The saying “if it isn’t broken don’t fix it” springs to mind, and for sure the mainstream AEC engines of the 1950s and 1960s weren’t broken. I also seem to recall that even as recently as the 1980s all the major engine manufacturers were publicly stating that a 12 litres capacity diesel was the optimum size for all existing and forseeable power requirements. There were numerous article in CM about this topic.
gingerfold:
The saying “if it isn’t broken don’t fix it” springs to mind, and for sure the mainstream AEC engines of the 1950s and 1960s weren’t broken. I also seem to recall that even as recently as the 1980s all the major engine manufacturers were publicly stating that a 12 litres capacity diesel was the optimum size for all existing and forseeable power requirements. There were numerous article in CM about this topic.
The idea that 12 litres + is good works fine as shown by the F12.The difference is that Volvo’s designers didn’t lumber the thing with a 142 mm stroke measurement just like Rolls and ■■■■■■■ long before that or the 760.On that note going by your example of the 1930’s choice of 142mm at 8.8 litre shows something went seriously wrong with AEC’s thinking as overall capacity increased.In which case it certainly was broke and needed fixing in the form of maintaining that type of bore/ stroke ratio in its larger capacity designs. 
Seeing how Dicksee, Pomeroy, Ricardo and Durrant all seem to have made the same mistake, I just wonder who it was in Detroit, with the advantage of another three or four years to laugh at their mistake, decided that 5 inches (127mm) was the way to go? Can we name him so that he can be pilloried as well?
cav551:
Seeing how Dicksee, Pomeroy, Ricardo and Durrant all seem to have made the same mistake, I just wonder who it was in Detroit, with the advantage of another three or four years to laugh at their mistake, decided that 5 inches (127mm) was the way to go? Can we name him so that he can be pilloried as well?
As I’ve said more would have been better but sharing the load across a power stroke every revolution of the engine is an apples v oranges comparison.On that note great if only AEC had increased the stroke of the V8 to 127 mm and then made it a two stroke,in production for 1957 not 1968.Together with a 136 x 152 TL13 from 1965,in answer to the 260 Eagle,they might have got somewhere. 
cav551:
Seeing how Dicksee, Pomeroy, Ricardo and Durrant all seem to have made the same mistake, I just wonder who it was in Detroit, with the advantage of another three or four years to laugh at their mistake, decided that 5 inches (127mm) was the way to go? Can we name him so that he can be pilloried as well?
Yes, Cedric Dicksee is well worth a mention as an acclaimed engine man. Just looking at the list of all the AEC engine variants available up to the 1960s for numerous applications then the reluctance, if there was one, to change a fundamental design is understandable. I also believe that a horizontal version of an engine needs a considerable amount of reworking and as a knowledgeable bus man CAV551 you might confirm that.
“But what if… then surely…in which case…” blah blah blah !
To answer the thread title Why did British Leyland fail ?
They never had Carryfast running the design team ! 
No engine is faultless but the AV760/TL12 seem to be on the end of repetitive criticism but with no justification. The AV760 wasnt known to be troublesome and neither was the TL12 . So they had probably reached the end of their development but im yet to hear anyone complain about the performance of either. If there had been endless warranty claims then yes but there wasnt . Shouldnt it be a pat on the back for the original designers and their successors who managed to develop these engines over the years . Not bad for a flawed design.
ramone:
No engine is faultless but the AV760/TL12 seem to be on the end of repetitive criticism but with no justification. The AV760 wasnt known to be troublesome and neither was the TL12 . So they had probably reached the end of their development but im yet to hear anyone complain about the performance of either. If there had been endless warranty claims then yes but there wasnt . Shouldnt it be a pat on the back for the original designers and their successors who managed to develop these engines over the years . Not bad for a flawed design.
Firstly the combined production life of the 760 and TL12 covered less than 20 years.By which point it predictably ran out of development potential at around 63 lb/ft per litre torque output .The relevant customers didn’t bother to complain about its performance because they walked away and specced ■■■■■■■ or Rolls from the assembly operations or bought the foreign in house competition instead.
The result being that Leyland Trucks had to join those assembly operations in using outsourced engines in order to offload what should have been the mostly in house T45 at least in terms of engine fit.Thereby removing the business case for Leyland Trucks as an in house manufacturer.I don’t think that’s any reason for cigars for it’s designers.
