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Small, model sized worm gear reducer

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  • Small, model sized worm gear reducer

    I have another project underway (which has to do with the hit and miss engine I recently finished) and I needed a small, powerfull gear reducer that wouldn't back feed torque thru the input shaft. A worm gear reducer was my first choice, because a worm gear drive with a ratio of greater than 40:1 won't back feed. I happened to be "browsing" in Princess Auto, and found brand new wiper motor assemblies for $9 and change. I bought one for my new toy.
    Brian Rupnow

  • #2
    I took it home and disassembled it, and found some very interesting things. First, the permanent magnets are glued into the motor casing, but readily release when the sides of the motor housing are heated with an acetylene torch. The housing itself is made from mild steel.
    Brian Rupnow

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    • #3
      The armature shaft is one straight peice, and the armature itself appears to be made from a stack of metal discs that are attached to the shaft with some kind of epoxy. It cuts easily with a carbide tool in the lathe. The copper commutator is not really attached to the shaft at all. It is held in place by the 2 miles of copper wire that are woven thru the armature discs and soldered to the copper commutator bars. Once the wires are cut away on the lathe, you can pull the copper commutator off the shaft easily.
      Brian Rupnow

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      • #4
        Since the motor housing is cylindrical with a flat on each side, the current plan is to make up a peice of aluminum plate that will fit into the peice of motor housing which has the flange on it and center drill it for a .3125 bushing. The shaft is 9mm, but since all my reamers are imperial sizes, I'll turn the end of the shaft down to .321' (5/16") 7.94MM and have enough shaft sticking out of the end of the housing/aluminum plate to mount a pulley on.
        Brian Rupnow

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        • #5
          And voila'---A really nifty little worm gear reducer. I will probably have to put some kind of collar on the shaft inside the aluminum endplate I will create, because depending on which way I rotate this thing the worm shaft will have a tendecy to "unscrew" itself from the worm gear. This wasn't an issue in its original shape, as there was a peice of nylon acting as a thrust bearing in the end of the motor housing.
          Last edited by brian Rupnow; 02-28-2011, 04:53 PM.
          Brian Rupnow

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          • #6
            So there we have it---a beautifull little gear reducer. And this one is a 60:1 ratio.
            Brian Rupnow

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            • #7
              Add a pulley, and we're good to go. Man, that was almost too easy!!! as you probably noticed, i didn't turn the shaft to a smaller diameter. I used the full 9M and bored a peice of brass to 9MM to make the bushing----No reamers involved!!! ;D ;D

              Brian Rupnow

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              • #8
                Good idea at a great price !

                Thanks,
                Randy C

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                • #9
                  I bought a similar motor at a similar price from PA in Cowtown for my pantograph tracer project.

                  IIRC, it was a RFE wiper motor.
                  Design to 0.0001", measure to 1/32", cut with an axe, grind to fit

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                  • #10
                    Ok, unless i missed something here, i,m wondering what this next project is?

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                    • #11
                      Originally posted by brian Rupnow
                      ...and found brand new wiper motor assemblies ...
                      That is what is known as a window regulator motor, for raising and lowering power windows. Years ago, I built a couple dozen durability test controllers for these things for a Fisher-Guide test lab. A similar but smaller motor was used in seat positioners.

                      The output gear engaged a stamped steel gear sector that had a lever that attached to the bottom of the window glass. When I wanted to repurpose the regulator, I found that a 3/4" (I think) socket wrench fit nicely onto the gear as an adaptor. From there I was able to fashion a square driving shaft.
                      Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                      ~Practitioner of the Electromechanical Arts~

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                      • #12
                        Originally posted by Weston Bye
                        That is what is known as a window regulator motor, for raising and lowering power windows.
                        yeah ..i thought it was that .

                        all the best.markj

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                        • #13
                          Nice hack. By the way, those motors are fairly powerful for their size, so someone could also hack one just for the motor. As a windshield wiper motor it could be used on a more or less continuous duty basis- not sure if the window motor would be the same, but I think so. This would NOT be the case for a window motor with a wound field, only for those that are permanent magnet.

                          Back to the gear box- where I worked a while ago we had a run of mixmasters come in, the cheap handheld ones that KitchenAid makes. Those have a worm gear shaft and two worm wheels in them, also a permanent magnet motor. I kept a few dead ones for myself, intending to possibly cobble up a power feed for a light duty machine. The mechanism is quite compact and the motors are good- it's usually the multi-speed digital display electronics part that goes bad. If you can find one it would be another source for a worm gear drive unit.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                          • #14
                            I stand corrected. I THOUGHT it was a wiper motor. I kind of wondered why it has "Right Hand" stamped on the case. What am I going to do with it---well, I want to build something to demonstrate how a hit and miss engine behaves under a load as opposed to under a "no load" situation. The gear drive is going to rotate an eccentric weight which will alternately load and unload the hit and miss engine.
                            Brian Rupnow

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                            • #15
                              What could be cooler than a hit & miss window regulator?

                              http://www.youtube.com/watch?v=GLsyM2Crhew
                              Jim H.

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