Meccanograph
Built by Richard Marsden in January 2023 for the Meccanographs Secretary’s Challenge
I opted to place the platter between the cranks rather than to one side. It made the design more compact and the effect of any slack in the crank pivots is halved by the lever action rather than amplified. The model is hand-cranked and quite simple. The gear ratios are fixed but one crank can be reversed by unscrewing a pinion from its shaft, sliding it to the other side of the contrate gear it drives, and re-tightening its grub screw. The crank action uses bush wheels so its phasing can be altered by moving the one of the pivots to a different hole. Each crank is actually two bush wheels one above the other to provide sturdier locations for the pivots.
The platter is a disc cut from a sheet of MDF. To stick the paper to the platter I attached a couple of strips cut from the top of a Post-it note, sticky side up, to the platter using double-sided adhesive tape. The Post-it ‘adhesive’ holds the paper more than adequately, makes it very quick to remove it and fix a new sheet, and seems to continue working for many, many sheets.