These may be of interest to some.
Again from CM in May 1968.
They are about as close as we can get now to asking Keith Roberts about his choice of bore / stroke dimension for the AEC V8.
Double click to read…
Rolls Royce Eagle Mk2 220:
From ERF spec sheet or identically from RR w/shop o/haul manual
capacity 12.17 lt 742.64 cu in Bore 5.125" 130.175mm stroke 6" 152.4 mm comp ratio 16:1
From CM road test quoting Net figures to BS au 141
Net output 214bhp @ 2100rpm
Net torque 594 lbft @1400 rpm
Rolls Firing order 142635
AEC V8 740 firing order 15486372 rh bank 1234 viewed from Flywheel end.
I can give valve and injection timing for AEC V8, AEC AV 760, Rolls Eagle 220, Gardner and various ■■■■■■■ , but I’m sure it would bore most to death.
So, the Rolls 740 cu in engine produces about 2% more torque than the AEC. Wow. The AEC makes 247/214= about 14% more power, which is the important figure. By using lower gears, to realise that advantage, the AEC wins by a mile.
We are working in the mid 1960s, remember. That is when Leyland and everyone else was making their decisions regarding engine type. The fuel crisis was nearly a decade over the horizon, but the market valued light weight because of gross weight restrictions. Every maker wanted a walk-through cab, so compact engines were attractive. There were about a dozen manufacturers working on V engines, to satisfy these demands.
The one criterion that most people on this forum usually miss, that every designer must take into account, is cost. A weight saving is also a cost saving. Does anyone have this information for the AEC versus competing types? I bet it wins handsomely. I also bet that the ■■■■■■■ VALE was equally impressive in that regard. Those are the two compact engines which gave the worst trouble in service; both projects were rushed too-fast to production by engineering-ignorant MDs, if I remember correctly. Is it too much of a coincidence that the commercial advantage offered by the engineering was a factor in that urgency?
Carryfast:
ramone:
The TL12 if launched 5 years earlier would have been a safer bet then , and then designing a larger V8 with more potential for higher outputs would have been a better bet with no rush for a launch . Everything was there in front of them , the Marathon cab the turbo TL12 in `68 would have definitely made the grade giving AEC a platform to work from and valuable time. But as usual decisions from Lancashire scuppered thingsCan’t see how struggling on with yet another compromised Ergo derivative beats using the 3 VTG cab.
While as shown in the figures the TL12 was always going to struggle v the ■■■■■■■ and Rolls for similar reasons to the V8 ( lack of torque potential ).While people seem to under estimate just what a formidable package the Rolls actually was and that’s the ideal which AEC needed to be following.Possibly in slightly bigger 13 litre form thereby fitting perfectly between the Rolls and the ■■■■■■■ in terms of capacity and keep the 690 type architecture for a proper V8.‘If’ they really needed a big V8 in their armoury ( doubtful ).
While it seems obvious that the basic design premise of the V8 had everything to do with AEC betting the farm on an already obsolete idea going back to the 1950’s of a pointlessly small V8 to fit in under an equally pointless silly small low set cab.Nothing to do with Lancashire.
You really are on cloud cukoo if the TL12 had have been launched in 1968 you are saying it wouldnt be able to cut it … against what because it did when it came onto the scene 5 years latter and as for the Marathon cab in 1968 most drivers would havýe given their back teeth for 1 .The Ergo was launched a few years earlier and was a huge step forward and even though it doesnt fit in with your little world the TL12 was reliable and did perform as well but more efficiently than the ■■■■■■■
leagely 32tonnes on 5 axle .but in pracsise they had a weight about 45 to 50 tonnes and night time even more 
ERF:
…0…
- They can’t spell “brake”.
- A 12 year old would have simplified that dog’s dinner of an equation before showing it to the teacher.
[zb]
anorak:
- They can’t spell “brake”.
- A 12 year old would have simplified that dog’s dinner of an equation before showing it to the teacher.
- Fair enough!. Nor could I in the post.
- Don’t shoot the messenger. Feel free to modify it!.
ERF:
Carryfast:
ERF:
All I am asking is… GIVE US SOME BMEP FIGURES to compare!!
