cav551:
We know how the bloody Yanks like to resort to court claims about the price of fish and here it is:
How would that have stopped AEC making a 130 x 152 6 or even a similar V8 to Scania’s.Even if such a ruling had been enforcable.
Although the V8 is really a pointless vanity exercise given the former.
Where do you get the idea that they wanted to mimic the Maxidyne? I must have missed that memo. As for the oversquare V8, that has been explained numerous times, it was to fit under the Ergo cab, therefore a long stroke version would not work, nor did the short stroke as everyone knows, which was why the idea was shelved until the clearly mental Lord Stokes stuck his bugle in and insisted it was production ready in a ridiculously short amount of time. As you are aware, the oversquare V8 was very successful for FIAT from 330hp to 520hp in road engines and over four figures in static and marine applications, so don’t get too caught up in the oversquare V8 diesel being a stupid idea.
The Crusader, don’t forget was a collaboration with the NFC, that’s where the RR idea came from, a proper lorry man speccing a jack of all trades for the BRS and the rest, initially it wasn’t ever going to be offered to the riff raff, as was the case for the Bristol that was the previous BRS only lorry.
You had started to make sensible contributions again, we all agreed with you at one point, but you hit the Cinzano again didn’t you [emoji6]
Back to the bore/stroke dogma, without even doing the calculation to verify it (which, I believe, is what started this thread off in the first place).
I have edited out several comments from Bob Fryars’ article which were extremely disparaging about you can guess who. You cannot libel the dead but there isn’t anyone to defend Donald Stokes, and certainly not one former AEC manager would choose to do so. There was a culture at Leyland in those years that you had to toe the party line to the letter or else you would be sacked. Donald Stokes wielded total executive power within the entire group.
The V8 plans were dusted off in a hurry because there was no indication that anything at all was going to be salvaged from the Tattersall engine fiasco, so a higher power output engine than the AV760 was thought to be needed. At the time of the resurrection of the V8 the AV760 was only just entering production and fitting. It turned out to be a fine fleet spec tractor unit engine at 32 tons gvw.
AS for the AV770 (TL12) I will stand by everything I have written about. It was a superb engine in operational terms, irrespective of what its “theoretical” shortcoming might, or might not, have been. We had several of them at Spillers and they never missed a beat.
■■■■■■■ lost the case in April 1969.
Is there any more interesting detail about this Tattersall engine which seems to be inspired by an opposed piston design with two crankshafts?
cav551:
Is there any more interesting detail about this Tattersall engine which seems to be inspired by an opposed piston design with two crankshafts?
It was designed in total secrecy… anyone who saw one or worked on one was sworn to secrecy by the threat of instant dismissal if they discussed it… it was a Donald Stokes project… I think this answers your question. If Dr Albert Fogg wouldn’t even talk about it to the Chief Engineer of Leyland Truck and Bus then that tells us what a massive disaster it was.
newmercman:
Where do you get the idea that they wanted to mimic the Maxidyne? I must have missed that memo. As for the oversquare V8, that has been explained numerous times, it was to fit under the Ergo cab, therefore a long stroke version would not work, nor did the short stroke as everyone knows, which was why the idea was shelved until the clearly mental Lord Stokes stuck his bugle in and insisted it was production ready in a ridiculously short amount of time. As you are aware, the oversquare V8 was very successful for FIAT from 330hp to 520hp in road engines and over four figures in static and marine applications, so don’t get too caught up in the oversquare V8 diesel being a stupid idea.The Crusader, don’t forget was a collaboration with the NFC, that’s where the RR idea came from, a proper lorry man speccing a jack of all trades for the BRS and the rest, initially it wasn’t ever going to be offered to the riff raff, as was the case for the Bristol that was the previous BRS only lorry.
You had started to make sensible contributions again, we all agreed with you at one point, but you hit the Cinzano again didn’t you [emoji6]
The Mack aspiration comment was made elsewhere by cav ? not sure where he got it from.
So we might agree on the basics but not the finer details and conclusions.No big deal.
That seems to be exactly what happened in this case.
