[TheForge] Treadle Hammer Springs

[Bruce Freeman]

Middle aged knees... I know about those.  I sometimes
wonder whether it's worse to exercise or not to
exercise!

Build a Grasshopper and you'll have NO spring tension
working against your leg!

Bruce
NJ

--- Marc <marc at ironringforge.com> wrote:

> Thanks, Bruce. I've got some extra spring and this
> would be real easy to
> try the next time I'm out there.
> 
> Another thing I did to help ease the stress on my
> knees was put a kind
> of "cushion" spring that attaches the treadle to the
> hammer connecting
> bar. Clay's design has a small section of leaf
> spring connecting the ram
> to the pivot point, which I also used, and the
> treadle connects to that
> in the center. I felt that was too short to protect
> my middle-aged
> knees, so I used a 24", or so, section of leaf
> spring bent in a 'C'.
> There's a slight lag when hammering heavy, but the
> cushioning works real
> nicely.
> 
> --Marc
> 
> On Sun, 2007-03-18 at 14:09 -0700, Bruce Freeman
> wrote:
> > Marc,
> > 
> > If you feel like messing with your spring
> > configuration, try this trick to save your leg:
> > 
> > Remove one or two of the springs you now have in
> use. 
> > Result should be a hammer hanging on one spring,
> hence
> > overcoming the initial tension.
> > 
> > Next get (or make from one of the discarded
> springs) a
> > short but heavy-duty spring, maybe 6" long. 
> Connect
> > this in parallel to the spring still on the 
> treadle
> > hammer by means of a length of steel cable.  The
> cable
> > should be long enough that this second spring is
> > relaxed until a few inches before hammer head
> meets
> > anvil.  At that point, it stretches, adding to the
> > return force on the hammer head.
> > 
> > The effect of this is to reduce the force against
> your
> > foot for most of the hammer stroke.  At the bottom
> of
> > the stroke (when the second spring cuts in) the
> hammer
> > is traveling fast, so the extra force against it
> does
> > not have much effect on its speed.  Furthermore,
> your
> > foot is near the floor where your mechanical
> advantage
> > is greatest, so you don't feel the extra spring
> force
> > much.
> > 
> > But once the hammer head hits bottom, that extra
> > spring force is there to help accelerate it back
> up
> > for the next stroke.  This extra  spring force
> cuts
> > out after a few inches, but by then the hammer
> head
> > has already been accelerated upwards and will
> continue
> > to go without ANY additional spring force.  But of
> > course in your case it has additional spring force
> > from the other spring.
> > 
> > I know this works because I do something similar
> on
> > the Grasshopper  Treadle Hammer.
> > 
> > Bruce
> > NJ 
> 
> 
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