THE JIMMY MEDCALF LECTURES
THIS IS A GLANCE BACK TO THE 1980`S AND 1990`S WHEN JIMMY MEDCALF HELD ANNUAL BENTLEY LECTURES, DURING WHICH, HE EXPLAINED TO THE LARGE AUDIENCES ATTENDING, THE INTIMATE INTERNAL DETAILS OF THE VINTAGE BENTLEY CARS. THE LECTURES WERE HELD IN HIS VERY LARGE WORKSHOP SURROUNDED BY HIS COLLECTION OF BEAUTIFULLY RESTORED VINTAGE BENTLEYS.
THEN, AS A FLEDGELING BITSA BUILDER, I ATTENDED SEVERAL OF HIS LECTURES AND THEY WERE INCREDIBLY INFORMATIVE, AS HE GAVE OUT INFORMATION THAT HE HAD DISCOVERED, SOME OF WHICH WAS NOT INCLUDED IN THE TECHNICAL FACTS. THE OTHER PLUS WAS THAT THE ACTUAL DIS-ASSEMBLED COMPONENTS WERE ON DISPLAY, WHICH WAS LIGHT YEARS BETTER THAN JUST PORING OVER THE SKETCHES IN THE TECHNICAL FACTS.
HOPEFULLY THIS DOESN`T SOUND LIKE AN OBITUARY BUT OVER THE YEARS, JIMMY HAS NEVER CHANGED AND CAN BE RIGHTLY DESCRIBED AS A TRUE BENTLEY ENTHUSIAST WITH A WEALTH OF KNOWLEGE THAT HE ENJOYS SHARING WITH OTHERS. THIS BLOG IS BASED ON JIMMY`S ENTERPRISE AS I ALSO WANT TO SHARE MY OWN ENDEAVOURS WITH OTHERS THAT ARE LOOKING FOR INFORMATION ON HOW TO BUILD THE BENTLEY OF THEIR DREAMS AND AS YOU KNOW, THIS KNOWLEGE IS RATHER HARD TO COME BY!
BELOW I WILL PUBLISH MY NOTES THAT I TOOK DURING THESE LECTURES. I USED THIS INFORMATION TO HELP ME DURING THE BUILD OF MY EXP2 BITSA.
BDC TECHNICAL MEETING 28 OCTOBER 1989
PLEASE REMEMBER THAT I HAD TO WRITE THESE NOTES DOWN AT THE SPEED OF THE LECTURE WITH THE PAPER RESTING ON MY LAP! CLICK ON THESE PAGES, SHOWN BELOW, TO ENLARGE THEM.
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THE FIRST SUBJECT ON THE AGENDA WAS THE ADJUSTMENT OF THE 4 WHEEL BRAKES, JIMMY DESCRIBED THAT BY PUTTING THE CAR ON BLOCKS THEN ADJUSTING THE BRAKE ADJUSTING SCREW BETWEEN THE PEDAL AND THE COMPENSATOR SO THAT THE WHEELS WERE JUST BINDING. THEN USE A SCALE TO CHECK SOMETHING OR OTHER. I DON`T QUITE UNDERSTAND THIS! AS CHECKING THE BRAKE SPRING PULL OFF FORCES, HAVE TO BE DONE WITH THE BRAKE DRUMS OFF! I PROBABLY MIS-UNDERSTOOD THIS DUE TO MY LACK OF BENTLEY KNOWLEGE.
THE LITTLE SKETCH IS HOW JIMMY DESCRIBED PARING AWAY THE NYLON IN THE BORES OF THE FRONT BRAKE SUPPORT BRACKET BUSHES TO REDUCE FRICTION DRAG.
THEN THERE IS A DESCRIPTION OF THE BRAKE ADJUSTING PROCEDURE. I`VE ADDED A QUESTION ABOUT THE HOLES IN THE LEVERS ON THE COMPENSATER AND DON`T REMEMBER IF I POSED THIS QUESTION TO JIMMY OR NOT, I STILL DON`T KNOW THE ANSWER TO THIS QUESTION! CAN ANYONE TELL US WHY THEY ARE THERE?
SPRINGS AND SHACKLES WERE NEXT ON THE AGENDA AND JIMMY TOLD US TO CHECK FOR UNDERCUTTING ON THE SHACKLES AND PINS AND ALSO, AS SHOWN IN THE SKETCH, THE CORRECT ORIENTATION OF THE 6.5 LITRE STYLE SHACKLES WHICH ARE THE PATTERN SUPPLIED BY THE SPARES SCHEME. HE MENTIONED "BRITANNIA SPRINGS" I DON`T THINK THAT THIS FIRM EXISTS ANY LONGER.
THE FIRST SUBJECT ON THE AGENDA WAS THE ADJUSTMENT OF THE 4 WHEEL BRAKES, JIMMY DESCRIBED THAT BY PUTTING THE CAR ON BLOCKS THEN ADJUSTING THE BRAKE ADJUSTING SCREW BETWEEN THE PEDAL AND THE COMPENSATOR SO THAT THE WHEELS WERE JUST BINDING. THEN USE A SCALE TO CHECK SOMETHING OR OTHER. I DON`T QUITE UNDERSTAND THIS! AS CHECKING THE BRAKE SPRING PULL OFF FORCES, HAVE TO BE DONE WITH THE BRAKE DRUMS OFF! I PROBABLY MIS-UNDERSTOOD THIS DUE TO MY LACK OF BENTLEY KNOWLEGE.
THE LITTLE SKETCH IS HOW JIMMY DESCRIBED PARING AWAY THE NYLON IN THE BORES OF THE FRONT BRAKE SUPPORT BRACKET BUSHES TO REDUCE FRICTION DRAG.
THEN THERE IS A DESCRIPTION OF THE BRAKE ADJUSTING PROCEDURE. I`VE ADDED A QUESTION ABOUT THE HOLES IN THE LEVERS ON THE COMPENSATER AND DON`T REMEMBER IF I POSED THIS QUESTION TO JIMMY OR NOT, I STILL DON`T KNOW THE ANSWER TO THIS QUESTION! CAN ANYONE TELL US WHY THEY ARE THERE?
