Chapter 4

The Benz Car

Fig. 6 is a skeleton section of the Benz car showing framing, wheels, and engines.

Fig. 7 is a plan showing the engine belts and chain gearing.

On opening the back of a Benz (see Fig. 9) the machinery is exposed to view. In the centre is the engine, with its fly-wheel on the right; then further to the right the two pulleys on the crankshaft for the fast and slow speeds; on the left, the carburetter, connected by a small copper pipe with the petrol supply tank, and from its upper part a pipe running forward  towards the throttle and mixing cock. By this throttle valve, which is moved by a handle on the driver’s left, the amount of gas and air admitted to the cylinder is regulated.

On each side of the engine, and forming part of the sides of the car, are two copper tanks—one for petrol and the other for water (but in some cars both are used for water, the petrol tank being under the seat). The water is necessary to keep the cylinder from becoming too hot from the explosion, or rather the combustion, of the gases within it. If the cylinder gets too hot there is a loss of power, and in time the excessive friction (for the lubricating oil supplied to the cylinder would be burnt or dissipated) would cause the bore of the cylinder and the piston to be seriously injured. It will be noticed that the water tank is connected with the water jacket of the cylinder by two pipes—one a flow and the other a return—so the water circulates round the cylinder in the same manner as it does in a greenhouse boiler and pipes. Above the cylinder is a brass or copper separator to separate the steam from the water. The steam escapes from this separator into an annular transverse tube fixed at the back of the seat. This is the condenser. Here a large part of the steam condenses, and runs back as water into tank. The rest of the steam escapes by a bent pipe towards the ground.

There is one objection, and only one, to water-cooled cylinders, that is, the liability to damage by frost. To have the cylinder of a Benz car cracked by ice would be a very serious affair, possibly costing £5 or £6 [2010 £450 or £540] to repair. It is absolutely necessary in winter to empty the tank by the tap provided for that purpose. The tap is very awkwardly situated, being almost in the middle of the car. A stick with a deep notch cut out at one end to fit the handle of the tap is very useful for the purpose. Glycerine mixed with the cooling water will prevent freezing; about one part glycerine to five of water is sufficient; the glycerine does not evaporate, so tank only requires to be refilled with water. Common salt also prevents water freezing, but as it causes everything that comes near it to rust, it is not recommended.

The De Dion motor tricycles, the Bollée, the early Decauville cars, and others are air cooled, a great number of radiating ribs being cast on the cylinders, which expose a large surface to the air. Fans have been tried to cause a strong air current to circulate round the cylinders, but at present only small cars have been made without water jackets.

The writer is of opinion that, however well the air cooling is arranged, there must not only be loss of power in these extremely hot cylinders, but that the bore of the cylinder and the piston must have a comparatively short life.

In the carburetter, which is the vertical copper drum on the left of the engine, the air is charged with petrol vapour. The air enters through the top of the vertical pipe through the wire gauze, and impinges on the surface of the petrol in the carburetter. Here it is impregnated with vapour, and passes off by the bent pipe to the engine. A float in the carburetter keeps the petrol at the proper height, shutting off and turning on supply as required.

Under the seat of the car is the mixing valve, which admits more air to the carburetted air and the throttle valve, which regulates the quantity of the mixture supplied to the engine, and thus regulates the speed of travelling. There are also a series of discs of wire gauze to prevent any premature explosion in the cylinder passing back and firing the petrol in the carburetter. These cut off the flame in like manner, as the wire gauze of a Davy safety lamp prevents an explosion in a coal mine.

Under the seat of the car is the electrical apparatus to fire the gaseous mixture in the cylinder. It consists of two accumulators and an induction coil.

