Feathering the Gamecock's Nest
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NOW that the oil engine is becoming more genera 11 y accepted b y operators of local delivery and municipal vehicles, it is not surprising that the Karrier Gamecock 3-4-tonner should be offered with the Rootes TS3 three-: cylindered two-stroke oil engine as an alternative power unit. The result is that this popular chassis, with its high degree of manceuvrability, comfortable three-man cab and low frame height. is now endowed with greater
operating economy and improved acceleration.
A road test carried out on one of ihese vehicles earlier this year (and delayed by the printing dispute) discloses that this oil-engined chassis shows an N% improvement in fuel consumption, returning 19.25 m.p.g. when carrying a 3--ton payload at an average speed of 28 m.p.h., and that the acceleration times were considerably better than those normally experienced from the petrol-engined version.
Even those users whose vehicles cover only relatively small annual mileages will find that the higher initial cost of the oil-engined Gamecock will be amply recompensed by this increased economy and liveliness. Less time on the road between stops will increase the number of deliveries possible per day, and the use of an oil engine does not drastically reduce the Gamecock's top speed. so it is still a fleet bird on the open road.
The engine used in this chassis is a down-rated version of the 105-b.h.p. unit used in Commer goods and passenger vehicles. This reduction in power output has been achieved by slight modifications to the fuelpump setting—the governed speed of 2,400 r.p.m.remains • unaltered. Similarly, the maximum torque is still delivered at 1,200r.p.m., but is
61 lb.-ft. less than in the Commer unit.
The Rootes TS3 engine, which was introduced in May, 1954, is of con siderable interest because of its unorthodox design. The features of this design are by now well known, but briefly the layout is such that the three cylinder bores are arranged transversely above the crankshaft, each bore containing two opposed pistons linked to, the crankshaft by connecting rods and rocker arms. The porting in the bores is based on Kadenacy principles and a Rootstype blower is employed for scavenging. The engine is notable for its high efficiency, economy, compactness and quiet running.
As with the petrol-engined version. the TS3 engine is mounted centrally in the chassis frame underneath the cab bench-seat. It is unit mounted" with the four-speed synchromesh gearbox, the complete assembly being suspended by a sandwich-type mounting at the front and twin Metacone units at the rear.
Other details of the specification included a spiral-bevel-drive fully floating rear axle, the drive to which is taken through a two-piece propeller shaft, and Girling hydraulic braking assisted by a Clayton Dewandre vacuum servo.
The vehicle supplied for test was a long-wheelbase model, the alternative version having a 9 ft. 7 in. wheelbase. It was fitted with the standard three-man cab and a special
timber platform body, and the high weight of this body brought the kerb weight up to 3 tons 2 cwt. The wheels were carrying 7.00-20 in. (10 ply) tyres which permitted a gross vehicle weight of 6 tons 15 cwt. With a test load of 3 tons 21 cwt. and driver, observer and test equipment, the gross weight of the test vehicle exceeded this figure by just 1 cwt.
The day of the test was cold and wintry and grey skies suggested that snow was not very far away. As the roads were dry when I collected the test vehicle, I decided to conduct the brake tests first and therefore took the Gamecock out to Gravenhurst Road, Barton-in-the-Clay. This is a reasonably straight length of level hard-surface road with little traffic to impede the tests.
Rear Wheels Locked
Several braking tests were made in each direction to compensate for any gradient irregularities, and consistent results were obtained in each case. When braking from 30 m.p.h., the rear wheels locked, with the result that the braking distances were increased because of the resulting skidding. The average retardation from 30 m.p.h. was .57 g. which, when compared with the maximum deceleration figure of 80% registered by the Tapley meter, indicated that there was a certain amount of surge present in the retardation. Some of this can be accounted for by the slight time delay in the system occasioned by the vacuum servo.
Braking reaction was proportional to pedal pressure and maximum pressure was applied during these emergency stops. When stopping from 20 m.p.h. by means of the hand brake alone, an average maximum retardation figure of 37.5% was achieved, showing the hand brake to be of considerable assistance in case of an emergency.
Good Acceleration Times . While on this road the acceleration tests were carried out. I was agreeably surprised by the short time required to reach 30 m.p.h. from a standstill. The times were considerably better than those returned by a petrol-engined chassis tested last year as a gully emptier. The directdrive tests between 10 m.p.h. and 30 m.p.h. were no less impressive, and from a speed of 8 m.p.h. the engine and transmission showed no signs of undue vibration.
Bison Hill, adjacent to Whipsnade Zoo, and having an average gradient of 1 in 101, was used for the hillclimb and brake-fade tests. These were conducted in an ambient
temperature of ,26° F., and at the foot of the hill the temperature of the coolant in the unblanked radiatoi: was recorded as 118' F.
The 0.75 mile to the summit was completed at an average speed of 15.4 m.p.h. and the lowest gear used was second, this being required only for a stretch of about 150 yards. At the top of the hill it was found that the coolant temperature had risen by a mere 2° F., and in view of the extremely low ambient temperature I realized that it would be useless to attempt to raise this temperature any higher.
A punishing descent of the hit] was made to discover what degree of fade it would be possible to pro duce in the system under the most detrimental conditions. With top gear engaged and the throttle pedal fully depressed, the Gamecock was driven down the hill with the foot brake applied to restrict the speed to 20 m.p.h.
