New Underfloor "Six" in the Gardner Tradition
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As already reported in The Commercial Motor," a new underfloor engine has been introduced by Norris, Henty and Gardners, Ltd., Patricroft, Manchester, in response to a demand from passenger operators , The new six-cylindered design becomes Model 6HLW, practically all major components of which are interchangeable with those of the well-established LW range. A notable exception is the sump, which has been specially designed for underfloor fitting and is cast in aluminium alloy, finned at the front for cooling.
The Treasury rating of the new engine is 43.5 h.p., and its capacity is 8.4 litres (511 cubic ins.). The bore is 41 ins. (107.95 mm.) and the stroke 6 ins. (152.4 mm.). Approximate bare weight is given as 1,490 lb., or 50 lb. heavier than the normal 6LW model.,
In most respects, Gardner vehicleengine traditions, which have proved successful for nearly 10 years, are followed, as in other LW types. The crankcase, cylinder heads and cylinders are separate, push-rod-operated valves are carried in the heads, and the camshaft is in the crankcase. Full-power rating at normal atmospheric temperature and pressure is 112 b.h.p. at 1,700 r.p.m. Ratings throughout the LW series have been increased and the figure of 112 compares with 102 b.hp. for 6LW types previously produced. On maximum load at 1,700 r.p.m., fuel consumption is 0.363 lb.-b.h.p.-hr. 10.345 pint) and at maximum torque,
0.351 lb.heh.p.-hr. (0.334 pint). Fullload torque at maximum speed is 346 lb.-ft., corresponding to a b.m.e,p. of 102 lb. per sq. in., rising to a maximum of 358 lb.-ft. and b.m.e.p. of 106 lb. per sq. in. over the range of 1,100-1.500 r.p.m and maintained at 340 lb.-ft. at only 600 r.p.m.
Certain modified features throughout the range have brought all-round improvements, a new exhaust manifold A32 being employed to give a better volumetric efficiency and more effective scavenging. The new piston, Type L.O.E.X.8, is mentioned later. In addition, a modified sprayer and injection pump have had a substantial influence on the combustion characteristics, ensuring economy in performance and reducing ignition noise.
There is, of course, no enginemounted fan on the underfloor model, but the fan and other auxiliaries are arranged for driving through the medium of an extension shaft, which has a flexible coupling to the forward end of the engine crankshaft. Alternatively, a V-grooved multiple pulley, mounted on the crankshaft, can be employed.
The modified sump, already briefly mentioned, carries four gallons of lubricant and the pressure system is fed by a large pump at the rear of the crankcase. A filter is fitted on the sump for easy accessibility and the pump forces the lubricant through it before it is driven into the bearings. The relief valve diverts excess oil .to serve as lubt leant to the fuel-pump cambox, governor assembly and the main timing drive.
As with the 6LW, the cylinders of the new engine are made up in two blocks of three cylinders each, the angle being 2 degrees upward when mounted in the frame. They incorporate renewable dry liners and are connected to the crankcase by 14 through 'bolts. Specially built for the horizontal engine, the cylinder heads are made up in two blocks, each serving three cylinders.
Connecting rods and pistons are inter
changeable throughout the LW range. The rods are of drop-forged alloy steel, with white-metal-lined bearing shells retained by two Fin, alloy steel bolts. Designed to meet the demands of the new engine in respect of cool running, the patented pistons are cast in specialpurpose heat-treated aluminium alloy. There are three pressure rings and one scraper ring, the peripheries of the upper two being chromium-plated. An open combustion chamber is formed in the piston crown.
Cast in aluminium alloy, the crankcase provides great rigidity, in consequence of the use of generous sections and ribbing, together with the extension of the walls well beyond the crankshaft' centre line. Of 31-in. diameter, the crankshaft has seven white-metal bearings and one roller bearing; the natural torsion oscillation characteristics of the assembly are controlled by an internal friction damper. which is located on the forward end of the crankshaft.
The engine is suspended at three points by the Gardner flexible system, having two rubber-busted swing links at the front and a rubber bush with supporting pad in the crankcase end plate, with a separately mounted torquereaction member with a hydrautc damper.
Mounted directly on the upper side of the crankcase and driven through helical sliding gears are the fuel-pump cambox and governor assembly, which embody two three-block pumps combined to make a unit with additional volume chambers.
Adjacent to the fuel pump there is an Amal diaphragm-type feed pump with a special delivery-valve assembly which is mounted on the crankcase and driven by an eccentric on the valve camshaft; this delivers fuel to a modified version of the patented fuel-filter overflow return system, comprised of a small combined overflow and separator unit, mounted to give a suitable fuel head for the injection pump.