Carryfast:
ramone:
No engine is faultless but the AV760/TL12 seem to be on the end of repetitive criticism but with no justification. The AV760 wasnt known to be troublesome and neither was the TL12 . So they had probably reached the end of their development but im yet to hear anyone complain about the performance of either. If there had been endless warranty claims then yes but there wasnt . Shouldnt it be a pat on the back for the original designers and their successors who managed to develop these engines over the years . Not bad for a flawed design.Firstly the combined production life of the 760 and TL12 covered less than 20 years.By which point it predictably ran out of development potential at around 63 lb/ft per litre torque output .The relevant customers didn’t bother to complain about its performance because they walked away and specced ■■■■■■■ or Rolls from the assembly operations or bought the foreign in house competition instead.
The result being that Leyland Trucks had to join those assembly operations in using outsourced engines in order to offload what should have been the mostly in house T45 at least in terms of engine fit.Thereby removing the business case for Leyland Trucks as an in house manufacturer.I don’t think that’s any reason for cigars for it’s designers.
Or you could look at it from another angle , that the 760/TL12 were the final chapter of a range of engines that first saw the light of day in the 30s such was the brilliance of the designers that they had foreseen the future of the diesel engine and put together something that could be developed over the years and sold to umpteen countries around the world where they would work in extreme weather conditions with what could be described as excellent reliability. What these designers didnt foresee was … Carryfast
There are numerous alterations for a horizontal version of an engine. The manufacturers of the period varied in what they did, but a few changes would be swapping the gudgeon pin offset from the thrust to the anti thrust side of the piston, retaining a previously deleted oil control ring in the piston skirt, different rocker arm oil feed drillings and different oil sealing arrangements for the rocker cover and injection pump. The obvious external differences are the repositioning of the oil filter, fuel filter, injection pump and/or the coolant pump thus requiring a new drive system and most noticeably a totally different sump with internal transfer pump. The coolant fan drive solutions were very varied. The one thing which causes the most potential grief is that the saloon heaters are always above the level of the radiator top tank and often above the header tank as well.
Horizontal engines also tend to wear out more quickly. The AEC AH 505 very rapidly gained an unfortunate reputation. Edit add: which was mainly to do with incorrect dipsticks being supplied and an unreliable coolant fan drive.
ramone:
Or you could look at it from another angle , that the 760/TL12 were the final chapter of a range of engines that first saw the light of day in the30s such was the brilliance of the designers that they had foreseen the future of the diesel engine and put together something that could be developed over the years and sold to umpteen countries around the world where they would work in extreme weather conditions with what could be described as excellent reliability. What these designers didnt foresee was … Carryfast
Or possibly thought that AEC engineering was so invincible they didn’t need to look at what ■■■■■■■ and Rolls were doing. 
Whatever the flaws in the 760 and TL12, as Ramone says, the engine worked for many years, I myself spent a lot of my childhood on top of a 760 and it never broke down once, unlike the F88 that followed it, not that the Volvo was unreliable, but it did drop a valve and that caused a bit of a catastrophic chain reaction within the engine, the 760 had no such problems, so I can absolutely say that the AEC lump was better than the Volvo.
Now history has proven that the 760 was at the end of its potential in the TL12 version, just as every other engine on offer at that time was to become at some point in the future. The same applies to the engines in the lorries on the market today, the newest designs like the DD in Daimler products, the MX range in Paccar etc etc will all become obsolete in the future. Engineers will do what engineers do and try to push the boundaries with revolutionary new designs, but they will have the benefit of hindsight, so they will know not to try and produce a monobloc design, or a gas turbine, but they will also look at the failed designs of their own engineering departments too and there will be many to choose from, a visit to any of the manufacturer’s museums will show you that there have been all kinds of weird and wonderful efforts at redesigning the way we power our lorries, up to now the only things that have changed from the first diesel engines to the most modern engines are pretty basic, the fundamentals remain the same.
Developments have been, OHC, multivalve heads, turbochargers, intercoolers, electronics and stronger lighter materials with better manufacturing tolerances. All of the other Carlos Fandango ideas have failed in one way or another. However the difference between the situation at the other manufacturers and BL was the real problem, none of its rivals had a car division hemorrhaging cash, so alongside their revolutionary designs that failed, they also had a more mainstream alternative to put out, BL never had this luxury, the three projects mentioned here, compact V8, 500 series and Gas Turbine swallowed up the complete R&D budget that was left after the car division had drained the piggy bank, so BL trucks became collateral damage in the fiasco that was created not by designers or engineers, but by politicians.