Anyone with any sense could see this car ( truck ) crash happening in slow motion.But the people who mattered making and designing the stuff were too scared to admit and tell Stokes that the things that they’d dream’t up and which seemed like a good idea at the time weren’t so good with just a little bit of hindsight, if not foresight.
It doesn’t really matter if we disagree ‘how’ and why Scammell came to put the Rolls Eagle in the Crusader the fact that they did rather than use the in house TL12, is enough and all that matters.
As for the FIAT V8 a 17 litre motor with a stroke not a million miles from that of the Scania’s was good enough to get the job done.
Scania being the last V8 standing in 16 litre form with a 6 inch stroke.
Which makes the case for AEC’s thinking how.
As opposed to this just ain’t going to work we’ll have to do something about the Ergo cab.You know like making a proper 6 cylinder motor fit under it.
Just like the idea that we have to move on/away from from the design limitations of our bus engine legacy.
Obviously a bit difficult to say that in a department obviously run on a regime of fear among the design team v their management.
All totally moot and water under the bridge by the the time the T45 project was nearing completion.
At which point the reference to Scammell’s motor of choice and its obvious superiority v TL12 is what matters, regardless of who chose it, and why in the light of that wasn’t it then the do whatever it takes to bring it in house default choice of both Leyland and its government handlers.Bearing in mind what happened next.
gingerfold:
I have edited out several comments from Bob Fryars’ article which were extremely disparaging about you can guess who. You cannot libel the dead but there isn’t anyone to defend Donald Stokes, and certainly not one former AEC manager would choose to do so. There was a culture at Leyland in those years that you had to toe the party line to the letter or else you would be sacked. Donald Stokes wielded total executive power within the entire group.The V8 plans were dusted off in a hurry because there was no indication that anything at all was going to be salvaged from the Tattersall engine fiasco, so a higher power output engine than the AV760 was thought to be needed. At the time of the resurrection of the V8 the AV760 was only just entering production and fitting. It turned out to be a fine fleet spec tractor unit engine at 32 tons gvw.
AS for the AV770 (TL12) I will stand by everything I have written about. It was a superb engine in operational terms, irrespective of what its “theoretical” shortcoming might, or might not, have been. We had several of them at Spillers and they never missed a beat.
The fact that the Eagle had the potential in it to cover all demands from 265 to 400, in large part because of its more under square design, is a bit more than ‘theoretical’.
This is all about what was needed to keep Leyland in the frame facing the combined might of DAF DK and Volvo TD120 not just the demands of Spillers at that point in time.
A Rolls 320 intercooled fuller 13 speed Roadtrain unveiled at the launch party was always going to make more of a statement in that regard.
It’s probably reasonable to say that the splitting of the truck and bus division and what happened next is a reasonable guide as to why Leyland and the government didn’t want that to happen.
The regime of fear among any of those who might have blown the whistle on the plan could also have only have helped such a nefarious agenda.
gingerfold:
cav551:
Is there any more interesting detail about this Tattersall engine which seems to be inspired by an opposed piston design with two crankshafts?It was designed in total secrecy… anyone who saw one or worked on one was sworn to secrecy by the threat of instant dismissal if they discussed it… it was a Donald Stokes project… I think this answers your question. If Dr Albert Fogg wouldn’t even talk about it to the Chief Engineer of Leyland Truck and Bus then that tells us what a massive disaster it was.
The whole idea of the laughable L60 idea being inflicted on Leyland seems to have been a German inspired sabotage plan sent across the Channel.
All fixed by the CV12 luckily for NATO.Interestingly so efficient and reliable that it filled the roles of tank and transporter engine. 
[zb]
anorak:
Back to the bore/stroke dogma, without even doing the calculation to verify it (which, I believe, is what started this thread off in the first place).
As I said working out the tensile load on the Eagle’s piston con rod assembly between Exhaust and Induction stroke at 2,100 rpm or for that matter 1,900 rpm v that of TL12 at 2,200 rpm is beyond my pay grade.
