FILENAMES: bellcrank.bmp DESCRIPTION: Drawing of a "bell crank" assembly as discussed in relation to chess tournament clocks. Posted by Bradley M. Small . Bradley provided the following description: ======================================================================== It never ceases to amaze me at the resourses available in the Internet community. Just a few more questions if you will indulge me. I have drawn up a quick bitmap showing what I think you mean. I labelled all the parts that may incite discussion with letters. (Makes for easier discussion) I am not certain I understand what you mean when you speak of "bending the horizontal bar". I am not sure how you mean with the cotton shoelace, though I illustrated it at 'B' near as I understood it. A - Button B - Shoelace C - Pivot Base D - Pivot for connection to Horizontal bar E - Base for switch and switch F - Toggle bar G - Pins to manipulate toggle bar H - Horizontal bar I - Bell crank "L" piece K - Push rod (dowel) L - Stop M - Push Rod supports/track As for Chess players getting angry... hmmm, I guess not, but when time is running out they tend to hit that button a bit harder than most... :-) If I am way off on this drawing let me know, but I figured it would be much easier to go from what I think you said in a drawing and be wrong, than doing itin metal and wood and being wrong... :-) Sorry about the crudeness of the drawing, I did it quickly in paint. It is only 15 K but if it is inappropriate to post binaries to this NG I appolgise in advance. James Wilkins wrote in message <01be2db6$2e694020$8b295381@wilkins-pc.mitre.org>... >Bradley M. Small wrote in article ><75m52q$2rp$1@news1-alterdial.uu.net>... >> I am still trying ot digest the "bell crank thing" though I think I have >a >> visual picture of what you mean. I assume that he motion is more like a >> downward and right or downward and left as the 'L' rotates? I assume it >wil >> still have somewhat of a downward movement if even slightly. >> >-- >> >James Wilkins > >Both lever-end pivots move in a circular arc, just like the end of your >switch handle. The equation for it is X^2 + Y^2 = R^2 where the pivot is at >the origin and R is the lever length. The bellcrank has two levers, one at >X=0, Y=R and the other at Y=0, X=R (or -R). The up and down (Y) component >of the circular motion is what bends the horizontal bar, and what makes the >bent bar help to complete the switch stroke. The bellcrank doesn't have to >have an L shaped outline. I'd do it as a solid right triangle, maybe cut a >square diagonally to make both pieces. > >There are other ways to connect the two buttons and switch but the one I >suggested should be easy to make out of hobby-store materials and can give >you a good low-friction snap action independent of the switch itself, plus >the shoelace isolates the buttons from the linkage so it won't be damaged >by pounding, pulling or twisting the buttons. Not that chess players ever >get angry..... >-- >James Wilkins >KB1DAL >jesw@mitre.org