The Carryfast engine design discussion

UK PROFESSIONAL DRIVERS FORUMS OLD TIME LORRIES, COMPANIES AND DRIVERS (INTERACT
1021

Joe Mac:

Carryfast:
In the case of the TL12 v Eagle you’ve got a 43% specific torque at the flywheel ( BMEP ) deficit.
You’ve got a 7% leverage deficit.
You’ve got a 2% net piston area v leverage deficit.
That’s 43% x 7 % more load required on your end bearings and 43% x 2% more load required on your head fastenings to match the Eagle’s specific torque ( BMEP ) output potential …

Shouldn’t that be a 3.5% leverage ‘deficit’ (5 mm)? And where is the ‘net piston area v leverage deficit’ coming from? Shouldn’t that be in the TL12’s favour?

Been reading threads here a while …

I would say that you have just taken a set of chopsticks into a soup kitchen but, if you are already aware of the challenge you are about to undertake, good luck. :smiley:

1022

Yeah, I’d say I have my work cut out alright!

1023

[zb]
anorak:

Carryfast:
I said you can’t determine the peak cylinder pressure from an abstract not real average figure .

I said you can estimate it, for the purposes of a rough calculation of loads on the containing parts, if you have an estimate of the ratio between peak and mean, for engines of that type. Don’t make me repeat myself again.

BMEP is pressure, measured in Bar (usually). If you understood how it is calculated, you would understand that it is a perfect representation of the pressure in the bore, over the whole cycle of the engine. I asked you to provide that derivation, but you ran scared from it. An engineer would have attacked that challenge like a scrap yard dog.

BMEP is simply an abstract non existent ‘pressure’ directly and only derived from the specific torque at the flywheel figure.

How can you ‘estimate’ any loads from that figure when 1 it’s only meant to be a comparator of output of different engines it doesn’t provide any measurement of the actual pressures in the cylinder at any point.

2 torque is a function of force meaning the ‘combination’ of cylinder pressure and piston area x leverage in the form of stroke.
Any of which are interchangeable to reach exactly the same figure.
But multiplying the force figure by more leverage means less cylinder pressure and/or less piston area thereby force on the piston to make the same amount of torque and thereby less stress on head fastenings and end bearings.

Remind me how you’re going to calculate all that from just the specific torque figure measured at the flywheel which is all that BMEP actually is.There is no actual pressures in the cylinder related to BMEP.

While all you’ve done is moan and tell us that you can do it.

You’re the barking scrap yard dog but so far you’ve chosen not to answer the questions.You know like exactly what is the extra loading on the TL12’s ends and head fastenings v the Eagle’s at 100 lbft per litre ( 43% more ).
Taking into account that specific torque deficit you’re starting with multiplied by the leverage deficit and piston area v leverage deficit.

1024

[zb]
anorak:

Joe Mac:

Carryfast:
In the case of the TL12 v Eagle you’ve got a 43% specific torque at the flywheel ( BMEP ) deficit.
You’ve got a 7% leverage deficit.
You’ve got a 2% net piston area v leverage deficit.
That’s 43% x 7 % more load required on your end bearings and 43% x 2% more load required on your head fastenings to match the Eagle’s specific torque ( BMEP ) output potential …

Shouldn’t that be a 3.5% leverage ‘deficit’ (5 mm)? And where is the ‘net piston area v leverage deficit’ coming from? Shouldn’t that be in the TL12’s favour?

Been reading threads here a while …

I would say that you have just taken a set of chopsticks into a soup kitchen but, if you are already aware of the challenge you are about to undertake, good luck. :smiley:

By that logic the difference between the TL12’s 71 mm v Eagle’s 76 mm actual throw is exactly the same 7%. :unamused:

The stroke measurement is always stated in total not from the throw.Just like you don’t need to be given a half diameter measurement on a drawing to know that the amount needed to be taken off has to be halved when you machine it on a lathe.

136 mm bore v 130 mm bore is 4.6% more.
Subtract your 7% leverage deficit that’s actually more than 2% extra cylinder pressure needed on the piston to make the equivalent torque.
So I was actually being generous to the TL12.