SPRINGS AND SHACKLES WERE NEXT ON THE AGENDA AND JIMMY TOLD US TO CHECK FOR UNDERCUTTING ON THE SHACKLES AND PINS AND ALSO, AS SHOWN IN THE SKETCH, THE CORRECT ORIENTATION OF THE 6.5 LITRE STYLE SHACKLES WHICH ARE THE PATTERN SUPPLIED BY THE SPARES SCHEME. HE MENTIONED "BRITANNIA SPRINGS" I DON`T THINK THAT THIS FIRM EXISTS ANY LONGER.
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JIMMY DESCRIBED HOW TO DIMENSION FROM A PIANO WIRE STRETCHED BETWEEN THE CENTRES OF THE FRONT AND REAR CROSS TUBES. PRESUMABLY TO CHECK THE STRAIGHTNESS OF THE CHASSIS. (THIS CAN ONLY BE DONE WHEN THE BODY IS REMOVED FROM THE CHASSIS). THEN HE TALKED ABOUT MACHINING THE REAR AXLE BEARING CAPS TO FIT SEALS THAT PREVENTED OIL FROM THE AXLE RUNNING UP THE HALF SHAFTS ONTO THE REAR BRAKE SHOES, WITH A WARNING TO COVER THE KEYWAY ON THE HALF SHAFT WITH TAPE TO PREVENT DAMAGE TO THE SEAL WHEN ASSEMBLING THE BEARING CAP ONTO THE AXLE. THE SKETCH IS FOR A TOOL TO ADJUST THE BEARING CAP IN ORDER TO AVOID CREATING THE DAMAGE THAT CAN OCCUR WHEN TIGHTENING UP THE CAPS USING INCORRECT TOOLS.
THE NEXT ITEM DISCUSSED WAS THE METHOD OF REMOVING WORN OUT THRUST BUTTONS ON THE HALF SHAFTS, THIS WAS DONE BY WELDING THE BUTTON TO THE BORE OF A HOLE DILLED IN A STEEL BAR TO ENABLE IT TO BE EASILY PULLED OUT.
THE SKETCH IS OF THE OUTER END OF THE HALF SHAFT, JIMMY EXPLAINED THAT IN THE CASE OF THE BORE FOR THE HALF SHAFT SUPPORT BEARING BEING WORN, THE BEARING COULD BE MOVED FURTHER INTO THE HOUSING ON TO THE UNWORN PART OF THE BORE BY MACHINING MATERIAL FROM THE FLANGE ON THE HALF SHAFT.
JIMMY THEN RECOMMENDED THAT THE CAR SHOULD NOT BE TOWED IN THE CASE OF A BROKEN HALF SHAFT AS THIS COULD RESULT IN THE BROKEN PARTS FALLING INTO THE CROWN WHEEL AND PINION!
THEN FOLLOWS AN EXPLANATION OF HOW TO REMOVE A REAR HUB AND THE RECOMMENDATION TO GRIND THE HUB ON TO THE NEW HALF SHAFT TAPER USING FINE GRINDING PASTE, (OF COURSE, NOT FORGETTING TO COMPLETELY REMOVE ANY TRACES OF THE GRINDING PASTE BEFORE RE-ASSEMBLING).
THE NEXT ITEM DISCUSSED WAS THE METHOD OF REMOVING WORN OUT THRUST BUTTONS ON THE HALF SHAFTS, THIS WAS DONE BY WELDING THE BUTTON TO THE BORE OF A HOLE DILLED IN A STEEL BAR TO ENABLE IT TO BE EASILY PULLED OUT.
THE SKETCH IS OF THE OUTER END OF THE HALF SHAFT, JIMMY EXPLAINED THAT IN THE CASE OF THE BORE FOR THE HALF SHAFT SUPPORT BEARING BEING WORN, THE BEARING COULD BE MOVED FURTHER INTO THE HOUSING ON TO THE UNWORN PART OF THE BORE BY MACHINING MATERIAL FROM THE FLANGE ON THE HALF SHAFT.
JIMMY THEN RECOMMENDED THAT THE CAR SHOULD NOT BE TOWED IN THE CASE OF A BROKEN HALF SHAFT AS THIS COULD RESULT IN THE BROKEN PARTS FALLING INTO THE CROWN WHEEL AND PINION!
THEN FOLLOWS AN EXPLANATION OF HOW TO REMOVE A REAR HUB AND THE RECOMMENDATION TO GRIND THE HUB ON TO THE NEW HALF SHAFT TAPER USING FINE GRINDING PASTE, (OF COURSE, NOT FORGETTING TO COMPLETELY REMOVE ANY TRACES OF THE GRINDING PASTE BEFORE RE-ASSEMBLING).
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JIMMY RECOMMENDED "RP ENGINEERING" FOR THE RECONDITIONING OF WHEEL HUBS, DONALD DAY TOOK OVER THIS SERVICE SOME YEARS AGO.
THEN AN IMPORTANT NOTE, THE RIGHT HAND SIDE OF THE CAR HUBS HAVE LEFT HAND THREADS AND THE LEFT HAND SIDE HAVE RIGHT HAND THREADS. TIGHTEN THE WHEEL NUTS IN THE DIRECTION OPPOSITE TO ROTATION.
THEN SOME NOTES ON WHEEL CENTRES, THERE ARE A LOT OF DODGY WHEELS OUT THERE! DONT FORGET TO READ THE TECHNICAL FACTS!
JIMMY MENTIONED THAT DICK MOSS SUPPLIED BRAKE SHOES AND HE RECOMMENDED THAT THE LINING MATERIAL BE MZ 41 WHICH OF COURSE IS NO LONGER AVAILABLE FOR HEALTH AND SAFETY REASONS!
