THE STRAKER-SQUIRE A TYPE CHASSIS.
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Preliminary Details of a New 3 to 5-ton Chassis Embodying Many Interesting Features.
THE STRAKER-SQUIRE new three
1 to five-ton chaesis, known as the A type; is one of the most interesting maehines which have been produced during the last few years. It is the result of a lengthy series of experiments, and embodies a considerable number of interesting and well-designed improvements both in its general and detailed design.
Though one example of the new chassis has been tested for many thouiands of miles without trouble developing, the manufacturers are not yet quite satisfied, and are making still further improvements in some of the details. WE therefore include in this Betide only the general features of the machine, and will publish a full technical description when the final model is definitely approved.
The company have adopted the principle of positioning the engine so that the rear half of it is within the dash. The engine is actually in its normal position, but the cab is moved forward, thus lengthening the body space. By this construction, if a platform body be fitted, a full five-ton load can be carried, without increasing the total load on the rear axle, to over six tons. The wheelbase has been increased by 6 ins.. to 14 ft. 6 ins., but the actual gain on the body space is 2 ft., as the cab is pushed forward 18 ins.
The engine is of particular interest. The cylinders and the top half of the crankcase form one casting, whilst the cylinder heads form another. The valves aro of the overhead type, and are operated by rockers which float in vertical spring -supports; there axethus no wearing surfaces to cause slackness arid lubrication is not required. The crankshaft is of the two-bearing type, Mit is short and
stiff, having a journal diameter of 3 ins.; it is supported in Hoffmann roller bearings.
The radiator presents a striking appe.iiranee. It is of the ordinary east aluminium type in which the water circulation is therniceeyphonic, assisted by a screw propeller driven by the fan.
The gearbox is very compact. It gives four speeds forward and a reverse. The gate box is carried in an extension casting bolted to the main gearbox casting. The drive to the gearbox ie through a single steet disc which is gripped between two rings made of Ferocle.
The back axle is of very stout constriction, and has a cast-steel casing of the " pet " type, with the worm gearing and differential gearing carried by the cover, so that they can be removed as a unit for inspection Or repair.
The springing is exceptionally wall designed. The rear springs are 5 ft. 6 ins. long and. 4 ins, wide, and are undersfung, and the front springs have a length of 4 ft. 5 ins., whilst the spring hangers are of the ball and cup type in which special care bee been taken to give adequate means of lubrication. Round section taper coil springs, fitted above the ordinary springs, take a iportion of the weight when the vehicle, is fully loaded.
Both brakes act on the rear wheel drums, the two sets of shoes being situated side by side. All the brake rod connections and croseshafts, also the brake pedal and hand brake lever, are carried on graphiteand bronze bearings and require no lubrication. The steering pillar hats a rake of 43 degrees. The gear is of the screw and nut type, a combined ball and thrust bearing being positioned at the top of the pillar near the .wheel. The gear itself is bolted te the frame dose behind the off-side dumb iron. The steering arias rod runs back to the, stub axle arm, and the tie rod is situated behind the axle.
The whedseare of the cast-steel tubular-spoked type and are of the same meter throughout. throughout.
The frame is very strongly built of pressedchannel section steel. An unusual-feature ineit.s construction is thatthe horizontal flanges of the channels turn out instead of in, By this construction new croesenembers may be fitted without the necessity of dismantling the whole frame.
The engine and gearbox are supported in a strong sub-frame, which is carried by a trunnion bearing at the front end. Allowance is also made at this point for a email amount of movement sideways. The other two points of support to the sub-frame are positioned between the gearbox anti the •dutch; by this construction distortion of the sub-frame is avoided.
That the sub-frame really eliminates bending stresses from the engine and gearbox is proved by the fact that during a Lancashire tour' which was made by the experimental model, a front wheel sank through the floor of a pit as far as the axle; so great was the twist on the main frame that the floorboards of the vehicle actually cracked, but owing to the careful. deigning of the,tbree-point suspension system the engine continued to tick round and it was found that the gears could be changed, also all the brakes would act.
A detailed improvement of exceptional merit was found in the design of the nnversal inints. The joints are threaded and split, and into them are screwed phosphor-bronze plug bashes, in wineIs
the arms of the star piecebear. These plugs are screwed up so that the end of each of the star arms actually bears on the, bottom of its bush. Bolts fitted. to , the split portions of the jaws are then tightened up and the plug bashes are Lek] firmly in position. There is thus no end play whatsoever. To prevent the entry of dirt and the loss of lubricant, fendl caps are pressed over the inner ends of the bushes' by Means of light spiral springs. A paint in the design of the brake rods is that, they consist of flat steel strips placed on edge and riveted to hooded jaws which protect the joints from mud and dust. These plates, though very strong in a vertical direction, are sufficiently flexible in torsion to yield when the axle is momentarily out of line with
the frame. . .
One of the main features of the new chassis is. that, owing tothe -lengthened body space, a char-b-bancs body capable of seating comfortably 40 persons can be fitted.
We have already given a short description of the engineabut we have made no mention of its capabilities. The maximum b,h.p. obtained with the engine is over . 65, and it gives 54 b.h.p. at 1,000 r.p.m. On the road it has been found that this engine is a better " puller " than many ordinary motors of 5 in. bore and Over, the reason being chiefly, in the overhead valve -design and the arrangement of theports, whereby all strangulation of the mixture is avoided.
With a full hiad the vehicle. has averaged just over 7. m.p.h. on etraightaavay runs, 'whilst, unladen, as much as 10 m.p.h. has been secured. The whole design of the engine is so clean and simple that distortion, owing to heating and cooling effects, is practically nonexistent. The crankshaft runs in two 7 in. diameter roller bearings, which are held by four .steel caps, the caps them selves being secured by in. diameter bolts. The endways location is' by a double ball thrust bearing. The big-end bearings are of phosphor-bronze, lined with white metal, and the caps are 'secured by four nickel chrome steel bolts. The gudgeon pins are hollow and are in. diameter; they are secured in. the connecting rod small-ends; and bear in ph-es/Mew-bronze bashes pressed into the pistons. The camshaft and magneto shaft are . driven by a special Renold silent chain, the magneto bracket being moveable for the purpose of chain adjustment, • Incidentally, the mae-neto is fitted with an impulse starter which gives a very hot spark, even if the engine be turned slowly.
As regards the road wheel bearings, unlike the method, adopted in the heavy vehicles, the phosphor-bronze bushes do not float, but are pinned to the axle casing sleeves.