Railstaff you’ve unfortunately fell into the bottomless pit of pointless argument and discussion that many before you have when replying to or trying to make sense of the ramblings of our dear CF. I never go back to a thread once his machinations and unfathomable statements begin to appear. I only return to see how many of those trying to have a sensible debate have turned into jabbering wrecks with no will to live, (your close to it but saveable) you will find your life takes on a new and refreshing outlook once you stop even attempting to decipher the process he uses to put his opinions across. There should be a warning next to his posts saying beware this could easily explode into verbal diarrhoea if replied to! 
Franky.
railstaff:
What I know of the 800 series could have easy been cured,the premature failure of the mains
As I read it big end and piston ring issues ?.Not to mention totally grenading engines ( rod failure ? ) conveniently blamed on drivers over revving the things.Obviously with no way of actually recording the supposed engine speeds in question.
While I’m not disputing the general design difficulties facing everyone in the day.What I’ve said is the stated premise that shows that AEC were prioritising the erroneous idea of maximising piston area,at the expense of leverage at the crank,with predictable results regarding stress levels in the piston to crank component chain.
Which is why many customers went for the opposite extreme of minimising the amount of force and maximising the amount of leverage in the form of the Gardner.Until ■■■■■■■ at least among others got the combination right in the form of the turbocharged 855.
As for V8’s the even the ■■■■■■■ 903 predictably didn’t take the market by storm let alone the AEC 800 in the way that the Scania and Merc did.Remind us what were all their respective stroke measurements. 
Dinna fret yersel Railstaff ! Matron will by now have removed “CF”'s lap top and given him his medication then he will have been returned to his cell, sorry, secure accommodation for the night. If he does start playing up as the Meds wear off a bloke in a White coat will fire a Taser at him through the peep hole then they stick him in a straight jacket for the rest of the night. He’s worst when it’s Full Moon as his rantings get worse mainly about the attributes of Detroit Diesels which he seems to think are superior to Gardners ! Really ! 
Oh! I’m actually in the next cell ! 
Don’t take him too seriously mate ! Cheers Bewick.
Railstaff,
Great advice by Dennis, the CF Thing is doing my head in as well 
42 years in this Business and often losing the will to carry on after reading his infectious posts, and now he has already taken over the Petrol v Diesel thread, in simplicity (something he has not heard of with his over complication of everything he touches) I wish I could have an hour with him in the real world!!! 
on 2nd thoughts maybe he is best kept under matrons orders
E.W.
Bewick:
He’s worst when it’s Full Moon as his rantings get worse mainly about the attributes of Detroit Diesels which he seems to think are superior to Gardners ! Really !
To be fair somehow I actually said that a Gardner 8 LXB was superior to an AEC V8 or TL12.
railstaff:
…What I know of the 800 series could have easy been cured,the premature failure of the mains was put down to not enough surface area and the oiling hole in the wrong place,the overheating was mainly due to the fan having a direct drive off the crank pulley,again lifting the cab could have ment relocation of fan and geared up the fan speed.Another problem seemed to be injectors sticking open,did the fuel pump not include delivery valves.All easy stuff to remedy.
There was the option to use harder materials for the bearings. IIRC, this was tried, with some success. The cooling problem was more complex- the routing of the coolant in the heads left the engine prone to hot spots. I think there was also an issue of too-short con rods? Again, I am only saying what I remember from reading this thread. You will have to trawl all the way through the thread, for confirmation of these recollections. Good luck. I look forward to your opinions.
Carryfast:
newmercman:
Why are we comparing the Paccar MX engine which is less than 10yrs old with an engine that hasn’t been built for over 30yrs (TL12) ■■?Because it proves that hp isn’t dependent on piston area just like the Rolls Eagle did v the TL12 40 years ago.In all cases BMEP ( specific torque ) being the usually accepted figure.Which is why DAF obviously chose to stay with the bore size of the old DK engine when going from 11.6 to around 13 litre.That obviously being less than the TL12’s.Probably also why ■■■■■■■ reduced the bore diameter of the ISX from that of the N14 in the move up to 15 litre.
I am unsure of how “he isn’t dependent on piston area”. The formula for engine power is Power = PLAN where P is Mean Effective Pressure, L is length of stroke, A is piston area and N is power strokes per second. If piston area is increased for the same MEP etc you get more power. Simple first principles.