Rolls 220 12.1 litres 610 lb/ft = 50.4 lb/ft per litre x 2.464 = 124 psi.
AEC 800 13.1 litres 580 - 638 lb/ft = 44.2 - 48.7 lb/ft per litre x 2.464 = 109 - 120 psi.
So there we have it 13.1 litres and 8 cylinders with at best worse specific torque of less than 50 lb/ft per litre than 12.1 litres and 6 cylinders.As I said might as well have condemned it at that point sooner rather than later.
.
While the Rolls 305 at 70 lb/ft per litre showed a similar advantage over the TL12’s less than 65 lb/ft per litre.Which again suggests that more leverage beats more piston area…
Thank you CF!.
At last!.
Although quite why have you chosen to compare the AV800 with the Rolls 220 I don’t know.
The AV740 engine makes a better comparison because both engines have the same bore size, both have the same 12.1 litre cubic capacity, and both produce their maximum torque at the same RPM - 1400, thus making the only difference their basic architecture (as you like to call it) - the ‘all important stroke’!.The first thing we need to do is to make sure we’re all singing rom the same sheet, ie all figures quoted are produced to the same standard. In the case of AEC, playing by the rules as ever, all figures were quoted to BSAU 141:1967 (Atmospheric pressure 760mm, Inlet air temperature 20 dec C…etc). Just at this exact moment I can’t find the figures for the Rolls 220 where they have been expressly quoted to this standard, but I will try when I have more time later so that we can complete our comparison.
The whole point of using BMEP figures is that they remove cubic capacity from the comparison.
This makes it possible to realistically compare the ‘work’ ability of engines produced with different overall capacities, which is why I can’t quite understand why you are re-introducing capacities, and different ones at that, into your thinking above.
With BMEP we can accurately asses the ability of an engine design to inhale air, compress it, inject fuel, burn it and get usable power from it.Without wishing to get into an argument on the why’s, the formula used in the engine development profession to calculate BMEP runs along these lines (sorry it is a scan of a sheet issued to Perkins students, but I’m not clever enough to get the characters on my keyboard)…
0
You will note that no torque figure is introduced into the actual equation, the torque being used to calculate the Break Power.
Using this formula, the AEC AV740 engine produces a BMEP of 115.1 psi - so actually not wildly different from your figures.
For a direct BSAU 141:1967 comparison, the Perkins V8 in both 510 and 540 form produce 112psi.
The 130mm bore AEC AV691 produces a BMEP of between 115 and 116 psi.
When we have confirmed the Rolls 220 figures to the standard, we will compare that too.
scammell-crusader.co.uk/imag … 0specs.PDF
Seems to be BS 141a 1971 according to the spec provided.I’d guess they didn’t relax the testing regime at that point v 1967.While it’s clear from that the Rolls is still making more than 600 lb/ft down to 1,200 rpm.
As for the formula to get a BMEP figure it seems to me that your way just needlessly goes to the power figure first to derive the required torque value and nor does it show that ‘specific’ torque isn’t the relevant figure that it’s based on ?.IE that’s exactly how it removes overall cubic capacity from the comparison. 
Which just leaves the questions over the inconsistencies in the 13.1 litre’s two different torque ratings and can we trust either the 740’s quoted figure,in addition to the big jump in the case of the 638 lb/ft figure for the 13.1 and Scammell at least obviously not seeming to buy it regarding transmission spec.All the signs are one of panic and a resulting damage limitation programme going on at AEC when they found that the small short stroke V8 idea predictably just doesn’t work.On that note I think we can take anything much over a BMEP of 110 psi for it with a pinch of salt as shown by Scammell’s transmission spec which seems to be clue.
[zb]
anorak:
So, the Rolls 740 cu in engine produces about 2% more torque than the AEC. Wow. The AEC makes 247/214= about 14% more power, which is the important figure. By using lower gears, to realise that advantage, the AEC wins by a mile.
Unlike Scania’s ( and Rolls’ ) designers I guess that’s exactly how Roberts and Fogg saw it.Less torque and 14% more power at 25% more engine speed than the seeming already obsolete NA Rolls Mk2.What could possibly go wrong we are invincible. 
