FOUR DRIVING WHEELS
Page 67
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TRACTOR-LORRY
TICEMENDOUS loads are often conveyed by vehicles of the tractor-trailer type, and yet the drive is transmitted through two ',wheels only. in this Connection au interesking arrangement in which four wheels can be employed as drivers for such a vehicle it shown in the recently published patent of William Jackson, of Manchester, the number of this being-306,860. The arrangement is Shown applied ta what is sometimes known as the " fifth-wheel" type of vehicle, in which a turntable is employed to permit of the trailing portion of the vehicle to assume an angle with the tractor Portion.
The axles are so placed that the wheels overlap, thus enabling the axles to be closer together than would be the case were the wheels not arranged so that they make separate tracks, one wider than the other. Owing to the axles being close together, the grinding of the tyres, which must occur to some extent in all rigid four-wheeled bogies, is reduced to a minimum.
The drive is entirely by means of chains, which extend back from a cross-shaft to the forward pair of bogie wheels ; it is then taken by means of coupling chains to the bogie rear wheels. A differential can be introduced in the crossshaft in order to balance the power transmitted to all wheels.
Radius rods are employed between the cross-shaft and the forward driving wheels, whilst the centrally pivoted members act as radius rods between the two pairs of wheels. The
springs are shackled at both ends to permit of adjustment Of the chains. One of the nicest interesting points if the manner in which the axles are arranged. These, instead of extending right across the bogie, stop short, each being' borne in bearings that form part of the swivelling frame that carries-them., Each of these frames being centrally pivoted, it ,cau allow the wheels to be in contact With the ground, no matter how uneven the surface. A universal joint takes the place of a king pin, and this allows the trailing part of the vehicle to move in all directions in relation. to the tractor part.
The designshould prove useful Where very heavy loads have to be carried, as with the usual typo of articulated vehicle only one pair of wheels is employed, whereas actually the greatest possible grip Of the 'road for driving is desirable.