The AEC had a long history of cooling issues with its post war engines. The late Colin Curtis, who was later to become vehicle engineering manager and head of the experimental department at London Transport, mentions in his “40 years with London Transport” that the 9.6 engine suffered at one point. As was a typical career path in the 1940s, having graduated in engineering he became apprenticed to the AEC where he progressed to the experimental department. While there he became involved in the investigation of engine seizure affecting the newly introduced A204 & 208 series engines.
Paraphrasing: ‘…which was traced to an inadequate water supply to the cylinders. By fitting transparent side cover plates it was seen that the water flow around the cylinders reduced almost to nothing as it proceeded from no 1 to no 6 cylinder. The problem arose because the water flow entered and left the cylinder heads at the front of the engine. A modification to create a flow in at the front and out at the back cured the problem’.
Silverdale:
Carryfast:
newmercman:
Why are we comparing the Paccar MX engine which is less than 10yrs old with an engine that hasn’t been built for over 30yrs (TL12) ■■?Because it proves that hp isn’t dependent on piston area just like the Rolls Eagle did v the TL12 40 years ago.In all cases BMEP ( specific torque ) being the usually accepted figure.Which is why DAF obviously chose to stay with the bore size of the old DK engine when going from 11.6 to around 13 litre.That obviously being less than the TL12’s.Probably also why ■■■■■■■ reduced the bore diameter of the ISX from that of the N14 in the move up to 15 litre.
I am unsure of how “he isn’t dependent on piston area”. The formula for engine power is Power = PLAN where P is Mean Effective Pressure, L is length of stroke, A is piston area and N is power strokes per second. If piston area is increased for the same MEP etc you get more power. Simple first principles.
Within that formula you can obviously create power by increasing MEP and L at the expense of A and N.So no power isn’t ‘dependent’ on piston area.It’s a combination of all of those and they can all be interchanged.
IE MEP is just based on specific torque ( torque per litre ) which means the overall capacity is a given ( fixed ).Which by definition means force on a ‘given’ ( fixed ) piston area x distance in the form of throw of the crank ( L ).You can’t increase piston area unless you also reduce the stroke to maintain the same overall capacity.Which means less leverage at the crank and more force required through the con rod to compensate for the lost leverage to retain the equivalent specific torque.The usual result of a too short stroke being a net reduction in specific torque MEP because you can’t compensate for the lost leverage with more force without more stress and risk of breaking things.Leaving the worst of all worlds option of the combination of more force and more engine speed.To the point of a net increase in piston speed,for the equivalent power output.
While the description given in the article suggests that they were concentrating their attention on and prioritising A and N at the expense of P and L.The result being that they ended up with a worse MEP than the Gardner and a more highly stressed engine for the privilege.Bearing in mind that the design ethos for a truck engine is all about making as much power as possible for the least engine speed which means maximising P and L and minimising A and N to get the equivalent power output.
Carryfast:
railstaff:
What I know of the 800 series could have easy been cured,the premature failure of the mainsAs I read it big end and piston ring issues ?.Not to mention totally grenading engines ( rod failure ? ) conveniently blamed on drivers over revving the things.Obviously with no way of actually recording the supposed engine speeds in question.
While I’m not disputing the general design difficulties facing everyone in the day.What I’ve said is the stated premise that shows that AEC were prioritising the erroneous idea of maximising piston area,at the expense of leverage at the crank,with predictable results regarding stress levels in the piston to crank component chain.
Which is why many customers went for the opposite extreme of minimising the amount of force and maximising the amount of leverage in the form of the Gardner.Until ■■■■■■■ at least among others got the combination right in the form of the turbocharged 855.
As for V8’s the even the ■■■■■■■ 903 predictably didn’t take the market by storm let alone the AEC 800 in the way that the Scania and Merc did.Remind us what were all their respective stroke measurements.
