[TheForge] Treadle Hammer Springs

[Bruce Freeman]

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 

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

> I used Clay Spencer's plans as a basis for TH and
> used his spring
> concept. Basically, they're half-springs from a
> garage door. You heat
> the center with a torch until you can fold the
> spring in half, then cut
> it and make a hook with each cut end. My hammer has
> three of these
> half-springs, and they're constantly under tension.
> 
> One difference I made was to go with a lighter
> hammer head, only about
> 35 lbs., and the three springs would normally be
> used for a 70-lb'er.
> But I wanted to get a quick return that way and get
> a higher rate of
> blows per minute. It's also easier to control light
> blows for things
> like veining leaves. I don't usually work anything
> heavier than 3/4", so
> I don't need a real big mass. This thing will draw
> out a 5/8" RR spike
> just fine. Much, much easier than by hand.
> 
> --Marc
> 
> On Sat, 2007-03-17 at 19:28 -0700, Bruce Freeman
> wrote:
> 
> > 
> > If a spring doesn't have an initial tension, this
> is
> > not an issue.  That is my guess as to why some
> people
> > prefer small springs to garage-door springs.
> > 
> > Bruce
> > NJ
> > 
> > 
> > --- xlch58 at swbell.net wrote:
> > 
> > > Steve Smith wrote:
> > > >
> > > >
> > > > Bruce Freeman wrote:
> > > >
> > > >> Rumor has it that multiple small springs are
> > > better
> > > >> than one large spring, and you see some
> treadle
> > > >> hammers so constructed.  I haven't given this
> > > enough
> > > >> though to explain why this should be true.  
> 
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