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Old car, new engine. Spanking...
Cars Modifications Aspects of car modifications (tuning, styling) (uk.rec.cars.modifications)
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#61
 
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Re: Old car, new engine. Spanking... -
04-26-2007
, 06:21 AM
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In article <f0orqe$sgc$1 (AT) registered (DOT) motzarella.org>, mrdoki (AT) gmail (DOT) com says... Moneywise now: 4 pistons (3000 UKP), new rods (those are not Carillo's nor titanium, 1000 UKP), billet crankshaft (7000 UKP), specific camshafts (1000 UK), headwork and valves (3000 UKP), ecu (2000 UKP). I'm no metallurgist, but why a billet crank? Surely the strongest crankshaft is going to be a forged one? Or is that far stronger and far more expensive than needed? A billet crank is a crank cut out 1 billet, a cilindre of (special) steel out of which the crank is turned on a lathe. It offres complete freedom, no distorsion, much stronger because the abscence of induced stresses, much more controlled as to dimensions and thus better balanced, better dimensionwise (so lighter), etc. Downside is the enormous "loss" of material and the work involved. There are around 10 companies worldwide who offre this service, all those I know are in the US. For small badges of special engines however (once power > 100 HP/liter) it is the only option. Prices start around 7000 UKP (on known engine, known dimensions) to 12000 UKP (on prototypes). CNC-cutting has however (for people like Prodrive etc) has reduced the workload on the lathe enormously and this means that on smaller badges (100-500) the cost per crankshaft descends enormously. Seems that all is as most on the times in numbers. |
in short runs, rapid prototyping etc. which is why it's used so much in
Aerospace development. What I don't understand is that 9 times out of 10
the lightest and strongest bike parts are forged...
#62
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In article <f0orqe$sgc$1 (AT) registered (DOT) motzarella.org>, mrdoki (AT) gmail (DOT) com says... Moneywise now: 4 pistons (3000 UKP), new rods (those are not Carillo's nor titanium, 1000 UKP), billet crankshaft (7000 UKP), specific camshafts (1000 UK), headwork and valves (3000 UKP), ecu (2000 UKP). I'm no metallurgist, but why a billet crank? Surely the strongest crankshaft is going to be a forged one? Or is that far stronger and far more expensive than needed? A billet crank is a crank cut out 1 billet, a cilindre of (special) steel out of which the crank is turned on a lathe. It offres complete freedom, no distorsion, much stronger because the abscence of induced stresses, |
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much more controlled as to dimensions |
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and thus better balanced, |
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better dimensionwise (so lighter), |
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etc. Downside is the enormous "loss" of material and the work involved. |
needed in consequence
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There are around 10 companies worldwide who offre this service, all those I know are in the US. |
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For small badges of special engines however (once power > 100 HP/liter) it is the only option. Prices start around 7000 UKP (on known engine, known dimensions) to 12000 UKP (on prototypes). |
mean that it's the best.
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CNC-cutting has however (for people like Prodrive etc) has reduced the workload on the lathe enormously and this means that on smaller badges (100-500) the cost per crankshaft descends enormously. Seems that all is as most on the times in numbers. |
reasons for choosing a billet crankshaft. Everything else is against it.
Forged crankshafts are lighter, stronger, more durable and can be
balanced and machined to the same tolerances as billet crankshafts.