In all fairness it was conrod bearings they seemed to suffer with,my mistake for referring to mains,as for the 903 take a look how many the military took and still use.Although slightly looked up on as being too big for automotive application.To explain that fully so it is understood and not questioned, due to the angle of the vee and around 15 litre displacement it may have posed a problem fitting it in parallel frame back in the late 70,s.Im fully aware Merc and MAN made vee engines but their frames were intergrated and swept down at the front.
railstaff:
In all fairness it was conrod bearings they seemed to suffer with,my mistake for referring to mains,as for the 903 take a look how many the military took and still use.Although slightly looked up on as being too big for automotive application.To explain that fully so it is understood and not questioned, due to the angle of the vee and around 15 litre displacement it may have posed a problem fitting it in parallel frame back in the late 70,s.Im fully aware Merc and MAN made vee engines but their frames were intergrated and swept down at the front.
In our application it was generally the choice between using the 903 or the Detroit options in which the former understandably met with more customer resistance than the latter.With the 903 having a reputation for being a grenade similar to the AEC again for similar reasons.In which case,by the standards of the day,the reduction in stress levels,provided by replacing the induction stroke with another power stroke,thereby almost halving the load on the engine components,in addition to having a longer stroke than the 903,made the choice between the AEC V8 or the ■■■■■■■ 903,as opposed to Detroit,a no brainer.Which seems to have also been confirmed in the case of Scammell’s choice for the Crusader.While Merc and Scania obviously also went for a relatively decent stroke length,compared to the AEC and the 903,in the case of their V8’s.
Carryfast:
windrush:
Have to admit that our two 250 ■■■■■■■ engined Fodens did manage around four years before requiring work so about the same time span as the Patricroft product. They were sold on after six years anyway and no more came, it was Rolls all the way then until Tilcon sold the fleet off. No AEC V8’s were bought either!Pete.
Bewick wasn’t exactly known for his fleet of AEC V8 powered Ergos either for some reason.
While to be fair the TL12 probably would have been fine in 6 and 8 wheeler rigids well into the 1980’s.So what did Leyland do they put the fixed head wonder in them instead.
Which leaves the question why was the 680 the motor of choice in the Scammell Routeman 8 wheeler and not the TL12 which would seem to be its natural home if anywhere ?.
Because there was no requirement, or demand, for a 273 bhp eight-wheeler in the 1970s. The Leyland O.680 at 200 bhp was deemed powerful enough for 30 tons gvw. Eight-wheeler tippers, of which the vast majority of Routemans were, didn’t exactly spend their time on Motorway long haul work. Honestly, it’s not rocket science to get the answer if you knew the 1970s truck market.
railstaff:
I’m sorry to say as a new member I’m starting to find this frustrating.You(CF) have no idea over the design problems engine manufactures face.When AEC were producing engines they were no worse than any other manufacture,■■■■■■■ have had plenty of problems over the years I don’t mind admitting,Volvos 290 hp TD100 was a complete wash out,Scanias vee eight had issues cracking blocks across the main housings,MANs D25/D28 had a variety of issues,the Rolls Eagle had liner protrusion problems cured in the end with the back bone gasket.The TL12 was one of the most reliable probably due to leaving the HP low(er).What I know of the 800 series could have easy been cured,the premature failure of the mains was put down to not enough surface area and the oiling hole in the wrong place,the overheating was mainly due to the fan having a direct drive off the crank pulley,again lifting the cab could have ment relocation of fan and geared up the fan speed.Another problem seemed to be injectors sticking open,did the fuel pump not include delivery valves.All easy stuff to remedy.
Don’t lose heart railstaff, your knowledgeable contributions are very welcome and please continue to keep us informed. Amidst all the written verbosity that typify Carryfast’s posts, occasionally, he will post something worthwhile that makes one think “erm he might have a point there”. (Can’t believe I’ve just written that… 
)
Graham, that kind of nonsense will not be tolerated here!
In all seriousness though, I’ve learned a lot from posts disagreeing with the insane ramblings from the Leatherhead Loony, he comes out with his “No brainers” and somebody who knows what they’re talking about posts a factual response. As frustrating as he is, in a twisted logic kind of way, he actually benefits the threads he infects. Ironic isn’t it.
Sent from my SM-G950W using Tapatalk
gingerfold:
Carryfast:
Which leaves the question why was the 680 the motor of choice in the Scammell Routeman 8 wheeler and not the TL12 which would seem to be its natural home if anywhere ?.Because there was no requirement, or demand, for a 273 bhp eight-wheeler in the 1970s. The Leyland O.680 at 200 bhp was deemed powerful enough for 30 tons gvw. Eight-wheeler tippers, of which the vast majority of Routemans were, didn’t exactly spend their time on Motorway long haul work. Honestly, it’s not rocket science to get the answer if you knew the 1970s truck market.
