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Aviation History
1928
1928 - 1019.PDF
OCTOBER 25, J928 THE NEW PALMER AIRCRAFT BRAKE Light Weight and Pneumatic Operation SHOWN to the public for the first time at the Berlin Aero*Show, the new wheel brake for aircraft which has just been produced by The Palmer Tyre, Ltd., of 100-106, CannonStreet, London, EC.4, is entirely different from anything hitherto put on the market, and incorporates certain featureswhich should reduce to vanishing point nearly all the diffi- culties that are met with in designing wheel brakes foraircraft. The fundamental principle of the new Palmer wheel brake is exceedingly simple, and consists in interposingbetween the fixed drum and the moving drum an annular inflatable member carrying a number of brake blocks. Our sketches, obtained from one of the demonstrationwheels exhibited at Berlin, will probably make the design of the brake clear. The wheel itself has been re-designed attached " breathes " in sympathy with any slight irregu-larities in the drums. For operating the brake blocks two distinct systems areavailable. For large machines, not already fitted with air compressors, an air cylinder of special design is provided.This is flexible, and consists of a rubber cylinder reinforced with Palmer cord, and is claimed to be at least equal instrength to steel cylinders, although having but a fraction of their weight. The air is transmitted from this cylinder tothe air tube via a relay valve, foot-operated. No effort is required for operating this valve, and yet it enables thepilot to retain the " feel " of his brake and to release the brake pressure as gradually as it was applied. For use on small machines, the air cvlinder can be dis- [" FLIGHT " Sketches THE NEW PALMER WHEEL BRAKE FOR AIRCRAFT : On the left a sketch of the special wheel, with letters indicating the location of details shown in the other two sketches. The outer end of the hub is fixed to the axle as is also the cupped disc D, which carries a trough C in which the brake element is accom- modated. This takes the form of a flattened air tube B carrying the friction blocks A, which are prevented from slipping in the trough by being notched into the castellations of C. When air is pumped into the tube B, this expands, and the outer surfaces of the friction blocks A'are made to bear on the drum E, which travels around with the main wheel. Being pneumatically operated, the brake cannot apply pressure unevenly to the drums C and F. to carry the two brake drums. The inner drum is fixed tothe outer portion of the hub, which in turn is fixed to the wheel axle and does not rotate. The outer drum is attachedto the rotating hub and also, by tangential spokes, to the rim of the wheel, and rotates with the wheel. Interposed between the two drums is the inflatable member,which takes the form of a flattened air tube carrying on its outside circumference a number of brake blocks. Theseblocks are stepped into recesses in the fixed drum, thereby being prevented from revolving around the drum. It willbe seen that when air is forced into the flexible tube the tube expands, and in so doing brings the brake blocks into contactwith the outer, rotating, brake drum, the amount of friction depending upon the air pressure in the tube. It is claimed for this arrangement, and appears obvious,that the drum distortion which may take place when internal expanding two-shoe or three-shoe brakes are employedis entirely avoided, as the tube to which the brake blocks are pensed with altogether, the pilot in this case providing theair pressure direct by means of a foot-operated plunger. In that case, of course, the relay valve is also omitted. Ithas been found that the air pressure necessary for even a very considerable brake effect is very small, and that itmay easily be provided by such simple means as a small cylinder in which the piston or plunger is depressed by thepilot's foot. In fact, on one of the demonstration wheels at theBerlin Show, the pressure is no more than that which can be applied by squeezing an ordinary car type hornbulb. Yet the braking effect is quite considerable. We have not as yet available any actual figures relatingto the weight of the new Palmer aero wheels with brakes, but it is quite obvious that the amount of weight which hasbeen added is quite negligible, and it should not be long before the new Palmer brake is seen on large number of air-craft, both small and large. Whose ? Two French fishing trawlers " caught " a Renault engine in their trawl off Collioure, near Pcrpignan, thought to belong to a machine which was lost at sea in 1923 when flying between Africa and France. . ,..,... . -•..... LZ. 127's Bearings DURING her recent flight across the Atlantic, from Friedrirhsafen to Lakehurst, N.J., the " Graf Zeppelin "(LZ. 127) took a very large number of bearings, which no doubt assisted her in getting safelv across. These bearings,of which there were some 465, were of the ball and roller tvpe, of course ! They were supplied by the Skefko Bal!-Bearing Co., Ltd., the manufacturers of the well-knoivn " SKF " bail and roller bearings. 941
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