BUILDING A 4.5 LITRE STEERING COLUMN FROM PARTS, MODIFYING A THREE LITRE STEERING BOX TO TAKE 4.5 LITRE STEERING GEARS.
BELOW IS AN EXTRACT FROM BENTLEY MOTORS GENERAL ARRANGEMENT DRAWING A142.
GA STEERING BOX (LOW RATIO)
THIS DRAWING SHOWS THE ASSEMBLY OF THE SO CALLED 4.5 LITRE STEERING BOX WHICH IS JUST A MODIFICATION TO THE ORIGINAL 3 LITRE STEERING BOX. AT ITS INTRODUCTION, AFTER ALL STOCK OF THE ORIGINAL 3 LITRE STEERINGS BOXES HAD BEEN USED UP, IT WAS FITTED TO BOTH 3 AND 4.5 LITRE CARS.
GA STEERING BOX (LOW RATIO)
THIS DRAWING SHOWS THE ASSEMBLY OF THE SO CALLED 4.5 LITRE STEERING BOX WHICH IS JUST A MODIFICATION TO THE ORIGINAL 3 LITRE STEERING BOX. AT ITS INTRODUCTION, AFTER ALL STOCK OF THE ORIGINAL 3 LITRE STEERINGS BOXES HAD BEEN USED UP, IT WAS FITTED TO BOTH 3 AND 4.5 LITRE CARS.
UNFORTUNATELY THIS DRAWING CONTAINS OMISSIONS AND I THINK THAT IT WAS TRACED FROM AN ORIGINAL WHEN THE FOURTH EDITION OF THE BDC "TECHNICAL FACTS OF THE VINTAGE BENTLEY" WAS PUBLISHED IN 1984.
A WORD OF WARNING TO THE UNINITIATED! ON NO ACCOUNT SHOULD YOU BUY THOSE GEAR SETS THAT GIVE THE 4.5 RATIO IN THE ORIGINAL 3 LITRE BOX. SEVERAL PEOPLE HAVE TRIED THIS AND SOLD THEM TO OTHER BENTLEY BOYS WITH UNFORTUNATE RESULTS AS THEY HAD NOT TAKEN THE TROUBLE TO CALCULATE THAT THE GEARS WERE REVERSIBLE, AND ACCORDING TO THE LAWS OF PHYSICS THEY WERE NOT! SO DON`T THROW AWAY YOUR VALUABLE CASH ON THEM DESPITE WHAT THE SELLER TELLS YOU.
i`VE DONE QUITE A FEW 3 TO 4.5 STEERING BOX CONVERSIONS OVER THE YEARS AND HAVE LEARNED THE PITFALLS THAT CAN DOG THIS SEEMINGLY SIMPLE TASK.
THE DESIGN OF THE ORIGINAL STEERING BOX IN THE EARLY PRODUCTION 3 LITRE CARS WAS BASED ON THE PROTOTYPE FITTED TO EXPERIMENTAL No 2 AND ALMOST CERTAINLY DESIGNED BY BURGESS. WHAT IS VERY STRIKING ABOUT THE DESIGN IS THAT THE BOX HAS NO FACILITY TO ADJUST FOR WEAR BETWEEN THE STEERING GEARS. I CAN ONLY PRESUME THAT WHEN THE ORIGINAL DESIGN WAS BEING CHURNED OUT ON BURGESS`S KITCHEN TABLE, IT WAS DECIDED THAT THIS WAS NOT NECESSARY AND WAS OMITTED AS A COST SAVING! HOWEVER THE 6.5 LITRE, THE SECOND BENTLEY TO BE PUT INTO PRODUCTION, WAS GIVEN A STEERING COLUMN THAT WAS ADJUSTABLE FOR WEAR.
THE 3 LITRE BOXES HAD A VERY NICE STEERING RATIO OF 6.75 TO 1 WHICH ACCORDING TO VARIOUS SOURCES, GAVE A BEAUTIFULLY BALANCED AND LIGHT STEERING WITH THE NARROW BEADED EDGE TYRES OF THE DAY.
WHEN BALLOON TYRES WERE INTRODUCED, THE STEERING RATIO WAS CHANGED TO 10.3 TO 1 TO HELP BENTLEY OWNERS WHEN MANEUVERING AT LOW SPEEDS SUCH AS PARKING BUT MOST 3 LITRES WERE FITTED WITH THE 6.75 TO 1 RATIO FROM NEW.
THE 3 LITRE STEERING BOX WAS MACHINED FROM CASTING BM 817 AND THE 6.75 TO 1 GEAR SET COMPRISING BM 830 AND BM 1748 WERE MADE BY ENV FROM THAT VERY EXOTIC MATERIAL OF THE DAY BND.
BENTLEY MOTORS REWORKED THE EXISTING 3 LITRE BOX TO TAKE THE NEW 10.3 TO 1 RATIO THAT COMPRISED BM 3327 AND BM 3328, THE NEW BOX WAS GIVEN THE DRAWING NUMBER BM 3333.
THE LOWER RATIO WAS OBTAINED BY RETAINING THE DIMENSION BETWEEN THE CENTRELINES OF THE SHAFTS AND BY REDUCING THE DIAMETER OF THE WORM AND INCREASING THE DIAMETER OF THE WORM WHEEL.
TO CONVERT THE 3 LITRE BOX TO TAKE THE 4.5 LITRE RATIO, THE CASTING BM 817 HAS TO BE MACHINED TO ACCOMMODATE THE LARGER DIAMETER WORM WHEEL AND THE LONGER WORM.
AN ANOMALY THAT I HAVE TO MENTION IS THAT ON THE DRAWING BM 3333 THE DIMENSION BETWEEN THE GEAR SHAFT AXES OF 2 15/16" HAS NO TOLERANCE ON IT WHICH PROBABLY MEANS THAT THE MACHINING OF THE BOX WAS PROBABLY DONE ON JIGS AND ENV SUPPLIED BENTLEY MOTORS WITH MATCHED PAIRS OF GEARS TO SUIT THE NOMINAL CENTRELINE DIMENSION. THE DRAWINGS GIVE NO CLUE TO THIS!
THE DESIGN OF THE ORIGINAL STEERING BOX IN THE EARLY PRODUCTION 3 LITRE CARS WAS BASED ON THE PROTOTYPE FITTED TO EXPERIMENTAL No 2 AND ALMOST CERTAINLY DESIGNED BY BURGESS. WHAT IS VERY STRIKING ABOUT THE DESIGN IS THAT THE BOX HAS NO FACILITY TO ADJUST FOR WEAR BETWEEN THE STEERING GEARS. I CAN ONLY PRESUME THAT WHEN THE ORIGINAL DESIGN WAS BEING CHURNED OUT ON BURGESS`S KITCHEN TABLE, IT WAS DECIDED THAT THIS WAS NOT NECESSARY AND WAS OMITTED AS A COST SAVING! HOWEVER THE 6.5 LITRE, THE SECOND BENTLEY TO BE PUT INTO PRODUCTION, WAS GIVEN A STEERING COLUMN THAT WAS ADJUSTABLE FOR WEAR.
THE 3 LITRE BOXES HAD A VERY NICE STEERING RATIO OF 6.75 TO 1 WHICH ACCORDING TO VARIOUS SOURCES, GAVE A BEAUTIFULLY BALANCED AND LIGHT STEERING WITH THE NARROW BEADED EDGE TYRES OF THE DAY.
WHEN BALLOON TYRES WERE INTRODUCED, THE STEERING RATIO WAS CHANGED TO 10.3 TO 1 TO HELP BENTLEY OWNERS WHEN MANEUVERING AT LOW SPEEDS SUCH AS PARKING BUT MOST 3 LITRES WERE FITTED WITH THE 6.75 TO 1 RATIO FROM NEW.
THE 3 LITRE STEERING BOX WAS MACHINED FROM CASTING BM 817 AND THE 6.75 TO 1 GEAR SET COMPRISING BM 830 AND BM 1748 WERE MADE BY ENV FROM THAT VERY EXOTIC MATERIAL OF THE DAY BND.
BENTLEY MOTORS REWORKED THE EXISTING 3 LITRE BOX TO TAKE THE NEW 10.3 TO 1 RATIO THAT COMPRISED BM 3327 AND BM 3328, THE NEW BOX WAS GIVEN THE DRAWING NUMBER BM 3333.
THE LOWER RATIO WAS OBTAINED BY RETAINING THE DIMENSION BETWEEN THE CENTRELINES OF THE SHAFTS AND BY REDUCING THE DIAMETER OF THE WORM AND INCREASING THE DIAMETER OF THE WORM WHEEL.
