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  • Modifying a chainsaw clutch

    Odd question.
    Is there a way to modify a chainsaw clutch to make the clutch engage at a lower rpm?
    I fabricate wind generator components and I was to experiment on using a clutch. This should allow the blades spool up in sooner then engage when the blades have develop enough torque to continue spinning.

    Ideas?

  • #2
    Is there a reason to need a clutch? I would think that any generator could be 'hard wired', or direct coupled, and when there's more than enough speed available it would either start to generate more voltage than the battery it's charging, if a permanent magnet design, or a relay would cut in to supply the field winding, if it was an alternator. In the case of an alternator, a circuit of some kind would have to sense the rpm and operate a relay to supply the field winding at the point where it could generate more power than the field would take.
    A chain saw clutch, or any similar one, is going to slip quite a bit at the point where it's just starting to cut in, so that might not be an optimum solution. That type of clutch is designed to respond to large increases in rpm, where the clutch action changes from not engaged to strongly engaged over a short period of time.

    In the case of a windmill, it's likely that the clutch would be slipping a large part of the time, so a lot of energy would be wasted, and it would wear out early.

    Ironic- lately I've been thinking of adapting a direct drive washing machine motor to a windmill. This would be direct drive, no gears or belts, etc. I figure that having a dual set of windings on it would allow me to charge a battery pack at a lower current, but sufficient voltage, when the rpm is low, then charge at a higher current from the other winding when the wind speed has picked up. A relay would operate from the higher voltage winding to switch over to the higher current winding when there's enough power in the wind to generate significant power.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

    Comment


    • #3
      The key is to make the weights heavier, or the feather weaker.
      Often there are no space that allows bigger weights, so
      i once drilled a couple of holes trough them and filled those holes with lead.

      you can also try to replace the feather that holds the weights with a weaker one.

      Comment


      • #4
        I'd look at a magnetic clutch like those used on automotive AC compressors. They get full engagement with 3 amps at 12 volts, but it takes a lot less input to get enough grip to transmit significant torque. You could put in a new coil to get the torque you need at a different combination of voltage and current.

        The magnetic clutch will have a superb double-row ball bearing that supports the pulley, and the clutch pulley is made of steel that machines and welds easily. You could mount a pretty large blade right on the pulley/bearing with a few easy modifications.



        They're readily available in a wide range of sizes for reasonable cost, too.

        You could get a junked compressor with the clutch, gut the compressor, and install the clutch mounting end of the housing right on your alternator. You could probably modify the hub of the clutch disc to fit the alternator shaft.

        Roger
        Last edited by winchman; 10-22-2009, 04:38 AM.
        Any products mentioned in my posts have been endorsed by their manufacturer.

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        • #5
          I have seen auto air con compressor clutches used for other stuff too, thats a good idea.
          If you guuted the comp, you could mill a slot in the side, fit a pulley on the shaft and connect a v belt to it to drive your alty.
          Build it, bodge it, but dont buy it.

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          • #6
            Scrap the idea of using a centrifugal clutch. They depend on the high rpm of small motors to operate. Simply modifying it by weakening the springs or similar will not work because at lower rpm it will have much lower friction and no effective grip. I know because I have tried it.

            The air con clutch is the way to go. They are made to last and have the ability to transmit at least several horsepower at any rpm you will require. Here is one salvaged and ready to use for whatever I decide.



            Free software for calculating bolt circles and similar: Click Here

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            • #7
              What's the point of trying to get the wind turbine to cut in earlier if you just throw the energy away in an electromagnetic clutch?

              Wind turbines have three speed ratings.

              Start up speed. The wind speed at which the friction is overcome and the blades start turning.

              Cut in speed. The wind speed at which the generator is turning fast enough to produce enough voltage to start pushing current into the battery.

              Rated speed. The wind speed at which the trubine produces it's rated output. This may or may not be the maximum output.


