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I found that no clearance (0.25-0.25) would not fit together, while 5 thou of clearance (radius) produced a rubbing fit. I found that 10 thou of clearance produced a free fit, with great joint mobility. Because of this, I chose to use 0.25 pin and 0.27 hole, as this allowed for the largest pins in my testing range and I was slightly worried about pins being too fragile. This extended to the slider block, in which I used the same 10 thou of clearance (on both sides, 0.75-0.77) to produce a sliding fit.(insert image of original cad
with pin interference)
I then began the initial CAD-ing process. I initially used the measurements directly taken up from the image of the mechanism in the project description. As I scaled up the image to a full 8"x11" page, the final dimensions conveniently fit within the 6in squared I wanted. From these measurements and the pin size, I put together the CAD above.
(close image of interference)
In assembling the links, I noticed the current measurements (and slot design) led to interference at the center pin. This was because (AB - O2A) ~= (O2O4) when the design calls for O2O4 to be slightly less, with the difference being the distance between the pin and the end of the slot. To resolve this issue, I slightly lengthened L3 (slotted, AB) and slightly shortened L2 (input, O2A) as I found this combination changed the resulting path of B the least.
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