SHOW DISCLOSURES IN COACHWORK DESIGN.
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Efforts of Coachbuiiders to Ensure Safety, Comfort, and Convenience for Passengers.
ANOTHER Commercial Motor Exhibition has come and gone, and Olympia's doors are closed. The massed forces of the heavy-vehicle industry have given of their best, and another year at least must elapse before, such a representative gathering of the clans once again takes place. To many, the 1921 Show has been a revelation, particularly in regard to the remarkable advances ' which have been made in the design and construction of bus and coach bodies, and the importance of this section of the industry was well reflected in the number of passenger-carrying vehicles on -view.
Lightness Combined with Rigidity. One of the outstanding aims of body designers, and particularly with regard to single-deck bus construction, is towards lightness, and the extent to which this worthy object has been accomplished can be gathered from the bodies built by Messrs. Strachan and Brown. The 20-seater bus body, for instance, weighs only 15 cwt., and the 33-seater but an additional 3 cwt.-3 owl. for 13 mms passengers. It is, of en'erse, impossible to reduce weight at vulnerable points without maintaining strong and rigid construction, and it is now becoming general practice to employ light steel pressings, or flitch plates, in conjunction with, or in preference to, ash and oak framing for securing the side pillars to the underframe and to the heap stickt in
the roof. In the Straehan and -Brown bodies this in is adopted, and the roof sticks are further strengthened right across their width by the insertion of T plates from the top. The Norfolk 26-seater body is another excellent example of lightness of construction compatible with rigidity, in
which flitch plates are used. Weight has also been saved in the -side panels, 424
which are strengthened by stout diagonal bracing, so -that the body weighs just under a ton, Weight has been saved in other directions, and that even small details have not escaped the notice of designers is suggested by the chamfering of the tops of the hacks of seats and parts of the frainewoi.k, and by the use of rounded steel corners at the back, lined inside with plywood.
It will be recalled that. at last year's Show a mild sensation was created by the Morgan all-metal coach body built on an ingeniously jointed tubular frame braced with steel wire, a body built on these lines weighing only 12 cwt. This year the closest approach to this design was afforded by the Mayrow system for
single-deck buses, in which the framework is built up of light fluted steel sections stromYty riveted together, into which panels of aluminium, steel, or five or three-ply wood can be built.
Two and Three. Compartments for Buses.
Buses can be divided into two types, i.e., those suitable for use in populous areas, and those designed to meet the needs of isolated and sparsely inhabited districts. The former type, with a seating capacity between 30 and 40, is usually of the two-compartment type, a partition, which, incidentally, serves to add strong-01 to the construction, also serving to separate a rear smoker's compartment from the main seating.
The seats in the main compartment face forwards, but in the smoker's saloon
they are usually ranged round the sides andends, as in the Buckingham 33-seater body. The two compartments are -usually interconnected, although it would surely be wise to fit a swing or sliding door between -them, for, although roof ventilators or, faMights arranged for emission, and a through current of air will disperse most of the smoke, some of it is bound tofind its way into the fore compartment, where it may offend the susceptibilities of other passengers. If the seats in, the smoker's saltion face forwards, it is desirable to shape the lower half of the partition, as in the case of the Straehan and Brown 33-seater, in order to give adequate knee room.
Types of Doors—Their Number and Position.
The question of doors—both for buses and coaches—is on important -one; and their number has a great bearing on the strength of the framework because the greater their number the greater the need For additional bracing of framework. On this score the pay-as;you-enter type of body has much to recommend it, since it calls for the provision of a single door at the front where the body is least subject to strain and whipping. The Norfolk body built by United Automobile Services, Ltd., is a good example of this type,' and provides a very safe entrance. It has a two-piece door, which is set slightly at an angle to the body side, and hinged in the centre and to the nearside front pillar; it can be opened or closed by the driver without leaving his seat., and when closed is flush with the outside of the lower step a. few inches off the ground.
Another typo of front entrance is that wherein access to the main saloon is by way of the driver's compartment. Small buses, used iu areas where stops are nfrequent, generally have a sliding door, sompletely to close in the interior, ilthough on larger models, in which the lort-di_stance fare is in the majority, his construction is not necessary.
Larger types of buses often have two mssenger doors, one fore and one aft, Ind, -where one is used as an entrance end the other as an exit, this is an added amvenience, but, generally speaking, one )assenger door is found to be sufficient, he position of it varying according to ndividual designer's ideas and to the .lass of service. Most of them are at he rear as in the Dennis, Maudslay, 3artle, Dodson, Sankey, and other mdies, although the Caledon 40-seater as its single passenger door in the centre
■ f the nearside.
