[zb]
anorak:Carryfast:
[zb]
anorak:
Have you read Edwardes’ autobiography?No I wouldn’t want to read his lies…
How do you know he’s lying, if you don’t know what he has said?
I’m guessing he didn’t say that turning Rover and Triumph into assemblers of Jap crap front wheel drive cars instead of meeting BMW head on and putting the TL12 in the Roadtrain instead of bringing Rolls in house was a bad thing.
Who cares what he said or did when Stokes was the scape goat for AEC’s and Edwarde’s zb ups.
[zb]
anorak:Carryfast:
[zb]
anorak:
Have you ever put any numbers to any of your statements? Try this: what is the tensile stress in the big end bolts of a TL12 at 2200rpm, under no load, at TDC, between the exhaust and compression strokes?You do know that the inlet stroke starts at around TDC after the exhaust stroke the compression stroke starts at around BDC like the exhaust stroke.
It’s obvious that it just ain’t going to get any more than at TDC between exhaust and inlet strokes at max gorverned engine speed under load or not.
You didn’t answer the question why are main bearing and head fastenings much stronger than big end bearing fastenings.The latter being all that’s stopping the piston and rod assembly going flying away from the crankshaft and under the most tension at which point and engine speed ?.
So WTF has 2 x BMEP got to do with it.It’s obvious that the tensile strength of the big end bearing cap fastenings will need to have a significant margin over over the kinetic energy contained in the piston and rod at max engine speed during the deceleration for the change over between the exhaust and inlet strokes IE massive deceleration followed by massive acceleration.That’s the max possible tensile load on the piston and rod assembly.
That margin doesn’t get close to the margin you’ll need in the main bearing and head fastenings to contain the compressive loadings between piston/rod assembly and the cylinder head during the power stroke at peak torque or for that matter peak power obviously at full load.That’s why blown up MX engines with broken big end fastenings aren’t littering the junk yards.
Also no surprise AEC rightly didn’t have the bottle to boost the TL12 to 100 lb/ft per litre + with an intercooler.^^^Laughable piffle. How many accelerations are there? LOLOL.
How many accelerations are there in which the big end bearing cap fastenings and therefore con rod are under maximum tension ?.
When would that possibly be between Exhaust and Compression.The clue is in the word Compression.What has the compression stroke got to do with TDC and tensile loading of the piston/rod assembly.
Yeah right so show me a main bearing fastening or head fastening with less tensile strength than a big end bearing cap fastening.Let alone all combined.
Oh wait you can’t.Tell us why that is.
Carryfast:
[zb]
anorak:Carryfast:
[zb]
anorak:
Have you read Edwardes’ autobiography?No I wouldn’t want to read his lies…
How do you know he’s lying, if you don’t know what he has said?
I’m guessing he didn’t say that turning Rover and Triumph into assemblers of Jap crap front wheel drive cars instead of meeting BMW head on and putting the TL12 in the Roadtrain instead of bringing Rolls in house was a bad thing.
Who cares what he said or did when Stokes was the scape goat for AEC’s and Edwarde’s zb ups.
If you haven’t read Edwardes’ book, how can you know what his decisions were? If you had, you would know that he had left before the Japanese-origin cars were introduced. The MD at the time was Harold Musgrove. Was he a liar too? 
Just checked a few figures: TL12 vs. RR Eagle 280, as fitted to the Crusader. To BS141Au gross, both had the same power, but the TL12 had an extra 5lbft of torque.
You done any calculations yet, since you chose to name the thread “Engine Design”? If you’re not happy with 2x BMEP as a ballpark figure to start your work, please tell us what peak cylinder pressures you would expect in either of the two engines mentioned above. A number will do- no words necessary.
gingerfold:
Carryfast:
Stokes WASN’T MD of Leyland Group at the time of the 691 and 760’s design stage.The RUN DOWN of Southall COMMENCED in 1977 remind me what was Stoke’s position in the group at THAT point in time and who was MD.
Strange double standards you apply regarding Edwardes.He was MD but supposedly had no input over truck and bus while Stokes did.
