WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
#1160335
01/18/12 08:19 PM
01/18/12 08:19 PM
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Joined: Apr 2005
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SCATPACK 1
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Have read a couple of post relating to reducing the outside diameter of a cranks counter weights. Why would u want to or need to do this
Old Geezer Racing
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Re: WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
[Re: SCATPACK 1]
#1160338
01/18/12 09:02 PM
01/18/12 09:02 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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I do it to MOST of my cranks for 3 reasons... 1 to get the counter weight close for balancing... 2, move the weight in closer to the center line so it can accelerate quicker and 3, move it farther away from the oil
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Re: WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
[Re: MR_P_BODY]
#1160339
01/18/12 09:16 PM
01/18/12 09:16 PM
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Joined: Apr 2005
Posts: 1,505 TN
SCATPACK 1
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Ok. Makes good sense to me.
Old Geezer Racing
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Re: WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
[Re: bwdst6]
#1160342
01/18/12 10:00 PM
01/18/12 10:00 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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Quote:
Quote:
I do it to MOST of my cranks for 3 reasons... 1 to get the counter weight close for balancing... 2, move the weight in closer to the center line so it can accelerate quicker and 3, move it farther away from the oil
Number 1 and 2 contradict each other.
Not really.... if you run light parts you dont need all that weight out far from center line
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Re: WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
[Re: bwdst6]
#1160344
01/18/12 10:26 PM
01/18/12 10:26 PM
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Joined: Nov 2004
Posts: 4,330 Lynchburg, VA
Leon441
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If you find your crank is heavy for your parts. You have a choice either cut holes on every counterweight to get in balance or simply trim the counterweights until you get close.
Career best 8.02 @ 169 at 3050# and 10" tires small block power.
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Re: WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
[Re: Leon441]
#1160346
01/18/12 10:32 PM
01/18/12 10:32 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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Quote:
If you find your crank is heavy for your parts. You have a choice either cut holes on every counterweight to get in balance or simply trim the counterweights until you get close.
Yep... if you need to drill... turn it down more... but alot of the guys that balance find it easier to drill
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Re: WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
[Re: Locomotion]
#1160350
01/19/12 12:27 AM
01/19/12 12:27 AM
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Joined: Jul 2010
Posts: 2,091 Delray beach, Florida
Performance Only
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if you have two crankshafts with identical weights, but crank # 1 has a circumference of 8" and crank # 2 has a circumference of 6", crank # 2 will need less force to accelerate because the mass is closer to the center of mass.
simple way to prove it to yourself. tie a 1 lb weight on a string 3 feet long, make up another one with a string 1 foot long. twirl them both and see which one is easier.
keep in mind that a crankshaft in a practical application still needs to overcome the forces working against it outside of the engine such as more rotating mass, vehicle weight, etc. in some cases a heavier rotating assembly can be more beneficial to overall performance. i.e. heavy vehicle with a high reving, low torque small CID engine.
Last edited by Performance Only; 01/19/12 12:33 AM.
machine shop owner and engine builder
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Re: WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
[Re: bwdst6]
#1160352
01/19/12 01:16 AM
01/19/12 01:16 AM
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Joined: Nov 2009
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dennismopar73
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I think every one is right ! Lite weight is always good, can be less bearing fatigue, mains can see longer use, increase in rpm range. Thus more harmonics the block has to endure, Loss of 'initial hit' over come by increase in tq rate of stahl, thus increasing thrust bearing issues? OO the domino effect, Ain't it great!! I will do it to clear the block,other wise I don't worry about it.
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Re: WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
[Re: bwdst6]
#1160353
01/19/12 01:24 AM
01/19/12 01:24 AM
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Joined: Jan 2003
Posts: 5,894 Florida
Locomotion
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I understand the "set" amount of rotational mass required to balance a rotating assembly. We're just saying that the distribution of that mass away from the centerline will affect how quickly the rotating assembly can be accelerated. I'm tired, gotta work early tomorrow & all this thinking is giving me a headache! G'nite.
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Re: WHY WOULD U REDUCE CRANK COUNTER WEIGHTS
[Re: Performance Only]
#1160354
01/19/12 01:25 AM
01/19/12 01:25 AM
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Joined: Dec 2008
Posts: 415 Peru
cbarracuda
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mopar
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Peru
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Quote:
if you have two crankshafts with identical weights, but crank # 1 has a circumference of 8" and crank # 2 has a circumference of 6", crank # 2 will need less force to accelerate because the mass is closer to the center of mass.
Nunber 2 will meed more weigts because tre mass is closer
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