverted to Tilling-Stevens Ltd in 1937. In the same year, Tilling-Stevens acquired the Vulcan truck manufacturing business and its range of 2.5-5.0-ton truck chassis.

 

 

At the 1937 Autumn exhibition in London, Tilling-Stevens caused a sensation by displaying a prototype six-wheel bus and coach chassis, powered by a 7.45-litre/110bhp, flat-eight diesel engine, coupled to a Maybach seven-speed gearbox and with independent rear suspension.

Other reports from the show suggest that the engine was a Ricardo-designed ‘boxer’ concept, with a centrally-mounted crankshaft, not an opposed-piston type.

According to the Commercial Motor Magazine’s show report, a Successor six-wheel bus chassis and Yeoman, four-wheel, eight-tonnes-capacity truck chassis were fitted with the same powertrain, although the truck had conventional leaf-spring rear suspension and a rigid live axle. Bus & Coach featured a Duple advertisement for the bodywork on the Successor.

Bus & Coach’s image of the Duple-bodied Successor coach

 

The Successor’s tandem rear suspension featured horizontally-arranged, cone-shaped-coil springs, with bell cranks and pull rods. The propshaft bypassed the leading tandem axle and was connected to the third axle.

However, nothing more was seen of those eight-cylinder show vehicles and some reports suggested that the engine suffered from many development issues, including broken crankshafts.

Also released was a TS19 petrol-electric truck chassis for the Army, to serve as a searchlight vehicle: handy, given the gathering war clouds. The company produced a wide variety of mechanical and electric components for the War effort.

 

Tilling-Stevens searchlight truck – Dave Gothard

 

Tilling-Stevens was still manufacturing buses after World War II and scored a large order in 1947/1948 for export to Hong Kong. However, the UK Government’s ‘export or perish’ policy to earn foreign currency disadvantaged specialised companies, including Tilling-Stevens, whose export opportunities were limited.

Tilling-Stevens was eventually purchased by Rootes Group in 1950 and became the manufacturing centre for the aforementioned TS3 two-stroke, opposed-piston engine. You can check out the TS3 story in our Truck Brands story on the Commer.

Tilling-Stevens truck and bus production ceased in 1953.

Doubtless, William Arthur Stevens would have loved to witness the increasing electrification of the 21st century’s commercial vehicles!

 

 

Petrol-electric vehicles

 

Les Chatfield

 

The Tilling-Stevens petrol-electric chassis was an early example of a petrol-engined vehicle using electric rather than mechanical transmission. It was not a hybrid vehicle, as it had no direct engine propulsion or battery storage. The electric dynamo and motor operated only as a replacement for the gearbox in a conventional internal combustion engine driven vehicle.

Because the motor/dynamo pair was heavier than a mechanical gearbox, it was less fuel efficient than a competing mechanical transmission chassis type. Also, its simple and inefficient electrical control system was all that could be achieved at the time, in the absence of modern electronics.

Many UK-market Tilling-Stevens petrol-electric vehicles ended their days as motorhomes or trucks, owned by travelling fair and circus people, where their electricity-generating ability was useful.

Driving a petrol-electric vehicle was different from operating a mechanical vehicle, although the accelerator, hand-throttle and brake pedals were familiar. There was also a choke lever and ignition advance/retard for starting the hand-cranked engine.

But instead of a mechanical transmission gearstick a lever was used to select running in either direction, or to operate the engine and dynamo in neutral. Another lever operated a wiper across a bank of wire-wound resistances. which altered the motor and dynamo fields, to give the electrical effect of gearing. 

The driver needed to use no more than engine idle speed when selecting the direction switch, to prevent unwanted movement. The resistance lever was then set to maximum torque and the accelerator pedal pressed to achieve a smooth lift-off. 

More accelerator pressure and gradually altering the resistance lever produced higher speed progressively and smoothly, with none of the pauses in acceleration of a manual gearbox. 

To slow down, there was no engine braking available, because of the lack of mechanical connection between rear axle and engine, so the accelerator pedal was released, the resistance lever brought back to the slow speed position and the wheel brakes applied. With the vehicle stopped, the forward/reverse lever was moved to neutral and the handbrake applied. 

On magneto-ignition models there was a switch to short the magneto, to stop the engine running.