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Crank Balancer snapped off (Whipple 2.9)

wazslow

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Cant be that hard of a concept for some thick skulls to get it thru their head. Turbos with untouched balancers had had broken snouts. Even Aldo from Aldowelds who sees more turbos in coyotes than most in here combined has said this is a “normal” thing on coyotes, cracked or broken snouts.
I wonder how many did OPG's as well. The stock balancer would have had to come off and could be reinstalled incorrectly/not seated.
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engineermike

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The raw weight of the balancer only is next to worthless with regards to predicting destructive resonance. This is such a complicated subject, seriously. I bet only a handful of people in the world have the knowledge and tools to accurately model the system.

Ford has so much as admitted that the coyote runs near a destructive resonance, so it’s not surprising that turbo cars are susceptible to similar failures, albeit at a lower likelihood. It’s probably the same resonance that breaks opg’s, timing gears, and crank snouts.
 

SolarFlare

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I wonder how many did OPG's as well. The stock balancer would have had to come off and could be reinstalled incorrectly/not seated.
Over the years a few people have broken it with untouched motors. It’s become more common now that a lot of Gen 3 guys choose not to do OPGs because, for whatever reason, OPG failures don’t seem to be as common.
 

80FoxCoupe

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The raw weight of the balancer only is next to worthless with regards to predicting destructive resonance. This is such a complicated subject, seriously. I bet only a handful of people in the world have the knowledge and tools to accurately model the system.

Ford has so much as admitted that the coyote runs near a destructive resonance, so it’s not surprising that turbo cars are susceptible to similar failures, albeit at a lower likelihood. It’s probably the same resonance that breaks opg’s, timing gears, and crank snouts.
Saying that weight driven by the snout is next to worthless is comical. As horsepower increases, so does the rate of acceleration. Driven weight and rate of acceleration would have to have a dramatic effect on snout life.
 

engineermike

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Saying that weight driven by the snout is next to worthless is comical. As horsepower increases, so does the rate of acceleration. Driven weight and rate of acceleration would have to have a dramatic effect on snout life.
I said it was worthless in regards to predicting *resonance*. What you describe is simple F=ma, which is a different phenomenon and about 100x simpler than what I’m describing.

Even still, the weight isn’t helpful in determining what you are describing either, because the how the weight is geometrically situated in relation to the axis of rotation matters immensely. A heavier damper with weight nearer to the center would impart less stress on the snout than a lighter one with a higher moment of inertia.

But again, none of this is even remotely close to enough information to figure out what’s going on with the harmonics, which was my point.
 

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shogun32

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oscillation shatters sintered materials, forged doesn't generate the same stress risers. putting more weight on the snout and especially outboard imparts a bending moment. If the bearing has anything more than C0 radial runout the end is going to have all kinds of wiggle to it. Given Ford is cheap to the point of nuts, I wouldn't be at all surprised they have a low precision bearing supporting the end of the crank and while they're at it, entirely too much overhang - ie unsupported length. A double-bearing can help but the cases have to be machined for it.

Putting belts on it, especially vastly overtight ones makes the situation hundreds of times worse and failure is to be expected.

On the simplistic basis of not deliberately making a bad situation dramatically worse, Turbos are the better choice. That of course doesn't mean that the elevated combustion forces (turbo or super) don't cause harmonics and excessive flex in the poorly supported crank and break things anyway.
 
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80FoxCoupe

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I said it was worthless in regards to predicting *resonance*. What you describe is simple F=ma, which is a different phenomenon and about 100x simpler than what I’m describing.

Even still, the weight isn’t helpful in determining what you are describing either, because the how the weight is geometrically situated in relation to the axis of rotation matters immensely. A heavier damper with weight nearer to the center would impart less stress on the snout than a lighter one with a higher moment of inertia.

But again, none of this is even remotely close to enough information to figure out what’s going on with the harmonics, which was my point.
While you are considering MOI of balancer weight being insignificant in comparison to harmonics, would you agree that a lighter balancer assembly is better?
 

shogun32

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would you agree that a lighter balancer assembly is better?
way too simplistic world-view. The radius of the weight absolutely matters. The evenness of the balance greatly more.
 

engineermike

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While you are considering MOI of balancer weight being insignificant in comparison to harmonics, would you agree that a lighter balancer assembly is better?
Neglecting harmonics completely, I still don’t have enough information to answer your question. If, and only if, the lighter one also has a lower moment of inertia AND the shell is where the weight is reduced, as opposed to the inertia weight, then it may reduce crank stresses resulting from rapid changes in average speed. If the inertia weight is lighter and/or the moment of inertia is higher, then it will make things worse. But this is grossly oversimplified because it neglects the harmonic effects.
 

80FoxCoupe

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way too simplistic world-view. The radius of the weight absolutely matters. The evenness of the balance greatly more.
It was explained above that harmonics are difficult to understand and record. With that being said, many of us are at the mercy of the balancer we run (its capability or lack thereof). Its obvious that one could keep the rpm's down, but lets focus on the basics.

Wouldn't you and @engineermike agree that reducing the parasitic load in the form of weight, driven by the crank snout will increase snout life?
 

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80FoxCoupe

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With respect to blower combinations dual key way in theory, more evenly distributes the load applied to the snout. Though this could also be considered insignificant, it is something we can do that is a step in the right direction.
 

engineermike

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It's worth noting that the "inertia weight" in a damper (internal on the ATI and early gen3, external on the stock gen1/2 and late gen3) matters and reducing weight here could make things way worse.
 

engineermike

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With respect to blower combinations dual key way in theory, more evenly distributes the load applied to the snout. Though this could also be considered insignificant, it is something we can do that is a step in the right direction.
In heavy duty machinery applications, you don't take credit for the second key. On a microscopic level, it's impossible to get both keys to carry the load simultaneously. Are the dual keys situated 180 apart?
 
 




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