09-21-2014, 05:56 PM
(This post was last modified: 09-21-2014, 05:58 PM by Hopefuldave.)
Good questions...
Speed - hand operating a selector fork to engage/disengage dogs on a shaft running at a few hundred RPM, accuracy and fine repeatability are secondary to the selector fork being able to return the operating shaft (rotation through 90 degrees) and vice versa. Think actuator, not positioner or leadscrew! A degree of 'feel' would be a Big benefit, so I.want to minimise friction and backlash as much as possible.
The selector fork needs to move 3/8 - 1/2 inch in each direction along the shaft axis or parallel to it for a 45 degree shaft rotation in each direction from a midpoint, there will be ball detents at start, middle and end of the shaft rotation (not on the.fork) and the shaft itself needs to have end float (1/8" or so each side of midpoint) relative to the actuator as there are some other bits and pieces built along with it.
The really difficult bit seems to be.fitting it in the available space (about 1" radius around the shaft axis, perhaps 6" long, which precludes using cranks, face cams etc... Using a long-lead ballscrew seems most apt, IF I can make one and IF it will work...
Speed - hand operating a selector fork to engage/disengage dogs on a shaft running at a few hundred RPM, accuracy and fine repeatability are secondary to the selector fork being able to return the operating shaft (rotation through 90 degrees) and vice versa. Think actuator, not positioner or leadscrew! A degree of 'feel' would be a Big benefit, so I.want to minimise friction and backlash as much as possible.
The selector fork needs to move 3/8 - 1/2 inch in each direction along the shaft axis or parallel to it for a 45 degree shaft rotation in each direction from a midpoint, there will be ball detents at start, middle and end of the shaft rotation (not on the.fork) and the shaft itself needs to have end float (1/8" or so each side of midpoint) relative to the actuator as there are some other bits and pieces built along with it.
The really difficult bit seems to be.fitting it in the available space (about 1" radius around the shaft axis, perhaps 6" long, which precludes using cranks, face cams etc... Using a long-lead ballscrew seems most apt, IF I can make one and IF it will work...
Rules are for the obedience of fools, and the guidance of wise men...
(Douglas Bader)
(Douglas Bader)