THEN A JUMP OVER TO RADIATORS, JIMMY TALKED ABOUT HAVING A VALVE IN THE OVERFLOW PIPE. I DIDN`T REALLY UNDERSTAND THIS, READING THIS TODAY, AS IF A NON RETURN VALVE WAS PLACED IN THE OVERFLOW IT WOULD HAVE TO PLACED WITH THE FLOW OUTWARDS WHICH DOESN`T REALLY ACHIEVE MUCH. (I PHONED JIMMY AND HE EXPLAINED THAT THIS VALVE WAS AN ADJUSTABLE PRESSURE RESTRICTING VALVE WHICH ADJUSTED TO GIVE A SMALL PRESSURE OF SAY 2 PSI, PREVENTED THE LOSS OF SURGING COOLANT VIA THE OVERFLOW PIPE FROM THE RADIATOR DURING HEAVY BRAKING. HE ADDED THAT THIS WAS A STANDARD FEATURE OF THE 6.5 AND 8 LITRE CARS).
BACK TO THE NOTES, HE RECOMMENDED OILS FOR THE VINTAGE BENTLEY BUT THIS INFORMATION IS PROBABLY OUT OF DATE!
THEN INFORMATION ABOUT 3L ENGINE OIL PRESSURE, THIS IS UNREADABLE SO WILL HAVE TO PHONE JIMMY AGAIN.
FANS WERE MENTIONED WITH THE WARNING THAT THE FAN PEDESTALS COULD BREAK! I HAD A NEW FAN BRACKET CATASTROPHIC FAILURE DUE TO METAL FATIGUE EVEN THOUGH THE ENGINE HAD BEEN BALANCED.
THEN JIMMY RECOMMENDED THAT WYNNES ANTI FREEZE INHIBITOR BE USED TO PREVENT INTERNAL CORROSION. ALSO THAT THE NORMAL RUNNING TEMPERATURE OF THE 3L BE 75 DEGREES CELCIUS.
THEN AN IMPORTANT NOTE, THE RIGHT HAND SIDE OF THE CAR HUBS HAVE LEFT HAND THREADS AND THE LEFT HAND SIDE HAVE RIGHT HAND THREADS. TIGHTEN THE WHEEL NUTS IN THE DIRECTION OPPOSITE TO ROTATION.
THEN SOME NOTES ON WHEEL CENTRES, THERE ARE A LOT OF DODGY WHEELS OUT THERE! DONT FORGET TO READ THE TECHNICAL FACTS!
JIMMY MENTIONED THAT DICK MOSS SUPPLIED BRAKE SHOES AND HE RECOMMENDED THAT THE LINING MATERIAL BE MZ 41 WHICH OF COURSE IS NO LONGER AVAILABLE FOR HEALTH AND SAFETY REASONS!
THEN A JUMP OVER TO RADIATORS, JIMMY TALKED ABOUT HAVING A VALVE IN THE OVERFLOW PIPE. I DIDN`T REALLY UNDERSTAND THIS, READING THIS TODAY, AS IF A NON RETURN VALVE WAS PLACED IN THE OVERFLOW IT WOULD HAVE TO PLACED WITH THE FLOW OUTWARDS WHICH DOESN`T REALLY ACHIEVE MUCH. (I PHONED JIMMY AND HE EXPLAINED THAT THIS VALVE WAS AN ADJUSTABLE PRESSURE RESTRICTING VALVE WHICH ADJUSTED TO GIVE A SMALL PRESSURE OF SAY 2 PSI, PREVENTED THE LOSS OF SURGING COOLANT VIA THE OVERFLOW PIPE FROM THE RADIATOR DURING HEAVY BRAKING. HE ADDED THAT THIS WAS A STANDARD FEATURE OF THE 6.5 AND 8 LITRE CARS).
BACK TO THE NOTES, HE RECOMMENDED OILS FOR THE VINTAGE BENTLEY BUT THIS INFORMATION IS PROBABLY OUT OF DATE!
THEN INFORMATION ABOUT 3L ENGINE OIL PRESSURE, THIS IS UNREADABLE SO WILL HAVE TO PHONE JIMMY AGAIN.
FANS WERE MENTIONED WITH THE WARNING THAT THE FAN PEDESTALS COULD BREAK! I HAD A NEW FAN BRACKET CATASTROPHIC FAILURE DUE TO METAL FATIGUE EVEN THOUGH THE ENGINE HAD BEEN BALANCED.
THEN JIMMY RECOMMENDED THAT WYNNES ANTI FREEZE INHIBITOR BE USED TO PREVENT INTERNAL CORROSION. ALSO THAT THE NORMAL RUNNING TEMPERATURE OF THE 3L BE 75 DEGREES CELCIUS.
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JIMMY RECOMMENDED KNOBBY GRAY OF SWISS COTTAGE FOR VALVE SEAT CUTTING, I DON`T KNOW IF HE IS STILL AROUND? ALSO DICK MOSS FOR OVERSIZE VALVES AND UNBURSTABLE VALVE GEAR.
THEN IT WAS STARTER MOTORS AND THE SKETCH SHOWS THE ORIENTATION OF THE BENDIX SPRING FOR THE ORIGINAL SMITHS STARTERS. JIMMY RECOMMENDED THAT AN OUTRIGGER BE FITTED TO THE FLIMSY PINION SHAFT AND GAVE THE WARNING THAT THE KEY IN THE COLLAR WAS A VITAL PART OF THE ASSEMBLY AND NOT TO BE FORGOTTEN.
BELOW THIS NOTE HE GAVE INFORMATION ABOUT THE INCREDIBLY HEAVY BS5 STARTERS STATING THAT THE CLEARANCE BETWEEN THE PINION AND THE FLYWHEEL RING GEAR SHOULD BE 1/8". HE FORGOT TO MENTION THAT THE BRONZE PINION GEAR BE REDUCED IN LENGTH TO ENABLE THE BODY OF THE MOTOR BE FURTHER INTO THE TUNNEL SO THAT THE LOCKING TAPER BOLT COULD ENGAGE BETTER WITH THE BODY.
NEXT THE MAGNETO TIMING WAS LOOKED AT AND JIMMY GAVE DETAILS OF A TEMPORARY SOLUTION TO CONVERT A MAGNETO TO COIL OPERATION IN CASE OF FAILURE AS SHOWN IN THE SKETCH.
