Reprinted from MODERN TRANSPORT February 18^, 1956

“The Times” of the Transport World

3-16 Woburn Place,  London, W.C.1

COMMERCIAL VEHICLE TEST

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Bold Design of the Birch Taxicab

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IMPROVED APPEARANCE, COMFORT AND ECONOMY

It requires a great deal of courage to attempt to break away from tradition and when it is a tradition supposedly dear to the hearts of Londoners, the risk of incurring wrath or ribaldry is great. The basic layout of the London-type taxicab has remained unchanged for so many years that it has become traditional; it has taken the courage and imagination of Mr. John Birch, of Birch Bros., Limited, bus, coach and taxicab operator, to attempt the design of a new London

proved. It is the intention of the Birch company to put the prototype in service with its own fleet for a period of six months or so, during which time decisions regarding production, selling price and any necessary modification of design will be taken.

Features of Body Design 

The Birch taxi has been designed from the premise that the traditional layout is wrong because the main passenger seat is in the most

taxicab that would be more in keeping with the high standards of comfort and appearance attained by other forms of road transport vehicles, while yet conforming with the precise constructional regulations laid down by the Commissioner of Metropolitan Police. That the new design meets the police requirements was proved by the issue towards the end of December of a licence to operate the prototype vehicle; that performance and fuel economy are good, even highly favourable, was indicated by our recent two-day road test of the same vehicle; that passenger comfort and convenience are of a high order was testified to by a number of critical passengers carried during the test; whether Londoners (taxicab operators, drivers and passengers) will take to the new vehicle has yet to be

uncomfortable position - over the back axle - and that luggage is carried where it is open to the elements, where it cannot be properly safeguarded and where it can overhang the near side of the vehicle. The new design removes these disadvantages by adopting a body style rather similar to a modem estate or dual-purpose car. The main passenger seat is placed well forward of the rear axle at about the midships position in the body, with the usual access doors on each side.  

Because service records show that in only about one hiring in ten are more than two passengers carried the principal seat provides exceptional comfort for two with a high squab brought up to form a headrest.  When more than two passengers are carried this seat, no longer restricted in width by the wheel arches, will seat three abreast and a

seat for a fourth passenger is fitted facing rearward in what was formerly the luggage space alongside the driver. The space behind the main seat provides more than twice the usual luggage space, to which wide access is arranged through a rear-hung door on the near side.  An automatically retracting sprag, by which the door can be propped open, is fitted.

The driver's compartment, which includes a space for the taximeter on the near side, is separated from the rest of the body by a half-glazed partition.  A sliding full-drop window, operable only from the driving side, is fitted in the partition to the left of the driver. Through this it is possible to operate from the driver's seat a full-drop outside window. A small sliding communication panel is fitted in the partition behind the driver. The driving-compartment door has a lever-operated quick-action full-drop window and the off-side panel of the deep two-piece windscreen can be opened. Additional body features include flashing direction indicators; a cab heater, which also

Sanders patented spherical combustion chamber system and C.A.V. fuel injection equipment. incorporating the latest renewable-element paper filter and variable-speed pneumatic governor giving regulation up to 3.600 r.p.m. at full load.  

The engine drives through a 9 in. diameter Borg and Beck single-plate clutch with hydraulic pedal linkage, a three-speed gearbox, tubular propeller shaft and hypoid bevel rear axle. The synchromesh gearbox has a patented gearchange control on the steering column and, in conjunction with the axle reduction, provides overall gear ratios of 16.38, 7.72 and 4.625 to 1. With the engine governed at 3.500 r.p.m. these provide maximum speeds of about 60 m.p.h. in top gear, 40 m.p.h. in second and 17 m.p.h. in first gear.

Performance

The prototype vehicle measures 14 ft. 4 in. long over deep wrap-round bumpers and 5 ft. 4 in. wide.  It has a turning circle of 24 ft. between kerbs.  As tested, with full fuel tank, spare wheel, tools and

TEST RESULTS AT A GLANCE

Vehicle Details

MAKER: Design by Birch Brothers, Limited: chassis by Standard Motor Co, Limited; body by Park Royal Vehicles, Limited.

TYPE: Birch Taxicab

ENGINE: Standard 4-cylinder diesel; bore 3 3/16 in  (80.96 mm.); stroke 4 in. (101.6 mm.), capacity 127.68 cu. in. (2.092 litres); compression ratio 17:1; Freeman Sanders spherical combustion chamber system; 45 b.h.p. at 3,000 r.p.m., 92 lb/ft. torque at 2,000 r.p.m.

TRANSMISSION: Clutch, Borg and Beck 9 in. dia. single dryplate hydraulically operated: Gearbox, 3-speed synchromesh with steering column control, ratios 3:54, 1:67 and 1:1 forward, 4.11:1 reverse; driveshaft, Hardy Spicer open tubular with needle roller bearing universals; rear axle, hypoid bevel gear with semi-floating half shafts. ratio  4.625: 1.

BRAKES: Lockheed hydraulic 11in. by 2 ¼ in., 2 l.s front.

Tyres: 5.75-16 tubeless.

WHEELBASE: 8 ft. 5 in.

WElGHT: 1 ton 9 1/2 cwt. unladen in full kerb trim.

Test Results 

ROUTE: Mainly in Greater London, total distance 212 miles.

CONDITIONS: Cold to very cold and dry.

RUNNING WEIGHT: Varying from 1 ton 11 cwt. to 1 ton 15 cwt.

PAYLOAD: Varying up to equivalent of two passengers and

luggage.

FUEL CONSUMPTION: Overall. 37.2 m.p.g.

MAXIMUM GRADIENT CUMBED: 1 in 4 ¼.

TURNING CIRCLE: 24 ft. wheeltrack.

