ERF's new bogie shows benefits
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BY JANUARY next year ERF will be fitting its new non-reactive bogie which is claimed not only to improve braking performance, but also to reduce tyre and brake shoe wear. Overslung springs which give an increased roll centre height will increase the roll stiffness and reduce the amount of roll..
, Balanced beam bogies have probably been used as long as there has been a commercial vehicle fitted with twin axles at the rear.
Much more recently manufacturers like Albion and later Mercedes looked to improve the known shortcomings of such a system. Under normal braking the weight is transferred from the front to the rear axle of the bogie. This often leads to the foremost of the two rear axles to lose contact with the road surface.
The net result is a loss in overall braking efficiency and uneven distribution of tyre and brake wear. In reverse on off-road conditions, especially where a lot of throttle is applied from a low speed, loss of traction can occur.
Recently at MIRA, ERF made two vehicles available, one fitted with a balanced beam suspension and one with the new non-reactive suspension. Both were eightlegged ERF B-Series vehicles fitted with the Rolls-Royce 220 Mk III engine and Fuller range-change eight-speed gearbox.
However, there were small differences between the two which should not go unnoted. Axle weights were within a couple of cwt and the overall weights were just under 30 tons. The non-reactive bogied vehicle had a wheelbase of 6.48m (21ft 3in), 0.59m (lft llin) longer than the balanced beam vehicle.
Brake shoes and drums were identical on both vehicles as were the actuators and lever movement on the front two axles but differed on the rear bogie layout of the nonreactive one. The nonreactive bogie uses type 24 actuators with 120mm (434in). _lever movement on both axles while the balanced beam bogie employs type 20s with 120mm '(434in) lever movement on the third axle and type 30 with 127mm (5in) lever movement on the fourth axle.
Braking stops in the laden condition (30 mph) showed an improvement of 3.3m (lift) for the non-reactive bogie and all sign of the third axle lifting was removed.
In the unladen condition axle hop is normally more pronounced, but a full-brake application from 40mph produced no sign with the non-reactive bogie and an improvement of 1.5mm (5ft) overall stopping distance was aChieved with the noi reactive bogie.
Purely as a demonstratic the park brake was aprilit fully from about 1541)1 Whereas the non-reacth bogie wheels followedth contours of the road, who this was repeated with th balanced beam bogie 01 wheels bounced up and dow clear of the road.
A similar result could Ii induced under violet accelerating from rest, buttoi lesser extent.
In the fully laden conditicl around the ride and handlin course the difference in rd was hardly noticeable, bu once in the driving seat became immediately obviou that the vehicle fitted with th non-reactive bogie rolled les and consequently allowed ai increase in speed of at leas 5mph with less discomfort.
The actual point of roll difficult to assess without th benefit of a tilt platform, bu up to that point the non reactive bogie has a lot ti offer.