Barn Door motor driven Mounts


Posted on Feb 4, 2014

The threaded drive rod was made from standard 5/16 inch Whitworth threaded rod (18 TPI), only because this was to hand. M8 metric thread could have been used. The radius of the curve in the drive rod (which must be equal to the distance between the hinge and the drive rod) was 300mm. As this drive and it`s angular drive rate were to be controlled


Barn Door motor driven Mounts
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via a computer, this dimension and thread type are not critical. The controlling software could be set up to match. Many simple barn door designs use a straight drive rod which is rotated within a fixed drive nut. This is not possible when using a curved drive rod. A curved drive rod must be constrained at one end by a gimbal mount so that the drive rod cannot rotate. The drive nut must be free to be driven to rotate round the drive rod. - on the left hand side (ie hinge side), a mounting plate for ball and socket head. This was bent so that the ball and socket head was approximately horizontal when the barn door is set for local latitude. - mounting for the gunsight is situated near the middle of the top board. To the right hand side is a plate supporting a gimbal bearing that fixes the top end of the drive rod. The centre of the drive rod gear was cut away to make room for a captive drive nut. The captive drive nut was made by soldering an ordinary threaded nut into a drilled mild steel plate. This was then bolted exactly centrally onto the drive gear. Parts associated with the drive system were obtained (collected ) from various old printers. The drive gears are approximately 70mm diameter for the drive rod and 50mm diameter for the stepper motor, so there is a small gearing advantage for the motor stepper motor. Again, the plastic bush that was used for the lower bearing support was found in an old printer. This centre...




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