[AT] Weird broken crank(not the 430!)

[k7jdj at aol.com]

I vote for imbalance and resultant harmonics. Crankshaft mechanics can be very complex and it takes very little imbalance to cause disaster.  That's why engines have harmonic balancers.

Gary

Renton, WA 
 

-----Original Message-----
From: Jason <dejoodster at gmail.com>
To: Antique tractor email discussion group <at at lists.antique-tractor.com>
Sent: Tue, Aug 1, 2017 6:46 pm
Subject: Re: [AT] Weird broken crank(not the 430!)

I'd guess there was an imbalance on the blower wheel and the harmonics
caused the fracture.

On Tue, Aug 1, 2017, 8:30 PM Spencer Yost <yostsw at atis.net> wrote:

> It's on a lawn vacuum, and it was running fine.  My wife was operating it
> so I didn't hear it.  She  said it just stopped, making a bunch of noise in
> the process.   The crack occurred right behind the bearing, inside the
> crankcase at the flywheel end, not the impeller end.
>
> There was a good level on the dipstick and an oil change in the winter so
> it was not oil related.
>
> Spencer Yost
>
> > On Aug 1, 2017, at 9:05 PM, vschwartz1 at comcast.net wrote:
> >
> > Spencer; I do not have any real knowledge about this kind of break but
> it would appear to me that one side or the other would be smooth. I simply
> have a case of nose trouble. What was the engine doing when the crank
> broke? Was the break at the throw? For both pieces of the crank to be like
> that photo looks I would think there must have been some end play. Maybe
> that is a normal thing, now define normal.
> > Just wondering,
> > Gil
> >
> > ----- Original Message -----
> >
> > From: "Spencer Yost" <yostsw at atis.net>
> > To: at at lists.antique-tractor.com
> > Sent: Tuesday, August 1, 2017 6:04:09 PM
> > Subject: [AT] Weird broken crank(not the 430!)
> >
> > I have a small Briggs that broke a crankshaft yesterday. The weirdest
> thing I've ever seen. Have you ever seen a crank break and leave this type
> of a star pattern on both ends?
> >
> >
> >
> > [image/jpeg:image1.JPG]
> >
> >
> >
> > Spencer Yost
> > _______________________________________________
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> > http://www.antique-tractor.com/mailman/listinfo/at
> >
> > _______________________________________________
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>
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