              Adding a clutch might improve the start-up speed, but won't do anything for the cut-in speed.
              Paul Compton
              www.morini-mania.co.uk
              http://www.youtube.com/user/EVguru

              Comment


              • #8
                why dont you just turn up the low idel so the cluctch will enguage sooner beats messing up the saw and its safer then messing with stuff you just shouldnt mess with...

                Comment


                • #9
                  How do you turn up the low idle on a windmill????
                  Free software for calculating bolt circles and similar: Click Here

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                  • #10
                    ya ya my bad i just woke up sorry , i miss the wind generator part lol

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                    • #11
                      use a ligher tension spring on the chain saw clutch and it will enguage faster/sooner then it normaly would,

                      Comment


                      • #12
                        Originally posted by EVguru
                        What's the point of trying to get the wind turbine to cut in earlier if you just throw the energy away in an electromagnetic clutch?

                        Wind turbines have three speed ratings.

                        Start up speed. The wind speed at which the friction is overcome and the blades start turning.

                        Cut in speed. The wind speed at which the generator is turning fast enough to produce enough voltage to start pushing current into the battery.

                        Rated speed. The wind speed at which the trubine produces it's rated output. This may or may not be the maximum output.


                        Adding a clutch might improve the start-up speed, but won't do anything for the cut-in speed.

                        Just dragging this over to this page as it's right on the money.

                        There's no need to use a clutch of any sorts, If mechanical it will simply result in more complexity and possible waste precious energies, If electrical it WILL result in wasted energies.
                        The only complex mechanical addition is to keep the blades from over running and destroying themselves --- this can be done by feathering the blades individually or a mechanism that rotates the tail vane 90 degree's and in some cases applies a brake,

                        Blade feathering is the preferred method due to being able to control the individual blades from a central centrifugal mechanism that unlike braking/tail vane systems will not wear out or need adjustment, if done properly it can also aid in the lowest start up/cut in/rated/ and maximum output.

                        Iv been kicking around an idea since i was young and found an example yesterday while browsing windmills, The low end torque of the old water pumping windmills were generally too slow for using in an electrical generator -- until now...
                        I thought about doing this but was going to use the blades to drive a large ring gear and massive planets and drive the generator with the sun.
                        I pondered about going gearless with a huge circumference motor but quickly abandoned the thought due to weight/awkwardness and unpractical.

                        The cut in speed for this windmill is an amazing 2mph, Im guessing start up and cut in are either extremely close or one in the same.

                        http://www.popularmechanics.com/tech...e/4332392.html

                        Comment


                        • #13
                          Stubby, doesn't the pitch of the blades control the speed of the wind generator? If so then why is there a high start up load? With the blades at a high pitch the wind would start the blades and gen. turning easily and as the speed increases the pitch control would reduce the pitch so the rpm of the gen is within the rated spec.

                          If there is no pitch control on the blades then the gen. would over speed so it has to have some kind of speed control.

                          EDIT: hmm, I got interrupted by a phone call as I was posting and Boomer posted much the same thoughts as I did.
                          Last edited by Carld; 10-22-2009, 11:53 AM.
                          It's only ink and paper

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                          • #14
                            Magnetic drag will limit most turbines from starting up at low speeds. The rotor with the magnets will cog past the windings. Takes a bit of power to overcomes this then it will start to rotate. A variable air gap axial design can eliminate a lot of the early drag but then again that makes it more complex. I built an axial design alternator for a turbine a few years ago with my son for a Science fair project. We could reduce the startup speeds by just spacing the coil /magnet further apart. Of course this reduces the efficiency so yes it turns but does not generate much energy!

                            .ps I really like that Honeywell design. Got the old gears turning on how to build one.

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                            • #15
                              That's good but you still have to control the rpm of the gen. to keep from over speeding it. I suppose you could put a system to move the magnet away from the rotor when it's not rotating and then when the blades reach a certain rpm the magnets move into their charge position but you still have to control over speed.
                              It's only ink and paper

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