TO CONVERT THE 3 LITRE BOX TO TAKE THE 4.5 LITRE RATIO, THE CASTING BM 817 HAS TO BE MACHINED TO ACCOMMODATE THE LARGER DIAMETER WORM WHEEL AND THE LONGER WORM.
AN ANOMALY THAT I HAVE TO MENTION IS THAT ON THE DRAWING BM 3333 THE DIMENSION BETWEEN THE GEAR SHAFT AXES OF 2 15/16" HAS NO TOLERANCE ON IT WHICH PROBABLY MEANS THAT THE MACHINING OF THE BOX WAS PROBABLY DONE ON JIGS AND ENV SUPPLIED BENTLEY MOTORS WITH MATCHED PAIRS OF GEARS TO SUIT THE NOMINAL CENTRELINE DIMENSION. THE DRAWINGS GIVE NO CLUE TO THIS!
ABOVE IS A CROSS SECTION THROUGH THE LOW RATIO SO CALLED 4.5 LITRE STEERING BOX. TAKEN LOOKING FROM THE REAR OF THE CHASSIS.
ABOVE LEFT IS AN ORIGINAL WORM WHEEL AND SHAFT BM 1748, PLEASE NOTE THAT THE WORMWHEEL IS INTEGRAL WITH THE SHAFT. ABOVE RIGHT IS THE GEAR SET FOR THE 4.5 LITRE 10.3 TO 1 RATIO. THE WORMWHEEL IS SEPARATE FROM THE SHAFT AND IS MADE OF BRONZE.
THERE IS ONLY ONE POSSIBLE WAY TO TRY TO AMELIORATE THE WEAR IN THE EARLY GEARS AND THAT IS TO MACHINE OR SPARK ERODE A NEW KEYWAY 180 DEGREES OPPOSITE TO THE KEYWAY SHOWN IN THE LEFT HAND PHOTO, TO BRING AN UNWORN PART OF THE WORMWHEEL INTO CONTACT WITH THE WORM.
THE 4.5 LITRE GEARS CAN BE IMPROVED BY ROTATING THE WORMWHEEL ON IT`S SHAFT TO BRING AN UNWORN PORTION OF THE WORMWHEEL INTO PLAY WITH THE WORM. THE TOTAL RADIAL MOVEMENT OF THE WORMWHEEL FROM LOCK TO LOCK OF THE STEERING IS LESS THAN 120 DEGREES SO THAT THE ROTATION OF THE WORMWHEEL TO THE SHAFT IS ONLY TWO BOLT HOLES TO GIVE A 120 DEGREE RADIAL MOVEMENT.
THERE IS ONLY ONE POSSIBLE WAY TO TRY TO AMELIORATE THE WEAR IN THE EARLY GEARS AND THAT IS TO MACHINE OR SPARK ERODE A NEW KEYWAY 180 DEGREES OPPOSITE TO THE KEYWAY SHOWN IN THE LEFT HAND PHOTO, TO BRING AN UNWORN PART OF THE WORMWHEEL INTO CONTACT WITH THE WORM.
THE 4.5 LITRE GEARS CAN BE IMPROVED BY ROTATING THE WORMWHEEL ON IT`S SHAFT TO BRING AN UNWORN PORTION OF THE WORMWHEEL INTO PLAY WITH THE WORM. THE TOTAL RADIAL MOVEMENT OF THE WORMWHEEL FROM LOCK TO LOCK OF THE STEERING IS LESS THAN 120 DEGREES SO THAT THE ROTATION OF THE WORMWHEEL TO THE SHAFT IS ONLY TWO BOLT HOLES TO GIVE A 120 DEGREE RADIAL MOVEMENT.
ABOVE LEFT IS THE STEERING BOX MODIFIED TO BM 3333 STATUS. ABOVE RIGHT IS A NEW STEERING BOX MOUNTING BRACKET BM 3334.
MODIFYING AN ORIGINAL 3 LITRE STEERING BOX TO 4.5 LITRE STATUS
DISMANTLING THE STEERING COLUMN IS RELATIVELY EASY BUT THE RUST OF AGES MAY MAKE THIS MORE DIFFICULT BY JAMMING PARTS TOGETHER. ONE STICKY PROBLEM IS REMOVING THE STEERING ARM FROM THE SHAFT WHICH USUALLY REQUIRES EXTREME VIOLENCE AND HEAT TO CARRY OUT. I REMEMBER DICK MOSS BACK IN THE SEVENTIES REMOVING THE STEERING ARM FROM MY ORIGINAL 3 LITRE BOX. I WATCHED AGHAST AS THEY HEATED UP THE ARM AT THE POINT WHERE IT FITS TO THE SHAFT AND BANGED AWAY WITH A LARGE HAMMER AND COLD CHISEL BETWEEN THE ARM AND THE BRACKET BEARING RETAINING CAP! THIS ONE WASN`T GOING TO BE A PUSHOVER. DICK TURNED TO ME WITH A SMILE AND SAID "WE DON`T USUALLY SHOW THE CUSTOMERS THIS".
BY CONTRAST, I WAS HELPING A BENTLEY MAN TO FIT NEW 4.5 GEARS INTO HIS 3 LITRE BOX AND THE PERSON THAT WAS DISMANTLING THE THE BOX PRIOR TO GIVING IT TO ME FOR THE CONVERSION, JUST COULD NOT REMOVE THE STEERING ARM. HE TRIED EVERYTHING HE COULD WITH THE FACILITIES AT HIS DISPOSAL BUT TO NO AVAIL! I TOOK THE PARTLY DISMANTLED BOX TO THAT BLACKSMITH GENIUS THE LATE DAVE WILSON, EXPECTING HIM TO GET OUT THE HEAVY BLACKSMITH TOOLS AND COMMENCE THE VIOLENCE, BUT NO, HE LIFTED THE BOX ASSEMBLY BY THE END OF THE LEVER AND LET IT DANGLE. USING A 5 LB HAMMER, HE GAVE THE BOSS OF THE LEVER A SHARP CLOUT AND THE LEVER AND SHAFT PARTED COMPANY!
THE STEERING BOX WILL HAVE TO BE SENT TO A PRECISION ENGINEERING COMPANY TO GET IT MODIFIED TO BM 3333 STATUS THE MOUNTING BRACKET DOES NOT NEED TO BE CHANGED, JUST GIVE IT A GOOD CLEAN AND REMOVE ANY BURRS AND PUT IT AWAY UNTIL NEEDED.
THE NEW PARTS THAT YOU WILL NEED ARE:
BM 3327 STEERING WORM
BN 3328 WORM WHEEL
BM 3330 PACKING RING STEERING BOX
BM 3331 BALL BEARING HOUSING (STEERING BOX).
BM 3329 SHAFT (WORM WHEEL).
BM 3332 PACKING RING STEERING BOX (THE LARGE ONE BETWEEN THE STEERING BOX AND BRACKET)
BY CONTRAST, I WAS HELPING A BENTLEY MAN TO FIT NEW 4.5 GEARS INTO HIS 3 LITRE BOX AND THE PERSON THAT WAS DISMANTLING THE THE BOX PRIOR TO GIVING IT TO ME FOR THE CONVERSION, JUST COULD NOT REMOVE THE STEERING ARM. HE TRIED EVERYTHING HE COULD WITH THE FACILITIES AT HIS DISPOSAL BUT TO NO AVAIL! I TOOK THE PARTLY DISMANTLED BOX TO THAT BLACKSMITH GENIUS THE LATE DAVE WILSON, EXPECTING HIM TO GET OUT THE HEAVY BLACKSMITH TOOLS AND COMMENCE THE VIOLENCE, BUT NO, HE LIFTED THE BOX ASSEMBLY BY THE END OF THE LEVER AND LET IT DANGLE. USING A 5 LB HAMMER, HE GAVE THE BOSS OF THE LEVER A SHARP CLOUT AND THE LEVER AND SHAFT PARTED COMPANY!
THE STEERING BOX WILL HAVE TO BE SENT TO A PRECISION ENGINEERING COMPANY TO GET IT MODIFIED TO BM 3333 STATUS THE MOUNTING BRACKET DOES NOT NEED TO BE CHANGED, JUST GIVE IT A GOOD CLEAN AND REMOVE ANY BURRS AND PUT IT AWAY UNTIL NEEDED.
