Warren Nakkela Posted December 17, 2008 Share Posted December 17, 2008 Since my post earler today I have some thoughts on building a power hammer that I wish to run past you-all. For the most part I would build this out of junk that I have on the farm. I am thinking of using a truck axle, narrowed down with flywheel on on end with a crank to drive the hammer, either through a helve arrangement using a leaf spring for the elastic element. The other brake drum on the other end of the axle would serve as the variable speed clutch. Or--I could us a spring toggle set-up like the Little Giant. I have some twenty inch pipe (3/8 inch wall) that I could use as the frame. I want to find some ten inch ship shafting for the anvil and would like to have it floating in a sleeve . This anvil would have it's own foundation buried in the ground maybe with piling underneath. Or perhaps a gridwork would be better. I also have good six and eight inch pipe. (sch. 40) Any thoughts, advice or criticizems are encouraged. Warren Quote Link to comment Share on other sites More sharing options...
Frosty Posted December 17, 2008 Share Posted December 17, 2008 How about posting some sketches of what you're considering. I find it a lot more efficient to brainstorm mechanisms when sketches are involved. Frosty Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 17, 2008 Author Share Posted December 17, 2008 hammer Frosty: You ask me to send a sketch. Here is one version. Might give you an idea of what I might be thinking, Some element have been left out but those are common design features in power hammers. I don't know if I can make this machine send my drawing but I will give it a try. If you can't fix it with a hammer it must be electrical. Warren Quote Link to comment Share on other sites More sharing options...
Frosty Posted December 17, 2008 Share Posted December 17, 2008 No sketch showing Warren. If you click on "Go Advanced" below the message window. Then click on "Manage Attachments" and browse to the picture you want and attach it, it'll get through. Frosty Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 18, 2008 Author Share Posted December 18, 2008 Take a look at this concept. It need some refinement. Warren Quote Link to comment Share on other sites More sharing options...
Frosty Posted December 18, 2008 Share Posted December 18, 2008 Got it Warren! I don't have time to get into it right now but will be back to you. What weight are you considering? Frosty Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 18, 2008 Author Share Posted December 18, 2008 Frosty, A fifty to seventy five pound hammer. If I make it like the sketch the anvil may weigh a ton. Still not set on a design. May consider air. Warren Clatskanie, Oregon Quote Link to comment Share on other sites More sharing options...
Frosty Posted December 18, 2008 Share Posted December 18, 2008 Being as hard to balance as a home made hammer can be it's a good idea to go over weight on the anvil. Have you seen the tire hammers? Far FAR simpler than the truck axle crank mechanism you're considering. I keep hearing good things about them and plan on putting together a 25-35 lb tire hammer maybe next summer myself. Down the road I want to build a self contained pneumatic ala 1902 Massey in the 100+lb range. In either case I want to experiment with a "scotch yoke" instead of a traditional crank mechanism. They're very robust and would eliminate the need for a swinging connecting arm and really simplify design. Frosty Quote Link to comment Share on other sites More sharing options...
frogvalley Posted December 18, 2008 Share Posted December 18, 2008 (edited) Remember in your designs that one of the reasons for a flexible or spring cushioned mechanism is to allow for the variables in height of the work piece as well as allowing for the rebound and stray forces that bounce around when swinging a heavy weight. The work piece changes in thickness, sometimes quite dramatically, say from 2 inch bar to a pointed 1/2"taper. I dont' know that a scotch yoke can absorb such variables. I could be wrong. The tire hammers are good and simple, although the tendency is to make them too light in terms of frame and anvil weights. Oversize the anvil and frame if at all possible. A ton is too much, but 6 -10 times the Ram weight is great. Common hammers such as the fairbanks and bradley had weights approaching 15-1 ratios for the anvil. An isolated anvil is great, much better than the LG. The Fairbanks and Bradleys had separate, removable and replaceable anvils isolated from the frame so as to minimize crystallization of the casting and help to eliminate vibrations. I see troubles with differential and axle designs, mostly its more complicated to modify what you have than to scrounge up the parts to make a simpler design. The tire hammer is a good option, although it is based upon the Dupont/Fairbanks design, which LG copied. Brakes are essential in my mind, so I like the designs for a clutch and brake in your plan. No need to go below grade for the anvil, stay up high and make it thicker. My homebuilt is a helve style of hammer. In my mind simpler and safer than the Tire hammer style. Mine has been in service for 6-7 years. Your mileage may vary. Edited December 18, 2008 by frogvalley Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 18, 2008 Author Share Posted December 18, 2008 Thank you for the comments. But what is a Scotch yoke? Does the leaf spring on helve hammers cause problems? It looks to me that this is a vulnerable element on the tire hammers. I am still considering a Pneumatic hammer if I can figure out the valving system. Warren Quote Link to comment Share on other sites More sharing options...
frogvalley Posted December 18, 2008 Share Posted December 18, 2008 The spring has broken twice in its life. Unlike an LG style or tire hammer where the spring is right in your face swinging very fast up, down and side to side, the helve spring is up high and moves only up and down. The broken spring simply drops down gently, the ram drops onto anvil harmlessly. Nothing flies far, but simply drops down with gravity. Since the ram cannot come out the top on my hammer, its much safer than other hammers. IMHO of course. Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 18, 2008 Author Share Posted December 18, 2008 What is the advantage in using a tire for a clutch? Has anyone tried using a two piece walking beam using coil compression springs? This feature could allow for rapid adjustment for different thickness of work.Never fall in love with your first idea. Warren Quote Link to comment Share on other sites More sharing options...
