don schad

Pretty simple, but a picture is worth 1000 words: So the rubber is sandwiched between the rigid rod mount and main tup. The thinking was that if the dies hit some iron which is off-center and want to twist that twisting motion will be absorbed in the compression/expansion of the rubber, instead of the rod fighting it. Or at least that is the theory (not necessarily related to any particular reality). don

Thanks for the comments. There are alignment couplers which I have heard of people using, but I've also heard they do break. I don't know what part of them breaks (they are a bit more complicated then a spherical bearing setup would be), so the question was intended to see if a people had a feeling if a ball might be more rugged. The original Kinyon plans from ABANA show specs for one. Regarding failure - I don't think catastrophic failure is actually much of an issue - worse case (where the bearing instantly turns to dust) the cylinder/tup would not disconnect, just become very loose, and still constrained by the guides. No flying hammer heads, just dust and no doubt some enhanced verbal expression. (The original idea basically amounts to inserting a spherical bearing into the hole in a pivot-mount on the top of the tup and clevis/pin on rod end. The impact on the bearing is in the "radial" direction, so if the bearing is gone there is just a very bad fit for the pin). Another different thought was to have a thin layer of hard rubber between the tup-to-rod connection, so that out-of-line motion of between the tup/rod could get taken up there instead of stressing the threaded rod end. This would be pretty easy to implement, and I don't think this would have an impact (pun intended) on the force of the blow. Thanks again, don

I was wondering what opinions people might have on the suitability of a ball-joint bearing for the cylinder-to-tup connection of a Kinyon (e.g., McMaster - Spherical Ball Joint)? This would seem like a very good connection for the top (assuming a suspended cylinder), but I am wondering about how these would fare given the impact they would be subjected to. Would the ball be pulverized in short order? All opinions welcome. Thanks, don

You can search the archives there and join. If you can read Japanese then I think there is some additional stuff, including some more recent modeling. One that might be of interest involves anvil weight ratio calculation...paper. I only looked quickly but it seems their magic number is around 10 (anvil:tup), but he sort of dances about the issue of actually saying what it is, vaguely saying "certain values which are far smaller then what others have said can be seen in figure x...". It seems to also address the question of the importance of what's under the anvil (comparing infinitely massive bases to those floating in space). I think this section deserves further study, but at quick glance I think the answer is that it isn't significant. don

Yes, it's true. Get out your slide rules and chart recorders. This is a 1961 journal publication from the Japan Society of Mechanical Engineers studying some of the physics of a big self contained hammer: paper. Click on the "FullText PDF" link for a scan of the paper. There is a bunch of stuff which may or may not be interesting depending on ones orientation. It looks like they calculate the overall efficiency of a 500kg at 52%. There is a test similar to the "squish test" here (using a lead block). Anyway, just thought people might find it interesting to look at. don

Actually I appreciate the need for the spring (both to lessen absorb the impact of the blow and for the "whip" when changing direction), but my question was more related to whether or not having flex on both ends would make the system more complex, or if having only one end with flex would be simpler. I believe (although I'm not 100% on that) that the winding up/unwinding of having a spring on one end would be equivalent to that which occurs with both ends flexing. BTW, thanks for your BP on the helve hammer. don

Hi all, I was wondering about the helve arm setup of the typical APH (an inline helve). In most cases the helve is a pack of leaf springs with a pivot somewhere in the middle. The pitman arm drives one end and the hammer head is attached to the other (often using rollers). On the other hand, the traditional helve hammers (those which travel in an arc) (e.g. Depew, irnsrgn's version of that (see BP0169)) most often have a solid arm on the head side of the pivot, and the spring on the driving end. So in the first case you have flex at both ends of the shaft, which would it would seem to me would be harder to tune and/or require stiffer leaves to achive such tuning. In the latter case, your flex is only in the driving end, which would seem to make tuning easier. So that said, is there anything to this thinking? Is there a reason for the predominant design? Am I missing something? Thanks for your thoughts, don

Thanks for your reply. That is interesting. I had considered straightening leaf springs, but I figured that I'd need to use heat and thus ruin the springs. I didn't expect that cold they would take very well to (staying) bent, but I can see it working using the incremental (FP) approach as you did. I was considering sandwiching them together with the concave sections facing each other, resulting in a straight string, which (I think) would be a lot stiffer (because the springs are under tension). don

What kind of leaf-spring(s) are using? It seems pretty flat - did you use flat leaf springs, or are they a typical arched pack that straightened out as you compressed them with the plates as part of the pivot mount? Thanks, don

Hi all, I've been toying w/ the idea of building a helve hammer for forging, and started to wonder about the different types which I have seen. Seems to be that there are at least two popular forms: the "Hawkeye" type (with the lift point between the pivot point and the dies), and the "Depew" where the lift point is on the end with the pivot point between in the middle. Are there significant pros/cons to the various configurations, esp with respect to their striking power and/or speed? What about the inline modifications? And, regarding usage - they look like they would be very useful for fullering work, but what about flattening things up after words? Can you do a good job with flat or large radius dies? Thanks for any thoughts, don