THE NEW PARTS THAT YOU WILL NEED ARE:
BM 3327 STEERING WORM
BN 3328 WORM WHEEL
BM 3330 PACKING RING STEERING BOX
BM 3331 BALL BEARING HOUSING (STEERING BOX).
BM 3329 SHAFT (WORM WHEEL).
BM 3332 PACKING RING STEERING BOX (THE LARGE ONE BETWEEN THE STEERING BOX AND BRACKET)
i BELIEVE THAT THERE ARE SEVERAL SUPPLIERS FOR THE GEARS, PERSONALLY I`VE ONLY USED ORIGINAL 4.5 LITRE STEERING GEARS IN THE PAST SO CANNOT GIVE ADVICE ABOUT THE REPRODUCTION GEARS.
THE GEARS ARE CRITICAL FOR SAFETY AS A FAILURE OF THESE COMPONENTS COULD BE LIFE THREATENING!
THE GEARS ARE CRITICAL FOR SAFETY AS A FAILURE OF THESE COMPONENTS COULD BE LIFE THREATENING!
BUILDING A 4.5 LITRE STEERING COLUMN FROM SCRATCH USING NEW PARTS
IF YOU HAVE LITTLE OR NO ENGINEERING EXPERIENCE THEN I WOULDN`T ADVISE YOU TO TAKE THIS ROUTE.
THE MOST DIFFICULT PART OF THIS EXERCISE IS GETTING CASTINGS MADE, OR IF YOU ARE FEELING RICH, THEN THE BDC VINTAGE SPARES SCHEME CAN SUPPLY THE MACHINED CASTINGS WHEN THEY COME INTO STOCK.
THERE ARE SEVERAL SUPPLIERS OF UNMACHINED CASTINGS OUT THERE IN THE UK AND THE PRICES ARE AFFORDABLE. THIS IS THE WAY I LIKE TO GO AND TAKE THE UNMACHINED CASTINGS TO RELIABLE PRECISION ENGINEERS IN COVENTRY TO HAVE THEM MACHINED.
OF COURSE YOU WILL HAVE TO GET THE DRAWINGS FROM THE BDC! NOW HERE IS A USEFUL TIP. THE BDC HAD THE ORIGINAL INSPECTION DRAWINGS SCANNED SEVERAL YEARS AGO AND CAN PRINT OUT STILL READABLE DRAWINGS IN A SMALLER FORMAT THAN THE ORIGINAL. THIS CAN SAVE YOU A CONSIDERABLE SUM OF MONEY IF YOU ARE BUYING SEVERAL DRAWINGS.(NOTE THAT THIS AVENUE IS NO LONGER AVAILABLE SINCE THE LATE TED AMERY RELINQUISHED HIS POST AS BDC DRAWING CONTROLLER. DRAWINGS ARE ONLY SUPPLIED IN THE ORIGINAL SIZE NOW!).
THE MOST DIFFICULT PART OF THIS EXERCISE IS GETTING CASTINGS MADE, OR IF YOU ARE FEELING RICH, THEN THE BDC VINTAGE SPARES SCHEME CAN SUPPLY THE MACHINED CASTINGS WHEN THEY COME INTO STOCK.
THERE ARE SEVERAL SUPPLIERS OF UNMACHINED CASTINGS OUT THERE IN THE UK AND THE PRICES ARE AFFORDABLE. THIS IS THE WAY I LIKE TO GO AND TAKE THE UNMACHINED CASTINGS TO RELIABLE PRECISION ENGINEERS IN COVENTRY TO HAVE THEM MACHINED.
OF COURSE YOU WILL HAVE TO GET THE DRAWINGS FROM THE BDC! NOW HERE IS A USEFUL TIP. THE BDC HAD THE ORIGINAL INSPECTION DRAWINGS SCANNED SEVERAL YEARS AGO AND CAN PRINT OUT STILL READABLE DRAWINGS IN A SMALLER FORMAT THAN THE ORIGINAL. THIS CAN SAVE YOU A CONSIDERABLE SUM OF MONEY IF YOU ARE BUYING SEVERAL DRAWINGS.(NOTE THAT THIS AVENUE IS NO LONGER AVAILABLE SINCE THE LATE TED AMERY RELINQUISHED HIS POST AS BDC DRAWING CONTROLLER. DRAWINGS ARE ONLY SUPPLIED IN THE ORIGINAL SIZE NOW!).
ABOVE, VIEWS OF THE MAJOR STEERING COLUMN COMPONENTS.
ASSEMBLING THE STEERING BOX
THIS PROCEDURE IS FOR BOTH CONVERSION FROM 3 TO 4.5 AND NEW BUILD 4.5 STEERING COLUMN. ONE OF THE PROBLEMS THAT LATTER DAY MECHANICS HAVE IN ASSEMBLING THE STEERING BOX THAT WAS NOT A PROBLEM FOR THE BENTLEY MOTOR MECHANICS WAS DUE TO THE METHOD OF MACHINING THE COMPONENTS AS EXPLAINED EARLIER, NOW THERE ARE SEVERAL NEW COMPONENTS THAT MIGHT HAVE BEEN MADE BY ENGINEERING SHOPS THAT PERHAPS DON`T FOLLOW STRICT INSPECTION CONTROL OF THEIR WORK AND IN MY EXPERIENCE DON`T MACHINE OUT THE 3 LITRE BOX EXACTLY TO THE ORIGINAL DRAWING BM 3333 EVEN IF THEY HAVE ONE!
HERE IS WHAT I MEAN, ABOVE IS AN EXTRACT FROM BM 3333. SHOWING A PART CROSS SECTION THROUGH THE STEERING BOX CASTING GIVING ADDITIONAL INFORMATION FOR THE INTERNAL PROFILE. PLEASE NOTE THAT THERE IS NO SECTION NUMBER TO IDENTIFY WHERE THIS SECTION IS TAKEN FROM AND IF YOUR MACHINIST DOES NOT READ THIS INFORMATION, THE CASTING MAY NOT BE MACHINED AS IT SHOULD BE AND YOUR WORMWHEEL WILL NOT ALIGN PROPERLY WITH THE CENTRELINE OF THE WORM! THE BENTLEY DRAUGHTSMEN WERE A BIT SLOPPY WHERE IDENTIFYING SECTIONS WERE CONCERNED.
SPECIAL TOOLS NEEDED
WHEN ASSEMBLING THE STEERING BOX, SEVERAL TRIAL ATTEMPTS WILL HAVE TO BE MADE AND TO USE THE BALL BEARINGS IS NOT REALLY AN OPTION AS THE SLIGHT INTERFERENCE FIT WILL HAMPER DIS-ASSEMBLY. I USE SLAVE BEARINGS MACHINED FROM ALUMINIUM TO HELP WITH EASY ASSEMBLY AND DIS-ASSEMBLY DURING THE TRIAL ASSEMBLIES OF THE BOX.
MAKE ALL THE DIMENSIONS ON THE SLAVE BEARINGS TO MINUS ONE THOUSANDTH OF AN INCH FROM NOMINAL TO GIVE A NICE SLIDING FIT IN THE BORES AND ON THE SHAFTS.
MAKE ALL THE DIMENSIONS ON THE SLAVE BEARINGS TO MINUS ONE THOUSANDTH OF AN INCH FROM NOMINAL TO GIVE A NICE SLIDING FIT IN THE BORES AND ON THE SHAFTS.
ABOVE IS SHOWN AN EXAMPLE OF THE ALUMINIUM SLAVE BEARINGS THAT I USE. ALSO SHOWN ARE THE SKF BEARINGS THAT I PREFER TO USE IN THE FINAL ASSEMBLY, THESE ARE MADE IN ITALY, HAVE PLASTIC SHIELDS EITHER SIDE OF THE BALLS AND ARE LUBRICATED FOR LIFE. IF USING THIS TYPE OF BEARING, THEN THE RATHER PRIMITIVE SEAL ON THE WORMWHEEL SHAFT CAN BE OMITTED. ALSO THE SEALS PREVENT DUST AND RUST PARTICLES FROM FALLING INTO THE BEARING AND SHORTEN IT`S LIFE, WHEN USED IN THE UPPER POSITION ON THE WORM SHAFT. IT`S NOT STRICTLY NECESSARY BUT I USE THESE SHIELDED BEARINGS IN ALL FOUR POSITIONS IN THE STEERING BOX, THEN THE ONLY PLACE THAT THE BOX LUBRICATING OIL CAN ESCAPE IS FROM BETWEEN THE FLANGES BETWEEN THE BOX AND THE MOUNTING BRACKET.