#63
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"Tom De Moor" <viperengine (AT) removethis (DOT) gmail.com> wrote in message news:MPG.209a65738e37a5b19898f6 (AT) news (DOT) telenet.be... In article <f0orqe$sgc$1 (AT) registered (DOT) motzarella.org>, mrdoki (AT) gmail (DOT) com says... Moneywise now: 4 pistons (3000 UKP), new rods (those are not Carillo's nor titanium, 1000 UKP), billet crankshaft (7000 UKP), specific camshafts (1000 UK), headwork and valves (3000 UKP), ecu (2000 UKP). I'm no metallurgist, but why a billet crank? Surely the strongest crankshaft is going to be a forged one? Or is that far stronger and far more expensive than needed? A billet crank is a crank cut out 1 billet, a cilindre of (special) steel out of which the crank is turned on a lathe. It offres complete freedom, no distorsion, much stronger because the abscence of induced stresses, much more controlled as to dimensions and thus better balanced, better dimensionwise (so lighter), etc. Downside is the enormous "loss" of material and the work involved. There are around 10 companies worldwide who offre this service, all those I know are in the US. For small badges of special engines however (once power > 100 HP/liter) it is the only option. Prices start around 7000 UKP (on known engine, known dimensions) to 12000 UKP (on prototypes). CNC-cutting has however (for people like Prodrive etc) has reduced the workload on the lathe enormously and this means that on smaller badges (100-500) the cost per crankshaft descends enormously. Seems that all is as most on the times in numbers. I know what CNC machining is, and as far as I can see its main advantage is in short runs, rapid prototyping etc. which is why it's used so much in Aerospace development. What I don't understand is that 9 times out of 10 the lightest and strongest bike parts are forged... |
Because the "grain" follows the shape giving better strength as in forged
pistons.
A billet crank does not have this advantage but to make small numbers of
good cranks to your own design (maybe a stronger design shape) a billet is
easier to work with.
#64
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| Tom De Moor wrote: In article <f0orqe$sgc$1 (AT) registered (DOT) motzarella.org>, mrdoki (AT) gmail (DOT) com says... Moneywise now: 4 pistons (3000 UKP), new rods (those are not Carillo's nor titanium, 1000 UKP), billet crankshaft (7000 UKP), specific camshafts (1000 UK), headwork and valves (3000 UKP), ecu (2000 UKP). I'm no metallurgist, but why a billet crank? Surely the strongest crankshaft is going to be a forged one? Or is that far stronger and far more expensive than needed? A billet crank is a crank cut out 1 billet, a cilindre of (special) steel out of which the crank is turned on a lathe. I've often wondered about why billet cranks are supposed to be better when the grain flow will only be in one direction, I would assume along the axis of the crank, and a forged crank should have grain following the crank profile so should be stronger. Maybe this is down to the use of steel for the billet which has superior properties compared to a forging steel although my experience with BMC A series tells me that the factory made forged EN40B cranks and that is a material often used for billet cranks. |
loss in strength after the heating cycles but that I do not know. My
lessons metallurgie are to far in the past.
Your assumption might even be correct that forging in the same steel is
better. Forging however is once again a very costly operation if done
for very small production numbers.
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| It offres complete freedom, no distorsion, much stronger because the abscence of induced stresses, much more controlled as to dimensions and thus better balanced, better dimensionwise (so lighter), etc. Downside is the enormous "loss" of material and the work involved. There are around 10 companies worldwide who offre this service, all those I know are in the US. Machining will produce distortion, a common problem, especially with such large metal removal and it is very likely the billet crank goes through various heattreat stages to relieve induced stresses to ensure a stable crank. Any reason why a forged crank can't be as accurate dimensionally, it can be fully machined just as easily to the same tolerances. |
exact wording in English but the large portions are taken away first in
big steps (torque and power of the lathe are determing factors), in
Dutch this is called "ruwen" -roughning translated. In this stage some
distortion can take place but the part after "ruwen" is still 1-2 mm
bigger than then final part. Controlling and escaping distortion is an
integral part of the machinist job.
The final part is obtained by very small increments, often -in CNC
always- with a special chisel and in steps of 0.1 to 0.4 mm.
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I suspect the main reasons are going to be down to the original engine having an iron crank or inferior grade steel crank so billet is the option for greater strength and fatigue resistance. |
doesn't exist. It can be that a long course crank is wanted (for extra
displacement) or lower course (so the engine can rev higher).
The engine in the cosworth of the Greek was stated as 1.9 l
displacement, so it is possible that he traded some 100cc (or more) for
revs. His revs com from smaller course and lighter (but maybe bigger)
pistons (The pistons are displayed but diameter isn't mentioned).
