A Compact Hydraulic TIPPING GEAR
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THE hydraulic principle is simple enough and is particularly suited for application to the tipping gear of motor lorries, but it is not an easy matter to produce a design which provides adequately for load distribution. The confined space in which the gear must be housed sets a task fcr the engineer who aims at overcoming the unequal imposition of load when tipping is in progress.
An hydraulic gear which is remarkable for the equal distribution of load which it permits is the Wirz gear, marketed in this country by Lawson Pigott Motors, of 320-322, King Street, London, W.6. The gear is well known in Switzerland tinder the name Wirz, and in Germany under the name Meiller (that of the licencee), and the English concessionaire is arranging to appoint manufacturers of British chassis as sole fitting agents for their respective makes.
The gear is adaptable to practically any make of vehicle. Sizes are available for machines intended for pay loads from 30 cwt. to 15 tons, and it was demonstrated at the Commercial Motor Exhibition at Olympia on a Berns model G5 six-tonner. In this case the housing for the three-cylindered oil pump is incorporated with a spur pinion and dog clutch in the gearbox cover, the pinion being permanently engaged with the constant-mesh wheel.
There are two outstanding advantages with the telescopic-ram principle. First, it occupies such a small space that it may be housed between the main frame-members, even when the vehicle has overhead-worm drive. This means that a single ram can be located just where it is required—in the middle of the body area, just before the driving axle. There it can be carried on strong crossmembers which brace the frame, and it B46 will thrust for side tipping without sideways stress on the frame-members, for the load is carried equally by both longitudinal members.
Greatest Leverage When Load is Heaviest.
The second advantage is that greater leverage is afforded when the load is heaviest, that is, at the beginning of the operation. The reason for this is that when the sections are telescoped their bases form a piston of large area against which the oil pressure acts. When the four inner sections have risen to the height of the largest sleeve this remains stationary and the other sec
tions continue upward, but with reduced leverage, their base area being less.
In addition to these advantages, two excellent features call for particular attention. The rain is spheridally moutited at top and bottom, this ensuring equal load distribution, even when the lorry is standing on irregular
ground surface. Secondly, the body frame rests upon two tubular crossmembers attached to the chassis so that the alignment is preserved and fulcrum load is distributed equally during the tipping operation, in w ichever direction it be applied.
To tip a load the driver disengages his clutch, pulls a lever which engages the I dog clutch of the oil-pump drive and then re-engages the engine clutch. Of course, th direction of tipping is prearranged by the remove of appropriate pins in the ordinary manner. While the oil pump is rotating the driver can control the tipping operation by an oil by-pass valve actuated from the dash bard, so that he is not bound to rely on the engine clutch. When the full angle of tip is rea ed the leaning of the ram causes the ram base to depress a valve, automatically by-Passing the oil flow back to the reservoir. The 6-8-ton model which we have seen costs £180, complete with body frame, chassis cross-members, etc., fitting involving an extra charge. This price includes the cost of casting a special gearbox cover to incorporate the drive and pump. Alternatively, for a price of £100 the gear itself can be supplied without the body frame, thechassis cross-members and any special drive for the gearbox. The device is easily fitted to chassis on which the ge rbox cover is not obstructed by sel ctor mechanism, etc. In other case a different form of power take-o ' arranged without difficulty.