[AT] O.T. Woodruff vs straight keys

Ken Knierim ken.knierim at gmail.com
Tue Aug 15 12:25:46 PDT 2017


Charlie,

You might find this if they were trying to get more timing advance as well.

Lots of different parts have been used in racing. I know of one (former)
snowmobile racer that used one smaller cylinder out of the 3 on his sled.
When they had to get a tech inspection after the race, he pulled the
(smaller) cylinder down for the inspection and it magically met the specs
for the engine. Interestingly enough, the other two were larger
displacement cylinders from a bigger engine variant but they had the same
exterior. The rules for the tech inspection only required one cylinder get
measured.

Ken in AZ

On Tue, Aug 15, 2017 at 11:33 AM, 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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