[Fot] Fw: Re: Broken Cranks: Was - Any connection between these problems?

[robert bownes]

My 1147 never broke a crank even after wrapping a rod around it.  But
it did rather religiously eat rod bearing #3. See aforementioned U
shaped rod.

Bob



On 5/14/09, EDWARD BARNARD <edwardbarnard at prodigy.net> wrote:
> --- On Thu, 5/14/09, EDWARD BARNARD <edwardbarnard at prodigy.net> wrote:
>
> From: EDWARD BARNARD <edwardbarnard at prodigy.net>
> Subject: Re: [Fot] Broken Cranks: Was - Any connection between these
> problems?
> To: "Norlin Engineering" <norlinengineering at comcast.net>
> Date: Thursday, May 14, 2009, 5:55 AM
>
>
>
>
>
>
>
> Jim: Five or six years ago we had a small journal 1296 that I built for
> Susan
> break between the rear main and the flywheel. I believe the circumstances
> were
> that it dropped out of overdrive at a very inopportune moment. The location
> of
> the break caused loss of propulsion without any further damage internally.
> If
> memory serves me correctly the engine was running it's strongest before the
> mishap, and Susan was mopping the track with her competition when it
> happened
> Do I remember correctly Susan and Brad?
>
> --- On Wed, 5/13/09, Norlin Engineering <norlinengineering at comcast.net>
> wrote:
>
> From: Norlin Engineering <norlinengineering at comcast.net>
> Subject: [Fot] Broken Cranks: Was - Any connection between these problems?
> To: fot at autox.team.net
> Date: Wednesday, May 13, 2009, 7:22 PM
>
> Interesting to read this thread as I suffered a broken crank on my 1296
> engine this past weekend.
>
> This is a small crank engine, prepared to SCCA limited prep rules for HP.
> Shift point is 6800-7000 and max revs are about 7500, so the engine is
> really not stressed that much.  The crank was balanced, but not nitrided or
> shot peened.
>
> The crank broke between the #1 con rod journal and the #1 main journal which
> is totally weird.  It's hard to tell looking at the two halves since they
> beat on each other for a few seconds before I could kill the motor, but if I
> had to guess, there was a fairly large internal flaw in the forging that
> didn't show up on the magnaflux test.
>
> I've been lead to believe that these cranks are virtually bullet proof, but
> now I'm not so sure.  How many others have suffered broken 1300
> crankshafts?
>
> The real bummer in this (besides the cost) is that I was leading HP in the
> National when the crank failed.
>
> "Helping to restore the economy thru racing" - Jim Norlin
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