FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1948
1948 - 2192.PDF
FLIGHT .DECEMBER 23RD, I94S PER ARDUA AD CUMULI Specially Designed Glider Winch at Redhill By F. G. IRVING 1AST year, it became manifest to members of the Surrey I Gliding Club that those who indulge in motorless * ^ flight really need an exhaustive knowledge of engines, for the standard post-breakfast ceremony of persuading the winch to work required considerable art. Both winches were of the traditional modified motor-car variety, and combined all the standard idiosyncrasies of cars with a few of their own. The more de luxe machine started life as a very superior Rolls-Royce untold years ago. A drum, driven from the transmission shaft, was fitted in front of the differential, and the cable passed over a pulley at the top of an erection like an oil-well derrick bolted to the chassis. This device was all very well in theory, but in practice, apart from almost hurling the driver from the seat at the start of a launch, caused an excessive amount of cable-wear. And steel aircraft cable is quite expensive. The French would justly term the engine "formidable." Nobody quite understood it, but it was said that if reluctant ' to start, a half-crown cunningly inserted in the carburettor worked wonders. Being a Rolls, a penny was by no means as efficacious. Apart from that, it had a fiendish cockpit drill, involving much twiddling of taps, pumping, priming and more twiddling. The other machine was Imperial College's de Soto, 1927 vintage, a machine of greater reliability but much less urge. Even so, it did about 3,500 launches. Its appearance tended to discourage the would-be glider-driver, being rather a la Heath Robinson, but it had many virtues. The chief of these was the speed at which the cable could be taken back to the launching point. The only limit to this was the speed at which it was safe to drive a Beaverette over the airfield. By the end of last year, the Rolls had been retired as causing too much cable wear, and the de Soto was showing excessive signs of decay. So the C.F.I., Lome Welch, took thought and designed a new winch. It was felt that the specification for the ideal winch was roughly as follows: — (a) It should be self-mobile. The ideal arrangement would probably be a winch mounted on a lorry chassis, driven from the engine via a power take-off from the gear box. A separate engine for the winch would not be economical. (b) Plenty of power is essential. Most converted motor- car winches are rather lacking in this respect, and it is a little disconcerting if the engine stalls at the wrong moment. The wrong moment is when you are about 100ft up, with the nose pointing upwards at 45° and with rather fewer m.p.h. on the clock. What is wanted is enough urge to launch 1,000 lb of two-seater in no wind. A Ford V-8 is by no means too big. (c) The whole affair should only need one man to operate it. This means having all controls ready to hand in the cab, and, if possible, a telephone to the launching point. (d) Coming down to details, an automatic feed-on for laying the cable smoothly on the drum is vital. The con- siderable extra complication is well worth while on account of the saving in cable wear and breakage. Another way of saving wear is to keep the moment of inertia of the rollers over which the cable passes to a minimum, and to keep the number of rollers down to one mounted horizontally, and two vertically. (e) A completely reliable method of chopping the cable in emergency should be fitted. The traditional method of having a man standing by with an axe is uncertain and unsafe (for the man as well as the pilot). (f) The driver should be as comfortable as possible, in a cab giving all-round visibility but protected from having the cable dropped on it by pilots trying to squeeze the last inch out of the launch. Few things are more discouraging to winch drivers than being the target for 1, oooft of steel cable. The winch machinery should also be well protected, so that if the cable breaks, the whirling end doesn't chew up innocent onlookers. Likewise the immediate surround- ings of the drum should be as free from projections as possible, so that if loose loops of cable form- on the drum when the cable is being pulled out, they will not tend to catch and break. So much for the specification. We had a balloon winch, and it was obvious that a half-hearted conversion would not suffice. The whole thing had to be taken to bits, and The new glider winch in action at Redhill airfield. then, armed with its engine, gear box and a lot of very substantial steel, it could be completely reorganized. Having consumed innumerable cigarettes in the small hours, and having held various hilarious mock-up confer- ences, the C.F.I, eventually produced his magnum opus. With only little modification the winch was duly built by a local firm of engineers. It does not quite fulfil the above specification, mainly in so far as it is not self mobile. It is a trailer, which is raised on a two-legged frame at one end and a jack at the other. This takes nearly all the weight off the springs so that it stands really firmly when in use. The jack unfortunately needs 250 turns to lower it and is rather too reminiscent of an Anson's undercarriage. The Ford V-8 engine drives the drum, which can take 6,000ft or 15 cwt 7 x 19 aircraft cable, through an ordinary four-speed gear box. Third gear is used for light winds and second when launching in a stiff breeze. The feed-on device consists of a left- and right-hand screw driven by a chain from a sprocket on the drum axle. This screw moves an assembly consisting of two vertical rollers which guide the cable on to the drum, and mounted behind the rollers is a large chisel, normally held up by a light spring. To reduce inertia, the '' rollers'' are actually stacks of ball races, clamped together with thin shims between the inner races. Their hard outer surface is also a great advantage. The chisel is for emergency B r8
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