ABOVE, VIEWS OF THE DEVICE USED TO MEASURE THE STANDOUT OF THE WORMWHEEL SHAFT.
ABOVE, THE DEVICE IS COBBLED TOGETHER USING BITS FROM THE SCRAP BOX AND THE WAY IT WILL BE USED TO GIVE YOU PERFECT ALIGNMENT BETWEEN THE WORM AND WORMWHEEL WILL BE EXPLAINED LATER. OF COURSE I COULD HAVE MADE A ROLLS ROYCE JOB OF IT BUT THIS DEVICE IS ADEQUATE FOR THE NUMBER OF TIMES THAT IT WILL BE USED. THE STAND OUT CAN BE MEASURED USING EITHER SLIP GAUGES OR A DIGITAL CALIPER AS SHOWN. NOTE THAT THE HEAD OF THE BOLT HAS BEEN MACHINED CIRCULAR AND WITH A SLIGHT RADIUS TO HELP THE TAKING OF THE MEASUREMENT. THIS SET UP IS ALL THAT IS NEEDED TO MEASURE WITHIN A COUPLE OF THOUSANDTHS OF AN INCH.
CHECKING THE IMPORTANT DIMENSIONS OF THE STEERING BOX
NOT STRICTLY NECESSARY BUT IT WILL HELP TO SOLVE PROBLEMS THAT ARISE WHEN ASSEMBLING THE BOX AS IT TAKES ONE UNKNOWN VALUE OUT OF THE EQUATION. BELOW IS A METHOD THAT I USE TO CHECK THE DIMENSION BETWEEN THE GEAR SHAFT AXES. AGAIN IT`S MADE UP FROM BITS OUT OF THE SCRAP BOX BUT GIVES GOOD RESULTS.
ABOVE LEFT, THREE OF THE SLAVE BEARINGS ARE SLID ONTO A 30mm BRIGHT DRAWN MILD STEEL SHAFT AND ASSEMBLED WITH THE BEARING CARRIER. ABOVE RIGHT, THE ASSEMBLY IS SLID INTO POSITION IN THE BOX. AT THE RIGHT OF THE BOX IS SHOWN AN ALUMINIUM ROUND NOT MORE THAN 2 7/8 DIAMETER WITH A 16mm LENGTH TURNED DOWN TO 62mm DIAMETER TO SLIDE EASILY INTO THE BORE OF THE SHAFT SUPPORT BEARING. I TURNED THE TWO DIAMETERS AT THE SAME TIME BY USING A MANDREL TO ENSURE THAT THEY WERE CONCENTRIC. ALSO A BOX OF SLIP GAUGES IS SEEN OPEN READY TO BE USED
ABOVE LEFT, THE ALUMINIUM ROUND INSERTED INTO THE BEARING BORE AND THE SLAVE BEARING SLID INTO POSITION ABOVE THE CENTRELINE OF THE ROUND BY EYE. THEN BY USING SLIP GAUGES WRUNG TOGETHER THE CORRECT GAP BETWEEN THE TWO DIAMETERS CAN BE FOUND BY TRIAL AND ERROR, IN THIS CASE THE GAP WAS FOUND TO BE 0.282".
THE TWO DIAMETERS WERE THEN MEASURED AND FOUND TO BE 2.437" AND 2.873" DIAMETER. THE DISTANCE BETWEEN THE AXES WAS FOUND BY ADDING THE TWO DIAMETERS TOGETHER AND HALVING THE SUM AND ADDING THE GAP DIMENSION:
X = 2.437 + 2.873 / 2 + 0.282 = 2.937" THE REQUIRED DISTANCE BETWEEN CENTRES ON BM 3333 IS 2 15/16 ( 2.9375) DUE TO THE WAY THAT I MEASURED THE DIMENSION MY RESULT SHOULD BE WITHIN ABOUT 0.002" OF NOMINAL WHICH INDICATES THAT THE PRECISION ENGINEERS THAT MACHINED THIS NEW BOX WERE UP TO SCRATCH.
THE TWO DIAMETERS WERE THEN MEASURED AND FOUND TO BE 2.437" AND 2.873" DIAMETER. THE DISTANCE BETWEEN THE AXES WAS FOUND BY ADDING THE TWO DIAMETERS TOGETHER AND HALVING THE SUM AND ADDING THE GAP DIMENSION:
X = 2.437 + 2.873 / 2 + 0.282 = 2.937" THE REQUIRED DISTANCE BETWEEN CENTRES ON BM 3333 IS 2 15/16 ( 2.9375) DUE TO THE WAY THAT I MEASURED THE DIMENSION MY RESULT SHOULD BE WITHIN ABOUT 0.002" OF NOMINAL WHICH INDICATES THAT THE PRECISION ENGINEERS THAT MACHINED THIS NEW BOX WERE UP TO SCRATCH.
THE NEXT CRITICAL DIMENSION TO BE FOUND IS THE DIMENSION BETWEEN THE AXES OF THE GEARS
PROFESSIONAL GEAR CUTTERS HAVE MACHINES WHERE THEY CAN SET UP THE GEARS AND FIND THE EXACT DIMENSION BETWEEN THE AXES. I DON`T HAVE ONE SO USE THE SIMPLE SET UP SHOWN ABOVE.
THE GEAR IS CLAMPED TO THE ANGLE PLATE USING WORKSHOP GRADE SLIP GAUGE PACKING TO BRING THE WHEEL TO THE CENTRE OF THE PINION AND IS MESHED TIGHTLY WITH THE PINION WHICH IS RESTING ON THE SURFACE PLATE. USING A HEIGHT GAUGE THAT IS SET UP WITH SLIP GAUGES THE LOWER DIMENSION OF THE WORMWHEEL BORE CAN BE FOUND RELATIVE TO THE SURFACE PLATE.
THEN IT`S JUST A QUESTION OF ADDING, DIVIDING AND SUBTRACTION TO FIND THE DIMENSION. IN THIS CASE, THE DISTANCE BETWEEN THE TWO AXES IS 2.927, THUS GIVING 10 THOUSANDTHS OF AN INCH CLEARANCE BETWEEN THE WORM AND THE WHEEL WHEN MOUNTED IN THE BOX.
THIS IS A GOOD RESULT AND NOW WE KNOW THAT ANY DIFFICULTY IN ASSEMBLING THE GEARS IN THE BOX IS NOT BECAUSE OF THE CLEARANCE BETWEEN THE GEARS.
THE GEAR IS CLAMPED TO THE ANGLE PLATE USING WORKSHOP GRADE SLIP GAUGE PACKING TO BRING THE WHEEL TO THE CENTRE OF THE PINION AND IS MESHED TIGHTLY WITH THE PINION WHICH IS RESTING ON THE SURFACE PLATE. USING A HEIGHT GAUGE THAT IS SET UP WITH SLIP GAUGES THE LOWER DIMENSION OF THE WORMWHEEL BORE CAN BE FOUND RELATIVE TO THE SURFACE PLATE.
THEN IT`S JUST A QUESTION OF ADDING, DIVIDING AND SUBTRACTION TO FIND THE DIMENSION. IN THIS CASE, THE DISTANCE BETWEEN THE TWO AXES IS 2.927, THUS GIVING 10 THOUSANDTHS OF AN INCH CLEARANCE BETWEEN THE WORM AND THE WHEEL WHEN MOUNTED IN THE BOX.
THIS IS A GOOD RESULT AND NOW WE KNOW THAT ANY DIFFICULTY IN ASSEMBLING THE GEARS IN THE BOX IS NOT BECAUSE OF THE CLEARANCE BETWEEN THE GEARS.
ABOVE, IMAGES OF A "GLEASON" GEAR MESHING MEASURING MACHINE. THIS IS THE TYPE OF MEASURING DEVICE THAT PROFFESSIONAL GEAR CUTTING MACHINE SHOPS USE TO CHECK THE MESHING OF PAIRS OF GEARS. I WOULD LIKE TO HAVE ONE AS IT REALLY MAKES LIGHT WORK OF THE JOB!
ASSEMBLING THE WORMWHEEL WITH THE SHAFT
THE WORMWHEEL MUST BE ASSEMBLED CORRECTLY ONTO THE SHAFT OTHERWISE IT MAY RUN OFF CENTRE WITH THE SHAFT. ONE OF THE BIGGEST ENEMIES OF GOOD ASSEMBLY ARE BURRS ON THE MACHINED PARTS THAT ARE NOT REMOVED COMPLETELY PRIOR TO ASSEMBLY
TAKE SOME TIME TO CHECK THAT THE ADJOINING FACES OF THE WORMWHEEL AND SHAFT ARE FREE OF BURRS AND THEN CHECK THIS BY USING ENGINEERS BLUE AS SHOWN BELOW.