Which part of,
Stokes over saw the design and production of your beloved TL12 not Edwardes and Edwardes wiped out AEC along with Leyland truck and bus division along with Rover and Triumph,
didn’t you understand.The Crusader 280 and the Rolls 265 were also bread and butter motors.The difference is they had a reliable 400 hp and 100 lb/ft worth of potential contained within their basic architecture, unlike the TL12 and Edwardes knew it.The rest is history.
Seems to me you’ve got issues with Stokes while at the same time defending those where the real blame sits for this debacle.
Ironically now admiring the foreign competitor’s takeover of the domestic customer base turning us into an assembler of foreign components which was behind it all.
No surprise that the end result of all that is a business plan based on a 123 x 152 11 litre and 130 X 162 13 litre motor.
I have never written that Stokes was MD in 1962 when the A691 / A760 was in the design stage. Markland signed-off the project as I have said on numerous occasions. It must really have hurt Stokes to approve the TL12 development based on the AV760, but even he realised that there wasn’t another group engine suitable.
Don Ryder took over the running of BL at nationalisation in 1975. By then everyone had realised how useless Stokes was as a Chief Executive, but in his new position as Non-Executive President he still had advisory powers. Stokes hated AEC because even as the “super-salesman” he had lost out on numerous occasions in competitive negotiations with customers and potential customers who placed orders with AEC. He tolerated senior AEC people such as Bob Fryars because even Stokes realised that there wasn’t anyone on the Leyland (including Scammell and Albion) team with Bob Fryars’ expertise and skills. Stokes had served an engineering apprenticeship so he had some technical knowledge. When Fryars took over as Group Chief Engineer the Leyland engineering team was young and inexperienced. Even dyed in the wool Leyland people acknowledge that Stokes had one aim in life with regards to AEC - that was to close Southall down, an aim that he finally achieved, whether he was running the company or not. I don’t believe in coincidences, so Stokes retired in 1979, just when Southall closed for good. Now, how strange is that?
I’m currently reading a newly published book about the RR Merlin engine. Now then CF, what did Mr Royce do wrong when he designed that engine?
Make your mind up you said Stokes was the man in charge of the 691/760’s design and signing off.
Now you’re saying it was Markland.You also said that at no time was Markland over Stokes.
I said that Stokes had no option but to sign off the TL12 which you say was a good thing.
Stokes retired in 1979 is as much total unadulterated bs as he was in charge of the 691/760.
Stokes took an honorary non influential position in 1975 and retired in '77.
Michael Edwardes was head of NEB who ‘would’ have overseen and controlled any move to bring Rolls into the Leyland Group before Vickers took Rolls over in 1979.
Edwardes was appointed as MD of Leyland Group in 1977.When you say the run down of AEC ‘commenced’.Big on defending bad truck design and a government appointed asset stripper but want to crucify a WW2 vet, like many of his work force, who’s skills helped to save the country in time of greatest need.
ramone:
The MX engine gets a mention now ffs.
Yes you know 123 x 152 and 130 x 162 without supposed piston speeds tearing it apart.
Who would have thought it.
ramone:
I read that Pete , in fact there was an article on AEC in one of the monthly vintage magazines again which came out with some pretty damning assumptions regarding Stokes and a few of his colleagues , there are a lot of people out there telling the same story , obviously all are wrong
Until inconvenient questions regarding dates and who was actually in charge get asked.
Truth is AEC were great bus engine producers not so good at producing truck motors.
Edwardes was the man who put the TL12 in the T45.He also turned over Triumph and Rover to making Jap crap to the advantage of BMW.He also ran down AEC and then closed it.
Stokes created the Triumph 2.5 and Rover V8 to compete with BMW’s laughable over priced ‘new class’ 4 cylinder heaps.Stokes also put the TL12 in the Marathon because that was the only choice AEC’s designers had given him.
Notice Stokes didn’t stand in the way of Scammell using Rolls engines and that would have been his choice for the T45 if Edwardes had provided it to him in the form of a Leyland takeover.
But DAF would obviously have hated it.
There are a lot of people denegrating Stokes.Yes usually the same lying zb’s who backed Thatcher asset stripping and selling out the country to the foreign competition.
gingerfold:
I’m currently reading a newly published book about the RR Merlin engine. Now then CF, what did Mr Royce do wrong when he designed that engine?
Luckily AEC didn’t design it they’d have given it a 114 mm stroke instead of 6 inches to reduce its cross section/height and increase its aerodynamic efficiency.
