Bedford Approve Six-wheeler Conversions
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FOR the first time, Vauxhall Motors, Ltd., have given their approval to two trailing-axle six-wheeler conversions for Bedford normaland forward-control 64and 7-tanners. The conversions accepted are those carried out by the York Trailer Co., Ltd., Corby, Northants, and the Primrose Third Axle Co., Ltd., Whalley, Lancs. In both cases much use is made of Bedford components to simplify the provision of spare parts.
Maximum permissible gross weights for all the six-wheelers offered are 15 tons when the Bedford 300-cu.-in, oil engine is fitted, and 15 tons 8 cwt. with the optional Leyland 0.350 oil engine. To run at the maximum weight, all models must have the Bedford two-speed axle with ratios of 6.4 and 8.72 to I.
Conversions are available for the normal-control .T6S tipper and J6L, and the forward-control SS tipper, SL and SE
• haulage models. All the conversions increase the wheelbase and the permissible body length. Body length available on the various converted models is as follows:
Bedford-York—J6S, 18 ft. or 16 ft. for tipper; .16L, 21 ft.; SS, 15 ft. 9 in. or 15 ft. 3 in. for tipper; SL, 21 ft.; SE, 22 ft. 6 in.
Bed1ord-Primrose—J6S, 14 ft. 4 in.; I6L, 19 ft. 3 in.; SS, 14 ft.; SL, 21 ft.; SE, 22 ft. 6 in.
Prices of the conversions, including tyres but exclusive of additional bodywork, range from £555 to 1578 for the Bedford-York and from £537 to £562 for the Bedford-Primrose. Standard tyres are 8.25-20 in. (12-ply) but 9.00-20 in. (12ply) equipment can be fitted at extra cost.
The conversions differ markedly in their approach to third-axle suspension. For -the York design two stub axles arc carried at the rear of hollow distributor beams pivoted on a tubular crossmember which is suspended on brackets from the chassis frame ahead of the trailing-axle centres. The forward ends of the beams are attached by shackles to the rear eyes of the leaf springs on the driven axle.
This arrangement provides independent suspension for each pair of wheels, with static weight distribution of 55 per cent. on the driven axle and 45 per cent. on the trailing unit.
Primrose employ a tubular axle with coil-spring suspension for their conversion. The axle is located and brake torque is absorbed by two trailing quarter-elliptic leaf springs pivoted on the lower flanges of the chassis side
members. These springs extend behind the axle where they are restrained from transverse movement by vertical guide rails. Damping is provided by telescopic shock absorbers on the trailing axle only.
A hydraulic compensating mechanism is incorporated to regulate the loading on the two axles of the bogie. It consists of two hydraulic cylinders fitted between the chassis frame and the casing of the driven axle. High-pressure piping connects their outlets to two other cylinders fitted inside the coil springs on the trailing axle. As the load increases, weightratios are adjusted automatically.
For both conversions the chassis sidemembers are extended by the addition of 10+-in.-deep channel sections with 3-in.wide flanges in f-in.-thick material. On the SS and SL forward-control models, these extensions are welded direct to the optional Bedford flitch plates which must be specified when ordering a chassis for conversion.
For SE, J6S and 36L conversions, the additional frame members are carried forward to the back of the cab.
Additional braking for both conversions is effected by a slave vacuum servo and hydraulic system.
The Commercial Motor has road tested both conversions. The vehicles tested had 300-cu.-in, engines and ran at the same gross weights under identical road and weather conditions with the same drivers. The table below gives brief details of the results obtained. Illustrated road-test reports will be published later.