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Question on eccentrics...

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56type

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#1
So I have a piston that needs to fit into a cylinder that is offset by 0.0285 in. from the centerline of the piston. My question is to get the needed offset to get the piston to drop the needed amount so that it is centered in the cylinder do I indicate it offset to 0.01425 ?? or do I dial it in at the 0.0285 ?? The difference between the centerlines of both pieces is 0.0285, in other words the cylinder centerline sits 0.0285 below the current centerline of the piston attachment point, so I need to cut the end of the piston shaft as an eccentric to drop the head of the piston enough to center it into the cylinder.

I just need to know if in setting it up in the 4-jaw how I should set the offset to to get the piston centerline to match that of the cylinder. I was watching some tubalcain videos on making an eccentric but wasn't sure if I was understanding the concept correctly... Thanks.
 

markba633csi

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#2
I think a picture would be helpful, I'm not sure I understand the offset and centerline you are describing
mark
 

.LMS.

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#3
When I read the title I thought it was about everyone on this site.
 

JimDawson

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#4
If your offset is 0.0285 then you would dial in 0.0285. If you were making a crankshaft or camshaft and wanted a 0.0285 total stroke then you would dial in 0.01425.
 

56type

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#5
Here's some scribblings and a couple of pics to show what I'm up to.... 0826182301.jpg 0826182301a.jpg 0826182302.jpg 0826182301.jpg 0826182301a.jpg 0826182302.jpg
 

56type

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You can kinda see in the third pic how the shaft of the piston is off center in regard to the attachment point when centered in the cylinder in the second pic. I made an adapter that let me turn an eccentric for a length of the piston shaft and insert that eccentric into the adapter at centerline. Just have to make sure I cut the eccentric right the first time to get the correct offset to allow the piston to be centered in the cylinder.

Only get the one bite at the apple so to speak, or I have to buy and cut down another piston.
 

56type

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#7
If your offset is 0.0285 then you would dial in 0.0285. If you were making a crankshaft or camshaft and wanted a 0.0285 total stroke then you would dial in 0.01425.
Thanks !!!.. I set it up initially at that offset and then got to second guessing it after watching some tubalcain videos. The part in question slides straight forward & back, it doesn't rotate like a cam lobe. It just has to find it's way back into the cylinder at the end of it's cycle as it will be "floating" in a larger tube as it cycles to a small degree.
 
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