Cameron Stoker's Grasshopper Treadle Hammer

Cameron Stoker, of Santa Fe, NM, has recently completed a Grasshopper 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
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The Grasshopper Hammer was developed a number of years back, basically on "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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Ron is, of course, entitled to his opinion, but I find the comparison 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
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First Bruce, you probably hit the nail on the head with your first comment 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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Golden Age Forge http://www.reil1.net/gallery.shtml E-Mail: snipped-for-privacy@reil1.net Boise, Idaho

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YES! Let us SEE Nahum's treadle hammer. You keep teasing us with 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?
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I assume you caught my posting of Nahum's hammer and some other tools Bruce.... If not, look for the topic I posted separately.
Ron
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Ron, 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
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