We know for a fact that the Rolls 265 was being specced in 6 wheelers in the day.As for powerful enough I’d guess this isn’t anywhere near 30t.
youtube.com/watch?v=FVE8s5aXkQs
Ironically I’d guess that a derated TL12 ( 240 hp ? ) put in rigids would have been a much better option for all concerned than the NA 680 let alone the headless wonder at least.
Carryfast:
railstaff:
In all fairness it was conrod bearings they seemed to suffer with,my mistake for referring to mains,as for the 903 take a look how many the military took and still use.Although slightly looked up on as being too big for automotive application.To explain that fully so it is understood and not questioned, due to the angle of the vee and around 15 litre displacement it may have posed a problem fitting it in parallel frame back in the late 70,s.Im fully aware Merc and MAN made vee engines but their frames were intergrated and swept down at the front.In our application it was generally the choice between using the 903 or the Detroit options in which the former understandably met with more customer resistance than the latter.With the 903 having a reputation for being a grenade similar to the AEC again for similar reasons.In which case,by the standards of the day,the reduction in stress levels,provided by replacing the induction stroke with another power stroke,thereby almost halving the load on the engine components,in addition to having a longer stroke than the 903,made the choice between the AEC V8 or the ■■■■■■■ 903,as opposed to Detroit,a no brainer.Which seems to have also been confirmed in the case of Scammell’s choice for the Crusader.While Merc and Scania obviously also went for a relatively decent stroke length,compared to the AEC and the 903,in the case of their V8’s.
What exactly was “in our application?”
Do you have reference to 903 “grenading” besides a snippet on you tube.They were thought to be bombproof,besides the cambushs spinning which was easy to diagnose as the idle speed decreased.In Aus they ran along side the 3408 and were loved.
Carryfast:
Silverdale:
Carryfast:
newmercman:
Why are we comparing the Paccar MX engine which is less than 10yrs old with an engine that hasn’t been built for over 30yrs (TL12) ■■?Because it proves that hp isn’t dependent on piston area just like the Rolls Eagle did v the TL12 40 years ago.In all cases BMEP ( specific torque ) being the usually accepted figure.Which is why DAF obviously chose to stay with the bore size of the old DK engine when going from 11.6 to around 13 litre.That obviously being less than the TL12’s.Probably also why ■■■■■■■ reduced the bore diameter of the ISX from that of the N14 in the move up to 15 litre.
I am unsure of how “he isn’t dependent on piston area”. The formula for engine power is Power = PLAN where P is Mean Effective Pressure, L is length of stroke, A is piston area and N is power strokes per second. If piston area is increased for the same MEP etc you get more power. Simple first principles.
Within that formula you can obviously create power by increasing MEP and L at the expense of A and N.So no power isn’t ‘dependent’ on piston area.It’s a combination of all of those and they can all be interchanged.
IE MEP is just based on specific torque ( torque per litre ) which means the overall capacity is a given ( fixed ).Which by definition means force on a ‘given’ ( fixed ) piston area x distance in the form of throw of the crank ( L ).You can’t increase piston area unless you also reduce the stroke to maintain the same overall capacity.Which means less leverage at the crank and more force required through the con rod to compensate for the lost leverage to retain the equivalent specific torque.The usual result of a too short stroke being a net reduction in specific torque MEP because you can’t compensate for the lost leverage with more force without more stress and risk of breaking things.Leaving the worst of all worlds option of the combination of more force and more engine speed.To the point of a net increase in piston speed,for the equivalent power output.
While the description given in the article suggests that they were concentrating their attention on and prioritising A and N at the expense of P and L.The result being that they ended up with a worse MEP than the Gardner and a more highly stressed engine for the privilege.Bearing in mind that the design ethos for a truck engine is all about making as much power as possible for the least engine speed which means maximising P and L and minimising A and N to get the equivalent power output.
