Date: Tue, 20 Feb 2001 01:14:47 -0000
Reply-To: John Pronk <john_pronk@STRATOS.CO.NZ>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Pronk <john_pronk@STRATOS.CO.NZ>
Organization: Stratos New Zealand Ltd
Subject: Re: Flexing cranks and Yielding Bolts one last time
Content-Type: text/plain; charset="iso-8859-1"
I would say one of the reasons the Vanagon case is less prone to centre main
"pounding" or wear than the type1 case because it is aluminium not magnesium
alloy. Magnesium alloy is quite soft compared to aluminium, but much lighter
and easier (therefore cheaper) to machine.
John.
----- Original Message -----
From: "Robert Donalds" <bostneng@FCL-US.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, February 20, 2001 00:10
Subject: Flexing cranks and Yielding Bolts one last time
> fellow listees and learkers
> I found a great article about the stretch to yield hardware in this
> months automotive rebuilder magazine it is also on line at
> http://www.automotiverebuilder.com under feature articles. I hope this
> will
> clear up the confusion about the hardware on the 2.1 rods
> the bug crankshafts as everybody knows flexes. when I was building
> formula vee engines that would spin up to 6k on the track flexing could
> be a
> problem. After all the 40 hp crank was much better at flexing than was
> the 1500 or
> 1600 cross drilled cranks To get around this problem I always had the
> center
> main ground .0015 ths. below the low limit and that gave the crank the
> needed
> room to flex, live and see yet another race
> The first symptom of a flexing crank is that the case takes a
> pounding
> at the center main web. The common belief is that the crank flexes when
> it is
> at top dead center There is a second symptom of the bug crank flexing
> that I
> have never heard discussed and that is the crank center main bearing
> journal
> ware. I have inspected and measured lots of cranks in my time and the
> one place the
> bug crank shows it ware first is at the center main oiling holes. It is
> not
> uncommon to see 0015ths. out of round at this spot This is not from
> lack of
> lubrication but a result of the crank flex then the pistons are half way
> in there
> travel. I have never seen any signs of this in any 1.9 or 2.1 crankshaft
> that I have
> measured ever.
> It is not uncommon to put a 2.1 case back into service after 150k
> because the case measures fine you could not say that with any bug case
> with even
> 1/2 that number of miles sure its been done but the person that did it
> never
> measured the case and sure it didnt bind until it got hot but how would
> whey
> know the cranks binding the only symptom of this is it ran really hot
> and didnt
> make allot of power
> Bob Donalds
> http://www.bostonengine.com
> as always
> all rights reserved
>
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