The induction coil may be best understood by reference to the electric bells of a house. If the wood case of the bell be removed a bright spark will be noticed at the point where the trembler or clapper breaks contact. This is a brighter or more flashing spark than can be obtained from the battery alone, and it is caused by what is termed the “extra current,” which is produced on the breaking contact of an electric current in any bobbin or coil of wire, but the flashing spark is required to be inside the cylinder; to get this an induction coil is used. Like the electric bell, it has its core of soft iron on this is wound the primary wire for the current from the battery; above this is wound the secondary coil, of very much finer wire, and threequarters or a mile in length; this latter is very carefully insulated, and in this secondary coil the induced current with a flashing spark is obtained. This spark will jump across an air space 3/8 in. or 1/2in. One end of the secondary wire is connected with the metal of the engine; the other end with the insulated wire running through the porcelain igniter, and causes an electric spark in the cylinder. The points of the wires in the igniter should be about 1/16in. apart. It must not be forgotten that if a coil gives, say, a 1/2in. spark in air it will only be able to give perhaps 1/8in. in the compressed mixture in the cylinder.

The accumulators require charging after twenty-five or thirty hours’ use. It is important to switch off the current as soon as the car is stopped, otherwise if the engine stops on the firing point and the coil is left working, the cells will soon run down. Directions for charging the accumulators are sent out by the maker or agents.

The electrical contact for making the spark, that is, starting the coil working, is by a light spring, which bears on an insulating disc on the end of the small revolving drum which opens the exhaust valve. In this insulated disc is a strip of brass, which is connected electrically with the metal of the engine, and to which one pole of the accumulators is connected. The light spring, it will he noticed, is fixed to an ebonite or vulcanised fibre, that is, an insulating support, and this spring is connected through the coil with the other pole of the accumulator. As the brass comes round and touches the spring, electrical contact is made, and the spark passes in the cylinder.

The steering-gear is simple, and hardly requires explanation. Some cars have lately come on the market with chains for steering. There must, however well the chains are made and proportioned to their work, be a risk of a link failing and the probability of a serious accident. A car in which a chain forms any part of the steering-gear should be avoided.

The belts which give motion to the countershaft must be of good quality, and as wide as possible to run on the pulleys; 1 3/4 in. is the best width. They should not be too thin, for with use they wear thinner, and are then liable to twist or turn on their edges in the guides, and not leave the fast pulleys as quickly as they should. The best dressing for these belts is castor oil on the outside; the belts must be kept at proper tension. This, however, is a matter of experience.

The countershaft really is in three parts—the inner shaft, which runs right across the car, and has the fast pulleys fixed to it; the outer shafts (which carry the sprocket pulleys for the chains) are tubes slipped over the inner shaft, but these are driven through the intervention of the compensating gear, sometimes called the Jack-in-the-box, which allows one wheel to revolve faster than the other for going round curves. This gear is used on traction engines and tricycles.

The differential gear may be thus explained. For instance, if two racks of considerable length are coupled by a pinion 1 (see fig. 10), when the pinion is moved in the direction of the arrow, if the strain on both racks 2 and 3 be equal, they will move on with the pinion; but if the strain on one be greater than the other, the rack which has the greatest strain on it will lag behind, the pinion turning on its axis and the other rack advancing, so that if anything checks the advance of a rack it will cause the pinion to revolve. If, instead of the racks, we have two bevel wheels, and each bevel wheel connected to one of the propelling wheels of a car, on a wheel moving more slowly, as going round a corner, the pinion will revolve, and by allowing the other wheel to over-run will compensate for the difference of the movement of the wheel.

Fig. 11 shows the Benz differential gear, 1 is one of the pinions (for there are two, one opposite the other); this has for its axis a pin, which really forms a spoke of the pulley 8, the pin being attached to the through shaft 4 and going round with it. The pinion gears into the bevel wheels 2 and 3, which are keyed on to the hollow shafts 6 and  7.

These shafts carry at their ends the chain sprocket wheels, each of which drives a road wheel. The pulley 8 is a stepped pulley, with two faces—one large for the slow speed, and the small for the fast; a flange between prevents the slow speed belt running off; 9 and 10 are the two loose pulleys.

This is the principle of all differential gears. There are many modifications of it in some cars and in motor tricycles it is on the main axle.