Oh look our wannabe barking dog didn’t correct you and I’m not the one professing to be an engineer.

1025

Carryfast:
BMEP is simply an abstract non existent ‘pressure’ directly and only derived from the specific torque at the flywheel figure…Blah…

It is what it says it is. " Abstract non existent" is your deduction. It is wrong. If you can’t do the derivation, just cut and paste it from one of the many schoolboy lessons online.

Carryfast:
… I’m not the one professing to be an engineer.

Yes you are. If not, what is all that 35 pages of piffle up there^^^?

1026

[zb]
anorak:

Carryfast:
BMEP is simply an abstract non existent ‘pressure’ directly and only derived from the specific torque at the flywheel figure…Blah…

It is what it says it is. " Abstract non existent" is your deduction. It is wrong. If you can’t do the derivation, just cut and paste it from one of the many schoolboy lessons online.

Carryfast:
… I’m not the one professing to be an engineer.

Yes you are. If not, what is all that 35 pages of piffle up there^^^?

In among those pages you’ll find plenty of references stating that I couldn’t get close to making that calculation call.Because it’s way above my knowledge, because I’m no design engineer and not even any type of qualified time served automotive engineer, and there are too many variables to deal with.

But what I do know is that the TL12 has to make up a 43% specific torque deficit multiplied by a 7% leverage deficit and a 2% + piston area v leverage deficit.Don’t ask me what the end calculation is because I don’t know it.But common sense tells me that you can’t meet that specific torque target without imposing an arguably unviable amount of stress on your end bearings and head fastenings v the Eagle because of the combined multiplying effects of all those deficits.

I did the derivation of BMEP it’s specific torque measured at the flywheel x 2.464.It’s used as a pointlessly over complicated comparator of different engine outputs no different to using just the specific torque figure for the same job.Nothing more nothing less.
Now tell me I’m wrong on all counts and provide your figures to prove it.
I won’t hold my breath waiting.

1027

Carryfast:

[zb]
anorak:

Carryfast:
BMEP is simply an abstract non existent ‘pressure’ directly and only derived from the specific torque at the flywheel figure…Blah…

It is what it says it is. " Abstract non existent" is your deduction. It is wrong. If you can’t do the derivation, just cut and paste it from one of the many schoolboy lessons online.

Carryfast:
… I’m not the one professing to be an engineer.

Yes you are. If not, what is all that 35 pages of piffle up there^^^?

In among those pages you’ll find plenty of references stating that I couldn’t get close to making that calculation call.Because it’s way above my knowledge, because I’m no design engineer and not even any type of qualified time served automotive engineer, and there are too many variables to deal with.

It is a dead simple calculation. If you are pleading ignorance, what about the 35 pages of guff? Too many variables my arse. It’s a doddle to do it, or learn how to do it. Just type “BMEP calculation” into Google.

Carryfast:
But what I do know is that the TL12 has to make up a 43% specific torque deficit multiplied by a 7% leverage deficit and a 2% + piston area v leverage deficit.Don’t ask me what the end calculation is because I don’t know it.But common sense tells me that you can’t meet that specific torque target without imposing an arguably unviable amount of stress on your end bearings and head fastenings v the Eagle because of the combined multiplying effects of all those deficits.

You don’t need to multiply any of those numbers together, whatever they are. If the capacities of both engines are the same, you want the same BMEP and one of them has a larger bore, then the ratio of the force on the head fixings is the ratio of the areas of the bores. Simple. In the case of the TL12 and RR Eagle, the difference is negligible, compared to the variation between comparable engines of the period.

Carryfast:
I did the derivation of BMEP it’s specific torque measured at the flywheel x 2.464.

That’s not a derivation. It is a statement and, unless you put units to it- N, m, ib, ft, in, whatever, it’s nothing. A derivation takes one set of variables- like bore, stroke and torque- and converts them into another variable, like pressure. You need to study algebra for 10-12 year olds.

