Adding weight to the crank

GOT-Torque said:
Probably a stupid question, but why not use a bigger bellhousing and just put a custom flywheel with extra weight out near the edge? It wouldn't take as much weight as that added to the crank (as shown above) since it would be farther from the center line?
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Yeah, I have a hard time following the logic in welding additional mass to the counterweights, unless there's so little room in the bellhousing that you don't have space for a 2X or 3X thick flywheel.

I can see where doing this on a manual-trans truck would help...the extra rotational inertia that you get "for free" while spooling would help keep it spun up as the clutch fully engages.

With an auto I'd think you'd be hard put to show where it helps at all since there's no free spool.

???
 
How would the mains feel about another 200 lbs. added to the flywheel only? Maybe just the weight distribution helps?
 
nwpadmax said:
Yeah, I have a hard time following the logic in welding additional mass to the counterweights, unless there's so little room in the bellhousing that you don't have space for a 2X or 3X thick flywheel.

I can see where doing this on a manual-trans truck would help...the extra rotational inertia that you get "for free" while spooling would help keep it spun up as the clutch fully engages.

With an auto I'd think you'd be hard put to show where it helps at all since there's no free spool.

???
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There wouldn't be any benefit in adding weight in anything other than a full competition only motor (for pulling)...not trying to take jabs here, but if you ever look in some high end tractor engines you will see they add weight all the way around so it almost looks like a tube looking down the crank...


...as for adding all the weight to the flywheel/clutch, having all that weight concentrated like that has to be much harder on twisting the crank than adding less weight along the entire length of the crank...just my $.02
 
Well one benefit would be if weight is added at the flywheel, it would require less than that added on the crank.

I also wondered about the twisting of the crank at the back bearing journal. But remember, where is all the twisting force at right now when you redline a truck and let the clutch out? crank trying to spin fast, driveline trying slow crank down when clutch engages...

You have all that hp trying to keep the crank spinning at 4000 rpm (for ex.) and as the clutch engages, the flywheel is trying to slow the crank down. So I think if the crank survives that twisting force fine (never hear of anyone having a problem there), I would think the weight added to the flywheel would do just fine.

And yes, the weight would only be practical for a pulling machine.
 
It's not done for inertia, (although I'm sure it helps with that). It's counterweighted so it's completely balanced. I never paid much attention but the stock crank doesn't have counterweights on every journal. And a crank like the one I posted above (which was from Woodruff Diesel webpage gotta give credit where credit is due) sitting next to a stock crank is QUITE a difference. Ted Sterner has his done this way also last year. I don't know if it's needed but it's a little extra insurance at high RPM (it's a heavy SOB now).
 
i was told by a drag racer that they did a crank and when it was all said and done it weighed about 200 lbs not added 200 lbs
and my buddy was quoted 3500 to add weight to the crank and then balance it

i have seen a stk motor with 560 000 miles on it break the crank and it still ran i have a pic of it somewhere we did a motor swap for the lady who owned the truck
 
not to take credit from woodruffs who sells for enterprise but i was told enterprise engine does it and does a good job
haisleys quoted my buddy i dont know if they can do it but they quoted a price and i was also told that if you arent turning like 6k rpm there is no real benefit other than everything is alot smoother
just what i was told nothing more nothing less
 
bonesmx2000 said:
not to take credit from woodruffs who sells for enterprise but i was told enterprise engine does it and does a good job
haisleys quoted my buddy i dont know if they can do it but they quoted a price and i was also told that if you arent turning like 6k rpm there is no real benefit other than everything is alot smoother
just what i was told nothing more nothing less
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Thank you !!!!!
 
jfaulkner said:
It's not done for inertia, (although I'm sure it helps with that). It's counterweighted so it's completely balanced. I never paid much attention but the stock crank doesn't have counterweights on every journal. And a crank like the one I posted above (which was from Woodruff Diesel webpage gotta give credit where credit is due) sitting next to a stock crank is QUITE a difference. Ted Sterner has his done this way also last year. I don't know if it's needed but it's a little extra insurance at high RPM (it's a heavy SOB now).
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I knew I should have kept my mouth shut...when I talked to my boss this afternoon about his tractor crank he said the same thing...it's done so it balances much more closely to perfectly neutral everywhere and he also added that the cranks with weight all the way around (a complete circle) are much stronger for pulling applications...he also said that most of the billet cranks for big tractor pullers are machined out like the welded-up ones...no weight hanging off one side, just machined out for connecting rods and mains and the other material is left...
 