Carryfast:
ramone:
Or you could look at it from another angle , that the 760/TL12 were the final chapter of a range of engines that first saw the light of day in the30s such was the brilliance of the designers that they had foreseen the future of the diesel engine and put together something that could be developed over the years and sold to umpteen countries around the world where they would work in extreme weather conditions with what could be described as excellent reliability. What these designers didnt foresee was … CarryfastOr possibly thought that AEC engineering was so invincible they didn’t need to look at what ■■■■■■■ and Rolls were doing.
Yeah youre right AEC should have been watching what ■■■■■■■ and Rolls were doing in the 30s ■■?
After rail traction, inner city service bus operation is probably the most taxing duty for an engine. The repeated heat cycling causes indigestion. The following quote from ‘Ian’s Bus Stop’ about the introduction of the vertical, rear mounted 0 680 powered Leyland Atlantean gives some idea.
“All did not go smoothly. The maintenance regime at London Transport was based around the phenomenal and unusual reliability of the RT and RF, with the RM close behind. LT was not used to the kind of mechanical failure rate considered normal elsewhere. Coupled with a strange mechanical layout, inevitable conservative prejudice and a preoccupation with having a handbook for everything, this caused grief in engineering departments.
A major problem was thermal expansion. In heavy traffic (either vehicular or passenger), the long idle times while stopped caused expansion along the main coupled axis of engine, flywheel and gearbox. As these were all mounted as a unit, the expansion stresses tended to pop the thrust bearings.”
RT = AEC Regent III, RF = AEC Regal IV, RM = AEC Routemaster
cav551:
After rail traction, inner city service bus operation is probably the most taxing duty for an engine. The repeated heat cycling causes indigestion. The following quote from ‘Ian’s Bus Stop’ about the introduction of the vertical, rear mounted 0 680 powered Leyland Atlantean gives some idea.“All did not go smoothly. The maintenance regime at London Transport was based around the phenomenal and unusual reliability of the RT and RF, with the RM close behind. LT was not used to the kind of mechanical failure rate considered normal elsewhere. Coupled with a strange mechanical layout, inevitable conservative prejudice and a preoccupation with having a handbook for everything, this caused grief in engineering departments.
A major problem was thermal expansion. In heavy traffic (either vehicular or passenger), the long idle times while stopped caused expansion along the main coupled axis of engine, flywheel and gearbox. As these were all mounted as a unit, the expansion stresses tended to pop the thrust bearings.”RT = AEC Regent III, RF = AEC Regal IV, RM = AEC Routemaster
I remember Scania double deckers joining the Bradford fleet in or around 74 - 75 , they made the local T & A newspaper , but for all the wrong reasons i can`t remember if it was engine or gearbox problems ,i think it was the latter but they cost a fortune
An urban bus experiences different temperature changes compared to a highway vehicle, constant stop/start work and a lot of sitting on tickover plus possibly slogging uphill results in excessive engine wear.
Pete.
Carryfast seems to have a real downer on AEC I think he must have had an unfortunate incident with one.
Possibly one run over his foot at the council depot
windrush:
An urban bus experiences different temperature changes compared to a highway vehicle, constant stop/start work and a lot of sitting on tickover plus possibly slogging uphill results in excessive engine wear.Pete.
Carryfast has a downer on nearly everything British and successful from what I can make out, maybe he’s one of those left wing apologists.
kr79:
Carryfast seems to have a real downer on AEC I think he must have had an unfortunate incident with one.
Possibly one run over his foot at the council depot
newmercman:
Carryfast has a downer on nearly everything British and successful from what I can make out, maybe he’s one of those left wing apologists.kr79:
Carryfast seems to have a real downer on AEC I think he must have had an unfortunate incident with one.
