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How Can I Slow This Motor Down a Little Bit?

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  • How Can I Slow This Motor Down a Little Bit?

    Laminate trimmers like the ones in the pic typically run at about 30,000 rpm no load. I need to slow slow this down to about 3,000 rpm.



    How can I do this without losing power, damaging the motor, or costing a pile of money?

  • #2
    Let us know when you find out

    A motor like that requires the fan for cooling, so if you slow it too much it won't get enough. You can still use it intermittently though. You can use a simple control designed for inductive loads, basically a dimmer. You will lose most of the rated power, and to get some of that back you will have to draw more current than the brushes would like. All in all, not a great idea- but having said that you can buy a router with a speed control, which is a pretty simple thing. It doesn't address any of these issues of course.

    If you really need the power, the only way is to gear it down in some way. A toothed belt would be my choice. You're looking for a 10 to 1 speed reduction- maybe you could get a satisfactory result by using both a speed control and a reduction of perhaps 5 to 1 or so. You could probably find something in the hobby industry as far as cogs and belts. Of course you'll need to have a second output shaft, bearings, etc.

    Could you use an angle grinder instead?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #3
      For 3,000 RPM you might be able to adapt an electric drill to provide the rotary power. You can often find older NiCad rechargeable drills with bad batteries or chargers, for free or cheap. It might require a "helper" bearing to provide support for radial forces. It also might be possible to cannibalize the planetary gear drive speed reducer, and adapt it to the router.
      http://pauleschoen.com/pix/PM08_P76_P54.png
      Paul , P S Technology, Inc. and MrTibbs
      USA Maryland 21030

      Comment


      • #4
        Most hand held routers that do not have a soft start circuit or a speed control on them can easily be speed controlled with a simple router speed control like those sold by Harbor Freight. At their core they are just a universal brush motor. In fact any universal brush motor can be controlled with one of those speed controllers.

        The problem is those motors don't have much torque at low RPM. For a 30-34K RPM trim router 3000 RPM is low speed. You will find as soon as it engages the cut it will slow down and you will need to adjust your speed back up.

        There is atleast one PID device designed with this in mind. It use a tach pulse input (you have to install the tach in the router) and adjusts the router on the fly to maintain RPM. The one I am familiar with is called a SuperPID. Its specifically designed to work with universal brush motor wood routers and can be POT controlled or use a signal source. Its typically used on CNC Routers, but it doesn't have to be. It also has an open loop configuration, but then you are back to the original problem of speed changes as load changes.

        In some cases even soft start or speed controlled routers can be used by removing their soft start or speed control circuit.
        *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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        • #5
          For the smaller routers a 600 Watt ceiling speed control may work well. To reduce load use small cutters.
          Anything larger the motor speed controls by Dart, Minaric or KB Electronics should work well.
          In all cases you will have to supply an enclosure, power cords and appropriate connectors.
          As mentioned be aware of motor heating at low RPMs.
          RichD (My Bridgeport mill uses a Minaric control with 3/4 HP DC motor)
          RichD, Canton, GA

          Comment


          • #6
            What would help is what are you trying to accomplish? I've used routers on aluminum, carbide bits and slow feed. My cheap mill.

            Comment


            • #7
              A router speed controller works well - like this one: https://www.busybeetools.com/search?...+speed+control

              I have two in use. One for controlling a vacuum cleaner when grinding or machining cast iron and the other on a router.

              Not sure about torque at the rpm you want to use though.

              Geoff

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              • #8
                There is a nice controller by Roman Black that he marketed under the SuperPID, it controls a Universal motor router down to 5krpm, very precisely.
                Without this type of feedback controller, Universal motors do not control at all well if you want RPM control under load.
                Max.

                Comment


                • #9
                  Originally posted by MaxHeadRoom View Post
                  There is a nice controller by Roman Black that he marketed under the SuperPID, it controls a Universal motor router down to 5krpm, very precisely.
                  Without this type of feedback controller, Universal motors do not control at all well if you want RPM control under load.
                  Max.
                  Hey Max. Missed you from RCM. I already mentioned the SuperPID a few posts up.
                  *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

                  Comment


                  • #10
                    I've tried it with a router speed control and a variac. They both did slow the trimmer down,but below 8,000 rpm the trimmer was very choppy and ran rough.Worse though was the total lack of usable power.
                    I just need one more tool,just one!

