How can I make a motor with a belt change directions?

Question

_{*Note: I've included question and answer since this is a lifehack I stumbled across and thought it was worth sharing. :)}

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I work in agriculture. One of the things that we frequently do is moving small square haybales from one place to another.

To facilitate the process, we frequently use hay elevators to bring hay up into the barn and down from the barn. One of the troubles, however, is that the motors typically run on alternating current, so there's no easy way to make the hay elevator in reverse.

Consequently, we frequently end up having to get 2-4 people to turn the entire machine around. It's annoying, cumbersome, and sometimes requires attaching ropes to keep it from falling.

One thing is quite frequent on these hay elevators, though, and that is that they typically (though not always) have a belt that transmits the power from the motor to the machinery. Is there some way I can make use of this to make the motor turn in reverse, preventing all the trouble of moving the hay elevator?

Answer 1

Frequently, there is. Simply loosen the strap, take it off the motor, give the strap one twist, reconnect it to the motor, and tighten the belt. The belt now makes a figure-of-eight instead of a simple loop, which effectively reverses the direction of the motor.

Though it does put a bit more wear on your belt since the belt will rub on itself at the X of the figure-of-eight, it is not significant, especially since usually the angle on the side of the belt fits into the angle of the belt it's rubbing on. And in any case, you have to pay people to change the hay elevators position, so a few times of doing it will pay off a new belt.

Hope this can help someone!

Answer 2

The most time-efficient method of reversing an electric motor's output is electrically. Single phase induction motors are (relatively) hard to reverse, but three-phase motors are easy -- all that's required is to swap any two phases of the stator winding. This can be done with a double-pole, double-throw switch with a reversing jumper connecting each corner terminal to the oppostite corner. Your supply goes to the two center terminals on the switch, the corner terminals on one end go to two of the motor's windings (the third winding gets the uninterrupted remaining phase), and the other end of the switch gets only the reversing jumpers. Now, with the switch set one way, the motor will run on direction; flip the switch over, and it'll run the other way.

Similar wiring can be used to reverse a brush type series wound motor, simply by reversing the connection of either the field or the brushes (though it's unlikely a motor larger than about 1/2 HP will be series wound) relative to the other. This is usually done by bringing the hot leg of the power to one center terminal, wiring the other center to one brush, connecting the field to the end terminals (so it gets reversed when the switch is flipped over), and running the other brush direct to the neutral leg.

If your motor is, in fact, a single phase, it's still possible to reverse it, but it's quite complex to do and beyond my ability to explain (I'm not at all sure I could do it myself, never mind explain how).

Obviously, unless you've got some experience working with electrical devices, you shouldn't try this yourself, but it's an easy task for anyone qualified to repair your equipment.

Answer 3

If you're dealing with a 3 phase motor then as Zeiss points out, swapping any two of the wires over (via switch is possible) will cause the motor to run in reverse

If you're dealing with a single phase AC large motor they typically will run in either direction and will carry on running in the direction they were started in. They have starter windings to get them going in the direction they're supposed to go, and then the main windings carry on running them in that direction. Perhaps you'd not be averse to disconnecting the starter winding (or having a switch to temporarily disable it) and then using your hand to start the motor going in the direction you require. I've had this problem with a cement mixer; the starter winding is burnt out, and now when powering it on it just sits and hums until you push it in either direction, whereupon it runs in tht direction all day

If you're not into an electrical solution, can the motor be unbolted and re-attached turned round 180 degrees so that it is is sticking out to the left instead of the right (or vice versa)? You might even be able to fashion some mechanical thing that lets you flip the motor over and back

Can you obtain an additional motor, one that turns the other way (or one that turns the same way but mount it sticking out the other way), and a longer belt to go round both motor pulleys? One motor can idle while the other one is powered, and swapping the power over to the other motor and idling the first will reverse the conveyor

https://woodgears.ca/motors/reversing.html is a great resource for info on how to reverse motors electrically