Carryfast:
It’s used as a pointlessly over complicated comparator of different engine outputs no different to using just the specific torque figure for the same job.Nothing more nothing less.
Now tell me I’m wrong on all counts and provide your figures to prove it.
I won’t hold my breath waiting.

You’re wrong on all counts. 0/100.

1028

[zb]
anorak:

Carryfast:
In among those pages you’ll find plenty of references stating that I couldn’t get close to making that calculation call.Because it’s way above my knowledge, because I’m no design engineer and not even any type of qualified time served automotive engineer, and there are too many variables to deal with.

It is a dead simple calculation. If you are pleading ignorance, what about the 35 pages of guff? Too many variables my arse. It’s a doddle to do it, or learn how to do it. Just type “BMEP calculation” into Google.

Carryfast:
But what I do know is that the TL12 has to make up a 43% specific torque deficit multiplied by a 7% leverage deficit and a 2% + piston area v leverage deficit.Don’t ask me what the end calculation is because I don’t know it.But common sense tells me that you can’t meet that specific torque target without imposing an arguably unviable amount of stress on your end bearings and head fastenings v the Eagle because of the combined multiplying effects of all those deficits.

You don’t need to multiply any of those numbers together, whatever they are. If the capacities of both engines are the same, you want the same BMEP and one of them has a larger bore, then the ratio of the force on the head fixings is the ratio of the areas of the bores. Simple. In the case of the TL12 and RR Eagle, the difference is negligible, compared to the variation between comparable engines of the period

Carryfast:
I did the derivation of BMEP it’s specific torque measured at the flywheel x 2.464.

That’s not a derivation. It is a statement and, unless you put units to it- N, m, ib, ft, in, whatever, it’s nothing. A derivation takes one set of variables- like bore, stroke and torque- and converts them into another variable, like pressure. You need to study algebra for 10-12 year olds.

Carryfast:
It’s used as a pointlessly over complicated comparator of different engine outputs no different to using just the specific torque figure for the same job.Nothing more nothing less.
Now tell me I’m wrong on all counts and provide your figures to prove it.
I won’t hold my breath waiting.

You’re wrong on all counts. 0/100.

Which part of you have a 43% specific torque deficit v the Eagle don’t you understand.

Which part of the TL 12, has a ( 2 % + ) leverage deficit v the Eagle, v its bore size advantage, don’t you understand.

How are you going to compensate for that piston area deficit without multiplying that same specific torque deficit by that same 2% + bore size v stroke deficit in your cylinder pressure requirement v the Eagle.

Multiplying specific torque in lbft at the flywheel x 2.464 will give you BMEP in psi.How does that relate to peak cyclinder pressure in any way shape or form bearing in mind all the other variables of piston area and force x stroke and the fact an average doesn’t provide a peak figure.

Just saying I’m wrong won’t cut it.
Now provide your figures showing that specific torque in lbft at the flywheel x 2.464 won’t give you BMEP in psi.How does the result determine peak cylinder pressure.

Then provide your figures as to how much extra stress that 43% more specific torque, with a 7% leverage deficit and a 2% + piston area deficit will put on your end bearings and head fastenings v the Eagle.

I’ve provided numbers and so far all you’ve provided is the barking dog.

1029

Carryfast:
…

I’ve provided numbers and so far all you’ve provided is the barking dog.

You started the barking- do your own calculations. The BMEP one is easy- you could even copy it, if you wanted, because it is all over the internet. It’s one of the first things a fresh student or apprentice learns. I suspect you don’t even know what to look for.

1030

[zb]
anorak:

Carryfast:
…

I’ve provided numbers and so far all you’ve provided is the barking dog.

You started the barking- do your own calculations. The BMEP one is easy- you could even copy it, if you wanted, because it is all over the internet. It’s one of the first things a fresh student or apprentice learns. I suspect you don’t even know what to look for.

Are you saying that BMEP isn’t simply specific torque lbft x 2.464 yes or no ?.That’s what ‘I look for’ that’s what I was taught to ‘look for’.

If not show any calculation of BMEP which isn’t consisistent at the end with that equation.
IE just an over complicated needless way of saying the same thing as specific torque.

