What is "CRANK RUN OUT"

[Ministik Man]

I have heard of the words CRANK RUN OUT

What is it?

What does it mean to the life of the motor?

Is it caused by bearings?


Thanks

 

[tex78]

Run out is the shaft moveing up and down and or side to side when turning

Yes its a way to tell how worn Ur bottom end is. At 8000 rpm just a hair of run out makes a hole bunch wobble

Sent from my HTC-Z710a using Tapatalk

 

[hdkawi]

When u blow out a belt it can cause your crank toGo out good idea to change belts before they go

 

[007sevens]

Crank Run out is the measurement for side to side movement in car engines and generally doesn't pertain to snowmobile engines that use roller bearings.

 

[snopro]

Hmmmm.........I may disagree. Crank run out is checked on either end of a crankshaft with a dial indicator in v blocks to determine how much "wobble" there is in the end of the crank to determine the integrity of trueness. Right out of any manufacturer shop manual. Hope that helps.

 

[overkill131313]

it is the measurement that tells you how much your PTO clutch can "wobble" before your clutch breaks off (with end of crank still attached lol)and wants to "run" out of your engine compartmant!....... clutch tries to run away at 8000 plus RPM when it goes! sorry but had to crack a funny, but there is always some truth to all funnies!

.002 of an inch on a dial indicator on the end of crank becomes .003 then .004 then more ad more till snap and good by clutch/crank!

 

[teeroy]

Crank Run out is the measurement for side to side movement in car engines and generally doesn't pertain to snowmobile engines that use roller bearings.

bzzzzt! sorry, wrong answer. we were looking for.....

Crank run out is checked on either end of a crankshaft with a dial indicator in v blocks to determine how much "wobble" there is in the end of the crank to determine the integrity of trueness.

 

[tex78]

sorry runout is run out... no matter what king of bearing it has

 

[WopOnTour]

I have built a few engines in my time, so have some experience in this. (as do many of the previous posters obviously- but if I might add to their comments)
As a few have indicated "runout" is any measurable radial or axial movement from "true" on any rotating assembly. Movement back and forth along the centerline is technically not "runout" but actually called "axial endplay".
These are often confused and a totally different issue.

In the case of a crankshaft, the levels of runout can typcially be measured with a dial indicator placed on many machined surfaces along the crank center-line. such as mounted on a lathe or on on V-blocks (as my old buddy snopro indicates) but only if removed.
Most manufacturer's list runout specifications at various points along the crank, usually in at least 3 spots- PTO end, midpoint and mag end and often specified to be 0.001-.002 ("one to two thousands") maximum.(less is better)When someone presses together a snowmobile crank, like when bearings are serviced, they attempt to true the crank as much as possible.

But while mounted in a sled crank runout is most often measured externally at the tip of the PTO end crankshaft taper where the primary clutch mounts.(clutch removed)
Issues with clutch imbalance, a hard crash, (and yes even breaking a belt) can "tweak" the crank.
Excessive runout here creates a 2nd order vibrational frequency that will amplifiy as RPM increases and can even become catostrophic (crank or bearing faliure) especially at a specific RPM levels (due to harmonics) dependant on the mass and balance of the clutch and the severity of the runut..

Runout can even be measured with a dial indicator placed directly on the fine-line top edge of one of the primary sheaves as a "quick" check and typically should be less than 0.004" ("four thou") or less when measured here as it's 6" further away from the crank centerline.But that's more of an "old-school" rule of thumb than a specification.
Sometimes having your primary clutched balanced and "indexed" (trying different spots of mountng the clucth, relative to the runout) can alleviate a serious vibration condition.
Below is a table of crank runout and axial endplay specifications for a typical Rotax crank.

hope this helps
WopOnTour

 

[plio7]

i thought you could tell by when you see them walking down the street asking for change again......but that might be coke runout too

 

[WopOnTour]

i thought you could tell by when you see them walking down the street asking for change again......but that might be coke runout too

LOL now that's funny. I hate a "run out" of rum myslef...
WOT

 

[markoo]

If your riding a polaris 900 and your clutch goes flying through your belly pan and rolls down the hill with the end of your crank still in the clutch it is called crank run out, or is that roll out?

 

[GYMBRAT]

i thought you could tell by when you see them walking down the street asking for change again......but that might be coke runout too

nooooo thats "CRACK run out"

 

[GYMBRAT]

if your riding a polaris 900 and your clutch goes flying through your belly pan and rolls down the hill with the end of your crank still in the clutch it is called crank run out, or is that roll out?

lol!!!!!