Cameron Stoker's Grasshopper Treadle Hammer
Bruce Freeman
Treadle Hammer, and has kindly provided photographs and commentary:
"www.monmouth.com/~freeman/bmf/CameronsGH.htm"
As far as I know, this is the first Grasshopper completed from the
plans. (The one in Marshall Bienstock's shop is the prototype. At
least two other people have begun work, but I haven't heard that
they've completed the hammer.)
Bruce
NJ
Ron Reil
"theforge" list, or at least was actively followed in its development on the
list. Personally, and this is only my personal opinion, I think it is far
more complex than needed, has way too many pivot points and bearings. The
"Big Lick" design is probably the best design there is out there, and is a
completely vertical acting hammer with very few pivots or bearings. No,
there are no Big Lick plans available, but it is an easy matter to build one
from a picture. There are plans out there for a Big Lick too, and are
actually an improved version of the hammer, but they are "black market" and
the designer of the Big Lick gets nothing from the plans, so I can't
recommend them to anyone. There is no reason anyone with a small amount of
mechanical ability can't build one from a simple picture though.
Ron
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"Bruce Freeman" <fre...@hotmail.com> wrote in message
news:f586f039.03110...@posting.google.com...
Bruce Freeman
between the Grasshopper and the Big Lick to be almost laughable. This
is not to say that the Big Lick is laughable, merely the comparison.
The Big Lick was my first inspiration for designing a vertical-motion
treadle hammer. I tried it at Caniron 1 and was impressed, but it was
clear to me I could do better - for a general purpose treadle hammer.
The Big Lick was designed principally for repousse work, and no doubt
it excells at that. Let me run a quick comparison of the two (from
memory) for the sake of those unfamiliar with them:
Features of the Grasshopper Treadle Hammer:
See: http://www.monmouth.com/~freeman/bmf/others.htm#Grasshopper
1) Accurate vertical hammer motion
2) No sliding or rolling parts to achieve the vertical motion -- only
pivots.
3) Accurate striking of the work or tool, regardless of its height or
thickness.
4) Anvil is free of obstructions in all directions, with ~22" clear
above anvil.
5) 34-inch hammer stroke.
6) Adjustable treadle height to accommodate different work heights.
7) Treadle doesn't fight you -- no return force exerted upward against
the foot.
8) A "kick-back" at the bottom of the stroke brings the hammer up for
the next stroke.
9) The kick-back is adjustable to accommodate different work heights.
10) Treadle and kick-back adjustments are made by means of cranks
mounted at the front of the hammer.
11) Hammer moves ~ twice the speed of the treadle.
Big Lick Treadle Hammer: ("Ditto" means "equivalent to Grasshopper.)
See: http://www.monmouth.com/~freeman/bmf/others.htm#Sheppard
1) Ditto.
2) Uses "sliding" guides to achieve the vertical motion. (These may
need cleaning or adjustment.)
3) Ditto.
4) Anvil is free of obstructions in front and sides, but not in rear.
Ther is only about 10" clear above anvil.
5) ~10-inch hammer stroke.
6) Not applicable. (Treadle height not adjustable.)
7) Like most other treadle hammers, you fight the springs of the Big
Lick.
8) Not applicable. (See 7)
9) Not applicable. (See 7)
10) Not applicable. (See 6 and 7)
11) Hammer moves at about the same speed as the treadle.
Overall, the Big Lick has about the feel of stomping on your work with
a ninety-pound boot on. There is no acceleration of the hammer,
because the hammer moves the same speed as the treadle, and with only
about a 10" stroke, there's no room for acceleration.
In contrast, the Grasshopper has a 2:1 hammer:treadle speed ratio, and
uses at least the first 12" for acceleration, with up to 22" of height
remaining for the work. This very long stroke was the main reason for
the grasshopper design, without rollers or sliders that have to engage
the ram.
This is not by any means to say that there's anything wrong with the
Big Lick. It may indeed be the perfect treadle hammer for you. If
you're thinking of making or buying a treadle hammer, I recommend you
first see what's out there:
http://www.monmouth.com/~freeman/bmf/others.htm
BTW, I am in the process of changing the design of the kickback
adjustment on the Grasshopper. Once this modification is completed,
the kickback will be adjusted once, upon installation (though it could
be adjusted anytime thereafter if desired), after which it will remain
in adjusment automatically. This is achieved by dynamically linking
the kickback height and the treadle height. This is actually a
simplification of the mechanism, though it may sound otherwise. It is
already working on the prototype in Marshall's shop (*) and as soon as
I work out some design modifications I will be drawing it up and
including it in the plans.
Finally, for those with limited needs or on a tight budget, I have on
the drawing board the world's cheapest treadle hammer since the Oliver
Hammer. It will have many of the features cited above for the
Grasshopper, though not precisely the same. The ram will be about 20#
- this will be a lightweight treadle hammer!
Bruce Freeman
Ron Reil
regarding Repousse'. I do a lot of Repousse' work, so you may have stated
one of the reasons I like that hammer in particular. I will not argue any of
the points you make, they are all valid, and I am sure are accurate. The
design I have for the Big Lick is not the same as you are referring to
however, as I said, there is a much improved design out there.
