Pulling a string with a motor

i building automatic chicken coop door opener. yes, can buy them wouldn't fun, it? door 200 gram (or 0.4 lb) mdf panel , want pull vertically string shown here:



but don't know how attach string the shaft of motor.

i know there gears (https://www.sparkfun.com/categories/254) , couplers (https://www.sparkfun.com/categories/255) still doesn't me.

i thinking of using wooden sewing bobine:



and connect shaft. how? coupler , shaft right diameter , hot glue 2 together? hold? there better way?

thanks!

a spool seem obvious solution...  that's how construction cranes & winches work...   if hot glue doesn't hold, epoxy will.

if can't find spool right dimensions, make spool dowel washers on ends ( (maybe fender washers).  if make own, may not able drill straight hole way through (depending on length), can drill holes on both ends "bearing" (just loose shaft) on 1 end.

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