Personally I prefer the 6.6 inch stroke Griffon.Without it in the MkXIV the Mustangs might not have had such an easy time of it v FW 190 D9 with the Jumo 213 and its 6.5 inch stroke.
ramone:
When Volvo started selling tractor units in Britain they offered the F86 and F88 , now i would guess the F86 at that time would be rated around 192bhp and the F88 at 240 bhp. Now anyone with a brain cell to their name would know that a 6.7 litre engine pushing out 192 bhp wouldn`t last 2 minutes or a 9.6 litre engine pushing out 240 bhp would either. Does anyone know what gross weights these motors would have been operating at in Sweden. I do know that the 1972 F86 my dad drove had a design weight of 36 tons. In hindsight we could have halted this madness and saved Volvo from bankruptcy .
To be fair the F86 with the 0.80 bore stroke ratio or 0.85 in the case of TD100 and TD120.So not exactly great believers in AEC design philosophy.
In all of your nonsense over the years I can’t recall Edwardes getting a mention until this thread, strange.
Stokes sorted the Rover V8 did he? The one designed by Buick? Or was there another one?
Yes, the RR diesel engine side should’ve been incorporated into BL truck and bus, but it wasn’t, that’s fantasy though, as was my post on the subject.
And to jump in on the tensile load question, common sense tells me that it would be halfway between TDC and BDC on a power stroke as the angle of the rod is at its greatest and so is the downward force.
[zb]
anorak:
please tell us what peak cylinder pressures you would expect in either of the two engines mentioned above. A number will do- no words necessary.
cycleworld.com/story/bikes/o … revisited/
The difference between a gun and an engine is that force acting on the piston can be multiplied by the distance equation provided by the leverage of a longer stroke.
[zb]
anorak:
If you haven’t read Edwardes’ book, how can you know what his decisions were? If you had, you would know that he had left before the Japanese-origin cars were introduced. The MD at the time was Harold Musgrove. Was he a liar too?
Musgrove bs.
Don’t even think of having a go at me about resorting to Wiki.
I’m a Triumph fan remember.
en.wikipedia.org/wiki/Triumph_Acclaim
BMC were zb so lets wipe out Rover and Triumph by turning them over to making Hondas.Yeah right.So what was Leyland’s answer to the BMW 3 series and 5 series after that.Remind us who bought up Rover and the Triumph name and made sure it kept Rover a second rate maker of Jap based crap. 
newmercman:
In all of your nonsense over the years I can’t recall Edwardes getting a mention until this thread, strange.Stokes sorted the Rover V8 did he? The one designed by Buick? Or was there another one?
Yes, the RR diesel engine side should’ve been incorporated into BL truck and bus, but it wasn’t, that’s fantasy though, as was my post on the subject.
And to jump in on the tensile load question, common sense tells me that it would be halfway between TDC and BDC on a power stroke as the angle of the rod is at its greatest and so is the downward force.
Designed by Buick bought by Rover under Stokes to make under licence because Buick thought it was too small to power their tanks.So where were BMW in 1967 v the might of the P5B and Rover 3500 P6.
How do you put the con rod and big end fastenings under TENSION during the POWER stroke.Downward force ‘compressing’ the con rod against the crankshaft which is what turns it and the opposite force acting on the head and putting the main bearing and head fastenings under tension.The piston and rod assembly is under Compressive load not tension through the power stroke added to by having to decelerate at BDC before the exhaust stroke.
The more specific torque the more the compressive loads.The more leverage in the form of stroke measurement the more torque for the equivalent shove or the less shove needed for the equivalent torque.
While the highest amount of pressure on the piston is before it reaches halfway.
It’s obvious that the tensile loads on the piston/rod can never exceed the tensile strength of the big end fastenings and tension obviously meaning pulling the con rod away from the crankshaft and from the big end bearing cap.
Not pushing it into it which by definition is what the power stroke does and that’s ultimately all about the tensile strength of the main bearing fastenings and head fastenings which are obviously more than the big end fastenings.Unless the piston and con rod assembly shears at some point in the chain under compression first.Alleviating those forces with as much leverage as possible obviously helps.