Let’s just say that maximum compressive loads on the power stroke will be the result of ( a lot ) more than 2 x BMEP which as you know is just an over complicated abstract figure to say the same thing as specific peak torque at the flywheel.It bears absolutely no relation to the actual peak pressures and loads within the cylinder and on the piston and rod assembly components to obtain that specific torque figure.
It’s obvious that the more leverage you’ve got then the less those loads can be for a given torque output.Or the more torque output for a given load.Force x distance is what matters here.Piston speeds don’t.
cav551:
■■■■■■■ lost the case in April 1969.
Ta for that 
. I was not looking forward to another session of gratuitous prevarication, which is what legal people openly indulge in, to the detriment of justice 
.
gingerfold:
cav551:
Is there any more interesting detail about this Tattersall engine which seems to be inspired by an opposed piston design with two crankshafts?It was designed in total secrecy… anyone who saw one or worked on one was sworn to secrecy by the threat of instant dismissal if they discussed it… it was a Donald Stokes project… I think this answers your question. If Dr Albert Fogg wouldn’t even talk about it to the Chief Engineer of Leyland Truck and Bus then that tells us what a massive disaster it was.
The idea worked well enough for Rootes. At least the Leyland engineers had a go.
[zb]
anorak:gingerfold:
cav551:
Is there any more interesting detail about this Tattersall engine which seems to be inspired by an opposed piston design with two crankshafts?It was designed in total secrecy… anyone who saw one or worked on one was sworn to secrecy by the threat of instant dismissal if they discussed it… it was a Donald Stokes project… I think this answers your question. If Dr Albert Fogg wouldn’t even talk about it to the Chief Engineer of Leyland Truck and Bus then that tells us what a massive disaster it was.
The idea worked well enough for Rootes. At least the Leyland engineers had a go.
I can understand that Leyland might have looked at an opposed piston 2-stroke design, but the L60 Chieftain tank engine was huge, 19 litres of it. So it probably wasn’t the best place to start from. There could possibly be more information if you Google Leyland L60 engine. It mentions something about secret projects, but I haven’t time to look at the moment.
Carryfast:
The TL12’s being a case of we’ve got this lump with the same stroke as a 7.5t Routemaster bus motor.It ain’t ideal.But should be ok with some more development and a turbo bolted to it hopefully might be as good as the Maxidyne.
I’ll repeat what I wrote earlier in relation to Mack for Newmercman.
QUOTE “Do you ever read what you have just written?.. Neither do you read what others have written - rather you read something entirely different but which suits your argument :eg you quote me as " which you yourself said was considered by AEC as a benchmark for the TL12”
What I actually wrote was: "There was one manufacturer they (Leyland) had been observing from afar whose ideas might be worthy of possible consideration for their own experimentation - Mack and the concept of turbocharger tuning and torque rise." Nothing about any benchmarks.
I mentioned Mack and the concept of turbocharger tuning and torque rise because it was a principle which was to be followed by many manufacturers. It had nothing to do with the internal dimensions of the engine. Mack wanted to uprate their Thermodyne engine and make it more driveable. They wanted to do away with the multispeed transmissions needed to keep the typical american engines of the day spinning at the upper end of the rev range which was necessary to maintain progress. By a clever and novel balance of turbocharging, manifolding, fuelling and timing they managed to broaden, boost and shift the torque curve of the engine so that it became more flexible and ‘powerful’ across its rev range. In doing so they transformed their old engine into the Maxidyne and did away - for Mack - with the necessity for a multispeed transmission.
As said this principle was at least partially followed by many manufacturers as de-speeded torque rise engines appeared. In fact the final production versions of the TL12 engine were described as ‘Flexitorque’ engines." END QUOTE
It is as riciculous as it is insulting to assume that the research designers and engineers of any company do not keep an eye on what their competitors have done and if possible discover what they are doing. What Mack had done was to radically transform the characteristics of the operation of their engine and done this without altering the displacement of their engine. That is all I was emphasising.
I also referred to a later article pointing at Volvo’s TD100 GA engine which reveals that it is possible to restrict the maximum cylinder pressure “by better turbocharger matching and fine tuning of the injection characteristics.”
archive.commercialmotor.com/arti … -of-its-td
This brings us on to the continued development of the TL12 post 1980 if it had gone ahead and not been the subject of management decision.
