[AT] Adventures with shear pins

[charlie hill]

Ralph it would seem that way but that was not the case.
I guess it happened occasionally but I think the main
problem is the fact that there is some space between the
input shaft on the mower and the PTO shaft. (not a tight fit).
No matter how tight you get it the bolt seems to work harden
in that gap and sooner or later it will crack and then break.
A few more revolutions and it slings the bolt out of the hole.
I would usually find at least one end of it laying on top of the
brush cutter.

Charlie

-----Original Message----- 
From: Ralph Goff
Sent: Sunday, July 27, 2014 10:45 AM
To: Antique tractor email discussion group
Subject: Re: [AT] Adventures with shear pins

On 7/27/2014 8:07 AM, charlie hill wrote:
>
> I've been through a few other brush cutters since that one and I have
> never yet had a sheer bolt to sheer when I hit something regardless of
> having a slip clutch or not.  In fact I've hit stuff so hard with that old
> D-10
> that with the engine running at wide open throttle it shut off dead in 
> it's
> tracks,  Sheer pin never budged.  Not even the brass ones.
>
> The best thing I've found is the slip clutch but they didn't have them 
> back
> in the
> old days or at least I didn't know about them until the 80's.   The only
> trouble
> with slip clutches is that if you set them loose enough to do any good 
> they
> tend
> to slip when you don't want them too.  It gets down to how much risk to 
> your
> equipment you are willing to absorb in order to get maximum production.
>
> Charlie
>
>
Sounds like your shear pin was working loose. We had that a lot on
square balers. A new shear pin would seem to "stretch" and work itself
loose after a few bales. Finally we started using double lock nuts on
the shear pin and it did make a difference. Those balers just used a
common 5/16 or was it 3/8 bolt. My newer NH 847 round baler takes a
rather odd sized shear pin on the gear box and I have not found a right
sized substitute other than the original NH parts. Luckily it does not
break many shear pins.

Ralph in Sask.
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