Having established that how will you determine the difference in peak cylinder pressure and end loadings for the TL12 v Eagle at 100 lbft per litre from that calculation if any calculation.

1031

Carryfast:

[zb]
anorak:

Carryfast:
…

I’ve provided numbers and so far all you’ve provided is the barking dog.

You started the barking- do your own calculations. The BMEP one is easy- you could even copy it, if you wanted, because it is all over the internet. It’s one of the first things a fresh student or apprentice learns. I suspect you don’t even know what to look for.

Are you saying that BMEP isn’t simply specific torque lbft x 2.464 yes or no ?.That’s what ‘I look for’ that’s what I was taught to ‘look for’.

If not show any calculation of BMEP which isn’t consisistent at the end with that equation.
IE just an over complicated needless way of saying the same thing as specific torque.

Having established that how will you determine the difference in peak cylinder pressure and end loadings for the TL12 v Eagle at 100 lbft per litre from that calculation if any calculation.

Good grief. You need to ask some school kids what a derivation is. In this case, you take the pressure in the cylinder and the dimensions of the engine, and end up with the pressure as a function of the torque and the capacity. While you are picking their brains, ask them what units they use for force, distance and energy- no one has used Imperial measure for engineering calculations this side of the war. No need to remember 2.46whatever for anything.

Edit- the ratio of the bore areas for the TL12/RR Eagle is (135/130)^2, which is about 8%. Given that the BMEP of diesels will increase by about 30% over the next 15 years, it isn’t something to worry about. It certainly would not have bothered the AEC engineers- they had been making the turbocharged AVT1100, long before the RR 280 was launched, and that had a bore of 156mm. For the same BMEP as the RR engine, that’s 44% more force on the cylinder head. LOL.

At the beginning of this thread, you were denying that there were any tensile forces on the engine parts, at all. Now, after 30-odd pages of whining, you accept that they exist and are relevant. It will be the same with compression inside the cylinder. From shouting about reducing it at all costs, you will come round to the realisation that it is not a problem to designers.

1032

[zb]
anorak:

Carryfast:
Are you saying that BMEP isn’t simply specific torque lbft x 2.464 yes or no ?.That’s what ‘I look for’ that’s what I was taught to ‘look for’.

If not show any calculation of BMEP which isn’t consisistent at the end with that equation.
IE just an over complicated needless way of saying the same thing as specific torque.

Having established that how will you determine the difference in peak cylinder pressure and end loadings for the TL12 v Eagle at 100 lbft per litre from that calculation if any calculation.

Good grief. You need to ask some school kids what a derivation is. In this case, you take the pressure in the cylinder and the dimensions of the engine, and end up with the pressure as a function of the torque and the capacity. While you are picking their brains, ask them what units they use for force, distance and energy- no one has used Imperial measure for engineering calculations this side of the war. No need to remember 2.46whatever for anything.

You didn’t answer the question.
Are you saying that specific torque x 2.464 won’t provide the BMEP figure in psi.Yes or no will do.

TL12 v Eagle all stated torque outputs you’ll find anywhere for them are in lbft.Even the latest DAF MX engine torque figures are also provided as lbft.Pressure load figures are still referred to in psi.

So now you’re hiding behind metric measurements as an excuse for your total bs here.You don’t ‘‘end up’’ with the peak cylinder pressure in the engine or the load on the ends from the BMEP ( specific torque ) figure.As in this case TL12 v Eagle at equivalent specific torque output.

Now tell us how you’re going to arrive at the end bearing loadings and cylinder head fastener loadings for TL12 v Eagle.From an abstract, non existent, average pressure figure derived from the specific torque output figure and as such is the same thing and only used to compare different engine ouptuts which in this case is already a known given at 100 lbft per litre.
Not to find out cylinder pressures and con rod loads.Bearing in mind that torque output is not a function of just cylinder pressure alone.It’s actually a calculation of cylinder pressure, piston area and leverage and in this case the specific torque figure is a known given.

Feel free to provide those figures in metric or imperial but what’s the point in changing them all to metric unless you’re not bright enough to understand lbft and psi.

