TheSamba.com :: View topic - how to measure the stroke of a crank out of the case?

Mon Jan 03, 2005 7:17 pm

how can i measure the stroke? I want to find find out what it is. there are no numbers are anything on it except 10 G VW. And DEW. Thats it thanks for any help and soory for the newb question.

Mon Jan 03, 2005 7:20 pm

Measure from the center of one rod journal the center of the rod journal on the other side.

Tue Jan 04, 2005 5:18 pm

it would be more precise and do-able to measure from the outside of one rod journal to the outside of an adjacent rod journal , convert from fractional to decimal, subtract 2.165. then multiply the inch measurement figure by 25.4. this will be the millimeter stroke. it will not likely come out as a round figure you will have to round up or down slightly, as it is necessary to eye up the first measurement, unless you have a height guage

Tue Jan 04, 2005 5:52 pm

To add a little more precision yet.... lay the crank down on a piece of paper on a nice flat surface Take a drafting triangle or speed square or just about anything with a right angle. Butt it up to the outside edge of each rod journal of the crank and make a small pencil mark on the paper. Move the crank out of the way and then draw a straight line between the marks for the left side of the crank and another line for the right side of the crank.

Measure the diameter of the rod journal of the crank with calipers.

Measure the perpendicular distance between the two lines you drew above. This distance will be the stroke of the crank plus the diameter of one rod journal.

Subtract the diameter of the rod journal from the distance between the lines and you have your stroke.

If you do all your measuring in inches, just multiply your final number by 25.4 to convert to millimeters. This number will likely not be a nice round 69, 74, 78, 82 millimeters due to measurement error and round-off, but it should be close enough to one of these to let you know what the crank stroke is.

Later,
John Jaranson
'66 Square (Sophy)
'71 Fasty (Jane - darkside project in waiting)
various parts.....don't we all.
http://mywebpages.comcast.net/jaransonT3/jaransonT3/
http://mywebpages.comcast.net/jaransonT3/2004Invasion/
http://mywebpages.comcast.net/jaransonT3/notavwclub/

Mon Oct 12, 2009 7:11 pm

I realize it's probably a trick that all the old-schoolers already knew but damn if this last post didn't help me out a ton tonight. Worked perfect. Thanks!

Mon Oct 12, 2009 8:09 pm

or lay it on a v-block made in some soft 2x4's and measure that way. You can check runout at the same time.