How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
- milnersXcoupe
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How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
Given the Weight of a 12 cwt crankshaft & inherent dynamic balance
how much can the counterweights be trimmed to reduce overall weight ?
I like the idea of uniform balancing via counterweights just not
the some 20 extra pounds of cast iron to spin up .
how much can the counterweights be trimmed to reduce overall weight ?
I like the idea of uniform balancing via counterweights just not
the some 20 extra pounds of cast iron to spin up .
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
Not sure anyone here has gone as far as knife edging a crank for these motors. The extra weight does help with the harmonics.
Honestly though, it would be way more cost effective and lighter for you to just go with a 4 cwt crank then to have your 12 cwt crank knife edged then balanced. Unless you plan on racing and spinning up to 7000 rpms you won't be gaining anything but a lighter wallet. Even then you wouldnt even notice a difference.
Honestly though, it would be way more cost effective and lighter for you to just go with a 4 cwt crank then to have your 12 cwt crank knife edged then balanced. Unless you plan on racing and spinning up to 7000 rpms you won't be gaining anything but a lighter wallet. Even then you wouldnt even notice a difference.
- Cheromaniac
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
On an engine that's rev limited to a modest 5250rpm, why bother?milnersXcoupe wrote:Given the Weight of a 12 cwt crankshaft & inherent dynamic balance
how much can the counterweights be trimmed to reduce overall weight ?
I like the idea of uniform balancing via counterweights just not
the some 20 extra pounds of cast iron to spin up .
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- IH 392
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
Trade your 12CW crank for a 4CW crank.
Properly balanced, I don't believe its been proven that a 4CW crank will spin up any faster than a 12CW crank?
Properly balanced, I don't believe its been proven that a 4CW crank will spin up any faster than a 12CW crank?
You can get more power out of ANY engine!!!
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
I agree with everybody statements up to this point.
Knife edging cast Crankshaft in a low RPM tractor engine is a waste of time and money.
Knife edging cast Crankshaft in a low RPM tractor engine is a waste of time and money.
- gradon
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
The 20# lighter 4-weight will absolutely spin up(and down) faster than the 12-weight. I was even contemplating a 10# lighter fidanza flywheel at one time. Even 5# lighter makes a noticable difference in the rotating assembly(I'm in the BMW world too with my '95 M3--there are many lighter flywheel and clutch assembly options). The bottom line is if you are off-roading you want the 12-weight and if not, you want the 4-weight.
- gradon
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
My brother Nick just told me his knife-edged(or semi-knife 'cause I thought it could be more aggresive), offset-ground(4.060" stroke) 12-weight 505 crankshaft weighs 60#, so that'll give you a clue how much you can lose.
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
I guess another question that needs to be asked is what is the application of your stroker project?
I ask because sometimes the purpose and budget of the build will help to determine the practicality of a upgrade.
For example. If you had a budget of less then 5K to build your stroker, knife edging a crankshaft would be a waste of money because you'd receive better gains or benifits if you applied your budget and other areas
There is definitely pros and cons to both 12 and 4 counterweight Crankshafts.
I ask because sometimes the purpose and budget of the build will help to determine the practicality of a upgrade.
For example. If you had a budget of less then 5K to build your stroker, knife edging a crankshaft would be a waste of money because you'd receive better gains or benifits if you applied your budget and other areas
There is definitely pros and cons to both 12 and 4 counterweight Crankshafts.
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
A lighter flywheel will give more benefit than a lighter crank, the mass is at a greater distance of the radius.
On our race car we cut a 199 9" clutch flywheel right down to the pressure plate bolts and carved it a lot more than that too, and used a flex plate to start it with, it really spins up fast!
On our race car we cut a 199 9" clutch flywheel right down to the pressure plate bolts and carved it a lot more than that too, and used a flex plate to start it with, it really spins up fast!
You can get more power out of ANY engine!!!
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
I used to think that as well. The crank is pretty much center mass so the extra 20# is negligible on spining up n down. Only a larger stroke could add rotational mass. The advantage that the 12cwt crank brings to the table is that it softens the harmonics at higher rpms and thats about it. Honestly a 4cwt crank would probably be more benificial for 95% of the people running 12cwt cranks. All for the simple reason that it would drop 20# off the nose of the jeep.gradon wrote:The 20# lighter 4-weight will absolutely spin up(and down) faster than the 12-weight.
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
Agree.IH 392 wrote:A lighter flywheel will give more benefit than a lighter crank, the mass is at a greater distance of the radius.
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
Like adding a crank scraper, welding an extra baffle inside the oil pan, adding a "kickout" to the sump to increase its capacity, and swapping in a HV oil pump. Perhaps an oil cooler too if you do a lot of offroading.Russ Pottenger wrote:knife edging a crankshaft would be a waste of money because you'd receive better gains or benefits if you applied your budget in other areas
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
1995 Mustang GT - 4AT - Modded Sold
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
Darn it.
Wrote a long explanation on the physics of rotational mass. Musta pushed the wrong button 'cause it anit in the thread.
Let's just say the guy with a bad haircut knew a few things way back when.
You cannot beat physics. You might think you can but it isn't gonna happen.
Wrote a long explanation on the physics of rotational mass. Musta pushed the wrong button 'cause it anit in the thread.
Let's just say the guy with a bad haircut knew a few things way back when.
You cannot beat physics. You might think you can but it isn't gonna happen.
- gradon
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
My brother told me the wrong weight. His scale might be off, but he weighed it to be:
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Re: How Much Can 12 cwt Crank Be Lightened & Knife Edged ?
Did your brother mention how much or how involved it was to rebalance the crank?
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