At the bottom of the hill it was almost impossible to see the tail of the body because of the smoke pouring from the rear drums, but from 20 m.p.h. an emergency stop produced a Tapley meter reading of 36 per cent. During this stop the pedal travel had increased by 3+ in., which brought the pedal almost to the floorboards.
It is extremely doubtful whether a vehicle of this nature would ever be subjected to such conditions under normal service but this test did show that the system possesses sufficient
anti-fade characteristics to cope with such an eventuality.
After allowing sufficient time for the drums and facings to become cool again, the Gamecock was returned to the steepest section of the hill where the gradient measured 1 in 61. On this gradient a smooth start was made using second gear and this was repeated several times with similar results. This test showed that under normal service conditions first gear would be required only rarely. The hand brake, which had been adjusted prior to the test, proved to be only just capable of holding the vehicle on this gradient. I would like to see some improvement in this respect.
A very comprehensive series of fuel consumption tests was made over a 5.9-mile return circuit between Barton and Clophill, these two villages lying on the main A6 road between Luton and Bedford. For the most part, the runs were made in driving snow and the average ambient temperature during the series was 28.5° F. The route itself is fairly undulating and a considerable amount of traffic uses the road, so conditions for the tests were not by any means favourable.
Despite these factors, however, the Gamecock was able to put up some reasonably high average speeds, although the maximum road speed was at no time allowed to exceed 33 m.p.h. Three series of runs were made with varying payloads, as indicated in the data panel.
During the non-stop runs the circuit was completed without the use of the intermediate ratios. When making the " stops-per-mile" tests the vehicle.was 'halted for 15 sec. at each stop, during which time the engine was left idling. Normal acceleration rates were used for the getaways from each of these Stops and the stopping points were not chosen to assist in this getaway, many of them being on uphill grades.
Consistent Fuel Economy Analysis of the figures shows that there is a difference in the consumption rate of approximately 2 m.p.g. between running under " full load," and "110 load" conditions. This in itself is sufficient to suggest that the Gamecock tends, if anything, towards being overpowered, but this is a fault to be praised rather than criticized. The sharp increase in the: consumption rate when making four-. stops-per-mile reflects the difficult conditions under which the test wasl made rand. the -high average speed. that was maintained during the runs.'
Making due allowances for these-. conditions, therefore, it becomes. apparent that the Gamecock will show consistent economy during varied types of operation and that this economy is not dependent uponreducti'on in road speed.
Having driven the vehicle for many miles during the period of testing, I am well satisfied with its handling and the degree of comfort present in the driving cab. The chesthigh steering wheel position took a little getting used to, but I eventually decided that it was quite comfortable after all. I must, however, make criticism of the gear-change linkage.
Difficult Gear Change Similar gearboxes to that employed 10 the Gamecock are used in normalcontrol vehicles produced by the Rootes Group, and with a central gear-lever their operation is positive and enables the driver to take full advantage of the efficient synchromesh mechanism. I have previously, however, encountered difficulty in making smooth arid positive changes with this gearbox When fitted, with a remote-control mechanism. A particularly bad fault is the poor reversestop effect. When making a quick' change from third to second ratio, such as is frequently. necessary on a gradient, it is very easy completely to muff the change by taking the „gear lever too far over and attempting to engage reverse. The remote-contrOI mechanism has, admittedly, to.take a tortuous course
• o clear the front of the bodywork, but I do feel that if some alternative and less rubbery linkage could be devised it would be well worth a little research.
Other than this heart-cry about the gear-change and a feeling that the
hand-brake action could be improved, I have no adverse criticism to make about the Gamecock and have plenty of admiration for its road performance.
I was unable to carry out 'my normal maintenance programme on the test vehicle because it was .
required for demonstration purposes in another part of the country and had to be checked by the Karrier service engineers before it was sent out.
Last year, however, I did a certain amount of maintenance on the short wheelbase petrol--engined version of this chassis, which was tested as a gully-emptier. From my experience with this chassis I can vouchsafe that there are no particularly difficult jobs in the normal run of servicing routine. The tool kit supplied with the chassis is reasonably comprehensive, although the three open ended spanners provided struck me as being a little flimsy for serious work on a commercial vehicle— something stronger than 3/16-in. stampings should be provided.
Good Engine Access
The under-seat position of the engine is advantageous, not only in respect of its space-saving propensities, but also because, by complete removal of the seat cushions and engine covers, the engine and fuel system are well exposed for attention. It is also necessary to remove the off-side covers to gain access to the braking system reservoir, whilst the triple oil-bath air cleaners are sited beneath the near-side covers.
The batteries are well exposed for routine checks, being carried in a cradle on the outside of the nearside frame member, directly behind the cab. The same braking system was fitted to the test chassis as was fitted to the gully-emptier, and during the latter test I adjusted all four brakes in a total time of ten minutes. This work was made much easier by the quick-acting LakeElliott 6-ton hydraulic jack. Adjustment of the brakes is particularly simple because the adjusters are of the external type.
As an alternative to the Rootes oil engine the Gamecock can be supplied with a six-cylindered petrol engine. This unit, which has a cubic capacity of 4.75 litres, develops 85 b.h.p. at 2,600 r.p.m. and 216 lb.-ft. torque at 1,200 r.p.m.