A Four-speed Countershaft Gear.

Latest Production of the Jardine Factory for 1915.

THERE was never any doubt that the greater the number of ratios a gear possessed, provided that the gear were not complicated and unreliable, the more suited it became to the needs of motor cyclists. Experience has proved that just as the two-speed gear is streets ahead of a single gear, so is the three-speed superior to the two, and now there are indications that the four-speed gear is to receive well-merited attention at the hands of manufacturers. The first of these ready for inspection is the Jardine, made by John Jardine at the huge factory in Nottingham, where a portion of the works and special plant have been set aside for the manufacture of the 1915 model gear. The name of Jardine as applied to gears is not new; as a matter of fact, the appearance of the latest gear is an interesting example of how experience favours an increased number of ratios, for the original Jardine "G. H." gear had two speeds, last year three speeds, and the new production four speeds.

The beauty of the latest gear is that the extra ratio has not been obtained at the expense of complication; in fact, the same number of gear wheels are embodied in the construction as in the three-speed gear, and the additional ratio has been provided by utilising the kick-starter gear and wheel carrying the ratchet, as driving gear wheels. Thus, by a smart piece of designing four ratios are obtainable with the complications of three, but that is not all, for in the latest box the whole of the parts, including kick-starter mechanism, are enclosed in an aluminium case formed in one piece, so that escape of oil is impossible, which not only spells economy in oil but also a clean exterior casing.

We publish with this description a drawing showing the interior mechanism of the new box, and before proceeding to describe its working may detail its main features. Firstly, all gear wheels remain always fully in mesh; secondly, the whole of the changes, are effected by a single dog clutch ; thirdly, the kickstarter mechanism, being part and parcel of the gear, is always lubricated so long as there is oil inside the box ; fourthly, two neutral positions are provided, viz., between The first and second, and third and, fourth ratios.

The Combined Drive Adopted.

Chain and belt transmission is provided for on the 1915 gear box, which method of drive has attracted, many makers of experience ; so long as the pulley is of large diameter, as in the case of the Jardine, which is 8in., this, form of drive is suitable for even high-powered sidecar outfits. As regards bearings, the main shaft itself revolves on caged ball bearings; whilst in the case of the layshaft and other loose wheels bronze sleeves are used. Nickel steel on bronze is the general order, as this combination is found to be less exacting in the matter of lubrication, though, incidentally, this important question has received especial consideration, holes being drilled at a tangent to the direction of travel to scoop tip oil, and the usual splines are also formed on the shaft.

The cork clutch has a single plate with a double row of corks, and has been found to answer all requirements, having been subjected to constant slipping with no ill effects. Certainly, in our tests the clutch took up the drive of an 8 h.p. sidecar outfit with wonderful smoothness.

In following the actual working of the gear it should be remembered that:

Pinion 9 is keyed to the main shaft. Gear wheels 10 and 11 are in one piece, and free to revolve on the layshaft.

Gear wheel 12 is secured to first reduction dogs 5 by phosphor bronze sleeve.

Top or Fourth Speed. On the main shaft driving dogs 2 are formed from the solid bar. A direct drive is obtained by coupling these driving dogs to the dog clutch 1 and the dogs on the main gear wheel 3, to which the belt pulley is secured.

Third Speed. The first reduction dogs 5 are coupled to the main gear wheel dogs 3 by sliding the dog clutch 1. The drive is then through 9 to 10 and 11 to 12 and 3.

Second Speed

Dog clutch 1 connects the driving-shaft dogs 2 to small gear wheel 6, which wheel revolves the lay axle gears 7 and 8, thereby rotating the main gear wheel 3 at a double reduction.

First Speed or Low Gear.

The dog clutch 1 couples the first reduction dog 5 to the small gear wheel 6, the drive then being through 9 to 10, 11 to 12 and 6, through the lay axle 7 and 8, to the main gear wheel 3, thus giving a triple reduction.

The ratios provided are approximately 4 to 1, 6 1/3 to 1, 8 2/3 to 1, and 14 1/2 to 1.

General details of design are: The use of gear wheels 5/8 in. wide, 10 pitch, each part made to jigs so that interchangeability is ensured, weights 28 lb. made up as follows: Gear, kick-starter and pulley, 21 lb.; clutch, 7 lb.

A Trial on the Road.

After examining the construction of the gear we were taken on the road by Mr. George Hunt, who has been testing the new gear on the 8 h.p. Campion side-car outfit with which he won a gold medal in the Six Days Trials. The ease of starting from a standstill we have already referred to, but it was the manner in which the gears could be changed that impressed us. A touch of the valve lifter and our driver slammed in the gears one liy one without difficulty, and then purposely resorted to the extreme test of changing from first to top, and suddenly down again. This sort of hard usage we are assured the gear has withstood for over a thousand miles. In Nottingham traffic our pilot changed up and down as certainly as with a variable pulley gear. In future, gear changing even with a four-speed box, need no longer worry the novice.

The Motor Cycle October 8th, 1914. p414