Gingerfold has mentioned something I had been deliberately avoiding because it is the critical factor in determining whether there was scope for further development of the AEC based engine: Crankshaft balance.
All the AEC technical bumph stipulates that if engine revs are to exceed 1800rpm then a crankshaft damper must be fitted allowing engine speed to reach up to 2400 rpm at governor no load run out. AEC actually went further than this however, some engines were supplied with crankshaft counterweights including some versions of the AV760. We do know that the AV760 had a habit of throwing fan blades so these weights may have been critical for that reason. These counterweights describe the same arc as the relevant crankpin. While clearance with the block and liner is OK these will foul the piston skirt at BDC if the stroke is increased to 158mm.
The tuning concepts from Mack and Volvo, allied to the despeeding trend actually copied in the Flexitorque engine introduce the possiblity of deleting crankshaft counterweights from the initial AEC design or modifying them to clear. What AEC or Leyland R&D might have done had the development continued is sadly lost to management decision. Who knows we may have seen an AV 840 TL14 utilising counterweights and a FIAT 8210 137x 156 structure which is known to have worked? We could equally have seen a reversion to AEC bore size and a 130x152 Rolls/■■■■■■■ copy. I have taken the view that AEC/Leyland may have insisted on retaining counterweights and maybe wanted to carry out other modifications, we know that there were cooling modifications and alterations to the cylinder head casting. They could equally have reached the conclusion that any capacity increase did not provide the benefits which they were seeking. They were always left with the option of employing a reworked block casting or anything else they chose. We could even have a grandson Common rail four valve head with central injectors and completely different overall displacement and internals.
Reading the recent posts it seems apparent that AEC designed and built the TL12 in good faith for the mid 70s market . Unfortunately the AEC designers didnt know that they wouldnt be able to or allowed to improve on it such was the idiotic decisions of Stokes (i think CF has championed this bloke on numerous occasions on different threads). I keep repeating my self in asking the question what problems did the TL12 cause in service to operators . Were there disastrous failings of some kind or other , were there big warranty claims ? It must have worried Volvo because they rushed the 290 F88 out in response and that wasnt the most reliable of engines compared with the 240.
Going back to Leyland taking on Rolls Royce, wouldnt that have lost more sales , or would Leyland still offer the ■■■■■■■ option . If they didnt offer ■■■■■■■ then the Roadtrain would be of very limited appeal to some customers.
Does anyone know which was the best selling variant of the Roadtrain .
A local haulier was used has an advertisement for the 290 L Roller in his recently purchased new Fodens and he said they were achieving good mpg figures , the next batch of Fodens didnt have Rolls in them , maybe he wasnt has impressed after evaluating them.
Another decisions which was a strange one concerned the ending of production of all AEC double deckers in favour of the Atlantean , Daimler Fleetline and Bristols why?
‘Torque rise’ isn’t going to be much use on an engine making less/not enough of it at its peak.
You know like the TL12.So let’s try to put Maxidyne’s boost/leverage combination lipstick on the TL12 pig that’ll work.The truth is there was no chance of any type of connection between the two totally different opposing designs.
It’s actually just another way of saying torque drop at peak power anyway.
Which like not really needed BMEP, specific torque is the same thing, is the usual yardstick that helps to compare engines and on that basis a large torque drop at peak power is actually an inferior characteristic.Because it means that you’re relying more on engine speed than torque to make the equivalent peak power meaning a wilder specific fuel consumption curve.
What’s the oxymoron of as much power as possible at as low rpm as possible and trying to make a crankshaft that can spin at silly rpm’s, all about. 
Especially when combined with forced induction boost.
It’s a heavy truck engine not a Ferrari F40 or an F1 motor.
When ideally we want 30 hp + per litre at 1,900 rpm and 100 lb/ft + per litre peak torque potential.You know just like the Eagle could do.
Not try to spin the thing up to 2,500 rpm + on the basis that the peak power figure then might look a bit better than the TL12’s 280 at 2,200.