ADJUSTMENTS DURING TEST: None.

ACCELERATION: Mean of opposite runs through gears:

0-30 m.p.h. 9.8 sec.

0-40 mp.h. 18.4 sec.

Top gear only.

10-30 m.p.h. 13 sec.

10-40 mp.h. 2I.5 sec.

BRAKING: Average of measured stops from 30 m.p.h., 37 ft., equivalent to 26 ft. per sec. Per sec. (0.81 g.) average retardation. Tapley meter readings 90-95 per cent.

ESIMATED TOP SPEED: 60 m.p.h. 

supplies warm air to windscreen demisting slots and to the main body through a closable grill in the partition ahead of the occasional seat; ventilating windows on each side of the main seats; a red light to warn the driver when any of the rear doors is not securely fastened; and locks on all doors. The body has been built to the requirements of Birch Bros. by Park Royal Vehicles, Limited.

Technical Details

The Birch taxi is based on a chassis produced by the Standard Motor Co., Limited, and is powered by a Standard diesel engine. The chassis has a wheelbase of 8 ft. 5 in. and incorporates linked wishbone and coil-spring independent front suspension, long semi-elliptic rear springs, piston-type dampers all round, cam and roller steering, Lockheed hydraulic brakes with tandem master cylinder and four accessible jacking points for use with the triangulated jack. Although the 5.75-16 tyres are of the tubeless type, a spare wheel is fitted in the luggage compartment.

The four-cylinder diesel engine is the type which is giving such excellent service in Birch conversions of London taxicabs and of which there are now 1,500 in service. Of 2.092 litres capacity, the original high-speed versions of this engine developed 40 b.h.p. at 3.000 r.p.m. and 85 lb./ft. torque at 50O r.p.m. Recent development has improved the performance and current engines produce 45 b.h.p. at 3,000 r.p.m. and 91 lb./ft. torque at 2,000 r.p.m. The engine employs the Freeman

out 20 lb. of test equipment, the vehicle turned the scale at 1 ton 9 ½ cwt., of which 16 cwt. was borne by the front axle. Our test extended over two days and of the total of 212 miles covered, about 150 miles was in Greater London, a good deal of it in short point-to-point journeys similar to normal taxicab service. The vehicle proved extremely pleasant to handle and although the pedals had the appearance of being set at a rather awkward angle, no discomfort was felt after long periods at the wheel. The steering-column gearchange was straightforward and positive and the well-chosen gear ratios and freely running engine permitted performance figures equal to those obtained with a four-speed gearbox in comparable vehicles. Actual figures obtained, after the speedometer had been checked and found correct at 30 m.p.h., were 9.8 seconds from rest to 30 m.p.h. and 18.4 seconds to 40 m.p.h.; these are average figures for two runs in each direction over a reasonably level road. Top-gear performance also proved lively and the lazy driver would find he could pull away from 10 m.p.h. in top without uncomfortable effects and reach 30 m.p.h. in about 13 seconds. Part of the MODERN TRANSPORT standard test route was covered with the cab to take advantage of the measured sections and to try the vehicle on the open road. With a new engine and the governor set rather below the normal maximum, speeds of 58 m.p.h. in top and 38 m.p.h. in second gear were recorded. The engine ran smoothly and quietly up

to its maximum and was noticeably quieter at idling speed than some contemporary diesel installations. Indeed, among the more outstanding impressions of the vehicle were the almost complete absence of vibration at all speeds and of a very comfortable ride even on badly paved roads. These point to a very close attention having been paid to

from 30 m.p.h. produced an average figure of 37 ft., equal to an average retardation of 26 ft.. per second per second or 0.81 g. and a result that few vehicles could better. 

Excellent Fuel Economy

As with most prototypes, there were a few odd

The Birch taxi earns full marks for exception accessibility of the Standard diesel engine; right, the luggage compartment door hinges on the rear panel to provide a wide doorway for bulky pieces.  

engine mountings and to the great improvements achieved in suspension systems in recent years.

Starting Aid

One important modification to the standard diesel engine in this application is the inclusion of a heater plug to assist cold starting. While we had the vehicle it was parked out of doors for three nights. On the first morning the outside temperature was at about freezing point and on the second there was about 6 deg.F. of frost. On both mornings the engine started immediately after about a 30-second application of the heater-plug switch and the setting of the extra-fuel button on the fuel-injection pump. On the third morning, which was rather milder, only the heater-plug was used.

Steering, suspension and brakes on the vehicle were fully up to modem private car standards and disposition of the odd loads carried (up to a total of 5 cwt.) in various positions in the body did not affect control. Even on good surfaces all four wheels could be locked with reasonable pedal pressure and under these conditions from speeds around 30 m.p.h. the vehicle pulled up squarely. Measured emergency stops on dry, level surfaces

points with which fault could be found; front comer pillars rather thicker than seemed necessary, outside light reflected by the glazed partition round the occasional passenger seat after dark and, we suspect, rather limited leg room even with the adjustable seat right back for the tall driver. But these are minor points capable of simple modification if shown to be necessary during service trials.

The Birch taxicab makes extremely modest demands on fuel. In our 2I2-mile run, which included much simulated taxi working in London, overall fuel consumption worked out at 37.2 m.p.g. An intermediate check carried out on the open road returned a figure of nearly 40 m.p.g. From these figures it seems reasonable to predict an average consumption in the region of 34-35 m.p.g. for a vehicle in good condition employed full-time on taxi work.

This and the advantages of improved driver and passenger comfort, together with a possibly enhanced resale value due to its easy conversion into a useful van or small multi-seat passenger vehicle, make the new taxicab an extremely attractive proposition and we have little doubt that the taxicab industry in London and the provinces will react accordingly.