Directly operated, even wearing floating band of the internal expanding brake.
A unique chassis construction. The frame is made up of a series of triangles; no stresses other than direct tension or compression are applied to any of the tubes. All loads are applied at the apices of triangles.
The Scott Sociable two-stroke engine (578 c.c.); a complete unit, with gears and clutch attached to the chassis with four bolts
Front wheel bracket; it is a structure which can only collapse or distort by the absolute fracture of one of its tubular members.
Unusual design of the piston; showing also a section of the cylinder and Scott patent double-pole sparking plug.
On the road the Sociable is remarkable for its accessibility. The "engine house," with its "roll-top" cover opened. The driver turns on the petrol and floods the carburetter preparatory to using the internal starting lever.
After Five Years of Testing, the Scott Sociable will be on View at Olympia.
First Description of the Final Production Model.
TWO or three machines stand out in the history of the motor cycle movement, since they bear that stamp of true inventiveness which marks the work of the creative engineer. It is significant that two such productions have been fathered by the same brilliant designer.
The Scott Sociable has had, in all probability, a more interesting and painstaking development than any other production which has been placed before the motor cycle public.
In the early days of the war the authorities who used the Scott machine gun side-cars demanded greater power and range of gearing. The designer realised that to do this would need much alteration of existing models, and, consequent iv, decided to lay down a chassis for the specific purpose of gun-carrying. All the qualities of the motor cycle and sidecar were to be retained, since, as a vehicle, the sidecar is not to be excelled in its lightness of weight, possibilities of load carrying, general handiness, and remarkable mobility owing to its extreme steering lock. The three-wheel two-track layout also permitted as a basic feature of design the very complete use of triangulated structure. Again, it frees the chassis of all the torsional stresses to which the conventional rectangular four-wheel construction is subjected when negotiating uneven ground.
Chassis Assembly.
The chassis consists of a tubular framework of triangular plan, truncated towards the front. Struts cross this frame in all directions, along which stresses exist, so that the whole structure becomes a series of triangles with apices wherever a load is applied. By this method of construction, the tubes are freed from torsional or bending stresses, and every frame member is in direct tension or compression.
A word is necessary as to the method of building. No brazing is employed in the chassis, since all the tubes are of standard lengths, formed with suitable eyes at the ends, through which bolts pass; the bolts also are alike in every case. Three standard tube lengths are used, and two lengths of standard eye-bolt, consequently one spanner is the only tool necessary in the assembly of the chassis from the component parts.
The suspension is by means of coil tension springs, used in pairs, and ten exactly similar springs are used in all.
At the front the wheel is carried on a "fork" swinging on trunnions upon a transverse member of the chassis. The fork is also built of standard tube lengths, and all its triangles converge at the steering head and stub axle which it carries. A rack and pinion steering gear is fitted.
A similar method is used in building up the back axle, which consists of four tubes. These are bolted at each end to aluminium castings, which serve to carry the brakework and the stub axles, upon which the ball-bearing hubs of the detachable wheels are mounted. (Only the off side wheel is driven, but an independent brake is fitted to each side.)
A system of links and coil springs insulate the chassis from the rear axle, which is located by radius rods at each side.
There is also a transverse distance rod from the near side of the chassis to the bevel gear casing of the off-side wheel in order prevent lateral sway when cornering.
Unit Engine and Gear Construction.
The base casting of the 578 c.c., two-cylinder, two-stroke, rotary valve engine contains a flywheel clutch, hand starter, and three-speed constant-mesh gear box.
The entire unit, together with the complete controlling gear, is removable from the chassis by loosening four nuts and the cover of the propeller shaft universal joint.
The engine has two cylinders (76.2x63.5 mm.) with cranks set at 180° and central flywheel. Symmetrical cylinders are used, machined all over, and the water-jackets are steel pressings welded into position. Bolting-down flanges are situated about half-way up the cylinder walls, so that a very long spigot projects into the crank case, and all the ports (both exhaust and transfer), as well as the lower water passages, are cast integrally with the []*. It will thus be seen that only one []king, common to all gas and water joints, is needed.
An unusual shape of gas deflector is used on the piston, which has three rings at the top and one at the skirt. A parallel gudgeon pin is fitted, secured by pins at each end; the latter are recessed in slots cut in the piston walls. The engine, except the small end, is equipped with double row roller bearings throughout. Gas is supplied by a Zenith carburetter by way of a cast aluminium combined inlet and exhaust manifold, while rotary inlet valves are employed to increase the efficiency of the engine.
