DonS Posted June 12, 2007 Share Posted June 12, 2007 Simmonds: As I mentioned, I considered my hammer "OK" in that it draws out 3/4 or 1 inch bar a lot faster and easier than by hand. All I can compare it to that I have briefly used, is a 25 lb Little Giant, which hits about a hard but with many more blows per minute, and a 100 lb Alldays & Onions self contained hammer which is in a whole different league. I have my hammer set up with at 1/2 inch gap between the dies when it is at rest. It works material in the 1/2 inch to 1-inch range quite well, but the blows are a bit softer on thinner material since the spring is already pulling up as the dies get that close. The spring constant is a linear 500 pounds per inch of deflection (on my hamer) so when the dies touch, the leaf spring is pulling back by about 250 pounds. That is the nature of this type of spring. The little giant uses a toggle link and the action is very loose in the center of the stroke and only gets stiff at the extreme ends of the stroke, so it is less sensitive to stock thickness. Those builders that used longer leaf springs than mine seem to have a more limber action and they seem to be quite pleased with the performance. Jeff Reinhard, who posts on Anvilfire and Forgemagic built a similar power hammer, with the belt and pulley drive, and switched to the spare tire drive, and recommends that as the better design. Those compact spare tires are quite heavy and would act as a good flywheel. They are also cheap, usually in new condition and readily available at the auto wreckers for $5-10. For a bearing assembly you can use a matching hub from the rear axle of a fron-wheel drive car. Some suggest a Plymouth Grande Caravan rear hub (also cheap and available). I have used Plymouth Horizon rear hubs which are nice because the back mounting face is flat- you just have to bolt it down to the support column with four (metric) bolts. I got my springs at an automotive spring shop. They had all kinds of widths and thicknesses in various lengths. They were all pre-curved though. I don't know where you can get straight pieces, but being curved does not seem to be a big problem. The geometry does change a bit since the pitman arm should push perpendicular to the end of the spring, and the front end of the spring at the rollers, should be perpendicular to the ram at mid-stroke. If you are using a drill press to drill the holes, consider adding a few extra holes to allow for adjustment later. It is a lot easier at that point than after it is partially assembled. Quote Link to comment Share on other sites More sharing options...
simmonds Posted June 12, 2007 Author Share Posted June 12, 2007 DonS, Thanks once again for the great info. I think I am convinced now to try the spare tire drive system for my hammer. As far as the die distance, couldn't you set the gap at about 1/8 inch less and does the flex of the springs cause the dies to hit when the hammer is in use and there is no material stock placed between them? I am going to start scrounging around today to try and find some springs for my hammer. As far as the motor is concerned, I took apart and cleaned the little 1 horse craftsman motor that I dug out of the blackberries and after cleaning out a couple wasp nests and drying the motor out real well with a hair dryer, I plugged it in and it spun to life and works perfect. Thanks for all the help everyone. Chris Quote Link to comment Share on other sites More sharing options...
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