THE FORD VAN CHASSIS DISSECTED.
Page 18
Page 19
Page 20
Page 21
If you've noticed an error in this article please click here to report it so we can fix it.
An Article of Particular Interest to all Those Ford Users, or Potential Users, who are Not Fully Acquainted with the Internal Mechanism of their Chassis.
IN SPITE of the fact that a very large proportion of the motor vehicles employed all over the world is comprised of Fords, there is even now a curious air of mystery about the chassis which, as a matterlof fact, is one of the simplest in existence. The mystery is mainly accounted for by the peculiar features contained in the design of certain of its units. Many owners of Ford vans, if asked to state exactly how a, Ford functions, give anything but a lucid explanation. This applies particularly to the Ford ignition system and transmission gearing.
In order to assist. those who are not fully cognizant with the Ford mechanism, whether they be Ford owners or intend to become such, we have prepared the accompanying part-sectional illustrations, which, we • believe, show 'clearly the arrangement, and operation of those units which it is otherwise difficult for the uninitiated to visualize. Further to assist in the settlement of.a,ny real donbts as to.the object of including any particular features, we will give a brief, but, we trust, clear, general description of the chassis, folioweJ by notes regarding the working of the different units.
So far as the engine is concerned, the Ford is very similar to. any other petrol vehicle, although even here there are features which were, at one time eecuZifer to the Ford but have since been adopted on certain other types. One of these is in the casting of the cylinders in one with the top half of the crank chamber and the embodying with this casting of the upper half of the transmission gear casing; the lower half of the casing for the unit being formed as
a single steel pressing. • The complete engine and transmission unit is supported in a pressed 'channel, steel ,frame at three points. The transmission gear prdvides two speeds forward and a reverse, and from it the drive is taken by a propeller shaft enclosed in a tubular torque member bolted to the rear axle at one end and sup. ported in a spherical joint at the front end, the final drive being by bevel gearing through a differential to axle shafts on which the wheels are mounted.
-.Reverting to the engine and transmission unit, a feature is that the cylinder heads are detachable in one piece, the joint between this piece and the main casting consisting of a copper asbestos gasket. The bore and stroke of the cylinders are 31 ins. and 4 ins. respectively, and they are cooled by water circulated thermo-siphonically—in other words, without the use of a pump.
The lubrication, both of the engine and of the transmission gear, is effected by a simple combined gravity and splash system. The flywheel, in rotating, carries the oil to a pipe inclined towards the front end of the engine, where it first lubricates the timing gears and then streams back, filling the big-end troughs. The main body of oil is contained in the lower half of the flywheel casing, and its correct height is determined by the provision of two oil-level cocks. The level should be such that the oil does not drip from the top cock, but does from the lower.
.Carburation is attended to by a very simple instrument, the main jet of which is provided at its upper end with a. small 1'N% into which dips a. slow-running tube communicating with the inlet pipe close to the throttle valve ; normally this well is full of petrol, but when the engine is turned this petrol is sucked up the tube and gives a priming effect.
Now we come to what is certainly peculiar to this make of chassis, and that is, the curious system of ignition. The actual principle is that of the trembler coil comb;ned with a commutator which determines the timing of the sparks at the plug points. What is unusual, however, is the *ay in which the primary current for operating the trembler coils is provided. The device for effecting this consists of a low-tension magneto built up as a part of the transmission. A number of horseshoe magnets is carried on the outer face of the flywheel. In close proximity to these magnets is a stationary ring carrying a number of wire cap known as stator coils. A peculiarity of a magnet is that surrounding its pales is what is called a field of magnetic force. If a coil of wire cuts through this field a current of electricity is induced in the coil, and that is what happens in the base of the Ford. The stator coils are connected together and the current from them is collected by an insulated Collector Carried on the upper portion of the transmission housing. From this collector it passes through an insulated wire to one con.-nection of the trembler coil box. A current, however, cannot pass unless it has a return path, this being provided by the metal of which the engine is built. In order to obtain the sparks at the plugs at the right time, the current passing from the collector through the coils has to find its path to earth through the commutator, but it can only do so when one of the four segments in this instrument is in contact with the commutator roller. It is thus possible to time the passing of the primary current, and, consequently, the sparks at the plugs aS desired.
In the latest model Ford there is a battery which provides current for starting and also for lighting, and, to render starting easier, this may be used to operate the trembler coils, of which there is one for each cylinder. The current from this battery is derived from a separate dynamo driven direct from the engine, as the current obtained from the magneto is alternating, and is useless for charging purposes.
The Ford self-starter is provided with what is known as the. Bendix drive. With this type of drive a pinion is drawn into mesh with a teethed ring on the flywheel immediately the starter pedal is depressed, and is drawn out of contact by means of a spring immediately the engine starts and the pedal is released.
We will now deal with the Ford transmission gear. This is of the epieyclic type. In its simplest form this type of gear is quite easy to understand, but in the Ford it is rather more complicated. To simplify the explanation, we wili deal first with the more usual type. In this there is what is known as the sun wheel, around which is a number of what are called planet wheels, and surroundingthe wholeis an internally toothed ring; thus the planet pinions mesh both with the teeth of the sun wheel and with those of the outer ring. Such a combination will provide two speeds forward and a reverse, the top gear being obtained by locking the different parts together, and low gear and reverse by locking the outer ring and the planet pinions respectively.