Another feature on which the large power output depends is the double pole ignition, which has finally been made satisfactory by the use of the Scott double pole plug; this enables the M-L magneto to give two simultaneous sparks at the moment of firing. An M-L impulse starter is fitted to the magneto, and it is found that this greatly facilitates starting.
Transmission Details.
The clutch is carried inside the flywheel, and is of such a nature that once assembled inside the engine it cannot be reached. No adjustments are either provided or needed, as the action consists of a combination of the metal cone and expanding ring type, which is entirely self-adjusting as wear proceeds.
The drive from the clutch is by a double helical pinion to the gear box, mounted in an extension of the crank case casting. Very simple construction has been achieved in the change speed mechanism, which consists of six wheels in constant mesh. The top gear is direct, and changes are effected by a cam mechanism, which is always locked until the clutch is released.
In the opposite end of the casting is carried a shaft which is concentric with the sear mainshaft. This shaft is used for the starting mechanism, and also is extended to drive the centrifugal water circulation pump.
Provision is made for a lighting dynamo on the top of the gear casing.
The drive from the gearshaft to the bevel-driven back wheel is through a simple sliding and universal joint, mounted in a spherical housing at the front end of the propeller-shaft torque tube.
Bodywork.
Bodywork is quite as unconventional as the chassis. In motor car construction the coachbuilder necessarily uses heavy framework of timber to resist the effect of torsion in the chassis; but as the Scott Sociable suffers little in this direction, and as the seats are directly mounted on the chassis, the body merely acts as an encircling shell (carrying only the hood and screen) for the purpose of protecting the passengers. It is noteworthy that number plates, lighting equipment, controls, and seats are all directly fixed to the chassis, and if the body be removed, the car still remains in a drivable state, complying with all requirements, mechanical and legal.
The seat and backrest are suspended from the apices of triangular chassis members, and are instantly detachable, while the body, being constructed of a fibrous material, is extremely light, does not suffer in minor collisions, and is easily cleaned. A sliding cover somewhat like a roll-top desk completely encloses the engine, which is carried outside the chassis on the off-side; the cylinders have a slightly outward slope, and are perfectly accessible from the driver's seat.
Over the front wheel the petrol tank is carried, so that it serves the additional purpose of a wing for the front wheel; otherwise there are no mudguards, for the body itself overhangs the rear wheels. A specially commendable feature is the fact that there are no excrescences on the body with the one exception of the radiator cap; cleaning is therefore a matter of a few minutes' work with hose and sponge. The wheels are also conducive to cleanliness, since they are constructed of sheet steel pressings.
Protection and Comfort.
In order to protect the occupants a V shaped screen is fitted, and this has an observation slit which permits the driver to obtain a clear view of the road, even when the screen is obscured with mist or snow. The angle of the screen is such that air is deflected past the slit and beyond the sides of the car; even when the hood is raised there are no back draughts inside the body.
During a shower it is the work of a moment to raise the hood, which can be secured and released without stopping, if the driver so desires.
At each side of the seats are capacious lockers, while there is a convenient shelf for oddments such as gloves, pipes, and so on, in the dash.
The spare wheel is carried beneath the seat, where it is kept free from mud and is clean to handle when required, while behind the seats is a large platform, covering a very capacious boot wherein spare petrol, suit cases, or any bulky luggage may be stowed; or if an extra passenger is to be accommodated, the lid of the boot may be instantly erected as the back rest of a dickey seat.
Wheels and Brakework.
Although the drive is to one wheel only, there is a brake on each near wheel; the foot-brake acts on the side wheel while the hand-brake works on the driver.
Internal expanding bands are used, and these are operated by a direct pull of the control rods which draw wedges into the joints of the fabric faced spring steel rings. These rings are not divided and hinged, but are merely prevented from rotating by a loosely fitting stop. In consequence the ring expands equally, and wear on the braking surfaces is distributed over the entire circumference of the shoe; the detachable wheel hub-shells are formed with an enlarged portion acting as the brake drum. Incidentally, the wheels themselves are most simple in construction, consisting of two stamped discs assembled over the hub-shell and electrically welded in position, after which the tyre rim is welded to the outside edge. Under test a dead weight axle load of six tons was found necessary entirely to collapse one of these wheels.
A ROAD TEST DESCRIBED.
After having carefully examined a number of machines in the course of erection, and also observed the accurate production of parts in the Scott Autocar Company's Works at Lidget Green, Bradford, we were handed over to the care of Mr. Frank Philipp, well known as a rider in pre-war motor cycledom, who is now demonstrating the possibilities of Mr. A. A. Scott's latest creation.
