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E of.T A pE

2nd April 1914, Page 13
2nd April 1914
Page 13
Page 14
Page 15
Page 13, 2nd April 1914 — E of.T A pE
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We have chosen as the second machine for treatment in the present series one of the most popular models that is produced by join], I. Thornyeroft and Co., Ltd. The particular example which figures in our illustrations is one of a range of machines which_ is not only thoroughly representative of Thotnyeraft petrol-vehicle praeticeabut is also undoubtedly a, first-. class example of modern. industrial-chassis design as it. has developed in this country.

The A-T. Type et Chassis.

Tliornyeroft's li a v e scored many successes with their motor-vehicle designs, both for pleasureear and industrial-ve.hiele purposes, but it would seem likely, from the reception already accorded to the A-T model, that the Basingstoke works will do as well, even if not better, with this particular machine than with its immediate predecessois. It is no secret that many of its special characteristics have been adopted to suit the strenuous service of that famous package carrier, Carter, Paterson and Co., Ltd. The example whi photographer was one of t well-known user.

Intelligently to Use What is Intelligently Designed.

As we have already, in our last issue, introduced the present series with a full and reasoned explanation of the purposo of theSe present articles, it is minecesfiery for us to do more in the way of preamble than again to repeat that it is our wish to give such inFormation with regard to certain chassis as to ensure, so far as possible, that the carefully-seliemed means of adjustment and of lubrication shall be skilfully and intelligently employed by the actual user of the vehicle, aird stall not, as is, we fear, so often the case, either be overlooked on account of lack of knowledge, or mishandled for the same reason.

The Thornycroft A-T model, from the constructional point of view, is a most taking design for the practical man. It abounds in evidence that the drawing office has not only profited by the company's ONVII very extensive manufacturing experience, but lia.s assimilated many lessons industriously acquired from the experiences of users of all kinds of machines in all classes of ivOrk up to the date of the present design. sturdy and efficient, this British conception is, as we have. aid, a particularly happy example of the progress which this country has made in the production of practical petrol-driven business motors.

A Chassis Without Etceteras.

A monobloc engine, with thermo-syphonie cooling through a realty practical radiator, a simple cone clutch, a leather-disc universal, a three-speed-andreverse gearbox, a big-diameter propeller shaft, and a. worm-driven back axle, these are the principal units in an essentially workmanlike chassis. Our task in respect of this model is comparatively an easy one, as the efforts of the designers have resulted in the elimination of as many as possible of the parts which, would neressitate adie slin cut on tic: count of wear and. teen We will, as in a previous ease, for simplicity of eon


Inter ...pass salon centre is "WAR on lap.

sideration , divide the. chassis into the following mechanical groups :--Engine. and clutch gear ; gearbox ; propeller shaft and live back axle ; steering-gear and control meehanisin ; springs, axles arid wheels ; and brakes.

As a sub-heading to all hese articles, we have written that it is well to leave well alone, but that it needs care to ensure that all is always well. It is that very care. of which we would write.

We will defer all consideration of lubrication until the latter part of the present article and deal with the chassis as a whole in that respect.. First of all, then, with regard to the engine. This has four cylinders, motiobloe fashion, of which the bore is ins., whilst. the pit-ton stroke is 51 ms. The principal engine adjustments, whelea may frem time to time become necessary, concern, of tiourse, the valves, the carburetter, and the magneto, but in ad these three cases periodic inspection and occasional slight modification are all that is necessary.

OF Valve Adjustments.

In regard to the valves, these, in order to ensure compact deign, are arranged with the inlets over the exhausts, and, in order mechanically to operate the former, long push rods transmit the cam metions to toggle levers, which are pivoted in the overhead valveboxes. As a general rule, we advise that valves, both inlet and exhaust, should be inspected once in every thousand miles, and it will then be. found that the ex

haust the better for •cleaning up nits-1. perhaps for being ,slightly rubbed down on to their seatings•again. After. some 'weeks of such treatment, some loss of adjustment necessarily takes place in respect of the .valve tappetaThis, however, can he rapidly and simply corrected by a slight lowering of

the setscrew which will be found in the top of each valve tappet proper. As the exhaust valve in particular must seat lower to just an appreciable extent, the clearance, of something like 1-1000th in., which should exist between valve stem and tappet will disappear, so that eventually the valve may not actually be able to seat properly, but may be just held off. This is an adjustment which is a simple one, butthe need for it should be ascertained conscientiously and with regularity. It will do much to ensure efficient running of the engine. It is preferable to make these tappet modifications when the whole engine is well warmed up.