TAKE SOME TIME TO CHECK THAT THE ADJOINING FACES OF THE WORMWHEEL AND SHAFT ARE FREE OF BURRS AND THEN CHECK THIS BY USING ENGINEERS BLUE AS SHOWN BELOW.
ABOVE LEFT, LIGHTLY SMEAR THE FLANGE WITH "STUARTS" MARKING BLUE AND ASSEMBLE WITH THE WORMWHEEL. THE LARGE DIAMETER OF THE BORE IN THE WORMWHEEL AND THE THIN FLANGE ON THE SHAFT CAN MAKE ASSEMBLY DIFFICULT AS ANY OUT OF TRUE MOVEMENT OF THE SHAFT AS IT IS ASSEMBLED WILL CAUSE SOME HEADACHES AS THE FLANGE WILL JAM IN THE BORE. NOW TWIST THE TWO PARTS TOGETHER TO TRANSFER THE BLUE ON TO THE WORMWHEEL. ABOVE RIGHT IS THE MARKING OBTAINED. WE CAN SEE THAT ALTHOUGH I HAD CLEANED THE BURR AWAY FROM THE DRILLED AND REAMED HOLE THERE WAS STILL SOME OF IT LEFT SO THAT THE FLANGE WOULD NOT SIT PROPERLY ON THE WORMWHEEL. I REMOVED THIS AND OTHER BURRS WITH A SCRAPER AND REPEATED THE OPERATION UNTIL THERE WAS AN EVEN BLUEING SHOWING ON THE WORMWHEEL FACE..
ABOVE THE FINISH SCRAPED FACE WITH ADEQUATE MARKING TO SHOW THAT THE FACE IS SUITABLY MATING WITH THE FLANGE ON THE SHAFT. IN THE BACKGROUND MY ORIGINAL TIN OF "STUARTS" MICROMETER BLUE STILL IN USE AFTER OVER 60 YEARS.
ABOVE THE PARTS BEING ASSEMBLED, THE NEXT PROBLEM IS TO GET THE HOLES IN THE PARTS TO ALIGN SO THAT THE BOLTS WOULD PASS THROUGH. I CHECKED THE BOLT DIAMETERS AND SELECTED SIX THAT HAD A NOMINAL DIAMETER OF 0.375 OF AN INCH. I HAD A BATCH THESE MADE BY A BOLT SPECIALIST FROM HIGH TENSILE STEEL AS USUALLY, THE BOLTS THAT ARE COMMERCIALLY AVAILABLE HAVE ROLLED THREADS AND REDUCED DIAMETERS SO THAT THEY ARE NOT ACCURATE ENOUGH. WHAT I DID THEN WAS TO FIND TWO OPPOSITE POSITIONS WHERE THE BOLTS WOULD PASS THROUGH BOTH PARTS AND LIGHTLY NIPPED THEM UP. DON`T FORGET TO CENTRE PUNCH THE TWO PARTS SO THAT THEY CAN BE RE-ASSEMBLED IN THE SAME POSITION.
THEN THE REMAINING HOLES SHOULD BE REAMED WITH AN ACCURATE HAND REAMER AS SHOWN AND THE REMAINING BOLTS ASSEMBLED AND TIGHTENED DIAMETRICALLY TO ENSURE A GOOD SEATING.AFTER REMOVING ANY BURRS CREATED BY THE REAMING OPERATION.
THEN THE REMAINING HOLES SHOULD BE REAMED WITH AN ACCURATE HAND REAMER AS SHOWN AND THE REMAINING BOLTS ASSEMBLED AND TIGHTENED DIAMETRICALLY TO ENSURE A GOOD SEATING.AFTER REMOVING ANY BURRS CREATED BY THE REAMING OPERATION.
ABOVE THE SHAFT ASSEMBLED WITH THE MOUNTING BRACKET. THE SLAVE BEARING IS LOCATED IN POSITION HELD IN BY THE BEARING CAP. THE LARGE PACKING RING IS ASSEMBLED SO THAT IT IS A LIGHT PRESS FIT ON THE FLANGE AND THE SMALLER DIAMETER ADJUSTED TO BE A SLIDING FIT IN THE BODY. THIS IS RECOMMENDED SO THAT THE RING DOES NOT FALL OFF EVERY TIME THAT IT IS DIS-ASSEMBLED. NOTE THAT I HAVEN`T SPLIT PINNED THE BOLTS YET AS THERE ARE TEMPORARY ONES IN PLACE, I WILL FIT THE PROPER BOLTS ONCE I HAVE MACHINED THEM UP AND SPLIT PIN THEM ON FINAL ASSEMBLY.
ABOVE LEFT, THE UPPER WORM SLAVE BEARING IS PLACED IN IT`S BORE AND ABOVE RIGHT, DITTO FOR THE WORMWHEEL SHAFT SLAVE BEARING. NOW ASSEMBLE THE BOX WITH THE BRACKET AND LIGHTLY NIP UP THE BOLTS. THE SITUATION IS NOW AS SHOWN IN SKETCH 1. FOLLOW THE INSTRUCTIONS SHOWN ON THE SKETCH AND OBTAIN DIMENSION A.
AFTER DIMENSION A HAS BEEN OBTAINED THEN ASSEMBLE THE PINION IN THE BOX AS EXPLAINED IN SKETCH 2. THE PHOTO BELOW SHOWS THE PINION IN POSITION
NOW OBTAIN DIMENSION B AS DESCRIBED IN SKETCH 2 BELOW.
NOW OBTAIN DIMENSION C AS SHOWN IN SKETCH 3 BELOW
WHAT WE ARE TRYING TO ACHIEVE IS TO FIND THE DIMENSION "X" FOR THE SMALL PACKING THAT WILL FIX THE POSITION OF THE TEETH CUT IN THE WORMWHEEL ON THE CENTRELINE OF THE WORM.
DIMENSION X.= A - ( B - C + B ) WHICH IN THIS CASE CAME TO 0.017 INCHES.
2
THE SPACER WILL HAVE TO BE MACHINED ON A LATHE SO THAT THE BOX CAN BE FINALLY ASSEMBLED AND THE POSITION OF THE WORMWHEEL RELATIVE TO THE WORM GIVEN A FINAL CHECK.
DIMENSION X.= A - ( B - C + B ) WHICH IN THIS CASE CAME TO 0.017 INCHES.
2
THE SPACER WILL HAVE TO BE MACHINED ON A LATHE SO THAT THE BOX CAN BE FINALLY ASSEMBLED AND THE POSITION OF THE WORMWHEEL RELATIVE TO THE WORM GIVEN A FINAL CHECK.
TROUBLE SHOOTING
WHEN ASSEMBLING NEW COMPONENTS INTO THE STEERING BOX, PROBABLY DUE TO THE COMPONENTS NOT BEING MADE TO THE BENTLEY DRAWINGS THERE MAY BE INACCURACIES THAT WILL CAUSE PROBLEMS THAT ARE NORMALLY ONLY DISCOVERED DURING ASSEMBLY.
ABOVE IS SKETCH 4 WHICH OUTLINES POSSIBLE PROBLEMS IN THE STEERING BOX ASSEMBLY.
ABOVE IS SHOWN THE FLATS BEING MACHINED ON ONE OF THE SPECIAL BOLTS USED TO CLAMP THE PINION FRONT BEARING CARRIER IN PLACE.
ABOVE ARE SHOWN SOME OF THE SPECIAL CLOSE TOLERANCE BOLTS THAT ARE NEEDED FOR THE STEERING BOX. I MACHINED THESE FROM HIGH TENSILE STEEL A BIT OF A BORING REPETITIVE JOB BUT IT HAD TO BE DONE!
SPLIT PINNING THE WORM GEAR MOUNTING BOLTS
JUST A FEW WORDS TO DESCRIBE HOW I SPLIT PIN BOLTS AS THIS SEEMINGLY SIMPLE TASK CAN BE CHALLENGING AND EFFORT HAS TO BE MADE TO CARRY OUT THIS WORK SO THAT IT IS SIMPLE TO DO AND SIMPLE TO UNDO! THERE IS NOTHING MORE BORING THAN HAVING TO MACHINE THE WASHERS THAT ARE UNDERNEATH THE NUTS THAT ARE TO BE PINNED, TO ALLOW THE SLOTS IN THE NUTS TO BE ALIGNED WITH THE HOLES IN THE BOLTS! NEITHER IS IT DESIRABLE TO OVER TORQUE THE BOLTS TO ACHIEVE THIS.