The fact that Rover and Triumph was destroyed by the decisions to not compete with BMW head on and instead go downmarket and the run down and closure of AEC and launching the T45 Roadtrain with TL12 power to the advantage of DAF and Volvo was all about Edwardes.
I’ve never seen the need to make that obvious connection.
Until now with this stupid unfounded witch hunt directed against Stokes based on untrue timelines and hear say when the the facts and dates regarding Edwardes’ part in all this are clear.
[zb]
anorak:
Just checked a few figures: TL12 vs. RR Eagle 280, as fitted to the Crusader. To BS141Au gross, both had the same power, but the TL12 had an extra 5lbft of torque.
Tell us more about the 305.How did it make over 280 hp at 1,800 rpm.
Yes you’re right, I had that arse about face, tensile strength is pulling not pushing. So then am I on the right track to think that the greatest tensile load is the point where exhaust changes to intake at TDC? The fractions of a second between the closing of the exhaust valve and the opening of the intake valve will create a vacuum as the piston is pulled down by the rotation of the crankshaft, so the time between TDC and the intake valve fully opening is the answer, or not lol
Leaving Leyland, AEC, Stokes et al to one side for the time being, (no doubt it won’t stay dormant for very long), I’m now almost half way through the RR Merlin engine book (witten by Graham Hoyland, published in 2020), and a good read it is too. Not too technical, and easily understood by such as I, who hasn’t got a degree in mechanical engineering.
In three paragraphs I read last night there were some very interesting comments about big end journals and connecting rod lengths for V configuration engines. The author comments that because in a V engine two con rods share a common crankshaft journal then the shorter the con rod stroke then the less strain there is on the con rods and the less likely they are to snap. Sadly I have yet to find anything in the book so far, about crank leverage.
It is a matter of record that Henry Royce never designed a brand new engine from scratch. He improved existing designs, whether his own earlier engines, or engine designs from his competitors in aviation engines and luxury cars. He is attributed as saying “I don’t design new engines, I improve to perfection existing designs. Inventors never make any money”. He did introduce the crankshaft damper to eradicate any roughness in his car engines. The unbeatable RR Eagle Schneider Trophy winning engine was apparently based on an American Curtiss aero engine.
newmercman:
Yes you’re right, I had that arse about face, tensile strength is pulling not pushing. So then am I on the right track to think that the greatest tensile load is the point where exhaust changes to intake at TDC? The fractions of a second between the closing of the exhaust valve and the opening of the intake valve will create a vacuum as the piston is pulled down by the rotation of the crankshaft, so the time between TDC and the intake valve fully opening is the answer, or not lol
Centrifugal acceleration creates tension in the conn rod at precisely the point you mention, proportional to the mass being accelerated, IE the mass of the piston and the bit of the rod above where you want to calculate the tensile load, T; T=mrω², where m is that mass, ω is the angular velocity of the engine and r is the radius of the crank. Dead easy to work it out, but the man we are addressing would rather bluff around the task, for some reason.
At lower loads- part throttle- there is less exhaust gas to compress, so the pressure above the piston is lower, so the tension is maximised. If fatigue strikes, it’s more often on the overrun, at high revs. In engines with tuned exhaust manifolds, there might even be less than atmospheric pressure there. Turbochargers mean there is always some pressure, whether it is exhaust or inlet.
newmercman:
Yes you’re right, I had that arse about face, tensile strength is pulling not pushing. So then am I on the right track to think that the greatest tensile load is the point where exhaust changes to intake at TDC? The fractions of a second between the closing of the exhaust valve and the opening of the intake valve will create a vacuum as the piston is pulled down by the rotation of the crankshaft, so the time between TDC and the intake valve fully opening is the answer, or not lol
‘Common sense’ says that its the period between exhaust and inlet strokes at max rpm, which also involves massive deceleration, reversal and acceleration, is when the big end fastenings are under the most tension and so long as they hold those tensile loads pass onto the con rod.
Just comparing those fastenings with the head and main bearing fastenings shows that those tensile loads never match the compressive loads resulting from the power stroke.
All the stresses in the piston and rod assembly during the power stroke result from and are proportional to the compressive forces involved in turning the cylinder into a similar environment as gun barrel when it’s fired and the piston/rod assembly is the bullet/shell.