In the ;Ford gear, the outer ring has been dispensed with, and each of the planet pinions takes the form of three pinions of different size riveted together and forming what is known as a triple gear. The outermost of the pinions of these triple gears meshes with the reverse gear, the centre one with the slow-speed gear, and the innermost with the driven gear.
The triple _gears, of which there are three sets, revolve on Tuns securely fastened to the flywheel, whilst the three sun wheels, around which the triple gears revolve, are connected to the transmission shaft, a reverse drum, and a slow-speed drum resepetively. Either of these drums may be held stationary by means of a friction band lined with bonded asbestos material. Embodied in the transmission unit is a multipledisc clutch. When the gears employed, are first speed and reverse, this clutch is held out of engagement, but for top gear it is engaged and then locks the whole transmission gear solid and gives direct drive.
In addition to the aforementioned drums there is a third functioning as a brake, the braking power being applied through a band similar to those used for operating the speeds. The clutch discs are forced into engagement by a stout spring acting through the medium of three fingers pivoted at their outer ends and each carrying in a central boss a screw which passes through an outer plate and pushes against a, pressure ring.
TVI'he operation of the transmission gearing, clutch, and brake is effected by the driver through three pedals and the hand brake lever. The last-named, when pulled right back, not only puts on the emergency brake on the rear wheels, but also holds the clutch out of engagement, so that in order to start the vehicle it is. necessary to push the hand ibrake lever forward.
If the reader imagines himself sitting in the driver's seat, the left pedal operates the clutch, first speed, and top gear, the central pedal is used for the brake, and the right pedal' when pressed forward, tightens the reverse band. The first pedal, when pressed half-way down, merely withdraws the clutch ; pressed right down it brings low gear into action if it is then brought back slowly to its highest position it releases the first speed band and lets in the clutch, thus locking the transmission gearing and giving direct drive.
Little need be said about the Ford back axle and differential gearing. The differential closely resembles that employed on other vehicles. First, there is the final drive gearing by bevel pinion and bevel wheel. The bevel wheel is bolted to a case containing the sun wheels of the driving shafts, and three bevel planet pinions, thus, while the whole casing turns with the bevel driving wheel, the sun wheels can move independently to permit one driving wheel to travel faster than the other when the vehicle is turned.
The driving shafts are carried on a curious form of roller bearing known as the Hyatt. In this bearing the rollers are hollow spirals of twisted steel, and thus give a cushioning effect as well as being flexible, over their length. Similar bearings are used at the wheel ends of the driving shafts and for the propeller shaft.
B34 , The "steering is somewhat unusual, In most vehicles the reduction gearing is at the bottom of the steering pillar, whereas in the Ford it is at the top, immediately under the steering wheel. It also takes the form of an epicyclic gear, which provides a ready method for obtaining the necessary gear reduction without causing wear, and with the gearing so accessible, replacements can be effected in a minimum space of time. The front or steering wheels are carried on bearings of the ball and cup type, somewhat resembling those of an ordinary bicycle. With the gear reduction so arranged, the steering is rendered very elastic. This may not be a disadvantage, but the front wheels of the Ford should certainly not be turned when the vehicle is stationary. We have not yet dealt with the springing. Only two springs are employed, both being fitted transversely. This, in a heavy vehicle, might cause rolling, but the Ford is saved by its light construction, and it is partly for this reason that overloading should be avoided.
We have already alluded to the Ford emergency brake. This takes the form of a pair of shoes in each of the rear wheel chums. Each pair is expanded into its drum by means of a lozenge-shaped cam. The standard Ford shoes press directly on the drums, and the brake is intended for use only in emergencies or for holding, the vehicle while it is stationary. The Ford lighting system consists Of two large-bulb headlights, two small-bulb side lights, and a tail light. These are controlled by a combination lighting and ignition switch located on the instrument board. The large lamps give 17 c.p., the smaller 2 c.p. All are connected in parallel, so that burning out or removal of any one does not affect the others as was the case in the older-type vehicles.
The current for these lamps is supplied by an accumulator charged from the dynamo and not from the magneto as was done previously., By referring to the large illustration of the partially dismantled chassi1s, the reader will be able to note some of the outStanding Ford features, most of which we have already dealt with. Amongst those not yet referred to are the radius rods for the front and back axles. These are rendered necessary by the special form of .springing utilized, and they certainly assist in bracing up the axles, particularly that at the rear, which has to take the driving and braking stresses. Between the hand-brake lever and the clutch pedal will be noted the connecting .device by which dual dutch operation is obtained, whilst projecting from the top of the carburetter can be seen the needle for adjusting the jet. -
In conclusion, we would point out that our information bureau is always available for the use of
those interested in the Ford vehicle and its work, and we will deal willingly with any technical or other problems connected with this make of vehicle or any other which our readers care to submit, if accompanied by a stamped addressed envelope..