My guess is that the 2.464 constant will probably work just the same with nm to kgcm2/bar etc etc if you must be that silly in converting it all.

1033

Edit to add.

100 lbft per litre = 135.58 nm per litre.

100 lbft per litre x 2.464 = 246.4 psi.

246.4 psi = 17.32 kg/cm2 and 16.98 bar BMEP regardless.

The torque outputs of both TL12 and the Eagle were quoted in lbft even up to the 1990’s in the form of the TX 400.So why the need for any metric conversion.

Remind me how do we get from the BMEP figure to peak cylinder pressures and end bearing loads TL12 v Eagle.Regardless of whether that BMEP figure is expressed as metric or imperial.

That’s assuming you accept the 246.4 psi or even 17.32 kgcm2 or 16.98 Bar BMEP figure.

Let me guess you’ll say that peak cylinder pressures and end loads are the same regardless of the Eagle’s leverage advantage v TL12’s leverage deficit and TL12’s net piston area deficit v Eagle’s leverage advantage. :unamused:

Feel free to show how often bolt tensile strength and bearing loads are quoted in bar or kg/cm2 as opposed to psi.

enginebuildermag.com/2015/12 … -pressure/

Good luck with that 43 % specific torque deficit x 7% leverage deficit.

1034

Carryfast:
…Blah…

My guess is that the 2.464 constant will probably work just the same with nm to kgcm2/bar etc etc if you must be that silly in converting it all.

Looks like we’re still at the stage of brake mean effective pressure not being pressure, then. Give it another couple of weeks. This should be a hint:

Carryfast:
BMEP figure in psi.

What else could possibly be measured in Pounds per Square Inch, I wonder?

I know- if my computer screen is 14" x 10" (I haven’t measured it), and is completely covered in finely repeated misinformation like that up there^^^, I could estimate that it amounts to a full 8 wheeler load of fertiliser from the bloke up the road with the beef herd, who does not do any milking. That’s about 20 tons x 2240 =44800.

44800/(14x10) = exactly 32 PSI.

1035

[zb]
anorak:

Carryfast:
…Blah…

My guess is that the 2.464 constant will probably work just the same with nm to kgcm2/bar etc etc if you must be that silly in converting it all.

Looks like we’re still at the stage of brake mean effective pressure not being pressure, then. Give it another couple of weeks. This should be a hint:

Carryfast:
BMEP figure in psi.

What else could possibly be measured in Pounds per Square Inch, I wonder?

I know- if my computer screen is 14" x 10" (I haven’t measured it), and is completely covered in finely repeated misinformation like that up there^^^, I could estimate that it amounts to a full 8 wheeler load of fertiliser from the bloke up the road with the beef herd, who does not do any milking. That’s about 20 tons x 2240 =44800.

44800/(14x10) = exactly 32 PSI.

The only 20t of bovine excreta here is your pathetic replies.

Yes BMEP is expressed as a pressure measurement.But it means the square root of zb all in relation to determining the load on cylinder head fastenings and end bearings resulting from peak cylinder pressure and the force x distance equation of that acting on your piston.
Less distance means more force required on the con rod for the same torque output at the crankshaft/flywheel.

BMEP just relates to a comparison of specific torque output of different engines.Might as well use the specific torque figure that it originated from.

So you’re saying that 100 lbft per litre doesn’t = 246.4 psi BMEP ?.

What relationship does that pressure figure have with peak cylinder pressure applied to your head fastenings and the pressure applied to your end bearings by the resulting force on the piston.Here’s a clue absolutely no relationship whatsoever or in fact any relationship with any other specific pressure in the cylinder.

In the case of the TL12 you’ve got a 43% deficit in the specific torque figure to make up with a 7% shorter lever and a 4.6% larger piston area.

No surprise you still won’t have provided any coherent answer to the difference that’s going to make to your end bearings and head bolts two weeks from now.Look on the bright side maybe it won’t take the two years it took Edwardes to knock the piece of junk on the head.

