A MORE POWERFUL DAIMLER COACH CHASSIS.
Page 13
Page 14
If you've noticed an error in this article please click here to report it so we can fix it.
New Points in Engine Lubrication. The Importance of Using Cool Oil. A Chassis for High-class Jobs.
ONE of the most striking chassis at the Commercial Motor Show held at Olympia in November last was shown on the stand of the Associated Daimler Co., Ltd. It was known as the model 423 chassis, having a six-cylinder, sleeve-valve engine, the maximum b.h.p. of whi,ich was 70, and in the construction of which weight reduction had been effected by the extensive employment of high-tension aluminium alloys. Experience with this chassis during the current year has coincided with the great development in the employment of motor coaches for long-distance travel and with an all-round increase of coach speeds.
We have now bad an opportunity for inspecting and testing the Model 0F6 Daimler chassis, and observe certain other changes in the design additional to the enlargement of t Ii e engine. The engine formerly employed had a bore of 81.5 mm. and a piston stroke of 114 mm.; the new engine has a bore of 97 mm. and a piston stroke of 130 mm. It will develop 50 b.h.p. at 1,000 r.p.m. and 90 b.h.p. at 2,000 r.p.m., whilst the maximum b.h.p. is well over 100.
Our run on the chassis was necessarily short and over the good roads on the outskirts of Coventry, with, however, a few short rises which gave an opportunity for listening to the note of the engine when it was accelerated on a rising gradient. The chassis was equipped with a test driver's cab with, of course, no pretence at a dashboard. The chassis was weighted to the equivalent of the normal load capacity.
The vehicle seemed to us to be admirable in its ease of steering and of general control. The employment of the 14Iarles type of steering gear is said to be responsible for one of these merits. Whenever the throttle was opened up for a clear
stretch of road, or when a gradient was met, there appeared to be ample power. Braking seemed to be excellent, and if we had a point of criticism at the end of our run it was on the question of noise. '
There was a certain amount of engine noise and the gearbox was not altogether silent whenever top gear was left. So far as we could see there was no reason why the engine should not have been quite silent, and it is highly probable that the temporary nature of the driver's accommodation was such as to enable the cab to pick up and amplify whatever sounds could be ascribed to .engine and gearing. However, we may be sure that the need for silent running is not overlooked and will be satisfied in chassis supplied to users.
We regard this matter as of considerable importance, because such a chassis as the Daimler CF6 will be used very largely for long-distance work and, in all likelihood, for sleeper-coach work, and we contend that the elimination or suppression of noise is absolutely essential. At night-time engine and transmission noises can be sufficiently discernible as to disturb the passengers; in 'day-time the hearing faculties pick up every sound that is emitted and transmit it to the nerve centres of the brain which have to deal with it, even if only from the point of deciding that it is of no importance. In the course of a day's run, however, the nerve centres of the brain must become excited by the continuous emission of noise, resulting in mental fatigue and even in nervous excitation.
However, to return to the CF6 chassis, we are informed by Mr. Pomeroy that the features which have been considered essential in the design of the engine have been long life between overhauls, economy in fuel and Oil, -simplicity and accessibility of all parts, silence and
smooth running. • The matter of lubrication has been delved into deeply and there has been introduced into the radiator, a section consisting of two flow and two return tubes cooled by fan, through which the oil from the engine is passed. The first advantage of using 'cool oil is increased efficiency, since the mean temperature of Abe engine oil arid circulating water is Maintained at a level which is economic. The radiator is, of course, large enough for the double purpose to which it is now put, and, in any ease, extracting heat from the oil takes it away from the engine just as much as extracting it from the water. The second advantage is the diminishing of the working temperature of the oil from, roughly, 190 degrees IP. to 120 degrees F., at which latter temperature the oil is five times as viscous as at the former. Under severe tests the highest temperature of the oil emerging from the radiator is shown to be 140 degrees F.; normally it is more than 20 degrees below this level. This on cooling allows of the use of a less viscous oil than the type used hitherto, one of the benefits then being easier starting from cold. A third claim is that the maintenance of a continuous film of cool oil between all the working surfaces enormously increases the life of the engine between overhauls.
Instant Lubrication of Moving
Parts.
A second improvement is the provisiOn of a primer which opens with the starter and remains open whilst the engine is runningand until the driver moves a small lever ; that is to say, a period of about 30 seconds. The oil from the primer is fed to the gudgeon pins, pistons, sleeves, cylinder walls and heads, all the moving parts being drenched within a few seconds of starting from cold. In order to prevent the primer being left in use, a trigger obtrudes over one of the control pedals and thus reminds the driver to put the primer out of action. The primer, however, can be operated independently by a. separate pedal if prolonged hillclimbing or other circumstances make its use desirable. A third improvement of the lubricating system is the feeding under pressure of oil to the gudgeon pins by means of specially drilled webs in the connecting rods.
Despite all these alterations in the lubricating system, the consumption of oil has actually been improved, and, since sound lubrication means less wear and tear of all working surfaces, the consumption of oil should not increase so much as is usually the case as an engine gets old.
A new laminated oil filter deals with a certain proportion of the oil lifted from the base chamber and it is readily removable for cleaning purposes.
The remaindbr of the chassis shows very few changes. It will be remembered that the power is transmitted through a single-plate fabriclined clutch and Spicer universal joints to a four-speed gearbox ; thence through a two-piece rear cardan shaft to the worm gearing in the back axle. The front springs have the shackle at the forward end and the wheels are detachable steel discs fitted with 38-in. by 81-in. Dunlop balloon tyres, with twin tyres en the rear wheels. The price of the chassis is £1,175, the wheelbase being 17 ft. 321 ins., the overall length 27 ft. 6 ins., and the distance from the rear of the dash to the end of the frame 23 ft. 2 ins., the over
hang being 8 ft.
A chassis with a shorter wheelbase, namely, 16 ft. 31 ins., is obtainable, the overall length then being 26 ft. and the body space 21 ft. 8 ins. and overhang 7 ft. 6 ins.