Any of the manually operated treadle hammer are of great value in a shop and
can do a lot of work for a guy, of that there is no doubt. Next time I am
down at Nahum Hersom's I will take some images of his treadle hammer and
post them for the group to look at. You may be interested too. Nahum's
hammer is the first one built in North America, and is patterned after one
built in Europe some 50 or 60 years ago that Nahum saw. It is a superb tool
due to a number of things Nahum has done to improve it, things that many
guys would be very interested in, especially the rotating tool receiver top
of the anvil, flip out foot pedal, and a rebound system to apply some of the
down force to send the hammer head back up much faster, allowing him to
reduce the spring tension necessary to carry the head back up. His is also
fully babbited for all bearings and is as smooth as silk to use and totally
stable laterally, even after 40 years of use. When you use the hammer there
is no perceptible spring resistance, just smooth power. I was down at his
place two days ago, but will make another visit shortly and take my camera
with me this time. It is a far simpler design, compared to the Grasshopper,
to build also. A guy could easily build one in a weekend.
Ron
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"Bruce Freeman" <fre...@hotmail.com> wrote in message
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Bruce Freeman
these descriptions! I'd like to post photos of Nahum's treadle hammer
on my "others" page, if that's okay with you and Nahum.
(Maybe we should do a comparative test of treadle hammers: Smash a
lead cylinder and see which hammer turns it into gold!)
It sounds from your description that Nahum hit upon a scheme rather
similar to what I've hit on in the Grasshopper combined with what I've
used in the Weightless Hammer.
To whit, if you use a weak spring (i.e., one with a low
force-per-inch-stretched) you'll have to stretch it a LOT to simply
support the ram. However, at this point the additional stretch needed
to bring the ram down to the anvil will involve a relatively small
increase in the spring force -- and hence rather little resistance to
the foot. However, the consequent problem is that the spring may be
so weak that it won't lift the ram back to the top quickly enough to
be useful.
This problem is easily overcome by bottoming the hammer against
another spring. By the time your ram hits your anvil, it's moving
fast and has considerable momentum. If it bottoms out on a spring (of
one sort or another) there will be little lost from this momentum, BUT
the spring can exert enough force to push the ram back up to the top.
That's exactly what I call "kickback" (in the Grasshopper).
From your description, it sounds like the main spring is not all that
week in Nahum's hammer. To see hot to "weaken it" practically, visit
my Weightless Hammer pages: http://www.monmouth.com/~freeman/wh/wh.htm
In that design, I use an ordinary garage door spring against with a
huge (~50:1) "mechanical disadvantage" (which is just "mechanical
AD-vantage" worked backwards) so that the effect is of a weak spring
stretched very far. (In the Weightless Hammer this is accomplished
with a bicycle wheel "pulley" system. That is not the only possible
means. For example, a block and tackle could achieve the same
mechanical disadvantage if moment of inertia were not an issue.)
Hence, the differential force from top to bottom of the stroke is very
little. (There is almost no return force at all in the case of the
Weightless Hammer. This hand-held hammer must be raised by the smith,
but it "weighs" virtually nothing, so this is easy to do.)
I've gone one step better on the Grasshopper. By a mathematical
analysis (that I wouldn't want to have to repeat) I determined that --
for the geometry of the Grasshopper mechanism -- I could virtually
completely balance the ram by means of simple springs (NOT greatly
extended, and hence less likely to fail catastrophically) and an
excentrically mounted round pulley. This works well. However, as
demonsrated by the Weightless Hammer, it is NOT absolutely necessary
to achieve such perfect balancing of the ram. Beyond a certain point,
you don't notice the difference anyway.
I, for one, would be very interested in what other improvements Nahum
has made in his design. Much of the Grasshopper design (anvil, etc.)
is obviously based upon Clay Spencer's design. There's much we can
learn from what others have done.
Now, one more point. Time and time again folks have claimed the
Grasshopper is SO SO complicated. I disagree. Yes, it uses two
crankshafts in addition to the (typical) two hammer arms, plus a
"grasshopper leg" strut. Big deal! As Cameron Stoker (see start of
this thread) reports, his Grasshopper took about 50 hours to make.
Not inconsiderable, but not excessive for a tool of this caliber.
MOST of the grousing seems to relate to the APPARENT complexity of the
machine. It is for THAT reason that the Grasshopper plans and
instructions are so complete. Every machined part is fully described
in a separate engineering drawing, and every assembly has a
corresponding engineering drawing, even including how and where to
weld, and the order of assembly. Even the procedure for adjusting the
Grasshopper, once assembled, is fully described. Cameron tells us he
used the Grasshopper plans to train a newby in fabrication. Can't get
much easier than that! (I never doubted the ease, however, since I
was a newby myself, going into this development.)
At this point I must toss out that the Grasshopper plans are not
currently available. I'm redesigning the kickback mechanism, and I
will not reprint until that redesign is complete. The new design will
be simpler to build AND to use. Namely, there will be one adjustment
crank, not two, at the front of the machine, that will adjust the
treadle height and the kickback simultaneously. (It took all these
years for it to dawn on me that this was both desirable and easily
possible! Good thing I can't literally kick myself in the head!) The
prototype Grasshopper is now equipped with a prototype such adjustment
that works well. I'm modifying the design further for good reasons
and hope to improve it further. When I am satisfied with the
redesigned kickback mechanism, I'll modify the Grasshopper plans and
reissue them.
Bruce Freeman
BTW: Aren't babbitted bearings a bit complex ;^) for a treadle
hammer?
Ron Reil
Bruce.... If not, look for the topic I posted separately.
Ron
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"Bruce Freeman" <fre...@hotmail.com> wrote in message
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Bruce Freeman
Yes, I caught it. I started to look at the pictures but just have
been up to my ears in alligators this week. I WILL get to it, I
promise!
Thanks,
Bruce