[zb]
anorak:
In the last century, successful engines were made with a wide range of bore/stroke ratios. The torque is proportional to the bore squared multiplied by the stroke. If you think that stroke is more important, how do you explain it in the context of that fact?
Because multiplying less bore squared by more stroke = less force required because it’s multiplied by more distance to obtain the equivalent torque just like using a longer lever.Distance costs nothing in terms of fuel or stress.Force does.
The story of The AEC’s pre war engine development is both interesting, confusing and complicated with a plethora of different type numbers for the same basic engine and a multitude of different design modifications; some produced in very limited numbers including just five 6.2 litre 8 cylinder in line petrol engines (87mmx 130mm & 85bhp) placed into service with the LGOC in: T43, ST4, ST84, LT35 & LT41.
Diesel engine R&D starts in October 1928 with the first 15.5:1 compression ratio six cylinder engine accredited to Charles Edwards installed a chassis in December 1928. This ‘air cell’ engine used a Robert Bosch patent ‘Acro’ combustion chamber in the piston and the injector in the cylinder head at an angle pointing downwards. Development under Cedric Dicksee continued of a complete redesign until October 1929 with the combustion chamber now in the head and the injector rotated 180 degrees and now pointing upwards from a position under the overhanging cylinder head. By October 1930 the engine was in production form as the A155 (110x142)
Many developments continued from 1932 onwards with various input from Sir Harry Ricardo, Cedric Dicksee and George Rackham resulting in successive changes to materials and design to the A155 (110x 142), A161 (115x142), A164 and A165 type engines with several Ricardo ‘Comet’ combustion chambers. We end up with indirect injection A165 “8.8” and A171 (106x146) “7.7” engines (1935). There appear to have been 63 A151 engines built; 96 A161, 76 A164 & 1753 A165 produced. These went into various bus and lorry chassis.
Around 1936/7 The “7.7” (actually 7,58L) becomes the A173 direct injection type employing a license built Leyland Pot Cavity (in Piston) combustion chamber originating from the Leyland 8.6, George Rackham designed, OHC engine along with a new cylinder head. At around the same time numbers of A165 8.8 engines are rebuilt with the same pistons and cylinder head becoming the type A180 and this engine enters production. During this period much experimentation was carried out using the Leyland Pot Cavity (Flower Pot), Gardner Hemisphere and an AEC deesign shallow cavity combustion chamber in addition to Ricardo Comet indirect injection systems.
Around this point the design of the 9.6 engine which was to power the RT bus and post war lorries commences as part of the above experiment/ project A 805/1 and an A 185 pot cavity (120x142) engine appears as the 9.6 engine for the first RT bus of 1939. However the very first experimental unit had a Ricardo Comet III* chamber which was recorded to produce 145 bhp @ 2050 rpm. The A185 pot cavity is fitted to the 1st chassis, but before delivery the engine is modified to in-piston AEC version toroidal cavity and finally the A204 9.6 is born.
All of these engines feature a separate crankcase and block. The 9.6 introduced a change from chain to gear driven camshaft and auxilaries.
newmercman:
The 2500nm/1850lb/ft Cursor 13 is to be found under the cab of the S-Way 570.
Oh wait it’s a 135 x 150 not 136 x 142.So 0.90 bore stroke ratio v 0.95.Why’s that ?.
Yep we can get away with way more stress with modern materials in 2020 than we could in 1973-90.Everything is relative.
At the end of the day the maths say that the MX will still be under less stress and more fuel efficient than the Cursor at the equivalent torque output because it’s making it with more leverage using a 0.80 bore stroke ratio.Instead of force using a 0.90 ratio let alone 0.95.
[zb]
anorak:
In the last century, successful engines were made with a wide range of bore/stroke ratios. The torque is proportional to the bore squared multiplied by the stroke. If you think that stroke is more important, how do you explain it in the context of that fact?
Because multiplying less bore squared by more stroke = less force required because it’s multiplied by more distance to obtain the equivalent torque just like using a longer lever.Distance costs nothing in terms of fuel or stress.Force does.
A longer stroke requires a bigger throw on the crank and a longer con-rod.
A longer con-red will require more material, hence more weight. Ditto with the crank.
You`re moving more material within the engine.
Imagine a tiny piston on a very long crank…
No such thing as a free lunch.
[zb]
anorak:
In the last century, successful engines were made with a wide range of bore/stroke ratios. The torque is proportional to the bore squared multiplied by the stroke. If you think that stroke is more important, how do you explain it in the context of that fact?
Because multiplying less bore squared by more stroke = less force required because it’s multiplied by more distance to obtain the equivalent torque just like using a longer lever.Distance costs nothing in terms of fuel or stress.Force does.
