[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]

[T3] Crankshaft throw tolerance


The question came up here a few days ago about why someone out there is 
marketing 78.8 mm stroker cranks, when 79 mm would be a more reasonable 
"standard." I finally ran into the guy I know who used to grind crankshafts for 
a living and asked him how this might have come about.

He told me that a reasonable tolerance on the throw (which is one half of the 
stroke) would be .005". Since the throw of the cranks in question is "off" by 
0.1 mm, or .004" this is within reason.

In the end, we came to the conclusion that they must have made a run of these 
cranks, all with the same setups. When they later measured them carefully they 
discovered that they were really all a little short of the desired 79 mm throw 
and they decided to be honest about it and sell them as what they actually 
were.

My friend thought that for most production cranks, even those used by major 
manufacturers, the acceptable tolerance might be as low as .010". Of course the 
actual journal diameters are held to tolerances much tighter than .001".

-- 
*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
*******************************

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]