The 3 page CM article is a very well written piece of journalism, for the simple fact that it is readable and understandable to non-technical dunderheads such as myself who have no more than basic knowledge of how an engine works.
The turbo-charged AEC AVT690 gave a torque output of 672 ft lbs @ 1,300 rpm.
ERF:
- Fair enough!. Nor could I in the post.
- Don’t shoot the messenger. Feel free to modify it!.
No shooting of messenger intended. I’m just a bit surprised that the people teaching the students were not up to the level of a school maths teacher.
The Wiki derivation I linked ends with the same equation, but in its simplified form. The method they use takes the average power over the combustion stroke to derive the average pressure on the piston. Engine speed cancels out later, to give torque. The mathematician in me instinctively wants to prove it, using the static case of pressure on the piston reacted by torque on the crank. I’m not that clever any more. At the age of17, I would have knocked out the proof in minutes. You just get the equation for the torque as a function of the angle of the crank, the pressure and the piston area, integrate that from 0 to π, then divide by π to give the average torque. The conn rod length will drop out somewhere, inevitably, and you will end up with the relationship between average pressure, average torque and swept volume. I’ve just had a go on a bit of paper and, after about 5 minutes of head scratching, thought, “sod it!” I would rather do something simple nowadays, like a bit of sheet metalwork.
ramone:
You really are on cloud cukoo if the TL12 had have been launched in 1968 you are saying it wouldnt be able to cut it … against what because it did when it came onto the scene 5 years latter and as for the Marathon cab in 1968 most drivers would havýe given their back teeth for 1 .The Ergo was launched a few years earlier and was a huge step forward and even though it doesnt fit in with your little world the TL12 was reliable and did perform as well but more efficiently than the ■■■■■■■
Firstly how does the Marathon cab beat the 3 VTG cab ?.
As for the TL12 it couldn’t even match the Rolls 305 in terms of output.Let alone later developments of the Eagle up to the TX providing near to 8 mpg at 38t gross.
Yesterday morning, Sunday, at 05.08 am to be precise, my 'phone at my bedside rang and it was a driver telling me that he had broken down just half a mile after leaving the yard. Yet here we are discussing engines of almost 60 years ago…yes so long ago, that had their imperfections. And gentlemen trucks STILL break down. We can theorise as much as we want but the inescapable truth is that the perfect engine has yet to be designed.
Carryfast:
ERF:
Carryfast:
ERF:
All I am asking is… GIVE US SOME BMEP FIGURES to compare!!
Rolls 220 12.1 litres 610 lb/ft = 50.4 lb/ft per litre x 2.464 = 124 psi.
AEC 800 13.1 litres 580 - 638 lb/ft = 44.2 - 48.7 lb/ft per litre x 2.464 = 109 - 120 psi.
So there we have it 13.1 litres and 8 cylinders with at best worse specific torque of less than 50 lb/ft per litre than 12.1 litres and 6 cylinders.As I said might as well have condemned it at that point sooner rather than later.
While the Rolls 305 at 70 lb/ft per litre showed a similar advantage over the TL12’s less than 65 lb/ft per litre.Which again suggests that more leverage beats more piston area…
Thank you CF!.
At last!.
Although quite why have you chosen to compare the AV800 with the Rolls 220 I don’t know.
The AV740 engine makes a better comparison because both engines have the same bore size, both have the same 12.1 litre cubic capacity, and both produce their maximum torque at the same RPM - 1400, thus making the only difference their basic architecture (as you like to call it) - the ‘all important stroke’!.The first thing we need to do is to make sure we’re all singing rom the same sheet, ie all figures quoted are produced to the same standard. In the case of AEC, playing by the rules as ever, all figures were quoted to BSAU 141:1967 (Atmospheric pressure 760mm, Inlet air temperature 20 dec C…etc). Just at this exact moment I can’t find the figures for the Rolls 220 where they have been expressly quoted to this standard, but I will try when I have more time later so that we can complete our comparison.
The whole point of using BMEP figures is that they remove cubic capacity from the comparison.