Possibly one run over his foot at the council depot
To be fair my argument is all about the definition of successful while British can be taken as a given.In which case going by Ramone’s idea of counting timelines which was more successful the Rolls with its origins in the 1950’s in terms of bore and stroke design choice.Or the 760/TL12 with its origins who knows where but logically if we’re discussing Leyland Group’s fortunes then the relevant point in time is the design and introduction of the 760.Bearing in mind that Leyland Group had no relationship with AEC before the 1960’s.On that note what would have happened to the Crusader and T45 sales without the Rolls choice being there and having been reliant on the 760 and TL12 instead.Also bearing in mind Saviem’s comments about the Rolls powered T45’s understandable popularity with its customers.
My thoughts from Aus.
I’d think there was plenty of subterfuge from Leyland distributors once away from the UK, if the Aus. trucks were anything to go by.
The tilting LAD cab, why not from Leyland many years before the ERGO? It would have given that old cab at least another 5-years life by which time the ERGO’s obvious design faults would have been sorted by home office. I loved that LAD cab, wasn’t the only one and the short door version was also popular with some odd Beaver/Hippos appearing locally.
Do you remember the appalling quality plastic of those years. That ERGO instrument binnacle would be a broken mess in a few weeks. Leyland was giving away their “new” GRP version but owners had to do the install themselves and what a mission that was.
Here in Aus, our regulations deemed a foot/hand control for trailer braking, a big piece of kit and normally “U” bolted around the steering column. Couldn’t do that on the ERGO so the binnacle had to be hacked to fit the trailer brake. Yes that lovely trailer brake valve we’d see in the UK brochures went straight to the bin here.
In West Aus. the locals (ref Dig) fitted the ERGO 680/690 with a water pump driven fan. Chucked that rubbish harmonic balancer mounted plastic thing, enlarged the radiator and cowl and suddenly no overheating problems.
The Maudsley diff problems…………
The lead time from the UK for a chassis meant the locals had to take a punt on forward orders, so 6 and 8-wheelers became the usual order. Gave the boys something to cut back to suit customer’s needs, plus an endless supply of tailshaft spares, cross members etc.
I saw a fair order for 8-wheeler AEC’s go through, but the client wouldn’t have a bar of AEC’s engine, wanted the turbo 680 so engines were removed from Beavers/Hippos, whatever was in the yard and swapped across.
The locals stripped down the brand new AEC’s and built up these odd trucks. You should have seen the pile of left over bits.
The semi auto box was another problem for Leyland and AEC. Could have been great but due to overheating it just cooked the oil. No speed interlocks also meant the slightest bump to the splitter button when at max rpm and you had rods out through the passenger’s feet.
Moving to the R/R manual box took way too long.
So you really had to be a dyed in the wool Leyland lover to continue with this brand, especially when their gun sales team had seen the writing on the wall and shifted across to Volvo.
Dumping, yes it was rife from Leyland in the mid 70’s, anything to sell a truck. They were the cheapest “large” truck around.
International finally had a half decent truck with pretty big Neuss or ■■■■■■■ engines available right up to the VT903.
Plenty of models from Mack,Volvo, Merc, Man, Scania and even Deutz was selling trucks!!! (Of course their spare parts was selling cylinder heads faster than the sales section was selling trucks)
And the US trucks were finally within the reach of operators. KW picked up the big name clients, fuel companies mainly who had previously been Leyland’s mainstream.
W.S. was assembled locally in the same factory as DAF. (I’d never heard of DAF)
Road speeds had changed too thus a plodding Octopus or Mandator was no longer viable. No engine braking so they couldn’t even make it across a set of traffic lights stuck in low gear. Something with a close ratio box and engine braking would out-accelerate most cars. And coming down mountain ranges without an engine brake, horse and buggy stuff, downright dangerous.
And this was mainly the larger sized trucks.
The smaller single drive stuff was all going to the Japs. who were offering far greater cab comfort, exhaust brake and usually a turbo engine making a heap of power considering the truck’s capacity.
Leyland countered with rubbish like the 4-cylinder Chieftan, they could not give them away.
The whole Albion range was dreadfully dated, not enough hp and even when the 410 ■■ (turbo 400) was fitted, it came in the non-tilting LAD cab, a truck from a past era.
The V8 BMC/Mastiff however wasn’t half bad but it also needed time for modification until it was reliable. The end truck with big Eaton diff plus R/R box was popular even though the cab comfort was still well behind the Japs.
I never saw the T45 Roadtrain?? out here, looked like a winner compared to the 8V71 GM non-tilting Crusaders, but the show was over.