The chains used in the present day are what are known as Brampton’s, but some of the cars that have been imported have French or German chains, which do not correspond with the pitch of English-made chains, and the owner of such a car may experience trouble and delay when he wants to renew his chains.

Of the Brampton chains, there are two sorts—the roller chain, which wears very well, and the block chain, which the author has found inferior. A pair of the former chains, if well looked after, should run 2,500 to 3,000 miles. It is to be regretted that a chain case cannot be fitted over the chains; it would increase their life, and in wet muddy weather the dirt and grit thrown on the chains must cause extra friction besides wear and tear.

Chains should he kept clean and oiled. The makers recommend occasionally taking off the chains, washing them in hot soda and water, and then soaking them in oil. In the case of the lighter or block chains, a pair of lubricators arranged to drop oil on the chains as they run is an advantage.

Most Benz cars have solid tyres; of these tyres there are two sorts. The tyre as originally fitted by Benz had a wire in the centre to hold the tyre in its place, as the wire is half-way between the base of the tyre and its outer surface. This wire must be bent or flattened at each revolution of the wheel, and consequently would soon snap; to avoid this, and to give it elasticity, the wire is twisted into a spiral, the outside diameter of the spiral being not more than two or three times the diameter of the wire. This elasticity is intended to prevent the wire breaking. For the front wheels, which only carry about one-fourth or less of the weight, this seems to answer, but in the large wheels the wire is sure to break in time, and the tyre to come off.

If a thin band of flat steel were used in place of the wire it would probably be more durable. But the chief reason of the breakage is that the wire is in the wrong place, namely, in the centre of the tyre. In the Ideal tyre (fig. 12) the wires, two or more in number, are at the base of the tyre, and not exposed to the continual bending strain as the centre wire is. In these Ideal tyres the wires are electrically welded. The rubber is of good quality, and wears very well. From the experience of others as to their durability, a pair of wheels on a Benz with this tyre should run 8,000 or 10,000 miles, or a distance equal to the diameter of the world before they were completely worn out.

The writer has had no experience with pneumatic tyres on his own car. They add to the speed and comfort. But the risk of puncture is great, and at present they seem hardly equal to the requirements of motor car work, except for very light cars.

A tyre has lately been put on the market which is somewhat similar to the Ideal. It is known as the Chalton, and has the twisted wires of the earlier Benz type, but two wires in place of one, and at the base of the tyre. The ends of the wires are apparently screwed together and soldered. This tyre is shown in figs. 13 and 14.

The law requires that all motor cars be provided with two independent brakes. The band brake on the hub of each wheel is worked by the foot; the band is lined with leather, but the eyes which are fastened to the band are secured by small bolts and nuts. Now, if the leather wears down considerably these bolt heads or the nuts must come in contact with the drum, and cut out a wide groove in it, not only damaging the drum, but considerably impairing the power of the brake.

The wheel brake is more powerful than the foot brake, but as it bears on the rubber tyre it must cause a certain wear and tear. The original brakes on the Benz were very inefficient; they were something like the spoon brakes on the old ordinary bicycle. They had comparatively little holding power, and in course of time the front edge of the shoe wore as sharp as a knife. If the car were to run back on a hill the Sharp edge would cut into the tyre and damage it, if not destroy it entirely.

Price’s brake blocks (Fig. 15) obviate this danger, as they are suspended on a point near their centre. Equal pressure can be given on all parts of the brake; this is not likely in any way to injure the tyre. Owing to their length (12in.), they get an excellent grip on the wheel, and this gives the driver great confidence in going down steep hills. A somewhat similar brake has been designed and brought out by Mr. Lyons Sampson.

The sprag or devil is simply a sharpened rod attached to the axle to prevent the car running back when stopped on a steep bill. It is raised or lowered by a cord close to the driver’s hand. It is necessary to see that the point, which is generally chisel shaped, does not wear down, otherwise it may fail to act promptly, and would then, after the car had run back a few feet, pull it up with a violent jerk, possibly shifting the axle from under the springs, or even causing the car to run right over the devil.