This makes it possible to realistically compare the ‘work’ ability of engines produced with different overall capacities, which is why I can’t quite understand why you are re-introducing capacities, and different ones at that, into your thinking above.
With BMEP we can accurately asses the ability of an engine design to inhale air, compress it, inject fuel, burn it and get usable power from it.Without wishing to get into an argument on the why’s, the formula used in the engine development profession to calculate BMEP runs along these lines (sorry it is a scan of a sheet issued to Perkins students, but I’m not clever enough to get the characters on my keyboard)…
You will note that no torque figure is introduced into the actual equation, the torque being used to calculate the Break Power.
Using this formula, the AEC AV740 engine produces a BMEP of 115.1 psi - so actually not wildly different from your figures.
For a direct BSAU 141:1967 comparison, the Perkins V8 in both 510 and 540 form produce 112psi.
The 130mm bore AEC AV691 produces a BMEP of between 115 and 116 psi.
When we have confirmed the Rolls 220 figures to the standard, we will compare that too.scammell-crusader.co.uk/imag … 0specs.PDF
Seems to be BS 141a 1971 according to the spec provided.I’d guess they didn’t relax the testing regime at that point v 1967.While it’s clear from that the Rolls is still making more than 600 lb/ft down to 1,200 rpm.
As for the formula to get a BMEP figure it seems to me that your way just needlessly goes to the power figure first to derive the required torque value and nor does it show that ‘specific’ torque isn’t the relevant figure that it’s based on ?.IE that’s exactly how it removes overall cubic capacity from the comparison.
Which just leaves the questions over the inconsistencies in the 13.1 litre’s two different torque ratings and can we trust either the 740’s quoted figure,in addition to the big jump in the case of the 638 lb/ft figure for the 13.1 and Scammell at least obviously not seeming to buy it regarding transmission spec.All the signs are one of panic and a resulting damage limitation programme going on at AEC when they found that the small short stroke V8 idea predictably just doesn’t work.On that note I think we can take anything much over a BMEP of 110 psi for it with a pinch of salt as shown by Scammell’s transmission spec which seems to be clue.
If we are to keep these comparisons credible and relative CF, we must all play by the rules!. The ‘squeaking wheels’ on those goalposts of yours have drawn attention to the fact that you seem to be comparing the Rolls 220 Mk3 from 1976, not the earlier Mk1 220 in production with the AEC V8 in 1968.
I was reluctant to do the AEC V8 AV740 / Rolls 220 BMEP comparison because even now, having just spent an hour looking, I still can’t find BSAU 141:1967 figures for the 1968 Rolls 220 Mk1. I can find the SAE GROSS figures (below), they are 220bhp @ 2100 RPM, and 605 lbs/ft @ 1400 RPM. You are not going to like that comparison though, because the SAE GROSS figures for the AEC V8 AV740 are 265bhp @ 2600 RPM, and 621 lbs/ft @ 1400 RPM
The Rolls 220 Mk2 engine from 1971, for which we DO have BSAU 141:1967 figures (thanks to ‘cav551’), didn’t even develop 600 lb/ft, it peaked at 594 lb/ft. If you are making a point (?) about a relatively flat torque curve, then the 220 Mk2 curve is relatively identical in form to the AEC V8 between 1200 and 1600 RPM, just 2% lower as ‘[zb] anorak’ said.
Please remember it’s not ‘my’ way of calculating BMEP. I’m not that clever. It’s just the way taught to Perkins students in the 1990’s, and confirmed as accurate by a former engine development engineer, so that is good enough for me.
The two torque ratings for the AEC V8 13.1 litre engine are fully explained a couple of pages back.
The spec sheet I posted shows two ratings for the 13.1 litre, the AV800 and AV801. I know from personal experience the difference in rating was down to the delivery elements in the fuel injection pump being smaller in the AV800.
I really don’t know why you keep pressing this issue about Scammell fitting that Fuller RT610 gearbox in the 1969 Scottish show Crusader 6x4 vehicle. To imagine, as you suggest, that Scammell dyno tested an AV801 engine, found that the torque output was ‘way below’ AEC’s quoted BSAU 141:1967 figure, and fitted that gearbox to ‘take the ■■■■■ (your words) is just complete nonsense. We will never know why they really did it, but as I have said before, when the vehicle entered service with Bass in 1970 the gearbox was a TET D251 ten-speed - as recorded in CM.