Met's machine can do this IIRC, and Gene's is capable also from what I hear... GMac knows he lives minutes from Met's. I'd feel better about a billet crank that was fully counterweighted than a welded one but I'm sure it will hold.
 
jfaulkner said:
It's not done for inertia, (although I'm sure it helps with that). It's counterweighted so it's completely balanced. I never paid much attention but the stock crank doesn't have counterweights on every journal.
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I'm not sure I follow....if you run a lighter low compression piston, and use the same rod, isn't it typical to need to take weight out of the counterbalances?

Now if you went with a billet rod, I imagine they're heavier, so it's somewhere in the middle.

I also remember reading somewhere about 6-cyl cranks being naturally balanced anyhow...."all ya gotta do is make sure the rods and pistons weigh the same."

V-8 balancing would be a whole 'nuther matter.

I hear you on equal distribution of weight.
 
nwpadmax said:
I'm not sure I follow....if you run a lighter low compression piston, and use the same rod, isn't it typical to need to take weight out of the counterbalances?

Now if you went with a billet rod, I imagine they're heavier, so it's somewhere in the middle.
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:umno: ...weight is only taken out of the crank to balance the crank itself...so that the crank can/will spin easier and with much less resistance in the bearings. By reducing friction against the bearings or evening the friction across the entire bearing to crank surface you free up a lot of power and engine longevity

...connecting rod and pistons have nothing to do with balancing the crank...:poke:
 
CTDYoungGun said:
...connecting rod and pistons have nothing to do with balancing the crank...:poke:
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In a V-8 they sure do!

We're not all in 6-banger land, there, youngster.
 
I'm not convinced just yet. I understand what people are trying to do in principle, but I don't think you can apply the same practices to V8 cranks in the exact same manner as I6 cranks.

I could have this all wrong, but from what I gather on an I6 you balance the crank by itself (so everything said above makes sense) but when balancing a V8 you need bobweights whose weight comes from a formula calculated using the weights of the components.

I have never ever heard of anyone adding weight to a V8 crank...only the opposite. But, I'm a small fish.
 
CTDYoungGun said:
:umno: ...weight is only taken out of the crank to balance the crank itself...so that the crank can/will spin easier and with much less resistance in the bearings. By reducing friction against the bearings or evening the friction across the entire bearing to crank surface you free up a lot of power and engine longevity.
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I'm not sure your verbiage is correct. The resistance / friction in the bearings has much more to do with things other than the crank mass. Of course balancing in and of itself will help remove pounding in the bearings, but in two perfectly balanced cranks of different masses, I think you'd be hard put to tell the difference, in terms of power output.

Ask any circle track racer....lightening the crank makes it spin up / accelerate quicker but makes no more HP. It's been done on a few Dmaxes but I think the results are similar. I have not heard of what it does in an I6 one way or the other.
 
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nwpadmax said:
I have never ever heard of anyone adding weight to a V8 crank...only the opposite. But, I'm a small fish.
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use mallory to balance them out.....especially when you modifiy them by removing metal, like knife edging the crank so it cuts through the oil better.....you can drill into the face of the filet and add the mallory there....


http://www.overbore.com/?go=Define.EngineBalance

look at the bottom of the article under "Special Balancing Processes"......

here is some more ready you guys can do....

http://www.circletrack.com/techarticles/ctrp_0504_engine_balancing_tech_terminology/index.html
 
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