WHEN I BUY IN OR MAKE BOLTS THAT ARE TO BE PINNED, I BUY OR MAKE THEM WITHOUT THE PIN HOLES, THEN ON ASSEMBLY, TORQUE UP THE NUTS TO THE REQUIRED VALUE AND THEN CHOOSING ONE OF THE SLOTS IN THE NUT WHERE THE PIN, WILL BE IN A POSITION FOR CONVENIENT ASSEMBLY OR DIS-ASSEMBLY, MARK THE BOLT BY SPOTTING WITH A DRILL THE SAME DIAMETER AS THE WIDTH OF THE SLOT.
IN THE CASE OF THE WORM WHEEL THAT HAS SIX BOLTS TO BE PINNED, THE PROCEDURE IS TO CLEAN UP ALL THE MATING SURFACES AND THEN ASSEMBLE THE BOLTS THROUGH THE WHEEL AND THE FLANGE AND TIGHTEN UP THE NUTS DIAGONALLY TO THE REQUIRED TORQUE, THEN SPLIT PIN THEM INDIVIDUALLY BY REMOVING THEM ONE BY ONE AS SHOWN IN THE PHOTOS BELOW.
WHEN I BUY IN OR MAKE BOLTS THAT ARE TO BE PINNED, I BUY OR MAKE THEM WITHOUT THE PIN HOLES, THEN ON ASSEMBLY, TORQUE UP THE NUTS TO THE REQUIRED VALUE AND THEN CHOOSING ONE OF THE SLOTS IN THE NUT WHERE THE PIN, WILL BE IN A POSITION FOR CONVENIENT ASSEMBLY OR DIS-ASSEMBLY, MARK THE BOLT BY SPOTTING WITH A DRILL THE SAME DIAMETER AS THE WIDTH OF THE SLOT.
IN THE CASE OF THE WORM WHEEL THAT HAS SIX BOLTS TO BE PINNED, THE PROCEDURE IS TO CLEAN UP ALL THE MATING SURFACES AND THEN ASSEMBLE THE BOLTS THROUGH THE WHEEL AND THE FLANGE AND TIGHTEN UP THE NUTS DIAGONALLY TO THE REQUIRED TORQUE, THEN SPLIT PIN THEM INDIVIDUALLY BY REMOVING THEM ONE BY ONE AS SHOWN IN THE PHOTOS BELOW.
IN THE LHS PHOTO ABOVE YOU CAN SEE THE DIMPLE IN THE BOLT THAT HAS BEEN MADE BY A DRILL WHILE THE BOLT WAS IN-SITU AND NOW THE BOLT HAS BEEN REMOVED FOR DRILLING THE PIN HOLE.
ON THE ABOVE RHS PHOTO YOU CAN SEE HOW I CENTRE THE BOLT IN THE VICE FOR DRILLING. SUBTRACTING THE DIAMETER OF THE DRILL FROM THE BOLT DIAMETER AND HALVING IT, I USE A SLIP GAUGE OF THAT DIMENSION TO CHECK THAT THE DIMPLE IS CENTRAL .
ON THE ABOVE RHS PHOTO YOU CAN SEE HOW I CENTRE THE BOLT IN THE VICE FOR DRILLING. SUBTRACTING THE DIAMETER OF THE DRILL FROM THE BOLT DIAMETER AND HALVING IT, I USE A SLIP GAUGE OF THAT DIMENSION TO CHECK THAT THE DIMPLE IS CENTRAL .
THE LHS ABOVE PHOTO SHOWS THE DRILLED HOLE BEING SLIGHTLY COUNTERSUNK TO REMOVE JAGGED EDGES THAT COULD PREVENT THE PINS FROM SLIDING THROUGH. AFTER COUNTERSINKING I RUN A DIE OVER THE THREAD TO REMOVE ANY OTHER JAGGED EDGES THAT COULD BE THERE TO PREVENT THE FREE RUNNING OF THE NUT. THEN THE BOLT IS RE ASSEMBLED AND PINNED.
THE RHS ABOVE PHOTO SHOWS HOW I`VE ORIENTED THE PINS TO MAKE ASSEMBLY AND DIS-ASSEMBLY EASY.
THE RHS ABOVE PHOTO SHOWS HOW I`VE ORIENTED THE PINS TO MAKE ASSEMBLY AND DIS-ASSEMBLY EASY.
ABOVE, THE FINAL RESULT! HOPEFULLY KNOBBY CLARKE THE EX RFC SHOP MANAGER AT BENTLEY MOTORS WOULD HAVE APPROVED BLESS HIM!
FINAL ASSEMBLY OF THE STEERING BOX
FIRSTLY DRIVE ,PRESS OR DRAW IN THE BALL BEARINGS, STARTING WITH THE ONE AT THE TOP END OF THE PINION. THIS HAS TO BE INSERTED BEFORE ALL THE OTHERS AS OTHERWISE YOU WILL NOT BE ABLE TO GAIN ACCESS TO THE HOUSING. THEN INSERT THE BEARING INTO THE INNER WORM WHEEL SHAFT BORE AFTER HAVING PLACED IN THE ALL IMPORTANT PACKING RING. INSERT THE BEARING INTO THE BORE FOR THE OUTER SPINDLE BEARING AND INSERT THE SHAFT.
ASSEMBLE THE SHAFT AND THE STEERING BOX MOUNTING FOOT ASSEMBLY INTO THE STEERING BOX CASTING TOGETHER WITH THE LARGE PACKING RING..
ASSEMBLE THE PINION INTO THE STEERING BOX UNTIL IT IS FULLY TO THE SHOULDER OF THE BEARING.
THEN INSERT THE BEARING INTO THE BALL BEARING HOUSING AND PUSH THIS INTO THE FRONT BORE OF THE BOX, THEN LIGHTLY TAP IT UNTIL THE BEARING IS FULLY ENGAGED ON THE PINION.
INSERT THE BOLTS THAT LOCK THE HOUSING IN POSITION AND ADJUST IT TO GIVE A LIGHT PRELOAD WITH A LENGTH OF 1/4" BAR INSERTED INTO THE HOLES IN THE HOUSING THAT CAN BE ACCESSED VIA THE OIL FILLER HOLE IN THE TOP OF THE BOX. THEN TORQUE THE BOLTS UP AND SPLIT PIN THEM
ASSEMBLE THE SHAFT AND THE STEERING BOX MOUNTING FOOT ASSEMBLY INTO THE STEERING BOX CASTING TOGETHER WITH THE LARGE PACKING RING..
ASSEMBLE THE PINION INTO THE STEERING BOX UNTIL IT IS FULLY TO THE SHOULDER OF THE BEARING.
THEN INSERT THE BEARING INTO THE BALL BEARING HOUSING AND PUSH THIS INTO THE FRONT BORE OF THE BOX, THEN LIGHTLY TAP IT UNTIL THE BEARING IS FULLY ENGAGED ON THE PINION.
INSERT THE BOLTS THAT LOCK THE HOUSING IN POSITION AND ADJUST IT TO GIVE A LIGHT PRELOAD WITH A LENGTH OF 1/4" BAR INSERTED INTO THE HOLES IN THE HOUSING THAT CAN BE ACCESSED VIA THE OIL FILLER HOLE IN THE TOP OF THE BOX. THEN TORQUE THE BOLTS UP AND SPLIT PIN THEM
ABOVE A VIEW OF THE FRONT END OF THE BOX WITH THE INTERNAL PARTS ASSEMBLED AND THE HOUSING BOLTS TORQUED UP AND SPLIT PINNED. THE 1/4" BSF STUDS HAVE ALSO BEEN INSERTED.
ABOVE LEFT, THE END CAP THAT KEEPS THE WORM SHAFT IN POSITION SHOULD BE TIGHTENED TO GIVE A LIGHT PRELOAD TO THE BEARINGS. THERE IS NO PROVISION ON THE CAP TO DO THIS AND THE WAY THAT I DO IT TO PREVENT DAMAGE TO THE CAP IS TO USE A LENGTH OF STOUT WEBBING AND A PAIR OF MOLE GRIPS AND USE THE TOGGLE ACTION OF THE MOLE GRIP WHILE GRIPPING THE WEBBING TO TORQUE IN SOME PRELOAD.
