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Hi everyone...I'm trying to construct a gizmo that can best be described as an electric see saw. Basically, it's for mixing fluids using a rocking motion. I have considered other mixing methods, and for reasons too complex to bother going into, have decided on this design.
First, picture a long box, about 10" by 30", that contains about a dozen cans of soda or small bottles all in a row, one level high, lying on their sides. The whole box must rock back and forth such that the contents of each bottle will slosh from the cap end to the bottom, and back (not from side to side). Picture a one-inch pipe running beneath the length of the box (yes, the long way), acting as a fulcrum.
My question is, what do I use to motorize this? I know nothing about motors and other such devices, but need to make this electrified so that I can step away while it rocks itself for an hour or two as I prepare the next batch. Your brilliance is needed, thank you in advance!
First, picture a long box, about 10" by 30", that contains about a dozen cans of soda or small bottles all in a row, one level high, lying on their sides. The whole box must rock back and forth such that the contents of each bottle will slosh from the cap end to the bottom, and back (not from side to side). Picture a one-inch pipe running beneath the length of the box (yes, the long way), acting as a fulcrum.
My question is, what do I use to motorize this? I know nothing about motors and other such devices, but need to make this electrified so that I can step away while it rocks itself for an hour or two as I prepare the next batch. Your brilliance is needed, thank you in advance!
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Tucson
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Re: Tips for building a miniature electric see-saw?
Sun, February 3, 2008 - 1:31 PMI think all you would need is an electric motor and an on/off switch. Attach a circle of wood or something to the shaft of the motor. Attach a rod to the outside edge of the circle, say with a nut and bolt -- not totally frozen in place; let it move with the rotation of the wheel -- and attach the other end of the rod to one end of the see-saw in a similar way.
Essentially that turns the rotation of the wheel into linear motion to push and pull the seesaw back and forth. You might need to split the connecting rod into two linked pieces to give a bit more freedom of movement. See the Wikipedia articles on "Crank" and "Piston" for some illustrations and an animation.
You also might need a rheostat ("dimmer switch") to control the speed of the motor; alternatively you can rig something up using gears or belts. You can probably scrounge a plenty powerful motor out of a free appliance on Craigslist, but be very careful: many of those things run on 120 Volts AC which can kill you quite easily! -
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Finding the right motor
Mon, February 4, 2008 - 10:01 AMThank you Sam! That made perfect sense... converting circular motion into reciprocating motion. Now I have questions about motor specs. I am considering a used Dayton gear motor, model no. 3M257: 25rpm, 1/70hp, .75 amps @ 115v 60hz, run torque 13 in. lbs. This should let the mixer rock back and forth about every two seconds, which is perfect, so I won't need to worry about a rheostat (just on/off).
As for the rest of the specs, does this seem like an appropriate match? There are 4-6 pounds of fluid to be sloshed. The weight is centered on the fulcrum and extends away from it on both sides by 3-4 inches, so the motor won't actually need to lift all six pounds. I don't know what "13 in. lbs. run torque" means in terms of power...do you think this will work? And what if I build a double-decker or double-length mixer (holding 8-12 lbs.) to increase my productivity...will the motor still have enough oomph? I am unfamiliar with the science of motors, and grateful for your suggestions! -
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Re: Finding the right motor
Thu, February 7, 2008 - 8:21 PMWell I am not a motor expert either, but it seems like it would probably work. 13 inch-pounds is not a lot of torque, but if you size the mechanical parts right I bet it will work out. The wheel should probably be as small as you can get away with. As I said above if you can rig up some gears or belts to it you can get it to drive a bigger load, but slower.
For the electrical setup you can get a single-gang metal box, a light switch, NM (Romex) connectors, and a metal switchplate at any hardware store. You'll also need an appliance cord with bare wires on one end. The only other suggestions I have are about electrical safety: make sure you switch the "hot" (black) lead and not the common (white), ground your enclosure, cover all exposed wires with electrical tape, and make sure you mechanically protect all the wiring (like, with a wooden box or something) so that it can't be shorted or damaged by stuff falling onto it. Good luck!
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