It is pleasing to observe, in the matter if char-a-banes doors, that the tendency s to keep their number down, and this lesirable object has undoubtedly been ,chieved by the virtual elimination of he, largest, type of vehicle. On a large timber of coachea the gangway method
construction is now adopted, and this nables one door to meet all requireRents, thus giving a strong and rigid ide framework. The central gangway 9 most favoured, as on the Tillinghavens and Guy de luxe coaches, ,lthough a point in favour of the gangray on the near-side is that it throws
added weight on to the off-side, and thus preserves adhesion and stability on well-cambered roads. Where doors are used to each row of seats it is the practice of all makers to reinforce the body by stiffening irons to counteract the weakness introduced by the doorway opening.
Coach Hoods and Their Accommodation.
The Show certainly revealed several good ideas in coach hood design, the Leyland and [Carrier being conceived on entirely new lines. In the former, four tubular uprights and two longitudinal supports form a framework on which the hood battens slide. The minimum effort is thus required to raise or lower the hood, because the weight of the hood is carried by these supports, and, moreover, it is not necessary to remove the i
tubular framework for it s not. unsightly, although it can be dismantled and accommodated in a locker on the off-side.
The Karrier is an ingenious hood, in which the twill is stretched from end to end on three runners, each of which is supported by two triple-arm link stanchions. Short locking rods are attached to the near-side arms, and these engage with studs secured to the hacks of the first seat and the last seat but one. When the hood is up, these, rollers being released, the hood pivots on the central arni:of eaeh:stanehion and folds clown to the off-side,-'where it is aveommodated in a concealed compartment at the top of the body panel. The difficulty that had to be overcome with this design of hood was to discover a quick method of stowing the hood in its compartment,
Other efficient hoods include the Bartle and the. Kopalapso. In the fernier tubular brass bows are mounted on ingeniously shaped bow. plates, ,the latter being secured to the body irties. When not in use the bows are accommodated at the back of each row of seats, the hood twill being housed at the back in a special tray provided with drainage holes. This type of hood, like the Leyland and the Karrier, removes considerable weight.from the back of the vehicle.
The Kopedapso hood is of the one-man type, and is of chief application to small coach bodies, such as those built by the Westminster Coach Works. It is in the method of supporting the forward portion of the hood where lies the chief feature of this hood, it being carried on what may be termed two outrigger sticks connected to the foremost side of the forward main stick through the medium of a system a levers.
The Jackson type of hood still appears to enjoy considerable.popularity. Most heeds are liable to damage through projection beyond the body sides and hack, and a way to obviate this is afforded in the Tilling-Stevens armchair coach, in which the hood is accommodated around a rear luggage locker.
Avoiding. the Wheel Arch.
The intrusion Of the paddle boxes for the rear wheels into the body interior invariably gives trouble on passenger vehicles, especially where the seats are disposed transversely in the forward direction, More attention could, with advantage, be given to this problem, as it materially affects the comfort of the passengee. In the Norfolk bus body the difficulty has been met by providing a foot rest placed at an angle on the wheel arch for the benefit of the passenger on the seat behind it In the Dennis 36-seater a seat. on either side over the paddle box is slightly carried round the body side, and this enables the passenger to stretch his legs inwardly. The best solution of the pro, blem is obtained by the use of longitudined seats, and, where a separate rear
compartment is used, it is possible to arrange a single seat so disposed on either side between the partition and the transverse seat in front. This construction, however, means the loss of two seats. The A.E.C. Edinburgh-type bus, has three compartments, the centre one, into which the wheel arch protrudes. having its seats ranged round the sides.
Emergency Doors.
On single-deck buses with a single front entrance, it is desirable to have an emergency door, such as that employed on the .t.rachan and Brown 33-seater holly and the A:E.C. 40-seater. On the former it is necessary to remove the seat and the inside body panel behind it before the lock of the door can be turned. Neither of these emergency doors has a step, so that small boys 'cannot seize an opportunity of .hanging on. = An enieegency deter must he able to be readily opened, although it must not be possible for passengers to mistake it for a normal means of exit.
Pneumatic Tyres.
The greater proportion of the passenger vehicles et. the Show were shod with pneumatic tyres, and this equipment has undoubtedly had a great bearing on the reduction of the weight of bodies and the supersession of the largest type of motor coach. Pneumatic tyres are rendered safe for a live load by such a warning device as is fitted on Michelin large section pneumatics, which, by the explosion of a blank cartridge, informs the driver when the air pressure falls below 40 lb..
Braking and Sprags.
Up till now all passenger vehicles have been fitted with two independent sprags, the foot. brake usually acting on the transmission, and the hand brake on the rear wheels, but at this year's. Show a radical departure was to be found in the Burford coach, in which the four wheels were equipped with brakes. It is very desirable to have a maximum braking effect on all passenger vehicles. It is rather curious that, with one exception, no eprags were to be found fitted to buses or coaches at the ...Show, and, although we do not say that a safety device of this kind is essential on all passenger-carrying vehicles, it is certainly very desirable on vehicles operating in hilly districts.