                    Comment


                    • #11
                      Pulleys would be the ideal way, but I suppose that they are totally out of the question.

                      How about running the shaft against a wheel with a rubber "tire"? Half inch diameter shaft against a five inch diameter wheel = 10 to 1 reduction. For a more compact arrangement the five inch diameter could be an internal diameter. Many phonograph turntables were driven this way with an idler wheel with a rubber tire between the motor shaft and the ID of the platter.
                      Paul A.
                      SE Texas

                      And if you look REAL close at an analog signal,
                      You will find that it has discrete steps.

                      Comment


                      • #12
                        Originally posted by darryl View Post
                        Let us know when you find out

                        A motor like that requires the fan for cooling, so if you slow it too much it won't get enough. You can still use it intermittently though. You can use a simple control designed for inductive loads, basically a dimmer. You will lose most of the rated power, and to get some of that back you will have to draw more current than the brushes would like. All in all, not a great idea- but having said that you can buy a router with a speed control, which is a pretty simple thing. It doesn't address any of these issues of course.

                        If you really need the power, the only way is to gear it down in some way. A toothed belt would be my choice. You're looking for a 10 to 1 speed reduction- maybe you could get a satisfactory result by using both a speed control and a reduction of perhaps 5 to 1 or so. You could probably find something in the hobby industry as far as cogs and belts. Of course you'll need to have a second output shaft, bearings, etc.

                        Could you use an angle grinder instead?
                        I agree with this. Anything you can find will either reduce the power or cost some money. Any sort of electronic speed control will drop the torque to nothing at the speed you want. Your best bet would be a mechanical reduction, either a gearbox or pulley arrangement, but both of those will cost

                        Comment


                        • #13
                          As mentioned before, I am a big fan of router speed controls with die grinders. At low speed the modulation of the cut is really outstanding and the torque is surprisingly good. Some speed controls perform better than others at very low speeds. Whether it will have sufficient torque for other situations just depends.

                          An example, when I need to grind with a 1/4" carbide bit inside a 3/4" hole.. At high speeds you will tend to catch the bit and then the whole thing goes crazy inside the hole, bouncing off the walls and chipping/destroying the bit. At low speed you can control it. It also allows you to use much greater force, which also aids control.

                          If you have ever ported cylinder heads with a 6" long carbide burr, intending to smoothly take 1/32" off the contour of the floor short side radius, and no more.. Blasting along at high rpm is not your friend.

                          There are also times I use a RSC with an angle grinder. Maybe I am grinding plastic, or using a rope wheel, and I just can't use the full speed. Wire wheels on die grinders also need to be slowed down significantly or they tend to destruct.

                          Comment


                          • #14
                            Your thread title is a bit misleading. Slowing it down to around 1/10 of its normal RPM is a lot more than a "little bit".

                            I'd look at adapting a geared tool of some form to do what you're after. Had drills might be a good place to look. Those with smaller chucks like 3/8 run at a higher RPM than those with 1/2" chucks. I've got a corded drill here with a 1/4" chuck which runs at 3K. Or perhaps some other battery or corded tool that has a built in gearing arrangement.

                            This means you won't have a collet chuck directly available but frankly I think it would be easier to make that sort of change than to run a router at only 3K and expect the motor to perform well. Especially if it's being asked to do heavier work. A good speed control that senses the RPM can maintain the RPM but in the end the motor can only run at the original maximum current. And since that 1HP rating (or whatever power it is) is the torque x the RPM at 1/10 the rated RPM you're still only going to get around 1/10 of the overall power. OK, maybe it can be run at a bit over the max current for a short while. But it'll still be maybe 1/15 of max or so.
                            Chilliwack BC, Canada

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                            • #15
                              https://www.harborfreight.com/router...rol-43060.html

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