My uncle's used a synchronous gearmotor, big cam, rubber bands,
striker weight, holder plate and counterweight. the striker and
counter sat on a track. The motor would pull the striker back against
the rubber bands, then trip. The counterweight was pulled forward and
back by hand. Load a pecan by hand, hold against plate with
counterweight, striker trips, breaks pecan, then starts retracting.
I don't remember all the details, particularly the cam and striker
arrangement, and the holder plate which would have to have some play.
The striker and counterweight were turned steel bars, around 1" dia.,
and there were machined recesses for the pecan ends. It did a perfect
job, breaking and popping off the shell, leaving some shell on either
end and unbroken halves. Force was regulated with more or fewer
rubber bands. I think it ran at 30 rpm. It'd do a bucket or a sack
quick enough, not commercial quantities.
Uncle Bill made a lot of stuff like that. His oyster washer would do
a towsack at a time, and man, they are easy to shuck when all the muck
and rough edges are gone. He was a grumpy old man, smoking all the
time, grease and dirt on his clothes, working in an old quonset hut,
no a.c., on the coast of Texas. I loved visiting that shop. Ancient
old lathe, maybe 16" swing or so, power hacksaw, horizontal hydraulic
press, welding stuff, original rusty cap and ball revolvers hanging on
nails, girlie calendars, and mountains of dirt, junk, and swarf.
Our Sawzall is at least 20 years old and came with a two-speed switch
and variable speed via the trigger. It was the run-of-the-mill version
at the time. I doubt if the versions have changed much today...
If it didn't already have variable speed and I wanted it, I would try
using the cheap HF Variable Speed Router control on it. See:
In my experience light dimmers don't work all that well with motors.
They are made to work with resistive loads. Router speed controls are
made to work with motors. But even then they don't regulate the speed
very well as torque requirements change during use...
If I was going to crack a few pecans (several buckets full) I would use
a small arbor press like this:
or maybe this one:
It would be good for other projects afterwards.
If I really wanted to build a commercial nut cracker I would go study
the patents first via Google at:
No reason to try reinventing something until you have studied what has
already been done...