[AT] O.T. Woodruff vs straight keys

[Rena Glover Goss]

I have not run into that particular scenario, but Tecumseh regularly used offset keys to adjust timing.  When I lived in Chicago, I was part of the pit crew for the Sunday afternoon Go-Kart races in Soldiers Field.  Stan Johnson was running a pair of Power Products engines on a custom cart.  They were too hot for their own good. Stan could get the pole position during time trials, but never finished a race--We could not hold the engines together for an entire race.  We broke safety wire right and left every week.  Stan used a helmut, but the rest of his safety equipment consisted of a war surplus leather aviator's jacket.  there was no suspension (of course) and the drivers seat was barely an inch above the pavement with absolutely nothing protecting the driver.  Stan often commented about the debris on the track threatening to turn him into a soprano.

Larry
---- charlie hill <charliehill at embarqmail.com> wrote: 
> Larry, you reminded me of something.  Years ago I had buddies who raced go 
> carts.
> They often ran souped up 5hp B&S engines.  One of the tricks was to run a 
> 3HP flywheel
> on the 5HP engine to reduce weight.  In order to do that they had a special 
> crank key
> with a slight offset in it to get the timing back to the correct setting.
> 
> Have you ever run into that?
> 
> Charlie
> 
> -----Original Message----- 
> From: Rena Glover Goss
> Sent: Saturday, August 12, 2017 11:42 AM
> To: Antique tractor email discussion group
> Subject: Re: [AT] O.T. Woodruff vs straight keys
> 
> A key can be used as a safety limiter on torque so that it shears instead of 
> breaking gear teeth, etc.  In that case, the length of the key can be used 
> to adjust the break-away torque load.  Some small engines (like Briggs) use 
> a particular metal for the key to get this type of safety.  In the lawnmower 
> repair shop business, I often ran into engines where the owners had replaced 
> the OEM key with a steel one.  I presume they thought that "any ol' key" 
> would do the job.  Never mind that when they hit a gas pipe with their 
> lawnmower, they twisted off the crank shaft!
> 
> 
> Larry
> ---- Dennis Johnson <moscowengnr at outlook.com> wrote:
> > I think there are 2 main reasons for woodruff keys
> > 1 - these keys are contained from side to side so they cannot slip. You 
> > can also use other types of key ways that enclose the keys, but the most 
> > common is to cut keyway to the end of the shaft.
> > 2 - the woodruff keys may take less material out of the shaft. This might 
> > weaken the shaft slightly less.
> >
> > Dennis
> >
> > Sent from my iPad
> >
> > > On Aug 11, 2017, at 8:13 PM, "joehardy at epix.net" <joehardy at epix.net> 
> > > wrote:
> > >
> > > My brother is rebuilding a corn chopper and having difficulty replacing 
> > > bearings on the pick up head. Couldn't get to slide the bevel gears off 
> > > drive shaft. He asked me why woodruff keys were used instead of straight 
> > > keys. Thought I'd throw his question out to our group. Ref: Read 
> > > discussion on Practical Machinist. Joe Hardisky, Ryman Farm, Dallas, PA
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