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[guppytrash]

Seems like this is a common topic among us 110 owners and it is a part of nearly all the 110 problem threads.
I have a very elementary understanding of what it is...
I was hoping that one of the engine builder types here would maybe give us some more info.
Pictures are always best, but any explanations of how to measure for it, or what the symptoms are would be helpful.

[cvobiker]

I don't think it's just the 110's... Lots of 'reads' here about run-out problems with the latest and greatest Jims 120 & 131 Race Engines....

I still can't get over another $350 for a Race Crank when you buy these "Race Engines".     so they build all that torque and HP with a pressed crank and really expect it to stay true......

[Twolanerider]

I'm no engine builder but will take a stab at a description that illustrates run out for you.  Words like "true" and "run out" don't mean a lot if their application here is outside someone's experience.

The crankshaft is basically a straight rod through the middle of the engine that has eccentric points in its middle for the piston rods to attach to.  Those eccentric points go up and down to raise the piston up and down in the cylinder.  The rest of the straight rod is supposed to be... well..... straight.  That is it is supposed to be "true."  

It being true (having no wobble) at its ends is important because things attach out there.  Oil pump and bearings and other things all need a relatively straight drive shaft going through them.  

Think of a pool cue laying on a pool table.  We roll the cue to see if it's straight.  If it is straight we see no wobble in the cue.  If it's not straight we see the end of the cue raise up and down off the table.  That raising up and down is run out of the pool cue.

[guppytrash]

Thanks Twolanerider

That is different than what I was thinking.  I thought it was more about the crank not staying centered and "runout" measurement was how much "slop" there was from true center.

Now I am a bit more confused.  How/Where do they weld the crank to help solve the problem?

[Twolanerider]

Thanks Twolanerider

That is different than what I was thinking.  I thought it was more about the crank not staying centered and "runout" measurement was how much "slop" there was from true center.

Now I am a bit more confused.  How/Where do they weld the crank to help solve the problem?

No, you're doing ok.  Picture looking at the end of a rod or shaft.  Perfectly round.  Picture it spinning.  If it's a "true" shaft there is no "wobble" on the end.  You only see the same size circle in a constant rotation.  If there is "run out" rather than shaft staying in a constant and and perfect (or nearly) perfect circle you instead seeing it wobbling. 

Think of a pool cue again that you're watching from its tip end.  If the cue is straight when you roll it the tip of the cue never leaves the table its rolling on.  If something isn't straight you see see that tip raise up off the table then fall back down.  It wobbles.  Now instead of looking at the end of a pool cue imagine looking at the end of a rotating crankshaft.  Same thing.  If the shaft is straight and "true" from one end to the other you see no up and down or side to side eccentricity.  If the shaft is straight you only see the same constant perfect circular rotation constantly and consistently.

[Twolanerider]

Now I am a bit more confused.  How/Where do they weld the crank to help solve the problem?

This part is a separate question.  Welding isn't a solution to a crank that has runout.  Runout is a problem (of straightness) along the longitudinal axis (through its middle) of the shaft.  Shafts are welded to keep the separate pieces that make make them up and that are pressed together from moving in relation to one another.  

If a crankshaft "slips" or the pieces move in relation to each other gaining run out wouldn't be unexpected.  But the real problem them is that counterweights aren't balancing anymore or that pistons aren't up or down when and where they are supposed to be.  

A crank gets welded as prophylactic to strengthen its rotating assembly and keep pieces from moving relative to each other.  Welded or not, however, that center line through its middle still needs to be straight so there is no run out.  Because too much runout wears out the other pieces that attach to and are driven by those shafts.

[guppytrash]

Thanks again

So I guess the slipping of parts on the crank is what causes the runout over time or are these crank problems coming straight from the factory?

[Unbalanced]

Some are coming right from the factory that way.  Its sad they got rid of the forged cranks and timkens just to save money. ... good for S&S though.   

The 96" motors have just as many problems its not unique to just the 110's.   

[Twolanerider]

Thanks again

So I guess the slipping of parts on the crank is what causes the runout over time or are these crank problems coming straight from the factory?

Generally separate issues.  If a crank has any of its parts "slip" there may be runout that is gained because something has moved and/or done other damage.  If the crank has slipped runout is the least of your worries though.  You might run for a long time with an amount of runout that is actually more than you're comfortable with.  You're not going far on a scissored or slipped crankshaft.

Runout is there on a crank that has all of its pieces still in perfect position relative to each other.  Runout is just that center line through the middle of the crankshaft not being straight.

[Twolanerider]

Hey, just thought of another more illustrative example to aid in the understanding of runout.  This should help .

Consider the following.  You're on Bourbon Street in New Orleans' French Quarter.  Standing at the entry to a bar is a buxom young lass sporting tassles on her nipples.  As you're engaging her in conversation on David Hume's treatise on religion and the existence of divinity she sways to the background music coming from the bar and her tassles rotates with her nipples as the center point of that rotation.

The tassle itself is exactly six inches long.  If she had perfectly firm breasts allowing no eccentric rotation of the nipple the outside diameter of the circle made by the swinging tassle would be exactly six inches.

If, on the other hand, she had some runout and the nipple wobbled a bit in the middle the outside diameter of the circle created by the swinging tassle would vary by whatever amount up and down and side to side the nipple (or center point of the crankshaft) wobbled.  The amount her nipple moved up and down would be the amount of her runout.

I love science.... 

[DavidB]

Would this be considered run out or wobble ?

[Twolanerider]

Would this be considered run out or wobble ?

There is definite runout happening there.  Good runout. 

[CVOJOE]

Er uh Don, what's the run out tolerance on nipple tassels these days?  As I recall Nawlins has a waiver based upon some environmental issues following Katrina. Just wondering...

Uh-Oh suppose the hijack thread police will be screening this one soon. 

Lots of articles on this on the HD Forum site as well (crankshafts not nipples.)

[Twolanerider]

Er uh Don, what's the run out tolerance on nipple tassels these days? 

Pretty much same as in an engine.  Any spec that's not so large it allows damage to the parts around it...   

[ual767plt]

Hey, just thought of another more illustrative example to aid in the understanding of runout.  This should help .

Consider the following.  You're on Bourbon Street in New Orleans' French Quarter.  Standing at the entry to a bar is a buxom young lass sporting tassles on her nipples.  As you're engaging her in conversation on David Hume's treatise on religion and the existence of divinity she sways to the background music coming from the bar and her tassles rotates with her nipples as the center point of that rotation.

The tassle itself is exactly six inches long.  If she had perfectly firm breasts allowing no eccentric rotation of the nipple the outside diameter of the circle made by the swinging tassle would be exactly six inches.

If, on the other hand, she had some runout and the nipple wobbled a bit in the middle the outside diameter of the circle created by the swinging tassle would vary by whatever amount up and down and side to side the nipple (or center point of the crankshaft) wobbled.  The amount her nipple moved up and down would be the amount of her runout.

I love science.... 

Now I understand.....thanks!