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Author Topic: Cylinder barrel heat expansion.  (Read 209 times)

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Tarnand

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on: November 03, 2018, 09:37:46 am
Would any one know by how much cylinder barrel expands, both iron and alloy, from being cold to when engine reaches operating temperature? 
Thank you.
2005 KS Bullet 500cc
1994 FLSTC


ace.cafe

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Reply #1 on: November 03, 2018, 02:48:47 pm
Approximately .001" for both.


Tarnand

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Reply #2 on: November 06, 2018, 01:48:53 pm
Thank you Ace.  I may be very wrong but would not it be rather .01"?  I am thinking that at .001" the valve clatter wold not be very audible especially that the valve stems also expand due to heat.
2005 KS Bullet 500cc
1994 FLSTC


cyrusb

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Reply #3 on: November 06, 2018, 02:22:17 pm
aluminum push rods expand as well...


Arizoni

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Reply #4 on: November 06, 2018, 05:51:32 pm
Thank you Ace.  I may be very wrong but would not it be rather .01"?  I am thinking that at .001" the valve clatter wold not be very audible especially that the valve stems also expand due to heat.
The way I read the question is, "how much does the cylinder barrel expand from cold to operating temperature?"

I take this to be asking how much does the bore expand.

Although some cylinders have aluminum fins, the bore is usually made from some type of cast iron and this is what controls the growth of the cylinder.

The coefficient of thermal expansion for a typical cast iron is about 6 millionths of an inch per degree F, per inch of size.

Figuring the typical cylinder will be about 250 degrees F at operating temperature that is about 175 degrees F above room temperature so we have, 175 X .000006 = .0011 (per inch).

The bore on a RE 500 is 84mm or 3.307 inches in diameter so, 3.307 X .0011 = .0035 inches of expansion at operating temperature.
Jim
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ace.cafe

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Reply #5 on: November 06, 2018, 06:10:36 pm
I took it to mean bore diameter expansion too.

For whatever reason, our actual measurements of bore expansion showed .001" to .0015" at running temp. Perhaps their cast iron has a lot of other impurities.

Anyway, if the question is about vertical expansion, it should be about .012". This is why the lash is set zero when cold, and the cam timing is spec'd at .012" lift points. The cam lobe lash ramps are designed to take up .012" lash prior to the lift ramp starting.
In reality, it will have some variations based on temp and conditions. I think the .012" is considered a nominal hot spec.


Tarnand

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Reply #6 on: November 07, 2018, 10:24:20 am
Thank you guys.  Now it makes sense to me. 
2005 KS Bullet 500cc
1994 FLSTC