New equipment and publications
Page 53
Page 54
Page 55
If you've noticed an error in this article please click here to report it so we can fix it.
Automatic brake adjustment would be counted by most vehicle engineers as a valuable contribution to maintaining efficiency and reducing servicing costs. But a problem with many designs of automatic adjuster unit can be that any re-setting of the shoe positions through extra movement of the brake shoes due to heat expansion of the drums can result in the brakes staying partly applied when the brakes cool.
An automatic slack adjuster which overcomes this difficulty is now generally available in the UK. It is the SAB Type AA1 marketed by SAB Brake Regulator Co. Ltd., the subsidiary of the Swedish manufacturer. The AA1 is suitable for use with air-operated S-cam brake units only and a number have already been fitted to British p.s.v., largely on a trial basis. Leyland has had 100 sets, 50 of which were fitted to Leopard chassis and the rest to Atlanteans. BET has nine vehicles fitted with AA1 units arid they appear to have performed satisfactorily as the adjuster has been specified on a BET order for 30 Leyland Leopards.
The main feature of the SAB AA1 adjuster is that the mechanism is actuated only by the clearance part of the total piston stroke. Excessive clearance is not taken up completely during a single application of the brakes as is often the case with this type of component. Adjustment takes place on the return stroke of the actuator and the amount depends on the degree of clearance existing. A very fine adjustment is possible and it will be seen from the accompanying graph that 40 brake applications are needed to reduce a shoe-to-drum clearance of 1.6mm to 0.5mm with a further 40 required to bring the clearance to 0.4mm. It is clear that if the brakes are applied with heat expansion present in the drums a fairly large number of applications with them in this condition will have to be made to cause the shoes to "rub" when the drums are cold.
Another point is that the mechanism is made inoperative when the brake camshaft is under load so there is not the slightest amount of adjustment if the drums expand while the brakes are applied—such as on a long descent. And due to the design, the exact adjustment is maintained continuously.
In general layout the SAB AA1 has similarities with some types with non-automatic slack adjuster. The position of the inter
nally splined worm wheel in relation to the arm is determined by a worm shaft in engagement with it. The shaft can be turned manually through a hexagon head at one end and automatic adjustment is provided through a rack and pinion system. The pinion, at one end of the worm shaft, is linked to a collar against which an angled face of the shaft bears. The connection between the pinion and the collar is through an internal, snugly fitting spring which provides a one-way clutch —in one direction the pinion moves freely over the spring but in the other the coils expand for positive drive. The shaft is kept in engagement with the angled face of the collar
Continued overleaf
which transmits the drive through Belleville washers at the opposite end of the shaft and these are compressed when the brake cam shaft is under load so freeing the drive.
One end of the rack locates in a gap in a guide disc on one face of the adjuster which has an extension for connection to a fixed part of the brake unit. There is no movement of the rack until the normal drum-to-shoe clearance is taken up but further movement of the actuator causes the rack to move and rotate the worm wheel.
Marketed by: SAB Brake Regulator Co. Ltd., Aycliffe Industrial Estate, Darlington, Co. Durham.
PD Superlift
A new hydraulic lorry-mounted hoist known as the Superlift was demonstrated in London recently by Powell Duffryn Engineering. To be known in Britain as the PD Superlift hoist, it is an early fruit of the acquisition of the Dutch engineering subsidiary company of Geesink NV, which has been successfully selling the hoist on the Continent. It has a capacity of 3+ tons at 58in. radius and with an optional jib extension fitted, giving 21 ft operating radius, 1,500lb can be lifted.
Two channels at chassis width, each 4ft long, provide the foundation for the hoist, giving maximum distribution of vehicle loading and thus avoiding localized chassis stress. Outrigger jacks are fitted to stabilize the vehicle in operation.
Levers to control the hoist operation are fitted to both sides of the vehicle. The main boom is raised and lowered by the vertical ram within the main turret, all cylinder pistons and rods being chromium plated. The second section is controlled by a separate ram and folds back fully on to the main boom by hydraulic operation to give compact storage when stowed. The third section is extended by an hydraulic cylinder positioned on top of the second section, and the fourth extension is manually operated. When a fifth extension is fitted as an optional extra, this also is manually operated.
The complete hydraulic circuit is protected by safety valves and a special feature of the Superlift is the smooth operating action achieved by the use of hollow spool valves for fine throttle control. This prevents jerking and swinging of materials being handled by the hoist, The price is £1,110 for the standard model —the boom extension and outrigger stabilizing jacks each cost an extra £25. Development work is in hand on 2+ and 4+ ton models.
