SERVICE ACCESSORIES.
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Types of Jacks Best Suited to the Requirements of Commercial Vehicle Users.
THE NEED for a jack which will lift easily and quickly, which will be absolutely secure when carrying the load for an indefinite time, and which will lower easily and. safely is known to all service vehicle users. Not a few mechanical and personal cases of damage have occurred through failure of jacks or the use of jacks which may be thought
lessly and easily deranged. , Amongst the large variety of these appliances which are manufactured we have selected a few as being typical of general varying practice. The selection, however, is by no means exhaustive.
Some of the requirements of a good jack may well be mentioned. The disposition of the load relatively to the base of the load should be such that the movement and direction of pressure when operating the jack does not tend to tilt it or move it relatively to the ground or the car. The leverage for lifting should be ample, so that great effort is not required. The jack should be capable of holding the load at any point in the rise. When disengaging the holding device far lowering, there should be no chance whatever of the jack falling suddenly. The lowering should be absolutely under the control of the lever, i.e., a positive manipulated lower. • The Duff-Barrett No. 411 Universal jack.
Hydraulic Jacks.
Hydraulic jacks are not common. in motor service work. They have proved themselves useful in general engineers' shops and on big civil engineering works, but only lately has attention been paid to the undoubted advantages of this system fey motor vehicle purposes.
The Ludas King of the Road hydraulic jack No. 10 is an example of extremely neat and effective design embodying the hydraulic system. This jack uses ordinary engine lubricating oil as the lifting medium. The base is the oil container and the lift is direct on top of the ram, a screw adjustment being provided for getting the jack to the work with the ram at the bottom of its stroke. It has a lift sufficient to deal with tyres up to 6 in. section. The operating lever is attached by a bayonet catch joint to the rocking bifurcated lever spanning the body of the device. This lever operates two plunger pumps, one at either side, so that a pump stroke is given either on raising or lowering the operating lever. This pumps the oil from the hollow body to the ram cylinder and lifts the ram. To
lower, the operating handle is shifted on to .a second lever, whioh is controlled by a ,powerful spring, and releases a, by-pass valve, allowing the oil to flow very gently from the ram to the oil chamber, t hus lowering the ram
The Toggle System.
Quite a novelty in the design of lifting tackle is the Hi-lo jack, which is Sold by James Bartle and Ca, Ltd. This jack utilizes the toggle mechanism, in which the leverage is greater as the lift is increased. The illustration shows the simplicity of the arrange. ment. A ratchet lever operates a bevel gear, which rotates the screw, drawing the two jointed side members of the jack together and raising the load seat. The folded height of the jack is 5 ins, and the extended height 17 ins., giving an available lift of 12 ins. It is made in four sizes to deal with loads of 1, 2, 3, and 6 tons, and is a wellmade appliance, which sells at a remarkably reasonable price.
The Variable Step Jack.
A form of jack which offers considerable advantages is that in which the lifting member is carried down one side and has an adjUstable step in addition to the top platform. Quite a variety of types of these was exhibited at the recent Olympia Show by Geo. Hatch, Ltd., of Upper Thames Street, E.G. 4.
The foot step-allows of a wide
range of lift and a wide range of commencement of lift—a point which is often overlooked in jack design. Thus the same jack will deal with a low front axle and .yet allow of the lifting of a higher rear axle, and give the maximum lift and drop in each case. The step, in fact, nearly doubles the available amount of lift and drop from minimum to maximum.
One type of Duff-Barrett jack, which is a, Britishmade tool, is shown in the sketch. The No. 411 is intended for heavy commercial vehicle service and will deal with loads up to 1 tons. The jack will raise or lower with as short or as long a stroke as may be convenient, according to the clearance available under the car. This is an important point when the operator is obstructed by such obstacles as low steps, rear petrol tanks, eta
Another feature is the arrangement for altering from lift to drop. This is done without having to get under the car to operate triggers, etc. A simple turn of the operating lever itself makes the change, and the jack can only lower or raise one step at a time by one complete movement of the lever. There is, therefore, no possibility of a sudden fall.
The operating handle is arranged to telescope so as to take little room if required to be stored on the car. The whole is a drop forging. All studs and bearings are of big diameter and well fitted. The jack will give a rise of 7 ins., starting from anywhere from 4 ins. to 11 ins, from the ground. =-ALSM,I,'2,!!1V:'%.•
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The safest jack is undoubtedly the screw jack, since it is impossible for it to run down, and the lift and fall can be varied to the smallest amount, which is a very considerable advantage in garage work, where the jack often is used to hold heavy parts which require to be placed in exact position relative to each other for fitting together. A jack with a step-by-step lift is unsuitable under these conditions. The screw _jack, however, is often heavy to operate on account of the friction.
In the Michelin jack the design, incorporating ball thrust, is such that the friction is reduced to the minimum. The sketch shows the internal mechanism. The outside is a plain bottle shape, with a very big diameter base. The Screw is driven by a substantial bevel gear shown, and there is a rapid adjustment for getting the head of the jack to the axle before lifting by unscrewing the upper adjusting pin. The heavy type of this jack will lift 4 tons le cwt., and lighter types are made for lighter loads. The full range of extension is 8 ins. to 17 ins.
Keeping Track of Running Time.
Instruments for keeping, on the car, a record of when running and when idle are available in a variety of types, incorporating a variety of ingenious mechanisms, generally driven by some flexible shaft or belt driving gear. A most simple and ingenious device, which requires no gearing to any part of the car mechanism, but
which can be simply screwed anywhere suitable on the vehicle, is the Servis recorder, which is handled by Brame°, Ltd., of St. Nicholas Street, Coventry. This device operates by the vibration of the car, so that when the car is running a. pedometer-like mechanism, enclosed, together with a time chart, in a lock-up case, marks a thick line around a time-divided chart disc, rotated by a clock. When the vehicle is stationary, a thin line is marked.
The result is a diagram showing exactly the times when the vehicle commenced -moving and when it stopped, with the duration of the movement and the duration of the stops. It provides an absolute check on the actual working ,time of the vehicle and the time lost in loading, delays, etc.
The Servis Recorder.
It has been adopted by over 150 firms on service vehicles of every description in this country—many of the firms having a large number of these devices in use. Its co et is low and its upkeep negligible. But it must save nsol'ey by keeping track of wasted time and a check on the driver. Messrs. Gamage have 16 of these devices at work on their delivery vans, and it is used by such firms as the Cunard Co., Boots' Pure Drug Stores, Anglo-American Peeroleum Co-., J. Lyons and Co., the Daimler Co., Hans Renold, Ltd., Cadbury Bros., Ltd., and Terry's, of Redditch. The use of the appliance by firms oi such business repute is ample proof of its service giving qualities.