HAhaha!!! Longer stroke= less fuel? How long does it have to be before the smoke gets sucked up the exhaust pipe and fuel is deposited in the tank?
There’s nothing wrong with force. It is what makes the vehicle move. Your next task is to calculate the force exerted by the road on the vehicle, when your 200mm stroke 11 litre 20 bar BMEP engine drives through a 3:1 diff and 1100x20 tyres.
newmercman:
Here’s another one to throw into the 13litre 1850 torque mix, the Volvo D13, 455hp to 500hp versions are available with 1850 here in the colonies, the corresponding Mack MP8 engines are the same obviously as the hardware is the same, just a different colour with Mack on the valve cover.
All as relevant to a TL12 or a Rolls Royce Eagle as a grapefruit is to a goldfish.
As an aside, I had four of the Cursor 13 engined Stralis 540s, they were powerful lorries, with an early downsplit to keep them in the boil they would go up most hills on the limiter, they were less than 1850, which i hadn’t realized.
I’ve also owned a 510hp 1850lb/ft Paccar MX and they go well too, but their 1850lb/ft is nowhere near as powerful as 1850lb/ft of CAT torque, even though it’s available over a wider rpm range which should give it the advantage, in the real world it doesn’t, the same applies to the Volvo torque, it can’t match a CAT even though the numbers are the same, so perhaps the bore/stroke ratio, engine architecture, BMEP and the rest of the nerdy stuff is only of any value in a game of Top Trumps, maybe that’s why people who actually had experience of a TL12 all say that they pulled like a train, regardless of what was on paper.
The published torque figures are only minima. Maybe the CAT engines were conservatively rated? In these days of turbochargers with electronic control, it would cost nothing to give an extra 200lbft. Maybe they quoted a low power output, to sell the engine to customers who thought less power=less fuel? Those customers are pleasantly surprised by the performance, so it gets a good reputation.
The only way to find the true power is to put it on a dyno, but who trusts the dyno operator? He is flogging his own “improvements” to your engine, so it is in his interests to give optimistic readings (or not!).
cav551:
The story of The AEC’s pre war engine development is both interesting, confusing and complicated with a plethora of different type numbers for the same basic engine and a multitude of different design modifications; some produced in very limited numbers including just five 6.2 litre 8 cylinder in line petrol engines (87mmx 130mm & 85bhp) placed into service with the LGOC in: T43, ST4, ST84, LT35 & LT41.
Diesel engine R&D starts in October 1928 with the first 15.5:1 compression ratio six cylinder engine accredited to Charles Edwards installed a chassis in December 1928. This ‘air cell’ engine used a Robert Bosch patent ‘Acro’ combustion chamber in the piston and the injector in the cylinder head at an angle pointing downwards. Development under Cedric Dicksee continued of a complete redesign until October 1929 with the combustion chamber now in the head and the injector rotated 180 degrees and now pointing upwards from a position under the overhanging cylinder head. By October 1930 the engine was in production form as the A155 (110x142)
Many developments continued from 1932 onwards with various input from Sir Harry Ricardo, Cedric Dicksee and George Rackham resulting in successive changes to materials and design to the A155 (110x 142), A161 (115x142), A164 and A165 type engines with several Ricardo ‘Comet’ combustion chambers. We end up with indirect injection A165 “8.8” and A171 (106x146) “7.7” engines (1935). There appear to have been 63 A151 engines built; 96 A161, 76 A164 & 1753 A165 produced. These went into various bus and lorry chassis.
Around 1936/7 The “7.7” (actually 7,58L) becomes the A173 direct injection type employing a license built Leyland Pot Cavity (in Piston) combustion chamber originating from the Leyland 8.6, George Rackham designed, OHC engine along with a new cylinder head. At around the same time numbers of A165 8.8 engines are rebuilt with the same pistons and cylinder head becoming the type A180 and this engine enters production. During this period much experimentation was carried out using the Leyland Pot Cavity (Flower Pot), Gardner Hemisphere and an AEC deesign shallow cavity combustion chamber in addition to Ricardo Comet indirect injection systems.
Around this point the design of the 9.6 engine which was to power the RT bus and post war lorries commences as part of the above experiment/ project A 805/1 and an A 185 pot cavity (120x142) engine appears as the 9.6 engine for the first RT bus of 1939. However the very first experimental unit had a Ricardo Comet III* chamber which was recorded to produce 145 bhp @ 2050 rpm. The A185 pot cavity is fitted to the 1st chassis, but before delivery the engine is modified to in-piston AEC version toroidal cavity and finally the A204 9.6 is born.
All of these engines feature a separate crankcase and block. The 9.6 introduced a change from chain to gear driven camshaft and auxilaries.
Which leaves the questions of why the move from 146 mm stroke of the 173 to the 142 mm of the 165.