With the lose lose that piston speeds then start to matter meaning shorter stroke = less leverage = less specific torque output = more rpm and boost to get the same power output, if you’re lucky and if it doesn’t go bang first. 
The AEC 505 engines we ran were good at throwing fanblades through their radiators as well! 
Crankshaft dampers: I know Gardner fitted them internally of course as they had plenty of room, but some engine makers used the front pulley instead as a damper with a rubber insert, couldn’t AEC/Leyland have used those to save internal space?
Pete.
ramone:
Reading the recent posts it seems apparent that AEC designed and built the TL12 in good faith for the mid70s market . Unfortunately the AEC designers didnt know that they wouldnt be able to or allowed to improve on it such was the idiotic decisions of Stokes (i think CF has championed this bloke on numerous occasions on different threads). I keep repeating my self in asking the question what problems did the TL12 cause in service to operators . Were there disastrous failings of some kind or other , were there big warranty claims ? It must have worried Volvo because they rushed the 290 F88 out in response and that wasnt the most reliable of engines compared with the 240.
Going back to Leyland taking on Rolls Royce, wouldnt that have lost more sales , or would Leyland still offer the ■■■■■■■ option . If they didnt offer ■■■■■■■ then the Roadtrain would be of very limited appeal to some customers.
Does anyone know which was the best selling variant of the Roadtrain .
A local haulier was used has an advertisement for the 290 L Roller in his recently purchased new Fodens and he said they were achieving good mpg figures , the next batch of Fodens didnt have Rolls in them , maybe he wasnt has impressed after evaluating them.
Another decisions which was a strange one concerned the ending of production of all AEC double deckers in favour of the Atlantean , Daimler Fleetline and Bristols why?
Stokes didn’t sign off the 691/760, let alone the 590 block dimensions it was based on and he was working for Triumph not truck and bus in 1965.
Which is the architecture that the TL12 took forward and that’s why it was never going to match the Eagle’s reliable output potential.
Stokes wouldn’t have had any say in what powered the T45 that would have been Edwardes.
The same Edwardes who put the Triumph Acclaim and Rover SD1 and Rover 820 up against BMW 3 and 5 series.
The government were in control of what Edwardes did from closure of AEC to splitting Truck and Bus divisions and whether the Eagle went to Leyland or Vickers.
Like Stokes he was a puppet of our treacherous government and it was Thatcher who sealed the deal with Lubbers ‘for some reason’ regarding Leyland’s fate.
Just like it was Thatcher who oversaw Rolls Royce diesels going to Vickers and the T45 being launched with the TL12.How convenient for DAF.
Stokes who would have been long retired at that point.
Carryfast:
‘Torque rise’ isn’t going to be much use on an engine making less/not enough of it at its peak.
You know like the TL12.So let’s try to put Maxidyne’s boost/leverage combination lipstick on the TL12 pig that’ll work.The truth is there was no chance of any type of connection between the two totally different opposing designs.It’s actually just another way of saying torque drop at peak power anyway.
Which like not really needed BMEP, specific torque is the same thing, is the usual yardstick that helps to compare engines and on that basis a large torque drop at peak power is actually an inferior characteristic.Because it means that you’re relying more on engine speed than torque to make the equivalent peak power meaning a wilder specific fuel consumption curve.What’s the oxymoron of as much power as possible at as low rpm as possible and trying to make a crankshaft that can spin at silly rpm’s, all about.
It’s a heavy truck engine not a Ferrari F40 or an F1 motor.When ideally we want 30 hp + per litre at 1,900 rpm and 100 lb/ft + per litre peak torque potential.You know just like the Eagle could do.
Not try to spin the thing up to 2,500 rpm + on the basis that the peak power figure then might look a bit better than the TL12’s 280 at 2,200.
With the lose lose that piston speeds then start to matter meaning shorter stroke = less leverage = less specific torque output = more rpm and boost to get the same power output, if you’re lucky and if it doesn’t go bang first.
You could be a politician , why don`t you answer the question , what problems in service did the TL12 cause hauliers .
It was economical and reliable and performed well what more would a haulier want?