THEN IT WAS STARTER MOTORS AND THE SKETCH SHOWS THE ORIENTATION OF THE BENDIX SPRING FOR THE ORIGINAL SMITHS STARTERS. JIMMY RECOMMENDED THAT AN OUTRIGGER BE FITTED TO THE FLIMSY PINION SHAFT AND GAVE THE WARNING THAT THE KEY IN THE COLLAR WAS A VITAL PART OF THE ASSEMBLY AND NOT TO BE FORGOTTEN.
BELOW THIS NOTE HE GAVE INFORMATION ABOUT THE INCREDIBLY HEAVY BS5 STARTERS STATING THAT THE CLEARANCE BETWEEN THE PINION AND THE FLYWHEEL RING GEAR SHOULD BE 1/8". HE FORGOT TO MENTION THAT THE BRONZE PINION GEAR BE REDUCED IN LENGTH TO ENABLE THE BODY OF THE MOTOR BE FURTHER INTO THE TUNNEL SO THAT THE LOCKING TAPER BOLT COULD ENGAGE BETTER WITH THE BODY.
NEXT THE MAGNETO TIMING WAS LOOKED AT AND JIMMY GAVE DETAILS OF A TEMPORARY SOLUTION TO CONVERT A MAGNETO TO COIL OPERATION IN CASE OF FAILURE AS SHOWN IN THE SKETCH.
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NOW HERE IS AN INTERESTING PAGE! JIMMY BRIEFLY MENTIONED THE DONALD DAY PEDAL RUBBERS RECOMMENDING THAT THESE BE SECURED TO THE PEDALS BY FOUR SCREWS.
THEN THE SUBJECT OF OIL FILTERS WAS RAISED, JIMMY MENTIONED THAT THE ORIGINAL 3L OIL FILTER BODY BE USED TO HOUSE A PAIR OF HILLMAN IMP FILTERS AS PROPOSED BY RICHARD WELLS. ( I BOUGHT ONE OF THESE CONVERSION KITS FROM LEN WILTON AND IT`S A VERY CLEVER SOLUTION AS THE FLOW THROUGH THE FILTERS HAS TO BE REVERSED. HOWEVER A WORD OF WARNING ABOUT USING FILTERS THAT DON`T HAVE A BY-PASS VALVE FITTED. IF WATER IS PRESENT IN THE OIL THEN THE FILTER WILL BREAK UP INTERNALLY AND BLOCK THE FLOW OF OIL, SO WITHOUT A BY-PASS VALVE THIS WILL MEAN THAT YOUR ENGINE WILL BE STARVED OF OIL AND YOU KNOW WHAT THAT MEANS! USE A PROPER AFTER MARKET OIL FILTER ASSEMBLY WITH INCORPORATED BY-PASS VALVE, IT MAY NOT LOOK PRETTY BUT IT WILL PROTECT YOUR ENGINE).
THE NEXT SUBJECT WAS MAGNETIC OIL PLUGS, JIMMY SHOWED US THAT A MAGNET COULD BE SWEATED TO THE OIL DRAIN PLUGS TO COLLECT DEBRIS FROM THE INTERNAL PARTS.
THE SUBJECT CHANGED TO THE REAR AXLE.
JIMMY RECOMMENDED FITTING A MECHANICAL OIL SEAL IN PLACE OF THE SCROLL ON THE REAR OF THE PINION. (DONALD DAY CAN SUPPLY THESE AND THE MODIFIED END PLATE OR YOU CAN MACHINE UP YOUR OWN. DON`T FORGET TO MACHINE OFF THE SCROLL FROM THE PINION DRIVING FLANGE, MAKING SURE THAT THE NEW OD IS POLISHED AND CONCENTRIC WITH THE BORE, AND ADD A BREATHER TO TO THE AXLE, IF YOU DO THIS CONVERSION!).
NEXT JIMMY EXPLAINED HOW TO SET UP THE REAR AXLE PINION, LOOKING AT THE SKETCH, HE SUGGESTED THAT A WASHER OF THE SAME THICKNESS AS THE WEB IN THE PINION SLEEVE BE PLACED BETWEEN THE TWO THRUST BEARINGS TO ALLOW EASY ACCESS TO THE ASSEMBLY WITHOUT THE HINDERANCE OF THE SLEEVE.
FROM LEFT TO RIGHT ON THE SKETCH, JIMMY RECOMMENDED USING A CAGED ROLLER BEARING, THEN HE FITTED A WASHER BETWEEN THE ROLLER AND THRUST BEARINGS (NON STANDARD). THEN EXPLAINED THAT THE ASSEMBLY BE FITTED TOGETHER WITHOUT THE SPACER BETWEEN THE PINION FLANGE AND THE REAR THRUST BEARING. THE GAP WAS THEN MEASURED AND THE SPACER MACHINED TO 0.003" LARGER THAN THE DIMENSION TO GIVE A PRELOAD TO THE THRUST BEARINGS. ONE OF JIMMY`S EXTRA TWEAKS WAS TO MAKE A 1/8" HACKSAW CUT ON THE PERIPHERY OF THE SPACER. ( I`LL HAVE TO ASK HIM WHY?).
THEN THE SUBJECT OF OIL FILTERS WAS RAISED, JIMMY MENTIONED THAT THE ORIGINAL 3L OIL FILTER BODY BE USED TO HOUSE A PAIR OF HILLMAN IMP FILTERS AS PROPOSED BY RICHARD WELLS. ( I BOUGHT ONE OF THESE CONVERSION KITS FROM LEN WILTON AND IT`S A VERY CLEVER SOLUTION AS THE FLOW THROUGH THE FILTERS HAS TO BE REVERSED. HOWEVER A WORD OF WARNING ABOUT USING FILTERS THAT DON`T HAVE A BY-PASS VALVE FITTED. IF WATER IS PRESENT IN THE OIL THEN THE FILTER WILL BREAK UP INTERNALLY AND BLOCK THE FLOW OF OIL, SO WITHOUT A BY-PASS VALVE THIS WILL MEAN THAT YOUR ENGINE WILL BE STARVED OF OIL AND YOU KNOW WHAT THAT MEANS! USE A PROPER AFTER MARKET OIL FILTER ASSEMBLY WITH INCORPORATED BY-PASS VALVE, IT MAY NOT LOOK PRETTY BUT IT WILL PROTECT YOUR ENGINE).