As for your equation at least give your poor computer a chance we’ll just drive a steer axle wheel over it trust me it will be fine.
Which makes any difference to the fact that the components in question are subject to 10’s of thousands of psi.
43% more specific torque to match the Eagle x 7% more force required on the con rod and 2% more cylinder pressure than the Eagle will need, matters.

Obviously your 32 psi estimate of 20t dropped across 140 sq inches was light only by a factor of 10.AEC would be proud.

Remind me what is the area of a big end bearing shell and a cylinder head bolt and how much is peak cylinder pressure and the tensile strength of a head bolt and main bearing bolt.

1036

[zb]
anorak:

Carryfast:
…Blah…

My guess is that the 2.464 constant will probably work just the same with nm to kgcm2/bar etc etc if you must be that silly in converting it all.

Looks like we’re still at the stage of brake mean effective pressure not being pressure, then. Give it another couple of weeks. This should be a hint:

Carryfast:
BMEP figure in psi.

What else could possibly be measured in Pounds per Square Inch, I wonder?
I can smell it from here
I know- if my computer screen is 14" x 10" (I haven’t measured it), and is completely covered in finely repeated misinformation like that up there^^^, I could estimate that it amounts to a full 8 wheeler load of fertiliser from the bloke up the road with the beef herd, who does not do any milking. That’s about 20 tons x 2240 =44800.

44800/(14x10) = exactly 32 PSI.

1037

ramone:

[zb]
anorak:

Carryfast:
…Blah…

My guess is that the 2.464 constant will probably work just the same with nm to kgcm2/bar etc etc if you must be that silly in converting it all.

Looks like we’re still at the stage of brake mean effective pressure not being pressure, then. Give it another couple of weeks. This should be a hint:

Carryfast:
BMEP figure in psi.

What else could possibly be measured in Pounds per Square Inch, I wonder?

I know- if my computer screen is 14" x 10" (I haven’t measured it), and is completely covered in finely repeated misinformation like that up there^^^, I could estimate that it amounts to a full 8 wheeler load of fertiliser from the bloke up the road with the beef herd, who does not do any milking. That’s about 20 tons x 2240 =44800.

44800/(14x10) = exactly 32 PSI.

I can smell it from here

1038

Take a breath of fresh air, Ramone:
sciencedirect.com/topics/en … r-pressure

Maximum cylinder pressure is 75 bar, according to their measurements. I was surprised it was so low, given that modern engines are making 25+ bar BMEP.

1039

Nothing like a good initialism .

In this case BMEP .

■■■■■■■■ mentioned every post

Brushes manically every pavement

Barks at Moon every post .

:unamused: :laughing:

1040

[zb]
anorak:
Take a breath of fresh air, Ramone:
sciencedirect.com/topics/en … r-pressure

Maximum cylinder pressure is 75 bar, according to their measurements. I was surprised it was so low, given that modern engines are making 25+ bar BMEP.

Yeah right all arrived at with no account of torque output, engine speed, stroke measurement and piston area.

All I’m seeing is around 70 bar at an output of less than 4 kw. :laughing: Even that means nothing if without the engine speed to calculate a torque output then we don’t know the engine capacity to calculate a specific torque output.

Yes modern diesels are more than 20 bar BMEP.
The difference is with a much larger leverage advantage over the TL12 than even the Eagle had and more modern materials tech.14% more leverage in the case of the MX for example.Again you’ve forgotten, more like don’t even know, that the BMEP figure, being based on specific torque output, also includes and is based on leverage multiplication and piston area.Not just cylinder pressure.It’s also just an average not a peak.

We’re clearly talking about cylinder pressures measured in Mpa not a few bar.The force created by that acting on the area of the piston and all that force then placed on the much smaller area of the small end and big end bearings.In addition to that pressure being contained by the cylinder head fastenings.
A 7% deficit in leverage is going to make a big difference to the force requirement on the piston and a 2% deficit in piston area regarding cylinder pressure and forces on the head fastenings.
Obviously all way over the AEC fan boy trolls heads. :unamused:

core.ac.uk/download/pdf/82115791.pdf