If you are going to continually disregard AEC quoted performance figures, but believe the figures from every other manufacturer there is little point in continuing with this line of discussion, is there?.
CM 12th September 1969.
[zb]
anorak:
…after about 5 minutes of head scratching, thought, “sod it!” I would rather do something simple nowadays, like a bit of sheet metalwork.
We really should have a chat!
The next project here has a Motor Panels cab…
ERF:
[zb]
anorak:
…after about 5 minutes of head scratching, thought, “sod it!” I would rather do something simple nowadays, like a bit of sheet metalwork.We really should have a chat!
The next project here has a Motor Panels cab…
There’s a lovely 5MW ERF rebuild here:
flickr.com/photos/3833861■■ … otostream/
ERF:
If we are to keep these comparisons credible and relative CF, we must all play by the rules!. The ‘squeaking wheels’ on those goalposts of yours have drawn attention to the fact that you seem to be comparing the Rolls 220 Mk3 from 1976, not the earlier Mk1 220 in production with the AEC V8 in 1968.I was reluctant to do the AEC V8 AV740 / Rolls 220 BMEP comparison because even now, having just spent an hour looking, I still can’t find BSAU 141:1967 figures for the 1968 Rolls 220 Mk1. I can find the SAE GROSS figures (below), they are 220bhp @ 2100 RPM, and 605 lbs/ft @ 1400 RPM. You are not going to like that comparison though, because the SAE GROSS figures for the AEC V8 AV740 are 265bhp @ 2600 RPM, and 621 lbs/ft @ 1400 RPM
The Rolls 220 Mk2 engine from 1971, for which we DO have BSAU 141:1967 figures (thanks to ‘cav551’), didn’t even develop 600 lb/ft, it peaked at 594 lb/ft. If you are making a point (?) about a relatively flat torque curve, then the 220 Mk2 curve is relatively identical in form to the AEC V8 between 1200 and 1600 RPM, just 2% lower as ‘[zb] anorak’ said.
Please remember it’s not ‘my’ way of calculating BMEP. I’m not that clever. It’s just the way taught to Perkins students in the 1990’s, and confirmed as accurate by a former engine development engineer, so that is good enough for me.
The two torque ratings for the AEC V8 13.1 litre engine are fully explained a couple of pages back.
The spec sheet I posted shows two ratings for the 13.1 litre, the AV800 and AV801. I know from personal experience the difference in rating was down to the delivery elements in the fuel injection pump being smaller in the AV800.
Firstly I wasn’t actually clear on all the exact respective output levels and timelines between Mk1 to Mk3 Rolls Eagle versions.Although my case is obviously based more on the differences between the ‘potential’ contained in ‘what type’ of design.Not its exact development status ‘when’ in time.Which obviously makes the comparison between Mk1 Eagle v AEC V8 moot regardless.
While you seem to have explained AEC’s thinking perfectly.IE our V8 beats the specific outputs of a Mk1 Eagle that obviously must mean it’s a winner. 
Remind us what was its production life v the Eagle ?.Let alone Scania V8 to date ?. 
[zb]
anorak:ERF:
[zb]
anorak:
…after about 5 minutes of head scratching, thought, “sod it!” I would rather do something simple nowadays, like a bit of sheet metalwork.We really should have a chat!
The next project here has a Motor Panels cab…There’s a lovely 5MW ERF rebuild here:
flickr.com/photos/3833861■■ … otostream/
Looks like the 6MW cab rebuild for the R-reg Leicester Heavy Haulage unit to me. Robert
ERF-NGC-European:
Looks like the 6MW cab rebuild for the R-reg Leicester Heavy Haulage unit to me. Robert
You’re right- one of the other photos shows the forward axle position. It’s nice work, either way. The corner panel is especially nice. He’s probably used a wheeling machine to get the compound curve. That or taken a similar panel off another vehicle- I reckon the corner of a Mini roof would not take too much attention from the mallet to look like that. 