frogvalley Posted December 18, 2008 Share Posted December 18, 2008 Tire clutches are simple, you gotta make a flywheel or offset drive anyway, might as well make it the power input as well. Saves by almost half. The coil springs could be interesting as part of a helve mechanism, but Bradley found that rubber cushions were safer for their big hammers, although they were alone in that, spring hammers are much more common. Their hammers have a relatively solid wooden beam, with the cushions or rubber springs at the crank or push rod end of the helve. You can see them in the pic below, the ram is on the left, the silvery looking banded eggs are actually 8 rubber cushions stacked up in pairs. Force is applied to them and they transfer it softly to the wooden helve and then to the ram which is attached with a leather or rubber strap. Springs eventually fail due to crystallization. But I wouldn't be afraid to try that idea with coil springs. Just be careful, we are the species on the planet with the greatest ability to kill ourselves. Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 18, 2008 Author Share Posted December 18, 2008 Since we have a crank that is jerking a heavy weight (hammer plus any arms and linkages) that will result in stress reversals which tend to be destructive, it behooves one to examine your design to eliminate as much as possible. i.e. In the Little giant design both up and down motions of the hammer compresses the coil springs. Some halve hammers employ a leaf spring which will flex in both directions. This must be hard on the steel. I am trying to come up with a design that will only allow the elastic members to flex in only one direction. Any ideas, anyone? Warren Quote Link to comment Share on other sites More sharing options...
dablacksmith Posted December 18, 2008 Share Posted December 18, 2008 Since we have a crank that is jerking a heavy weight (hammer plus any arms and linkages) that will result in stress reversals which tend to be destructive, it behooves one to examine your design to eliminate as much as possible. i.e. In the Little giant design both up and down motions of the hammer compresses the coil springs. Some halve hammers employ a leaf spring which will flex in both directions. This must be hard on the steel. I am trying to come up with a design that will only allow the elastic members to flex in only one direction. Any ideas, anyone? Warren if you cand find a copy of "pounding out the profits " it would help a bunch! a lot of the dezign work has been done in the past.that book is a gold mine of ideas ! good luck! Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 18, 2008 Author Share Posted December 18, 2008 Thanks, I will try and find this book. These post have been helpfull. Thank you everyone. Never fall in love with your first idea. Warren Quote Link to comment Share on other sites More sharing options...
brucegodlesky Posted December 18, 2008 Share Posted December 18, 2008 check ebay or amazon for 'Pounding out the profits". I fgot mine 6 months ago for about $70 +or- Quote Link to comment Share on other sites More sharing options...
Frosty Posted December 19, 2008 Share Posted December 19, 2008 A web search for Scotch Yoke will turn up lots of hits from bare bones basic to proper scientific and engineering level explanations. This is a good illustration with a movie of one in action. KMODDL - Kinematic Models for Design Digital Library Yes, no matter how you convert rotary motion to linear motion you need a cushion or things will break. It'll be a caged linear coil spring rather than toggled leaf or coil springs though because it won't have any lateral motion to compensate for. A helve is a fine design but it takes up more floor space than I'd prefer. No matter what it is, if it has large springs they should be caged for safety's sake. Just because they've broken in a safe manner so far doesn't necessarily mean they will next time. A brake is easy to rig on a tire hammer. Simply add a friction brake to the motor mount so the brake is engages when the drive wheel is disengaged. Frosty Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 19, 2008 Author Share Posted December 19, 2008 The Phoenix pneumatic hammer looks cool in their video, simple too. Simple like a lot of us folks could build one. The controls/valving might be a little challenge but one should get past that part. So what are the strong and weak points to a pneumatic hammer? Don't fall in love with your first idea. Warren Quote Link to comment Share on other sites More sharing options...
Frosty Posted December 19, 2008 Share Posted December 19, 2008 The big downside is needing a sufficient air compressor which will add several hundred $ to the cost of the build. If you don't already have one of course. CFM is king for modern utility hammers. Frosty Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 19, 2008 Author Share Posted December 19, 2008 I already have shop air and have another compressor that I want to hook up in parallel. Besides air supply limitations are there any down sides? Warren Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted December 19, 2008 Author Share Posted December 19, 2008 Frosty, It should be possible to design a helve hammer that takes little floor space by designing the beam to be vertical and linking this motion to the hammer through a bell crank. Warren Quote Link to comment Share on other sites More sharing options...
Frosty Posted December 19, 2008 Share Posted December 19, 2008 I don't have a lot of experience on modern utility hammers so I'll leave that for the guys who do. Vertical helve linked through a bell crank, toggle, etc. is getting way too complicated. Like most devices the simpler you can keep them the better they work, longer they last and safer they are. Adding something to turn the motion through 90* when this much force is being applied is just asking for trouble. When I had my foot on the treadle I really didn't notice any difference in performance between a helve and LG type mechanical hammer. So, I don't see quality of blows as an issue. In the early days a helve was what there was for a power hammer known as a "tilt" or trip hammer. Earlier still were "walking beam" hammers. These had unguided heads so the longer the length of the helve the more parallel the hammer and anvil were at different distances. Now however there are options made possible by modern machine shop precision and materials. Regardless a helve is pretty easy to build and tune ala Rusty, they just take up more floor space and I'm kind of selfish where floor space is concerned. Frosty Quote Link to comment Share on other sites More sharing options...
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