The inlet valves will, of course, require to be ground in but seldom. Should slight adjustment eventually become necessary, similar screwing in of the valvetappet setscrews will readily and quickly effect the desired result. It is hardly necessary to mention that the valve tappets can be reached by removing the special cover, which is normally held in place by two thumb screws.

The Proper Valve Setting.

Actual "timing of the valves" will not be necessary unless the engine has been dissembled, and then no mistake can be made if the erecter put back the two helical gears, viz., that on the crankshaft and that on the camshaft, into their proper relative positions, which are clearly marked on the two wheels. Should there, however, be any confusion or doubt as to the setting, we refer our readers to the special diagram which we have prepared from Thornycrofts' official setting, and which we reproduce in a form that should enable any normally-intelligent person to assure himself that the valves will act as the makers originally intended—by reference to the position of the flywheel in respect to its relationship to the up or down positions of the various cranks.

About the ZU4 and the Solex.

The crankshaft has only two main bearings, the four crankpins being supported by exceptionally-stiff webs. The ignition is. of a type familiar to all modern users, consisting only of a 'Bosch ZU4 high-tension magneto and its connections and plugs, and with an interrupter switch on the dashboard and an advance lever on the steering column.

Magneto adjustment is a subject upon which much may be written, but concerning which, on the present occasion, we need say little, even had we the apace available. We would remind users to lubricate the magneto regularly and to keep the platinum points clean and properly flat. The correct setting of the ZU4 Bosch on the engine of this chassis is hown on the valve diagram to which we have already made

refrirencs. For further instructions as to the proper care of a Bosch magneto we cannot do better than suggest consultation of one of the admirable handbooke which are issued by the Bosch Magneto Co., Ltd. ; the Lendon headquarters are at 204, Tottenham Court Road. Our unvarying advice to the user is never to at-tempt to take a magneto to pieces, this is work, seldom required, for the expert only.

The carburetter adopted is of the Solex latest pattern. This corresponds in principle with the model which is familiar to so many users, but it is of the new design, with vertical throttle, for use with monobloc engines. If it be desired to change the choke ring the air-inlet cover may be readily removed. We again counsel " letting well alone." Jet modification or float, adjustment should only he undertaken at the instance of an expert—for whom these articles are not primarily intended. Above all, keep the utrainers and filters clean in the fuel-supply system.

Where the Petrol Comes From.

The fuel-supply fystena is as carefully thought out as the rest of the engine installation ; gravity feed is relied upon, so that there are no air-pump or exhaustpressure valves to be worried about in order to maintain the supply. The petrol tank is wedge shaped and attached to the metal dashboard. It is fitted with a big handhole in the top which houses a long conical strainer, as shown in. an illustration on page 117. A shut-off cock and a drain plug are provided at the outlet from this tank, and the supply pipe has attached to it a small filter, which contains an easily-removablrS gauze that should be cleaned at least once a week, or even more frequently. It is good practice to blow through all the petrol pipes every 1000 miles or so, in order to ensure their complete cleanliness.

No Fan and No Pump Troubles.

Of the circulating system we need say little, as it has been expressly designed to give efficient service with the minimum of attention. There is no pump, nor is there a fan. A big-bore pipe leads from the ho Item of the radiator to the bottom of the singlecasting water jacket, and the water flows in a free stream, thence, via another big pipe, out a the tap of the latter to the top header of the very eensibly constructed radiator, which latter is of large proportions. Once now and again a new short length of flexible webbed tubing may be needed if it has been necessary, through accident to the radiator, to dismount the latter at all frequently. With that exception, nothing need he done to the whole system.

Periodic cleaning is advisable and easily effected. The top and bottom headers should be removed, and the centre battery of tubes should be cleaned witli'hot water and a long tube brush. If badly choked, soda or some equally efficient cleanser may be employed ; 2 lb. of soda to each gallon of hot water is a useful mixture. A small plug is provided at the right-hand corner of the bottom header to enable the whole of the water to be drained out in frosty weather--a point which any intelligent man in charge of a chassis nowadays bears in mind—see illustration on page 116. For the air circulation, the external vanes fixed to the periphery of the flywheel do good service, providing reasonable care be taken to see that the more or less airtight condition of the bonnet and of the undershield is maintained.