Finally : there is a cheap mans version of the special crank with either
longer or shorter course. The standard crank can be regrinded ex center.
Most cranks take accept excentergrinding to 1 mm for the main bearings,
0.5mm for the bearing of the conrods. It means a variation on the
course of -3 to +3 mm.
Big disadvantage is that the crank is weaker: bad news as the aim of the
operation is more power and/or higher rpm
All this said: safety margins on any crank are huge, so the cheap man
version is a tale of "it is not supposed to work but it works".
Tom De Moor
#65
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In article <463070CE.2000304 (AT) djbillington (DOT) freeserve.co.uk>, djb (AT) djbillington (DOT) freeserve.co.uk says... Tom De Moor wrote: In article <f0orqe$sgc$1 (AT) registered (DOT) motzarella.org>, mrdoki (AT) gmail (DOT) com says... Moneywise now: 4 pistons (3000 UKP), new rods (those are not Carillo's nor titanium, 1000 UKP), billet crankshaft (7000 UKP), specific camshafts (1000 UK), headwork and valves (3000 UKP), ecu (2000 UKP). I'm no metallurgist, but why a billet crank? Surely the strongest crankshaft is going to be a forged one? Or is that far stronger and far more expensive than needed? A billet crank is a crank cut out 1 billet, a cilindre of (special) steel out of which the crank is turned on a lathe. I've often wondered about why billet cranks are supposed to be better when the grain flow will only be in one direction, I would assume along the axis of the crank, and a forged crank should have grain following the crank profile so should be stronger. Maybe this is down to the use of steel for the billet which has superior properties compared to a forging steel although my experience with BMC A series tells me that the factory made forged EN40B cranks and that is a material often used for billet cranks. I guess it is indeed down to the quality of steel used. Maybe there is loss in strength after the heating cycles but that I do not know. My lessons metallurgie are to far in the past. Your assumption might even be correct that forging in the same steel is better. Forging however is once again a very costly operation if done for very small production numbers. It offres complete freedom, no distorsion, much stronger because the abscence of induced stresses, much more controlled as to dimensions and thus better balanced, better dimensionwise (so lighter), etc. Downside is the enormous "loss" of material and the work involved. There are around 10 companies worldwide who offre this service, all those I know are in the US. Machining will produce distortion, a common problem, especially with such large metal removal and it is very likely the billet crank goes through various heattreat stages to relieve induced stresses to ensure a stable crank. Any reason why a forged crank can't be as accurate dimensionally, it can be fully machined just as easily to the same tolerances. Machining if done properly doesn't produce distortion. I don't know the exact wording in English but the large portions are taken away first in big steps (torque and power of the lathe are determing factors), in Dutch this is called "ruwen" -roughning translated. In this stage some distortion can take place but the part after "ruwen" is still 1-2 mm bigger than then final part. Controlling and escaping distortion is an integral part of the machinist job. The final part is obtained by very small increments, often -in CNC always- with a special chisel and in steps of 0.1 to 0.4 mm. I suspect the main reasons are going to be down to the original engine having an iron crank or inferior grade steel crank so billet is the option for greater strength and fatigue resistance. The main reason for a billet crank is that the desired crank as such doesn't exist. It can be that a long course crank is wanted (for extra displacement) or lower course (so the engine can rev higher). The engine in the cosworth of the Greek was stated as 1.9 l displacement, so it is possible that he traded some 100cc (or more) for revs. His revs com from smaller course and lighter (but maybe bigger) pistons (The pistons are displayed but diameter isn't mentioned). Finally : there is a cheap mans version of the special crank with either longer or shorter course. The standard crank can be regrinded ex center. Most cranks take accept excentergrinding to 1 mm for the main bearings, 0.5mm for the bearing of the conrods. It means a variation on the course of -3 to +3 mm. Big disadvantage is that the crank is weaker: bad news as the aim of the operation is more power and/or higher rpm All this said: safety margins on any crank are huge, so the cheap man version is a tale of "it is not supposed to work but it works". Tom De Moor |
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