THE NEXT SUBJECT WAS MAGNETIC OIL PLUGS, JIMMY SHOWED US THAT A MAGNET COULD BE SWEATED TO THE OIL DRAIN PLUGS TO COLLECT DEBRIS FROM THE INTERNAL PARTS.
THE SUBJECT CHANGED TO THE REAR AXLE.
JIMMY RECOMMENDED FITTING A MECHANICAL OIL SEAL IN PLACE OF THE SCROLL ON THE REAR OF THE PINION. (DONALD DAY CAN SUPPLY THESE AND THE MODIFIED END PLATE OR YOU CAN MACHINE UP YOUR OWN. DON`T FORGET TO MACHINE OFF THE SCROLL FROM THE PINION DRIVING FLANGE, MAKING SURE THAT THE NEW OD IS POLISHED AND CONCENTRIC WITH THE BORE, AND ADD A BREATHER TO TO THE AXLE, IF YOU DO THIS CONVERSION!).
NEXT JIMMY EXPLAINED HOW TO SET UP THE REAR AXLE PINION, LOOKING AT THE SKETCH, HE SUGGESTED THAT A WASHER OF THE SAME THICKNESS AS THE WEB IN THE PINION SLEEVE BE PLACED BETWEEN THE TWO THRUST BEARINGS TO ALLOW EASY ACCESS TO THE ASSEMBLY WITHOUT THE HINDERANCE OF THE SLEEVE.
FROM LEFT TO RIGHT ON THE SKETCH, JIMMY RECOMMENDED USING A CAGED ROLLER BEARING, THEN HE FITTED A WASHER BETWEEN THE ROLLER AND THRUST BEARINGS (NON STANDARD). THEN EXPLAINED THAT THE ASSEMBLY BE FITTED TOGETHER WITHOUT THE SPACER BETWEEN THE PINION FLANGE AND THE REAR THRUST BEARING. THE GAP WAS THEN MEASURED AND THE SPACER MACHINED TO 0.003" LARGER THAN THE DIMENSION TO GIVE A PRELOAD TO THE THRUST BEARINGS. ONE OF JIMMY`S EXTRA TWEAKS WAS TO MAKE A 1/8" HACKSAW CUT ON THE PERIPHERY OF THE SPACER. ( I`LL HAVE TO ASK HIM WHY?).
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ON THIS PAGE A BRIEF NOTE ABOUT LUBRICATION, JIMMY RECOMMENDED THAT THE REAR AXLE OIL BE EP90 AND SHOULD BE CHANGED ANNUALLY.
THE GEARBOX SHOULD USE 50 STRAIGHT OIL AND 30 IN WINTER.
THE CHASSIS AND STEERING BOX SHOULD USE 140 OIL BUT NOT EP!
THEN A RECOMMENDATION THAT 2 STAR DIFFERENTIALS SHOULD HAVE AN EXTRA PAIR OF STAR GEARS ADDED. (DETAILS OF THIS CAN BE FOUND IN THE TECHNICAL FACTS).
THE GEARBOX SHOULD USE 50 STRAIGHT OIL AND 30 IN WINTER.
THE CHASSIS AND STEERING BOX SHOULD USE 140 OIL BUT NOT EP!
THEN A RECOMMENDATION THAT 2 STAR DIFFERENTIALS SHOULD HAVE AN EXTRA PAIR OF STAR GEARS ADDED. (DETAILS OF THIS CAN BE FOUND IN THE TECHNICAL FACTS).
THAT WAS THE FIRST LECTURE AND VERY INTERESTING IT WAS TOO!
BDC TECHNICAL MEETING 28 OCTOBER 1990
PAGE 1 ABOVE LHS
THE LECTURE KICKED OFF WITH A QUESTION ABOUT TOE IN OF THE FRONT WHEELS, JIMMY GAVE THE FIGURES OF 1/8-3/16".
THEN HE RECOMMENDED DIFFERENT OILS FOR THE STEERING BOX WHICH ARE PROBABLY OUT OF FAVOUR TODAY BUT HE MENTIONED THAT THE PENRIGHT OIL CO. WAS COMING ON THE MARKET IN FEBRUARY AND THEIR STEERING BOX OIL IS A GOOD ONE TO USE.
RESPONDING TO A QUESTION ABOUT DYNAMOS JIMMY GAVE DETAILS ABOUT THE WIRING AND ROTATION FOR THE SMITHS DYNAMO, THE QUESTIONING THEN LED TO THE SUBJECT OF ALTERNATORS AND JIMMY GAVE INFORMATION AS TO WHAT TO PURCHASE FOR THE CONVERSION. THE ALTERNATOR SHOULD BE A SELF SENSED ONE AND BE MOUNTED TO THE LEFT HAND SIDE OF THE CHASSIS. THE DRIVING PULLEY TO BE MADE FROM A PICADOR 8" ONE SPLIT IN HALF LONGITUDINALLY AND THE GROOVE SKIMMED TO BRING IT BACK TO CIRCULAR. THIS WAS TO ENABLE IT TO BE RETRO FITTED TO THE GEARBOX DRIVE SHAFT WITHOUT HAVING TO DIS-ASSEMBLE IT. ANOTHER TIP WAS TO TAPE A SPARE DRIVE BELT TO THE FRONT GEARBOX CROSS MEMBER, SO THAT IN THE CASE OF THE FAILURE OF THE BELT, THE SPARE COULD BE FITTED WITHOUT HAVING TO UNBOLT THE DRIVESHAFT SPIDER. ( NOWADAYS THERE IS NO NEED TO HAVE THIS SPARE BELT IN SITU AS YOU CAN CARRY A LENGTH OF "FENNER" LINKED BELTING WHICH CAN BE SPLIT TO ENABLE IT TO BE ASSEMBLED).
