Re: C/W Cranks etc.

["Melissa & Jim" <jadney@vwtype3.org>]

On  1 Sep 97, Patrick Joel Morton wrote:

> At 00:46 3.1.1980, Toby Basiliko wrote:
> 
>  * Huh?
>  *   I thought that a (properly) counterweighted crank helped reduce
>  wear * and friction at just about any speed over 2000 rpm?  Or is
>  this not true * in a horizontally- opposed 4?
> 
> It has nothing to do with the type of engine.  A counterweighted
> crank (with other parts like lightened and balanced rods, a
> lightened flywheel, balancing from the fan through to the clutch and
> so on) will not reduce wear.  Rather it will free up potential
> horsepower - in theory.  There are many other variables that factor
> in.  Stock Volkswagen cranks are very good.  Even when opening up
> the top end.

Much of what you say is clearly true:  Competition engines run to the 
limit will not last as long as conservatively driven engines.  OTOH, 
there is much here that I must take issue with.  A counterweighted 
crank (of any kind) has a larger moment of inertia than the stock 
crank, so, all other things being equal, it will take a bit longer to 
rev up.  In reality, I suspect the difference is unnoticable, but 
whatever effect there is, it is in the opposite direction than you 
imply.

There is no extra HP to be had from a CW crank, unless you count the 
HP that might otherwise be wasted in the flexing of the stock crank 
at high revs.  I don't know if you count beating up the center main 
bearing saddles in the case as wear, but I think it would be fair to 
do so.  At any rate, this is what the CW crank will help avoid.

> Contrary to popular advertizements in several popular Volkswagen
> magazines, you cannot just 'drop in' a counterweighted crank and
> expect to notice any difference when you step on the gas pedal. 

I agree that a CW crank is not a performance item.  Rather it is a 
longevity item which allows you to run at higher revs withoud damage. 
It would also be fair to agree that the CW crank is pointless unless 
the rest of the rotating parts are also balanced properly.  
Lightening of certain components has performance benefits, but 
they also carry a durability cost.

My personal emphasis has always been to go with those things which 
enhance durability and/or performance withoug bearing a durability 
cost.  YMMV. 

>  * Melissa & Jim wrote:
>  * <<snip>>
>  * ...the only
>  * > thing that I could add to the rebuild is a counterweighted
>  crank, * > which is probably somewhat pointless in an AT.
> 
> A counterweighted crank is pointless in a stock engine anyway,
> unless you do a lot of other things.  Had it been a _good thing_ I
> think that we would all have counterweighted cranks in our
> Volkswagens.  The engines in our Type IIIs were not meant to see
> revs of 6,500 or higher, thus they were not built to achieve engine
> speed like that.

According to the Bill Fisher book, damage to the case starts around 
5,000 rpm.  It is true that I don't spend a lot of time there, but 
it's nice to know that when I rebuild the engine I will find do new 
case damage.

> A cheap counterweighted crank (welded) is even more pointless. 
> Reading too much Volkswagen Trends can cause brain sanding.

I have no doubt that there are bad welded CW cranks out there, but I 
have had excellent experience with a number of Berg's #188s over a 
period of more than 20 years.  Berg's forged CW cranks are probably 
better, but the price is astonishing and I can't see where there 
would be room for improvement., except for the larger center main 
bearing that he offers.

I agree completely that all advertizing should be read with a 
jaundiced and critical eye.  My personal pet peeve is the selling of 
anything as "billet" when any machinist can tell you that if you are 
after strength and fatigue resistance you need to be looking at a 
forging.  Turning something from a billet is just a cheap way of 
doing low volume production.

As to why VW didn't do this from the start I suspect that the answer 
is simply that VWs were for the masses and the enthusiasts were 
expected to drive Porsches (which came with CW cranks.)

Jim 
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       Melissa Kepner                                    Jim Adney
                             Laura Kepner-Adney
                         jadney@vwtype3.org      
                             Madison, Wisconsin
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