THE RIGHT HAND PHOTO SHOWS THE BEST WAY TO DRILL THE HOLE FOR THE 1/8" DIAMETER LOCKING WIRE, BETTER THAN BY HAND! THEN INSERT THE LOCKING WIRE WHICH IS QUITE DIFFICULT.
LOUSY DETAIL DESIGN BY "MONKEY" BURGESS BUT BENTLEYS DIDN`T CHANGE IT FOR PRODUCTION!
THEY RADICALLY IMPROVED THE DESIGN FOR THE 6.5 LITRE, THE NEXT BENTLEY TO BE PUT INTO PRODUCTION,
THE RIGHT HAND PHOTO SHOWS THE BEST WAY TO DRILL THE HOLE FOR THE 1/8" DIAMETER LOCKING WIRE, BETTER THAN BY HAND! THEN INSERT THE LOCKING WIRE WHICH IS QUITE DIFFICULT.
LOUSY DETAIL DESIGN BY "MONKEY" BURGESS BUT BENTLEYS DIDN`T CHANGE IT FOR PRODUCTION!
THEY RADICALLY IMPROVED THE DESIGN FOR THE 6.5 LITRE, THE NEXT BENTLEY TO BE PUT INTO PRODUCTION,
ABOVE LEFT, THE PLATE THAT LOCKS THE STEERING COLUMN CONTROLS IS PLACED IN POSITION AND ABOVE RIGHT THE WITCHES HAT PLACED ON TOP AND BOLTED TO THE BOX. CASTLE NUTS NOT NECESSARY BUT I JUST LIKE THE LOOK OF THEM!
ATTACHING THE STEERING COLUMN SHAFT TO THE STEERING PINION
NOW THIS IS A NICE PIECE OF DESIGN, BOTH BELT AND BRACES, TO KEEP THESE, IMPORTANT FOR SAFETY, COMPONENTS IN A LIFE LONG EMBRACE!
ABOVE, TWO VIEWS OF THE SAME COMPONENTS IN THE LHS PHOTO THE MUFF COUPLING THAT HOLDS THE TWO PARTS TOGETHER IS SHOWN ABOVE AND BELOW THIS THE COLUMN TUBE AND BELOW THIS, THE STEERING GEAR PINION.
PLEASE NOTE THAT THE COMPONENTS ARE SO DESIGNED THAT THEY ARE ALL LOCKED TOGETHER BY THE BRACE OF HIGH TENSILE BOLTS THAT DO THIS POSITIVELY BY BEING THROUGH DRILLED ALL THREE COMPONENTS.
THE RHS PHOTO SHOWS THE SAME COMPONENTS NOW TURNED, WITH THE EXCEPTION OF THE MUFF COUPLING, THROUGH 180 DEGREES SO THAT THE KEYWAYS MACHINED INTO THE COMPONENTS CAN BE SEEN.
THE KEY WHICH IS INSERTED IN BOTH THE TUBE AND THE PINION IS SHOWN BELOW THEM..
PLEASE NOTE THAT THE COMPONENTS ARE SO DESIGNED THAT THEY ARE ALL LOCKED TOGETHER BY THE BRACE OF HIGH TENSILE BOLTS THAT DO THIS POSITIVELY BY BEING THROUGH DRILLED ALL THREE COMPONENTS.
THE RHS PHOTO SHOWS THE SAME COMPONENTS NOW TURNED, WITH THE EXCEPTION OF THE MUFF COUPLING, THROUGH 180 DEGREES SO THAT THE KEYWAYS MACHINED INTO THE COMPONENTS CAN BE SEEN.
THE KEY WHICH IS INSERTED IN BOTH THE TUBE AND THE PINION IS SHOWN BELOW THEM..
ABOVE, THROUGH DRILLING THE 21/64" HOLES IN THE COLUMN TUBE. THE MUFF COUPLING IS CLAMPED IN POSITION ON THE TUBE, MAKING SURE THAT THE KEY SLOT IS IN THE CORRECT ORIENTATION WITH IT, AND A PLUG HAS TO BE PLACED IN THE TUBE SO THAT THE DRILL DOES NOT WANDER DURING DRILLING. THIS PROCEDURE IS BEST CARRIED OUT ON A DRILLING MACHINE.
ABOVE, WITH THE MUFF COUPLING ASSEMBLED ON THE TUBE BUT PUSHED UPWARDS CLEAR OF THE KEY SLOT, THE TUBE IS SLID ONTO THE PINION AND THE PREVIOUSLY MACHINED KEY PUSHED INTO THE SLOT TO ENGAGE WITH BOTH THE TUBE AND THE PINION (THE KEY IN THE PHOTO IS SHOWN SLIGHTLY PROUD FOR CLARITY, THE TOP OF THE KEY SHOULD BE PROFILED FLUSH WITH THE TUBE.
THEN THE MUFF COUPLING IS SLID INTO POSITION OVER THE KEY AND THE PRE DRILLED HOLES IN THE TUBE, THEN THE BOLTS INSERTED, TORQUED UP AND SPLIT PINNED. NOTE THAT BECAUSE OF THE CLOSE PROXIMITY OF THE NUT TO THE INSIDE RADIUS OF THE ALUMINIUM TUBE THE PINS SHOULD BE INSERTED AND BENT OVER AS SHOWN TO PREVENT CONTACT WITH THE TUBE. CHECK THE CLEARANCE BETWEEN THE MUFF COUPLING ASSEMBLY AND THE INNER DIAMETER OF THE TUBE BY PLACING A STRAIGHT EDGE ON THE OUTER DIAMETER OF THE STEERING BOX AND ROTATE THE TUBE TO SEE IF THE COUPLING CLEARS THE TUBE.
ASSEMBLING THE ALUMINIUM TUBE
THE 3" DAMETER WITH A WALL THICKNES 0,08" THAT SUPPORTS THE TOP BEARING OF THE COLUMN SHAFT IS SURPRISINGLY STRONG AND THE WAY THAT IT IS ATTACHED TO THE STEERING BOX AT THE LOWER END AND THE BEARING AT THE UPPER END, LOOSELY FOLLOWS THE DESIGN OF THE MUFF COUPLING BUT WITHOUT BEING KEYED IN POSITION.
HERE IS A SHOT OF THE SLITS IN THE TUBE BEING MACHINED.
ABOVE IS SHOWN THE TUBE BEING ASSEMBLED WITH THE STEERING BOX AND THE TOP BEARING. WITH THE STEERING BOX HELD IN THE VICE AND WITH THE ALLY TUBE PUSHED ONTO IT, USING A SPIRIT LEVEL CHECK THAT THE CLAMP IS ASSEMBLED IN THE CORRECT ORIENTATION, CLAMP THIS IN POSITION WITH A "G" CLAMP AND DRILL THROUGH THE CLAMP BOLT HOLE FROM EITHER SIDE UNTIL THE DRILL BREAKS THROUGH.
REMOVE THE TUBE AND HOLDING IT IN THE VICE WITH THE CLAMP IN POSITION, DRILL THROUGH THE TUBE AND THE TOP BEARING USING THE SAME PROCEDURE AFTER USING THE SPIRIT LEVEL TO DETERMINE THAT THE UPPER TUBE CLAMP IS IN EXACTLY IN THE SAME ORIENTATION AS THE LOWER. IN THE PHOTOS YOU CAN SEE THAT THE BOLTS HAVE TO BE SHORTENED TO SUIT ASSEMBLY.
REMOVE THE TUBE AND HOLDING IT IN THE VICE WITH THE CLAMP IN POSITION, DRILL THROUGH THE TUBE AND THE TOP BEARING USING THE SAME PROCEDURE AFTER USING THE SPIRIT LEVEL TO DETERMINE THAT THE UPPER TUBE CLAMP IS IN EXACTLY IN THE SAME ORIENTATION AS THE LOWER. IN THE PHOTOS YOU CAN SEE THAT THE BOLTS HAVE TO BE SHORTENED TO SUIT ASSEMBLY.
MACHINING UP THE WITCHES HAT
ALTHOUGH I USUALLY HAVE MY TAME PRECISION ENGINEERS IN COVENTRY CARRY OUT THE DIFFICULT MACHINING FOR ME, THE COLUMN CONTROL COVER BM 1816 BETTER KNOWN AS THE "WITCHES HAT" FOR OBVIOUS REASONS, HAS LITTLE IN THE WAY OF PRECISION ABOUT IT TO WORRY A MEDIOCRE TURNER SUCH AS MYSELF.