Something tells me you do not understand diesel engine engineering principles or physics. Power is dependent on all of the items in the formula - change any of tne conditions and it will affect the output - but to blithly state power is independent of piston area is not only wrong, it is disingenuous. As with all science years of experiment and experience have found the best balance between PLAN to give what is the optimum at present - that is not to say it will change to something else in the future.
I remember Volvo saying that the 12litre inline six was the optimum engine size, it was after one of the updates to the D12. The next upgrade to the D12 was an increase in cubic capacity to make it the D13. Things are constantly changing these days.
Back in the 50s and early 60s, there wasn’t so much change, you wanted more power, you added cubic capacity, the average power rating was around the 150 to 180hp range.
Then in the late 60s, turbocharged engines started appearing in lorries, it was a revolution, but not all manufacturers adopted the philosophy, FIAT, MAN, Mercedes Benz and Scania being four big players that carried on adding cubes by adding cylinders to create V8s and V10s in the case of Mercedes and MAN (it was a joint venture along with rear axles) AEC had a bash at a V8 too, but because of internal politics and the requirement for it to fit under an Ergomatic cab, it wasn’t a great success, so it got binned. Next on their list was updating the AV760 to incorporate turbocharging.
Then nothing much happened for a few years, the 70s saw the advent of charge air cooling, either air to air, or water to air. Scania for example had their 8 litre engine available in naturally aspirated form, turbocharged and turbocharged and intercooled. There was overlap between the top power 8 litre and naturally aspirated 11 litre, so that was offered as turbo and turbo intercooled. Along the lines of what the L12, TL12 and had it still been around the TL12i.
Progressive evolution they call it, using the technology and engineering available at the time. The next step would have been electronic fuel control, but nobody at AEC had a crystal ball.
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railstaff:
Carryfast:
What exactly was “in our application?”
Do you have reference to 903 “grenading” besides a snippet on you tube.They were thought to be bombproof,besides the cambushs spinning which was easy to diagnose as the idle speed decreased.In Aus they ran along side the 3408 and were loved.
Let’s get this right I hear in the day that the 903 can be a grenade because they designed it with a too short stroke.Then around 40 years later I go looking for confirmation of what I’d heard then surprise surprise on youtube there’s a 903 with a rod having gone flying through the side of the block together with a comment posted on the vid to exactly the same effect as I’d heard all those years ago. Then not content with that you obviously think that’s not enough so I go looking for more.Then surprise surprise I find this.
thecombineforum.com/forums/606857-post6.html
Ironically the sad part of all that is the unfair stereotypical views that zb short stroke designs like the AEC and the 903 can unfairly create,regarding the V8 configuration,as a whole.
As for ‘our application’.
youtube.com/watch?v=MDUxLjOJrIE
From memory,like the Carmichael example shown here,
fire-engine-photos.com.s3.amazon … /27842.jpg
that chassis type was originally fitted with a VT 903 in it as supplied by Scammell in the form of the Thornycroft Nubian Major 2 which I,for one,didn’t like for its zb power delivery characteristics,although to be fair it didn’t blow up.
But which had obviously then later been based on the firm’s own chassis assembly model after I’d gone and somehow predictably,found itself specced with,the well proven and liked in other types,8v92 in it instead.Just like the Oshkosh HET. Obviously no point in me trying to explain the finer points as to why getting rid of the induction stroke in favour of another power stroke is a game changer regarding the stroke measurement part of the equation and why the customers didn’t choose the 903 in those applications.
Silverdale:
Carryfast:
Within that formula you can obviously create power by increasing MEP and L at the expense of A and N.So no power isn’t ‘dependent’ on piston area.It’s a combination of all of those and they can all be interchanged.rSomething tells me you do not understand diesel engine engineering principles or physics. Power is dependent on all of the items in the formula - change any of tne conditions and it will affect the output - but to blithly state power is independent of piston area is not only wrong, it is disingenuous. As with all science years of experiment and experience have found the best balance between PLAN to give what is the optimum at present - that is not to say it will change to something else in the future.
You’ve contradicted yourself.In that I can make the same or even more power,by increasing specific torque ( P ) by increasing the leverage of crankshaft stroke ( L ) at the expense of reducing piston area ( A ) and engine speed ( N ).So no power obviously isn’t ‘dependent’ on piston area and/or piston speed,as suggested in the article.