nonjic Posted January 13, 2017 Share Posted January 13, 2017 Hello ! I'm seeking advice on a type of hammer I don't have a great deal of experience with, hope you can help ! Are there any golden ratios for the pivot point centers (ram and pitman end), arm lengths and toggle lengths on a 'dupont' type linkage for optimal performance, as used on the tire hammers etc ? how is spring rate calculated for this type of linkage, or is it a suck it and see ? When the pitman is at bottom dead centre, spring compressed, should the dies have a small gap between them, with the toggles parallel ? Thanks, John Quote Link to comment Share on other sites More sharing options...
arftist Posted January 14, 2017 Share Posted January 14, 2017 Hi John I don't have your answers but to clarify for others Little Giant hammers also use the DuPont linkage. Quote Link to comment Share on other sites More sharing options...
nonjic Posted January 17, 2017 Author Share Posted January 17, 2017 Has all the know how on this site really 'done one' ? real shame. Ill go old skool and work it out myself. Quote Link to comment Share on other sites More sharing options...
CMS3900 Posted January 17, 2017 Share Posted January 17, 2017 What type of hammer are you working on? Are you homebrewing a hammer? You mention a tire hammer, are you using any plans? Generally speaking when the hammer is at rest with the pivot at BDC, the toggle links should be almost perpendicular to the ram, with the inner ends of the links 1/2 to 3/4's of a inch lower than the outer ends, and the ram should have a gap between the dies. This gap is usually adjustable on most Dupont Linkage machines IE Duponts, Fairbanks, Little Giants, Mayers, and others by sliding the cross head up and down the pitman arm. This variable gap is there to allow the hammer to have a proper cycle when working various size stock. Spring pressure is based on the amount of force required to overcome the weight of the ram and leverage from the toggle arms pulling the links outward to lift the ram, and still having room to compress during the cycle. Spring rate is linear. The length of the toggle arms and links would be a function of both ram travel distance as well as room for spring compression, which is different for ever hammer. Quote Link to comment Share on other sites More sharing options...
BeaverNZ Posted January 18, 2017 Share Posted January 18, 2017 Hi John Could you measure up an existing machine and just scale it to get the sized machine you want? Cheers Beaver Quote Link to comment Share on other sites More sharing options...
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