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Reply to "Replacement Belt for MTH Dispatching Board"

Big Jim posted:

I am curious as to how this whole thing works? What does the pin do?

The belt simply rotates a complete loop. If you watch the pin from the side, it moves in one direction, stops horizontal motion at the pulley, then turns and moves the other direction creating the back and forth motion of the figure. The pin simply is the method the belt transfers the motion to the slotted moving gantry with the figure. Think like a crankshaft that converts rotary motion to linear reciprocating motion, but the belt is an oblong crankshaft, and the resulting motion is extra long linear motion. The pin is literally the pin of the crankshaft. Go back and look at the pictures I posted earlier. The pin is just stuck into the side of the belt. The belt then is stretched over the 2 pulleys. The motor only turns the belt one direction however, in doing so, the pin actually moves back and forth when looked at from the front. That pin pushes the little rolling carriage on the metal rail via a slot, which is what allows it to make the full 360 loop rather than having to reverse the motor. The limit switch is there to park the belt and thus figure at the one end. You press the button, the motor turns the belt, the figure moves down the track to the end, then pauses for a second as the pin now slides down in the slot following the pulley turn, then pulls the carriage back until it hits the limit switch and stops, thus externally the little man parks at one end, then then commanded to "change the board" moves down until the end- then due to the slot has a minor pause, then moves back to the starting point and stops. The little carriage has a rack and pinion shaft such that the brass rack rod hitting the endstops at either end of the travel turns the little man on the shaft to face or walk in the direction of travel. The motor turns the belt, the belt pin drives the moving carriage, the moving carriage carries the little man.

Last edited by Vernon Barry

OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
800-980-OGRR (6477)
www.ogaugerr.com

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