Hexagon Heads with a Purpose.

We consider that it is always as well to draw attention to the actual purpose of any visible nuts or bolt heads on a chassis of which the use is not readily apparent. Two or four, as the case may be, hexagon setscrew heads are to be found on the nearside of the cylinder jackets of these T-type engines. We have known eases where setscrews of this type have been removed in order to ascertain why they have been put there. To avoid such interference, we would point out that the two or four in question are merely plugs to fill up holes that are left in the easing to facilitate removal of core refuse after casting. They need only be removed if it be desired to make sure that the water jackets have not become choked through continued I1Sp of particularly bad water.

You Can Get at the Clutch Springs.

For clutch engagement the twin laminated-spring arrangement has been adopted in preference to the use of a coil spring. This is presumably the result of the lesson as to accessibility taught by the successful adaptation of this method on the L.G.O.C. B-type chassis. One of our illustrations shows that these two springs are clamped and located one on each side of the clutch centre, their respective ends being anchored under adjustable crossbars which are mounted on the flywheel edge. Should it be desired to put a little more pressure on the clutch, these cross pieces may be screwed down and locked ; care should be taken that both Hides are altered similarly. When it becomes necessary to reline the male member of the clutch, the universal joint ring should be uneimplecl, the clutch springs released, and the clutch drawn back. The pressed-steel portion of the clutch ear., if desired, be unbolted from its steel centre.

A Practical Clutch Stop.

A large clutch stop, in the form of a steel ring, is mounted just ahead of the leather-disc universal joint, which latter corrects any slight lack of alignment as between gearbox and engine. Adjustment of the clutch stop is simply effected by sliding the crossbar backwards or forwards slightly, so as to bring the fibre strip which is attached to it into or out of engagement. The crossbar is fastened to the main frame

members by bolts in slotted holes, to facilitate the necessary adjustment. The clutch can be withdrawn by depression of the clutch pedal only so far as the clutch stop will permit. As, therefore, the clutch lining wears down, the avaiiable travel on the clutch pedal will become greater. When this results in the full travel of the pedal becoming too much for convenience, then it becomes necessary to advance the stationary portion of the clutch stop in the way indicated.

No Speedometer "Flex" to Cause Anxiety.

There is nothing in the nature of maintenance adjustment to be considered in connection with the gearbox. This is a stiffly-constructed unit mounted at three points, the two rear ones consisting of long tubular extensions housed, respectively, in suitable brackets mounted on the side frame mem

b e r s. Capital evidence of the tendency nowadays to make definite provision for whatever accessories are coneidered necessary on a high-grade commercial vehicle is evident by the manner in which a mileometer has actually been built into the gearbox as a component. Room is found for a slow-pitch worm wheel on the top gearshaft inside the box, and a light shaft, carrying a worm, drives thence to the milometer, which is mounted on the nearside gearbox bracket outside the frame. The striking gear is carried on another tubular extension independent of the frame ; any adjustment as between gate and spur-wheel positions is only necessary when first erecting or after dissembling for any purpose. So satisfied are we as to the constructional features of the gearbox as a whole, that we commenced the present paragraph by indicating that no anxiety need be felt in respect of adjustments from time to time of the various striking-gear components. We, of course, do not wish it to be understood that we would discourage periodie inspection of this unit and its parts, in order to ensure that there is no slacking back of nuts and other fastenings which may occur even on the best behaved of assemblies.

After the gearbox, the main drive is taken through a large-diameter tubular propeller shaft to the worm, and thence to its wheel and through the differential gear and the differential shafts to the rear road wheels. Once assembled and properly lubricated, there is no need for adjustment either at the front or back universal joints on the propeller haft. They should, of course, be occasionally inspected to see that nothing has worked loose, the leather sleeves being removed for this purpose. The front joint is of the ring pattern ; a solid-forged pin is pivoted in the heavily jawed front end of the shaft. Given proper lubrication and occasional inspection, this should require very little attention indeed.

The back-joint end embodies the familiar square block universal design which permits a certain amount of endwise extension. This also requires periodic inspection and regular lubrication. Should the blocks become worn, they can be replaced with the minimum of ease.

We will defer our consideration of the adjustments of and care for rear axle, brakes, steering gear, and for the proper lubrication throughout this interesting Thornycroft Model until our next issue.

(The remainder of this article will be pnbliAhed in cur next i's-rce..)

The big handhole and the filter in the petrol tank.