Let alone the difference between the chosen bore stroke ratio of the 204/590 v the 760.Surely the alarm bells were ringing somewhere.
The resulting 130 x 154 760 and its TL12 development could/would have been one of the best truck engines ever produced anywhere from 1965 to let’s say 1995.
Certainly trumping the Eagle and the TD120.
Also why the 173 not the 165 or the 204 used in the Matador even the 6 wheeler Matador version ?.
IE the smallest capacity of the three different options chosen for the job ? and I think I know why.
essexpete:
So regarding engines in the BL group at the end of the 60s which truck performed more efficiently:
Leyland Octopus with the 0.680 or the Mammoth Major with the AV 760?
Then throw in the Routeman with the Leyland or out sourced engines?
The Octopus O.680 was discontinued in 1970 in favour of the Scammell Routeman eight-wheeler, that retained the O.680 engine, and I’ll refer CF to this comment rather than repeat myself in CF’s post. The Routeman had the RR Eagle 220 as an option to the O.680. The rationale for boosting output at Scammell was to keep Tolpits Lane busy as the Scarab / Townsman and Highwayman models had all been discontinued, falling victims to C&U regulations.
The Routeman was a good and popular eight wheeler, especially as a tipper. BL offered the Mammoth Major AV760 until 1977, popular as a tanker chassis, and a small number of Guy Big J eight wheelers with ■■■■■■■ engines. So the group had applied a bit of logical thinking with its 1970s eight wheeler models. It kept customers happy by offering them choices of makes and engine options. With the impending and actual cessation of Mammoth Major production in 1977 the Octopus was re-introduced, initially in 1975 with the 502 engine (205 bhp), then the 511 engine from 1976 (230 bhp), then for former AEC customers the L12 Octopus (203 bhp) came along in 1977, and the final Ergo cabbed Octopus offering was the TL11A option in 1979 (TL11 engine de-rated to 209 bhp). This was something of a stop-gap until the T45 Scammell Constructor was introduced with engine options.
Whilst BL was faffing about with its 32 tons tractor unit range in the 1970s it actually got its eight wheeler offerings more or less spot-on, able to satisfy all its customers wherever previous marque loyalties were. In the 1970s the eight wheeler market was still very important.
Thanks Gingerfold, very informative for an uninformed anorak. Would it not have been better to at least dump the Guy product and perhaps offer an 8 wheeler with a choice of AEC, Rolls or ■■■■■■■■ with perhaps a site type cab and a more trunking based cab both tilt?
essexpete:
Thanks Gingerfold, very informative for an uninformed anorak. Would it not have been better to at least dump the Guy product and perhaps offer an 8 wheeler with a choice of AEC, Rolls or ■■■■■■■■ with perhaps a site type cab and a more trunking based cab both tilt?
Generaly I don`t point out spelling mistates, but who would want like to be associated with a noisy, oily, waste of space?
■■■■■■■ might be offended.
Carryfast:
.Distance costs nothing in terms of fuel or stress.Force does.
A longer stroke requires a bigger throw on the crank and a longer con-rod.
A longer con-red will require more material, hence more weight. Ditto with the crank.
You`re moving more material within the engine.
Imagine a tiny piston on a very long crank…
No such thing as a free lunch.
A longer rod by how much.
As opposed to the net reduction in compressive load on it and net increase in torque provided by the extra leverage for the equivalent force on the piston.
A possibly relatively longer rod but a smaller piston.
A crankshaft is also stronger than a con rod/small end/big end joint.
At the end of the day more leverage at the crankshaft means less stress and fuel for the equivalent specific torque output.Or more torque for the equivalent force applied to the piston/rod.The forces involved are also being transferred to the strongest component in the chain.
The fact that a production intercooled version of the TL12 and boost pressures then increased to provide around 100 lb/ft per litre didn’t happen, is no coincidence in that regard.
[zb]
anorak:
HAhaha!!! Longer stroke= less fuel? How long does it have to be before the smoke gets sucked up the exhaust pipe and fuel is deposited in the tank?
There’s nothing wrong with force. It is what makes the vehicle move. Your next task is to calculate the force exerted by the road on the vehicle, when your 200mm stroke 11 litre 20 bar BMEP engine drives through a 3:1 diff and 1100x20 tyres.
Let me guess you’d also say that when you try to undo and tighten up a truck’s wheel nuts with a spanner.Force is good …at least until the point when your wrist snaps.
It’s torque that makes the vehicle move and the longer lever you’ve got the less force you need for the equivalent torque.How do we create the force if not by burning fuel.
The road exerts no force at all the only force exterted is at the input shaft of the transmission taken from the flywheel/crankshaft.
That’s why transmissions are rated by input torque not the size or load on the tyres v the road or the final drive ratio choice.