Optional extras include a 9 cu.ft. clamshell bucket, an octopus grab of 7 cu.ft. capacity, pipe-laying forks, a brick clamp and a skywork platform. These were not available for the demonstration but are on show at the Mechanical Handling Exhibition at Earls Court which ends on May 24.
Made by: Powell Duffryn Engineering Co. Ltd., Materials Handling Division, Cambrian Works, Maindy, Cardiff.
Quick connection
An easily fitted connector for vehicle wiring is now available from Stellar Components Ltd. The company recently began fitting the connector to the leads of its Headlight DimDip and Crashflash hazard warning systems and is now offering it separately.
The insulation-piercing crimp connector is a 0.75in. curved-brass strip with wrapround tags at one end for clamping on to the wire to be attached and a curve with two protruding points at the other end. This is connected to the vehicle's wiring by squeezing the brass curve with a pair of pliers so that the two points penetrate the plastic insulation making a positive connection. A polythene sleeve is then slid over the joint and fastened to give a weather-proof seal.
Made by: Stellar Components (Sales) Ltd., The Causeway. Maldon. Essex.
Price: 2s 6d for five.
Joloda aid
A new Joloda development utilizing portable tracks will interest transport and warehouse managers responsible for container packing. The tracks may be laid on an ordinary container floor and after loading any size of palletized load—up to full width and full length—the load is lowered on to 3in. dunnage, allowing the Joloda tracks and equipment to be removed.
The Joloda fork-lift roller conveyor can be extended to any required length, the box tracks being extended out of the container for loading by crane, or bridging the gap where a container may be loaded in the middle of a skeletal trailer.
Made by: Joloda Transport Equipment Ltd., Seaman Road, Liverpool 15.
Swivelling connector
Pneumatic or hydraulic hose of any length can now be used without kinking or strain. claims Jayroc Swivel Joints Ltd., when its new swivelling connector is used to join the hose to a supply outlet or dispensing nozzle.
Because the connector swivels as the hose is moved, the connector is not strained if the hose is suddenly jerked sideways. Consequently, the danger of the hose being disconnected from its supply is considerably reduced. The connector can be fitted to hose for filling barrels and storage tanks, or used to connect rock drills and other air-operated tools to their air supply lines. It has already been used in a new mobile plant for washing vehicles.
The joint will withstand pressures up to 150 p.s.i. (10,5kg/cm2). The frictional torque is approximately 30Ibs. inches at maximum pressure, and the standard connector has threaded outlets measuring fin. B.S.P. and B.S.P., but other sizes are available. Marketed by: Jayroc Swivel Joints Ltd., Westwood, Margate, Kent.
Flange plates
U.C.C. Filters (Hydraulics) Ltd. has made available a comprehensive range of suction and return flange plates ready for immediate installation to any oil reservoir to ensure a leak-proof seal for pipes and tubes passing through the top of the tank. Each unit is individually packed and includes gaskets, screws, washers and a template.
The use of these units is claimed to halve assembly time, reduce pipework to a mini mum and eliminate the necessity for the welding of unions and connections. They can also be considered for use as a low-cost inspection cover, and for the removal of suction filter elements from the tank for cleaning.
Two sizes of suction flange plates are available: the first permits the removal of suction filters up to 4.5in. diameter (114.3mm). and the second will accommodate filters up to 6.5in. diameter (165.1mm).
Marketed by: U.C.C. Filters (Hydraulics) Ltd., P.O. Box 3, Thetford, Norfolk.
All-night petrol stations
The latest revised edition of the RAC's booklet listing all-night petrol stations will be useful to drivers.
It covers England, Scotland and Wales with separate sections for garages in London and Scotland.
Published by: The RAC, 83-85 Pall Mall, London, SW1 (obtainable from local offices).
Pto/purnp unit
The Spenborough Engineering Co. Ltd. has announced a pto/pump unit of an improved type. It has been endurance tested for 100 hours at pressures from 2,500 p.s.i. to 3,000 p.s.i. and a temperature of 140deg F Special features of the unit include an aluminium swab with radial ball race that is supported by a heavy-duty thrust race. The power take-off unit has the sliding wheel mounted on needle roller races and has an improved short gear-shift mechanism which is detent located. The sliding wheel can be operated by control cable or turn-control rod arrangement.
If required the unit can be supplied in separate sections, in which case the sections would normally be coupled together with a flexible drive shaft.
Made by: Spenborough Engineering Co. Ltd., Union Road, Heckmondwike, Yorks.