M6 clearance fit holes on plate not big enough

larrykvit / dynamite_force_plate_physical

Physical components of the dynamite force plate: drawings, cad, BOM, etc

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M6 clearance fit holes on plate not big enough #1

Open larrykvit opened 3 months ago

larrykvit commented 3 months ago

It looks like when the mavin na128 loadcell is compressed in the long axis, it will produce a reading. When the plate is attached to the loadcells and the M6 bolts are tightened, the reading changes. I suspect it is because the tolerance of the holes such that the bolts apply a compression load between the two loadcells.

Making the hole bigger seems to solve this problem.

Figure out how big the holes should be and update the drawings.

larrykvit commented 2 months ago

An alternative would be to have slots instead of holes. This remove the compression issues as well.

larrykvit commented 2 months ago

Tested slots with teflon washers - they seem to perform really well.

Tightened bolts so that the back plat no longer moves
placed a weight on several locations. The measurements were accurate to ~10 grams, and always went back to 0 after.
Hung body weight several times and afterwards the reading was back to 0

TODO - test the slots without washers. Maybe with the slot there is no need for washers.

larrykvit commented 2 months ago

Slot without washers doesn't work. There is hysteresis. Hung body weight in the middle, let go. Left load cell was reading 0.8kg with no load.