Before leaving the works several of the features which will appeal, to the owner-driver were demonstrated For instance, in order to examine the action of the brakes, it was shown that the wheels could be detached (with the use of a tyre lever) in a matter of ten or fifteen seconds; the arrangement of the hub lock nut, however, is such, thanks to the positive locking device which operates at any position that it cannot come off the hub unless it is released by hand, even though it be only engaged upon one or two threads.
The light weight of the Sociable was shown by lifting both back wheels off the ground, while the side wheel may be lifted to almost any height, thus giving easy access to the underneath parts for cleaning purposes : incidentally the effectiveness of the springing was also made clear, since after lifting up the wheels to a height of at least 5ft. the machine was dropped suddenly, and the resilience. of the suspension simply allowed the machine to rise and fall at a gradually diminishing rate until it finally came to rest.
An Inside Starting Lever.
Everything now being ready for our trip upon the road we took our seats, and the driver, leaning over the sides opened the "roll top" cover above the engine. Having primed the engine, the cover was closed down again and a pull given to the starting lever beside the driver's seat; the engine at once responded, and after freeing the gear lever by withdrawing the clutch, low gear was engaged and the car started away up a steep and rough gradient. (Mr. Scott appears to have a penchant for situating his works at the foot of freak hills of the A.C.U. type!)
Once out of the congested traffic of Bradford, we took over the steering-wheel and found that the driving of the Sociable was delightfully easy - in fact, after the usual motor cycle or light car control, it was found a little difficult at first to accommodate ourselves to the delicacy of all the operations. For instance, the steering is managed with one finger on the wheel, while the three-speed constant mesh gear box, being spring operated, causes the lever to go almost of its own accord into the various notches of the quadrant.
Power and Speed.
There was no suggestion of the machine being under-powered, since all ordinary running, even up quite considerable hills, was done on top gear, while congested traffic scarcely ever calls for a gear change, thanks to the remarkable acceleration which this 578 c.c. engine affords.
On the level the speed (by Bonniksen speedometer) is from 40 to 42 m.p.h., and this was reached in a surprisingly short distance; when hill-climbing, if the speed in top gear drops to about 18 m.p.h., it is advisable to change to second in order to keep up a higher average pace, since 25 to 28 m.p.h. can easily be attained up hill on second.
As the engine is lubricated by the petroil system, the driver has no worries regarding the continuity of oil supply. Oil consumption is about one pint per 2OO miles, while the amount of fuel used is one gallon per fifty miles under average touring conditions.
Ease of Steering.
One of the most attractive features of the Sociable is its extraordinary mobility. No reverse is fitted, nor is it necessary, for it can be turned quite easily in its own length; for example, a signpost was over-shot in a narrow lane where an ordinary light car could not have been turned until a suitable opening was found for reversing. With the Sociable, however, it was no trouble simply to swing round in the road, using the side wheel as a pivot. So great is this power of turning in a confined space that the designer has fitted "rubbing strips" of hard wood around the engine casing, so that accidental impact with gate posts, or the corners of walls, may not cause any damage; this idea, of course, has been adapted from boat practice.
The springing is probably better than that of most motor cars, and full speed may be maintained over roads of any description. Even over the worst potholes the shocks felt by the occupants are only of a minor nature, and have nothing in common with the sickening jolts experienced with most light vehicles.
Curious Braking Effects.
The foot brake has most general use, and this acts upon the side wheel. The hand brake works on the driving wheel. When decellerating on a straight road, we found that when the clutch is withdrawn and the foot brake applied, the tendency is for the car to run towards the left-hand side. If, however, one slows down by simply releasing the accelerator pedal or by applying the hand brake, the tendency is for the side wheel to over-run the driving wheel, and so swing the machine over to the right. After a little practice, these tendencies are automatically corrected by the steering wheel, and we were told that after more experience the driver is able to use braking to considerable advantage when taking corners.
Afterword.
Altogether, we were very much impressed by our experiences of the Scott Sociable, alike as regards its design, the methods employed in this production, and its performance on the road. It is perhaps but seldom that the journalist finds a machine which is so replete with innovations that he can thoroughly extend himself. The vehicle under review, however, has so many new features (even the door latches and the strap buttons on the hood have their points) that amidst such a mass of interesting details it becomes almost impossible to do more than hint at the possibilities of the design. All we can say is that the Scott Sociable strikes a new note in machines of the motor cycle type; the claims made for it are very ambitious, and yet appear to be fulfilled entirely. To describe closely every one of its commendable features would require more than a complete issue of The Motor Cycle, and we can only advise our readers to make a point of inspecting this production at the forthcoming Olympia Motor Cycle Show. Those who are not able to do this will no doubt see it upon the road in numbers which will assuredly increase as time goes on.
The Motor Cycle October 25th, 1920. pp494-497