THEN HE RECOMMENDED DIFFERENT OILS FOR THE STEERING BOX WHICH ARE PROBABLY OUT OF FAVOUR TODAY BUT HE MENTIONED THAT THE PENRIGHT OIL CO. WAS COMING ON THE MARKET IN FEBRUARY AND THEIR STEERING BOX OIL IS A GOOD ONE TO USE.
RESPONDING TO A QUESTION ABOUT DYNAMOS JIMMY GAVE DETAILS ABOUT THE WIRING AND ROTATION FOR THE SMITHS DYNAMO, THE QUESTIONING THEN LED TO THE SUBJECT OF ALTERNATORS AND JIMMY GAVE INFORMATION AS TO WHAT TO PURCHASE FOR THE CONVERSION. THE ALTERNATOR SHOULD BE A SELF SENSED ONE AND BE MOUNTED TO THE LEFT HAND SIDE OF THE CHASSIS. THE DRIVING PULLEY TO BE MADE FROM A PICADOR 8" ONE SPLIT IN HALF LONGITUDINALLY AND THE GROOVE SKIMMED TO BRING IT BACK TO CIRCULAR. THIS WAS TO ENABLE IT TO BE RETRO FITTED TO THE GEARBOX DRIVE SHAFT WITHOUT HAVING TO DIS-ASSEMBLE IT. ANOTHER TIP WAS TO TAPE A SPARE DRIVE BELT TO THE FRONT GEARBOX CROSS MEMBER, SO THAT IN THE CASE OF THE FAILURE OF THE BELT, THE SPARE COULD BE FITTED WITHOUT HAVING TO UNBOLT THE DRIVESHAFT SPIDER. ( NOWADAYS THERE IS NO NEED TO HAVE THIS SPARE BELT IN SITU AS YOU CAN CARRY A LENGTH OF "FENNER" LINKED BELTING WHICH CAN BE SPLIT TO ENABLE IT TO BE ASSEMBLED).
SHOWN ABOVE ON THIS 3 LITRE IS THE BENTLEY "TRADE STANDARD" FOR MOUNTING AND ADJUSTING THE ALTERNATOR
PAGE 2 ABOVE RHS
JIMMY GAVE THE SMITHS STARTER BENDIX SPRING ORIENTATION AGAIN IN RESPONSE TO A QUESTION, THEN THE REAR AXLE WAS RE-VISITED, JIMMY GAVE DETAILS OF THE HALF SHAFT OILS SEALS THAT WERE FITTED TO THE HALF SHAFT OUTER BEARING CAPS BY MACHINING THEM TO SUIT. ADDING THE INFORMATION THAT A BREATHER FROM A ROVER CAR BE FITTED TO THE PLUG FOR THE INSPECTION HOLE IN THE NOSEPIECE. HE RECOMMENDED EP80 OIL FOR THE REAR AXLE AND THAT A MAGNET BE ADDED TO THE DRAIN PLUG.
IN RESPONSE TO A QUESTION ABOUT THE CLEARANCE BETWEEN THE CROWN WHEEL AND PINION TEETH, HE SUGGESTED USING A STRIP OF 0.003" THICK PAPER TO BE FED BETWEEN THEM TO ESTABLISH THIS CLEARANCE.
THEN THE CONE CLUTCH WAS GIVEN A BRIEF MENTION, JIMMY GIVING DETAILS OF THE SETTING FOR THE "FINGERS" ON THE CLUTCH PRESSURE RING. LASTLY ON THIS PAGE, HIS RECOMMENDATION FOR THE SPRING SHACKLE PINS, THAT THE AREA AROUND THE LUBE HOLE BE SLIGHTLY GROUND AWAY TO IMPROVE LUBRICATION.
IN RESPONSE TO A QUESTION ABOUT THE CLEARANCE BETWEEN THE CROWN WHEEL AND PINION TEETH, HE SUGGESTED USING A STRIP OF 0.003" THICK PAPER TO BE FED BETWEEN THEM TO ESTABLISH THIS CLEARANCE.
THEN THE CONE CLUTCH WAS GIVEN A BRIEF MENTION, JIMMY GIVING DETAILS OF THE SETTING FOR THE "FINGERS" ON THE CLUTCH PRESSURE RING. LASTLY ON THIS PAGE, HIS RECOMMENDATION FOR THE SPRING SHACKLE PINS, THAT THE AREA AROUND THE LUBE HOLE BE SLIGHTLY GROUND AWAY TO IMPROVE LUBRICATION.
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IN THE FIRST SKETCH JIMMY SHOWED HOW TO RETAIN A HIGHER LEVEL OIL BATH FOR THE WATER PUMP DRIVE GEAR BY SIMPLY BLOCKING THE EXISTING OIL DRAIN HOLE IN THE WATER PUMP SPACER CASTING AND DRILLING A NEW HOLE HIGHER UP. THEN HOW TO IMPROVE THE LUBRICATION TO THE CAMSHAFT BY CLEANING OUT THE CARBON FROM THE OIL HOLES AND BY BLOCKING OFF THE OIL HOLE IN THE END OF THE CAMSHAFT.
HE THEN DESCRIBED THAT DRAIN HOLES BE DRILLED IN THE POCKETS IN THE EXHAUST SIDE OF THE CAMCHEST TO ALLOW EXCESS OIL TO DRAIN AWAY.
THE TURRET WAS THEN FEATURED AND JIMMY RECOMMENDED THAT THE STEEL SIDE OF THE CROSS SHAFT GEAR BE PLACED TO THE OFFSIDE AND THE CLEARANCE BETWEEN THE GEAR AND THE THRUST SIDE OF THE CROSS SHAFT BRONZE SUPPORT BEARING BE SET AT 0.003". (I`M ASSUMING HERE THAT HE WAS INSTALLING A RECONDITIONED CROSS SHAFT GEAR THAT HAD BEEN FITTED WITH A NEW BRONZE GEAR). JIMMY RECOMMENDED THAT THE AXIAL CLEARANCE OF THE OIL PUMP GEAR BE MINIMAL AND THE CLEARANCE BETWEEN THE BOTTOM BEVEL GEAR AND THE THRUST FACE OF THE BRONZE BEARING IN THE TURRET BE 0.012" TO CATER FOR THE LONGITUDINAL EXPANSION OF THE TURRET BODY. THEN AN IMPORTANT NOTE THAT I DON`T UNDERSTAND! BOTTOM BEVEL MUST BE HORIZONTAL AT 45 DEGREES BEFORE TOP DEAD CENTRE?