That torque figure is entirely dependent of the force applied to the piston and con rod multiplied by the leverage at the crankshaft.
The more leverage you’ve got the less force you’ll need for the equivalent torque output or the more torque output you’ll get for the equivalent force.
If I’ve read it right you’re saying no problem we can substitute lack of torque at the flywheel with lower final drive gearing.Blimey why didn’t everyone think of that then we could use an F1 engine to power a 44 tonner just think of the payload advantages of the smaller engine with the win win that Volvo wins its horsepower race with Scania if they take your advice.
newmercman:
I’ve also owned a 510hp 1850lb/ft Paccar MX and they go well too, but their 1850lb/ft is nowhere near as powerful as 1850lb/ft of CAT torque,
Whatever the comparisons the CAT’s 165 mm stroke isn’t doing to make the case for the TL12.
Then they only went North on that for some reason.Ending up with 0.8 and 0.79 ratios for the C15 and C18 respectively.Leverage matters.
[zb]
anorak:
HAhaha!!! Longer stroke= less fuel? How long does it have to be before the smoke gets sucked up the exhaust pipe and fuel is deposited in the tank?
There’s nothing wrong with force. It is what makes the vehicle move. Your next task is to calculate the force exerted by the road on the vehicle, when your 200mm stroke 11 litre 20 bar BMEP engine drives through a 3:1 diff and 1100x20 tyres.
Let me guess you’d also say that when you try to undo and tighten up a truck’s wheel nuts with a spanner.Force is good …at least until the point when your wrist snaps.
It’s torque that makes the vehicle move and the longer lever you’ve got the less force you need for the equivalent torque.How do we create the force if not by burning fuel.
The road exerts no force at all the only force exterted is at the input shaft of the transmission taken from the flywheel/crankshaft.
That’s why transmissions are rated by input torque not the size or load on the tyres v the road or the final drive ratio choice.
That torque figure is entirely dependent of the force applied to the piston and con rod multiplied by the leverage at the crankshaft.
The more leverage you’ve got the less force you’ll need for the equivalent torque output or the more torque output you’ll get for the equivalent force.
If I’ve read it right you’re saying no problem we can substitute lack of torque at the flywheel with lower final drive gearing.Blimey why didn’t everyone think of that then we could use an F1 engine to power a 44 tonner just think of the payload advantages of the smaller engine with the win win that Volvo wins its horsepower race with Scania if they take your advice.
Why don’t you start by reading some ‘O’ Level Physics and Theoretical Mechanics books? You will find this subject much more interesting, I guarantee it.
gingerfold:
The 8.8 litre engine was used in pre-war AEC lorries and PSVs, it was a relatively short-lived engine and was available with options of indirect or direct fuel injection. It was notable for being a high-revving engine for its time, up to 2,400 rpm. The 7.7 litre was the more numerous engine, being used in the heavy AEC lorries as well as PSVs. The experimental 9.6 litre engines were trialled in the early years of WW2,
If I’ve got it right the 8.8 is where we’re seeing the 142 mm stroke being introduced ?.
As opposed to increasing the bore of the 173 to 120 giving 9.9 litres and still respectable ratio of 0.82.
That translates as a 130 x 158 12.5 litre TL12.Put that in the Pete knock off game on.
It’s unbelievable.
My guess is that the bus engine requirements had much to do with the debacle from the point of the 8.8 being introduced and maybe the driving force behind it.
They just didn’t seem to want to move from the 142 mm block after going backwards from the 7.6’s 146 mm.
This is an interesting listen if you have 45 mins spare bbc.co.uk/sounds/play/m000lz6n
Radio 4’s Reunion programme on the collapse of BL, it’s obvious that there’s no love lost between management and workers and Edwardes certainly wasn’t popular.
Contrary to Carryfast’s advice there’s not one mention of the company being saved by putting a V8 into an obsolete car
ramone:
And still no answer from CF what problems did the TL12 or even the AV760 cause operators?
By all accounts not too bad at all IF the aim is only something with 200 - 270 hp max produced at 2-2,200 rpm and 12.5 litres to do it.
Not much use in keeping Leyland ticking over v the DAF DK and Volvo TD120 competition though.
So you dont know then
Well that must be a first then “ramone” if The Great Man is stumped for an answer even if it was only bollox he usually has summat to say ! Cheers Dennis.
essexpete:
Thanks Gingerfold, very informative for an uninformed anorak. Would it not have been better to at least dump the Guy product and perhaps offer an 8 wheeler with a choice of AEC, Rolls or ■■■■■■■■ with perhaps a site type cab and a more trunking based cab both tilt?
Generaly I don`t point out spelling mistates, but who would want like to be associated with a noisy, oily, waste of space?
■■■■■■■ might be offended.
Quite right. I think my phone selected that for some reason. No excuse. Sah!