It’s obvious that the more multiplication that can be provided by leverage at the crankshaft then the less those forces applied to the ‘shell’ need to be for an equivalent effort at the crankshaft/flywheel.
Which means less compressive load on the piston/rod assembly and head fastenings for a given output and which matters when we’re going for 100 lb/ft + per litre.Also bearing in mind that 280 hp at 1,800 rpm ( or 400 hp at 1,900 rpm ) actually means less piston speed with a 152 mm stroke than 280 hp at 2,200 rpm with a 142 mm stroke.So even Anorak’s piston speed bollox is moot.
While as I said if AEC had designed the Merlin, with the same stroke as their V8, or the 760, we’d all now be speaking German.No doubt Stokes would still have got the blame.
[zb]
anorak:newmercman:
Yes you’re right, I had that arse about face, tensile strength is pulling not pushing. So then am I on the right track to think that the greatest tensile load is the point where exhaust changes to intake at TDC? The fractions of a second between the closing of the exhaust valve and the opening of the intake valve will create a vacuum as the piston is pulled down by the rotation of the crankshaft, so the time between TDC and the intake valve fully opening is the answer, or not lolCentrifugal acceleration creates tension in the conn rod at precisely the point you mention,
That’s what I said.
Not just acceleration it’s also deceleration.
In both cases exhaust and inlet strokes the piston is pulled away from the crank shaft firsly under deceleration before TDC then acceleration pulled down by the crankshaft after.Oh and all those forces also actually result from the shove put into the flywheel during the power stroke.
Every force produced by the engine was produced by putting in the energy first in the form of the …compressive force applied during the power stroke on the con rod.
So remind us why are the big end fastenings not as strong as the main bearing and head fastenings ?.Why does distance supposedly not matter to the force equation by reducing the compressive load required to be applied to the piston/con rod assembly for a given specific torque output and resulting tensile load on the head fastening ?.
Carryfast:
[zb]
anorak:
If you haven’t read Edwardes’ book, how can you know what his decisions were? ……
BMC were zb so lets wipe out Rover and Triumph by turning them over to making Hondas.Yeah right.So what was Leyland’s answer to the BMW 3 series and 5 series after that.Remind us who bought up Rover and the Triumph name and made sure it kept Rover a second rate maker of Jap based crap.
I agree, the 3 and 5 series were head and shoulders above anything Triumph could knock together, but the SD1 was a strong competitor, surely?
gingerfold:
Leaving Leyland, AEC, Stokes et al to one side for the time being, (no doubt it won’t stay dormant for very long), I’m now almost half way through the RR Merlin engine book (witten by Graham Hoyland, published in 2020), and a good read it is too. Not too technical, and easily understood by such as I, who hasn’t got a degree in mechanical engineering.In three paragraphs I read last night there were some very interesting comments about big end journals and connecting rod lengths for V configuration engines. The author comments that because in a V engine two con rods share a common crankshaft journal then the shorter the con rod stroke then the less strain there is on the con rods and the less likely they are to snap. Sadly I have yet to find anything in the book so far, about crank leverage.
It is a matter of record that Henry Royce never designed a brand new engine from scratch. He improved existing designs, whether his own earlier engines, or engine designs from his competitors in aviation engines and luxury cars. He is attributed as saying “I don’t design new engines, I improve to perfection existing designs. Inventors never make any money”. He did introduce the crankshaft damper to eradicate any roughness in his car engines. The unbeatable RR Eagle Schneider Trophy winning engine was apparently based on an American Curtiss aero engine.
Trust me if RR thought that leverage didn’t matter they wouldn’t have given the Merlin and Griffon a 6 inch and 6.6 inch stroke respectively.
As for the Curtiss V1570 you’ll find no AEC short stroke thinking there either.
Nor as we know DB601-5 and Jumo 213.Whatever the author was referring to the relatively narrower big ends of a V engine won’t be helped by reducing the leverage and increasing the shove at the con rod for the equivalent torque output.
If piston speeds with 6 inch + stroke are manageable at around 3,000 rpm I think the Eagle diesel was safe enough at 1,800- 1,900 rpm. 
Not to mention the undersquare BMW M54-S54 car engines which were happy enough at 5,900 - 8,000 rpm respectively.
Just like pushrod engines will happily rev to over 7,000 rpm busting yet more myths.