HE THEN DESCRIBED THAT DRAIN HOLES BE DRILLED IN THE POCKETS IN THE EXHAUST SIDE OF THE CAMCHEST TO ALLOW EXCESS OIL TO DRAIN AWAY.
THE TURRET WAS THEN FEATURED AND JIMMY RECOMMENDED THAT THE STEEL SIDE OF THE CROSS SHAFT GEAR BE PLACED TO THE OFFSIDE AND THE CLEARANCE BETWEEN THE GEAR AND THE THRUST SIDE OF THE CROSS SHAFT BRONZE SUPPORT BEARING BE SET AT 0.003". (I`M ASSUMING HERE THAT HE WAS INSTALLING A RECONDITIONED CROSS SHAFT GEAR THAT HAD BEEN FITTED WITH A NEW BRONZE GEAR). JIMMY RECOMMENDED THAT THE AXIAL CLEARANCE OF THE OIL PUMP GEAR BE MINIMAL AND THE CLEARANCE BETWEEN THE BOTTOM BEVEL GEAR AND THE THRUST FACE OF THE BRONZE BEARING IN THE TURRET BE 0.012" TO CATER FOR THE LONGITUDINAL EXPANSION OF THE TURRET BODY. THEN AN IMPORTANT NOTE THAT I DON`T UNDERSTAND! BOTTOM BEVEL MUST BE HORIZONTAL AT 45 DEGREES BEFORE TOP DEAD CENTRE?
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JIMMY MENTIONED THE HOBSON TELEGAUGE BUT I DIDN`T, FOR SOME REASON, WRITE DOWN WHAT TRANSPIRED! THEN IT WAS ON TO MAGNETO TIMING. A FULL DESCRIPTION OF HOW TO STRIP DOWN THE CROSS SHAFT GEARS AND RE-ASSEMBLE THEM IS GIVEN IN THE TECHNICAL FACTS WHICH ALSO GIVES DETAILS OF HOW TO TIME AND SYNCHRONISE THE MAGNETOS AND GIVES DETAILS OF THE SPECIAL TOOLS REQUIRED. JIMMY MENTIONED A SPECIAL TWEAK, THAT IN THE CASE OF THE LATE TYPE OF VIBRATION DAMPENERS, THE BRONZE INSERT TO BE PINNED TO THE TURRET IN ORDER TO IMMOBILISE IT.
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IN THIS LAST PAGE OF THE LECTURE JIMMY MENTIONED THAT IN THE CASE OF THE SU HV5 CARBURETTORS THE JETS AND PETROL LEVEL IN THE FLOAT CHAMBERS SHOULD BE ADJUSTED SO THAT THEY WERE FLUSH WITH THE CASTING AT THE BOTTOM OF THE INLET TRACT.
ANOTHER RECOMMENDATION WAS THAT A SMALL HOLE BE DRILLED IN THE UNDERSIDE OF THE INLET TRACT TO ALLOW THE PETROL TO ESCAPE IN THE CASE OF THE CARBURETTORS FLOODING.
ANOTHER RECOMMENDATION WAS THAT A SMALL HOLE BE DRILLED IN THE UNDERSIDE OF THE INLET TRACT TO ALLOW THE PETROL TO ESCAPE IN THE CASE OF THE CARBURETTORS FLOODING.
BDC TECHNICAL MEETING OCTOBER 1991
THIS WAS THE LAST LECTURE THAT I WAS ABLE TO ATTEND DUE TO TIME AND GEOGRAPHIC RESTRAINTS.
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THE LECTURE KICKED OFF WITH A CHAT ABOUT LINING WORN BRAKE DRUMS, JIMMY EXPLAINED THAT IT WAS DIFFICULT TO RELINE DRUMS DUE TO THE PROBLEM OF ATTACHING THE THIN LINER TO THE DRUM SATISFACTORILY. ( TECHNICAL FACTS RECOMMEND THAT THE DRUM INTERNAL DIAMETERS BE NO MORE THAN 403 MM IN DIAMETER AND SLIGHTLY WORN DRUMS CAN BE MACHINED TRUE ON A SPECIAL LATHE. THE BIGGEST PROBLEM WITH USED BRAKE DRUMS IS THAT THERE IS USUALLY DISTORTION PRESENT DUE TO OVERHEATING AND UNFORTUNATELY MOST OF THE BEAUTIFUL ALFIN STYLE DRUMS THAT I`VE EXAMINED HAVE HAD THIS PROBLEM. I REMEMBER EXAMINING A PAIR OF REAR BRAKE DRUMS THAT WERE FOR SALE AND WHEN I FELT THE THICKNESS I MENTIONED TO THE RATHER SNOOTY SELLER THAT THEY WERE SCRAP, HE MEASURED THEM AND SURE ENOUGH THEY WERE ONLY 1/16" THICK! NOWADAYS THE BEST SOLUTION IS TO BUY THEM NEW FROM THE SPARES SCHEME).
NEXT ON THE AGENDA WAS WHITE METALLING OF THE CRANKSHAFT AND CON ROD BEARINGS BUT I MADE NO NOTES ON THIS. ( IN THOSE DAYS WHITE METALLING WAS ALWAYS A PROBLEM DUE TO LACK OF SKILL BY SOME OF THE SPECIALISTS, EVEN TODAY IT CAN BE A PROBLEM AS THE MAIN PROVIDER HAS NOT BEEN UP TO SCRATCH LATELY. PROBABLY THE BEST RESULTS CAN BE ACHIEVED BY HAVING MODERN SHELL BEARINGS FITTED, THE ORIGINAL CRANKSHAFTS SHOULD NOT BE USED UNLESS THEY ARE NITRIDED, IT`S BEST TO BUY A NEW CRANKSHAFT AND CON RODS. THERE IS ONE SPECIALIST THAT DOES LINE BORE THE ENGINES FOR SHELL BEARINGS WITH THEIR ORIGINAL BRONZE CAPS FITTED BUT I HAVE NO FEED BACK FOR THE EFFICACY OF THIS METHOD).