I FORGOT TO TAKE A PHOTO OF THE CASTING BEFORE STARTING THE MACHINING BUT THIS PHOTO OF THE ROUGHED OUT VERSION IS PRETTY WELL AS THE ORIGINAL CASTING LOOKED. THE CASTING ALREADY HAD THE APERTURE FOR THE CONTROL LEVERS CAST INTO IT AND THIS PRESENTS PROBLEMS, AS A FIXED STEADY CAN`T BE USED TO STEADY THE CASTING FOR MACHINING INSIDE THE BORE.
ABOVE LEFT IS THE WAY THAT I TACKLED THE SUPPORT PROBLEM. IT`S IMPORTANT TO FIND THE ACTUAL TAPER OF THE CONE AND NOT USE THE DRAWING AS THE CASTING MAY DIFFER SLIGHTLY! ONCE THE TOP SLIDE IS SET OVER DO NOT CHANGE THIS SETTING UNTIL THE MACHINING IS FINISHED! THIS ENSURES THAT THE INNER AND OUTER TAPERS WILL BE PARALLEL. I BOLTED SOME CUT OFF PLANKS OF WOOD TO THE FACEPLATE AND THEN MACHINED THE TAPERED HOLE INTO THEM. NOTE THAT THE BORING TOOL IS PLACED UPSIDE DOWN AND THE TAPER IS MACHINED FROM THE FAR SIDE WITH THE SPINDLE ROTATING IN THE NORMAL SENSE.
IN THE RHS PHOTO THE CASTING HAS BEEN LIGHTLY TAPPED INTO THE HOLE TO GIVE ADHESION TO THE ROUGHLY TURNED WOOD. THEN THE INTERNAL TAPER IS CLEANED UP USING THE SAME TOOL AND SETTING.
IN THE RHS PHOTO THE CASTING HAS BEEN LIGHTLY TAPPED INTO THE HOLE TO GIVE ADHESION TO THE ROUGHLY TURNED WOOD. THEN THE INTERNAL TAPER IS CLEANED UP USING THE SAME TOOL AND SETTING.
ABOVE LHS, I`VE GRIPPED A LENGTH OF 50mm STEEL BAR IN THE THREE JAW AND MACHINED IT WITH THE MALE TAPER NOW WITH THE CUTTING TOOL IN THE FRONT OF THE BAR AND IN THE RHS PHOTO I`VE TAPPED THE CASTING ONTO THIS TAPER AND CENTRE DRILLED THE OTHER END AFTER MAKING SURE THAT THE CASTING IS RUNNING TRUE. THEN PUT A CENTRE INTO THE TAILSTOCK BARREL SO THAT THIS END OF THE CASTING IS SUPPORTED WHILE MACHINING.
IN THE LHS PHOTO ABOVE, I`VE FINISHED MACHINED THE OUTER TAPER DIAMETER AND ROUGHED OUT THE FRONT OF THE FLANGE WITH A TEMPORARY STEP TO ACCEPT THE LITTLE DRILLING TEMPLATE THAT WILL BE USED FOR DRILLING THE MOUNTING HOLES. THEN IN THE RHS PHOTO I`VE REVERSED THE CASTING IN THE LATHE SO THAT THE REAR OF THE FLANGE AND DIAMETER CAN BE FINISH MACHINED.
ABOVE LEFT IS SHOWN THE DRILL TEMPLATE IN POSITION ON THE FLANGE MAKING SURE THAT THE HOLES WILL BE IN THE CORRECT ORIENTATION ACCORDING TO THE DRAWING. ABOVE RIGHT YOU CAN SEE THE STEP ON THE FLANGE AND THAT THE HOLES HAVE BEEN DRILLED. THE NEXT STEP IS TO MOUNT THE CASTING IN THE LATHE AGAIN AND FINISH MACHINE THE FRONT OF THE FLANGE.
ABOVE TWO VIEWS OF THE FINISHED ARTICLE. HERE IS ANOTHER CASE WHERE THE ORIGINAL BENTLEY DRAWING IS NOT THE SAME AS THE ACTUAL PARTS THAT WERE PRODUCED!
ON THE ORIGINAL BROKEN WITCHES HATS THAT I HAVE, OBVIOUS FROM THE CUTTING MARKS IN THE APERTURE, THAT IT WAS CUT OUT BY HAND AND THE DIMENSIONS OF THE CUT OUT DIFFER FROM THOSE ON THE DRAWING!
I FILED THE CUT OUT IN THE CASTING TO THE DIMENSIONS ON THE ORIGINAL BENTLEY PART, NOT THE DRAWING!
ON THE ORIGINAL BROKEN WITCHES HATS THAT I HAVE, OBVIOUS FROM THE CUTTING MARKS IN THE APERTURE, THAT IT WAS CUT OUT BY HAND AND THE DIMENSIONS OF THE CUT OUT DIFFER FROM THOSE ON THE DRAWING!
I FILED THE CUT OUT IN THE CASTING TO THE DIMENSIONS ON THE ORIGINAL BENTLEY PART, NOT THE DRAWING!
IMPORTANT INFORMATION AND REMARKS ON ASSEMBLING THE STEERING COLUMN
WHEN LOOKING AT THE OUTSIDE OF THE STEERING BOX, ASSEMBLING IT WOULD SEEM A SIMPLE TASK BUT THE WORK INVOLVES A LOT OF FIDDLY PROCEDURES, THAT IF NOT CARRIED OUT CORRECTLY, WILL RESULT IN DISAPPOINTMENT AS TO IT`S FUNCTION AND POSSIBLE DANGER!
IT IS ESSENTIAL THAT PROPER FITTED HIGH TENSILE BOLTS BE USED IN THE CRITICAL AREAS AND CARE SHOULD BE TAKEN TO SOURCE THESE FROM A RELIABLE SUPPLIER.
IN THE ABOVE ASSEMBLY THE STEERING RATIO PINION IS A GENUINE BENTLEY ONE ORIGINALLY MANUFACTURED BY ENV AND CRACK DETECTED BEFORE USE AND THE BRONZE WORM WHEEL MADE TO SUIT THE PINION BY A RELIABLE GEAR CUTTING COMPANY. THE RESULT IS A COLUMN THAT IS BEAUTIFULLY SMOOTH IN OPERATION AND WITH MINIMUM BACK LASH BETWEEN THE GEARS. THIS HAS NOW FOUND A NEW OWNER.
IT IS ESSENTIAL THAT PROPER FITTED HIGH TENSILE BOLTS BE USED IN THE CRITICAL AREAS AND CARE SHOULD BE TAKEN TO SOURCE THESE FROM A RELIABLE SUPPLIER.
IN THE ABOVE ASSEMBLY THE STEERING RATIO PINION IS A GENUINE BENTLEY ONE ORIGINALLY MANUFACTURED BY ENV AND CRACK DETECTED BEFORE USE AND THE BRONZE WORM WHEEL MADE TO SUIT THE PINION BY A RELIABLE GEAR CUTTING COMPANY. THE RESULT IS A COLUMN THAT IS BEAUTIFULLY SMOOTH IN OPERATION AND WITH MINIMUM BACK LASH BETWEEN THE GEARS. THIS HAS NOW FOUND A NEW OWNER.
ABOVE IS AN EXAMPLE OF WHAT I`VE BEEN TALKING ABOUT, THE 5/16" BSF CASTLE NUT ON THE RIGHT WAS BOUGHT AT THE BEAULIEU AUTO JUMBLE SEVERAL YEARS AGO FROM ONE OF THOSE SUPPLIERS THAT SELL NUTS AND BOLTS IN PLASTIC BAGS.. WHEN I USED ONE FOR THE MUFF COUPLING ON A PREVIOUS STEERING COLUMN REBUILD, TO MY HORROR, THE THREADS IN THE NUT JUST PULLED OUT WHEN TORQUED UP BECAUSE OF THE POOR QUALITY OF THE STEEL!
THE CASTLE NUT ON THE LEFT IS ONE OF A BATCH MADE FOR ME BY "BROCOL" A COMPANY IN COVENTRY THAT WILL SUPPLY DIFFICULT TO FIND IMPERIAL FASTENERS TO ORDER. ORIGINALLY RECOMMENDED TO ME BY THE LATE PETER BUTLER, THEY SUPPLY QUALITY.!
THE CASTLE NUT ON THE LEFT IS ONE OF A BATCH MADE FOR ME BY "BROCOL" A COMPANY IN COVENTRY THAT WILL SUPPLY DIFFICULT TO FIND IMPERIAL FASTENERS TO ORDER. ORIGINALLY RECOMMENDED TO ME BY THE LATE PETER BUTLER, THEY SUPPLY QUALITY.!