[TheForge] Treadle Hammer Springs

[Marc]

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