SPARK PLUGS WERE THEN DISCUSSED WITH JIMMY RECOMMENDING M50 OR M60 OR NGK A6 OR A7. THEN IT WAS A RE-VISIT TO THE MAG TO COIL CONVERSION AND JIMMY WENT OVER THE SALIENT POINTS OF MAGNETO TIMING, THIS IS ALL IN THE TECHNICAL FACTS BUT JIMMY`S TWEAK FOR SYNCHRONISING THE MAGS SHOULD BE MENTIONED. HE RECOMMENDED THAT THE LH SIDE MAG LEVER BE ADJUSTED FOR ADVANCE BEFORE THE RIGHT HAND IN ORDER TO ELIMINATE THE TORSION IN THE CROSS SHAFT.
NEXT ON THE AGENDA WAS WHITE METALLING OF THE CRANKSHAFT AND CON ROD BEARINGS BUT I MADE NO NOTES ON THIS. ( IN THOSE DAYS WHITE METALLING WAS ALWAYS A PROBLEM DUE TO LACK OF SKILL BY SOME OF THE SPECIALISTS, EVEN TODAY IT CAN BE A PROBLEM AS THE MAIN PROVIDER HAS NOT BEEN UP TO SCRATCH LATELY. PROBABLY THE BEST RESULTS CAN BE ACHIEVED BY HAVING MODERN SHELL BEARINGS FITTED, THE ORIGINAL CRANKSHAFTS SHOULD NOT BE USED UNLESS THEY ARE NITRIDED, IT`S BEST TO BUY A NEW CRANKSHAFT AND CON RODS. THERE IS ONE SPECIALIST THAT DOES LINE BORE THE ENGINES FOR SHELL BEARINGS WITH THEIR ORIGINAL BRONZE CAPS FITTED BUT I HAVE NO FEED BACK FOR THE EFFICACY OF THIS METHOD).
SPARK PLUGS WERE THEN DISCUSSED WITH JIMMY RECOMMENDING M50 OR M60 OR NGK A6 OR A7. THEN IT WAS A RE-VISIT TO THE MAG TO COIL CONVERSION AND JIMMY WENT OVER THE SALIENT POINTS OF MAGNETO TIMING, THIS IS ALL IN THE TECHNICAL FACTS BUT JIMMY`S TWEAK FOR SYNCHRONISING THE MAGS SHOULD BE MENTIONED. HE RECOMMENDED THAT THE LH SIDE MAG LEVER BE ADJUSTED FOR ADVANCE BEFORE THE RIGHT HAND IN ORDER TO ELIMINATE THE TORSION IN THE CROSS SHAFT.
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ON THIS PAGE THE CROSS SHAFT GEARS WERE RE-VISITED AND THE ONLY NEW INFORMATION WAS THE CLAMPING OF THE OIL THROWER SCROLL ON NEW HALF SHAFTS BY MEANS OF 2BA GRUB SCREWS.
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THE WATER PUMP SPACER WAS MENTIONED AGAIN WITH THE ONLY NEW COMMENT BEING TO CHECK THE SQUARE ON THE WATER PUMP SHAFT FOR CONCENTRICITY.
THE LAMINATES ON THE MAGNETO DRIVE SHAFT WERE COVERED AGAIN AND SOME NOTES ON THE BRAKE PULLOFF SPRING VALUES AND SOME BASIC INSTRUCTIONS ABOUT SETTING UP THE COMPENSATOR WERE DISCUSSED.
THE LAMINATES ON THE MAGNETO DRIVE SHAFT WERE COVERED AGAIN AND SOME NOTES ON THE BRAKE PULLOFF SPRING VALUES AND SOME BASIC INSTRUCTIONS ABOUT SETTING UP THE COMPENSATOR WERE DISCUSSED.
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A NOTE ABOUT LUBRICATING THE STEERING BOX, PENRITE STEERING BOX OIL WAS RECOMMENDED. JIMMY ALSO SAID THAT THIS OIL WAS SUITABLE FOR THE LUBRICATION OF THE KING PINS. THEN THE CENTERING OF THE GEARS IN THE STEERING BOX WAS BRIEFLY MENTIONED BUT WITHOUT FULL INSTRUCTIONS ON HOW TO DO THIS. ( FOR FULL INSTRUCTIONS ON HOW TO SET UP THE 3/4.5 STEERING BOX CLICK HERE).
THE LAST SUBJECT COVERED WAS ANTI FREEZE BUT I THINK THAT THE INFORMATION GIVEN IS NOW OUT OF DATE.
THE LAST SUBJECT COVERED WAS ANTI FREEZE BUT I THINK THAT THE INFORMATION GIVEN IS NOW OUT OF DATE.
SUMMING UP
JIMMY`S LECTURES WERE VERY INTERESTING AND THERE WAS A GREAT ATMOSPHERE WITH THE CHANCE TO MEET OTHER BENTLEY ENTHUSIASTS SUCH AS MIKE HAY AND TIM HOULDING. SPECIAL TWEAKS DEVELOPED BY JIMMY WERE COVERED, WHICH WAS VALUABLE INFORMATION TO THOSE THAT WERE ABLE TO TACKLE REBUILDS OF BENTLEY COMPONENTS. INEVITABLY, SOME SUBJECTS WERE RE-VISITED AT EACH LECTURE AS QUESTIONS FROM THE PARTICIPANTS WERE ANSWERED BY JIMMY.
THIS WAS A GREAT TIME FOR ME AND I WILL ALWAYS BE THANKFUL TO JIMMY FOR SHARING HIS TIME AND KNOWLEGE WITH US.
THIS WAS A GREAT TIME FOR ME AND I WILL ALWAYS BE THANKFUL TO JIMMY FOR SHARING HIS TIME AND KNOWLEGE WITH US.