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explaining the slider clutch

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  • explaining the slider clutch

    Here's an explanation of how a slider clutch works. This also pertains to Top Fuel bikes, Top Fuel dragsters and nitro Funny cars

    The clutch is used to slip on purpose to prevent/control wheel spin.

    Sitting on the start line the inner is connected to the mainshaft and not spinning,the outer clutch basket is connected to the crank and is spinning. On clutch drop the springs are too weak and it slips just like if you did it by hand. As the bike begins to move the inner is now spinning "a little" and as such the weighted arms begin to apply pressure to the clutch pack to make it not slip and "lock-up". By adjusting the initial spring pressure and weights on the arms and even later versions with arms with springs as counter weight can cause a multistage lock up.

    The slider type clutch the weighted arms are on the basket so spin with the engine. It is a big mini bike clutch that engages by centrifugal only,the springs keep it disengaged. By adjusting the springs and the weights can adjust the engage rpm,ie "stall point". Since the springs keep the weights from engaging then adusting to get more lauch rpm also takes away amount of total pressure on the pack.
    This is why slider rpm engage is like say 5000 rpm or less where a lock-up can be any launch rpm you wish. Now as to having a clutch lever with a slider,it would then work like a lock-up.

    If you are sitting on a regular bike and just throw the lever,the engine dies. More rpm and the tire spins. A slick you "may" find the rpm that just "black tracks",but street tire is just happy spin,like a dirt bike in mud.

    Now a "good" rider can hold rpm and "slide" the clutch vs just throwing it. A lock-up acts just like this but pass after pass. It does not really "slip" but a quick engage not sufficient to break the tire loose,ie a smoother start. By putting more initial spring it "bites" harder. Extra weight on the arms,say a washer at a time,makes it get to full lock-up say 5 ft out of the gate vs say 10 ft.

    A stock clutch bike with a slick just thrown takes only a certain rpm to not just spin away,say 7000 rpm. Now the lock up can make it go to full throttle and max torque point,not spin but feed it clutch till peak power /shift point.

    The early lock-up had "L" shaped arms. Now they have "T" shaped arms. The one arm of the "T" does what it always did,the other arm has a spring under it. This prevents that arm centrifugal from making any contact till sufficient RPM to over come the spring. Say you have a 6 spring clutch. You can get either all 6 or 3 and 3 or 3 X 2. Maybe even 6 all at separate times.

    The clutch never "bites" hard enough to pull it down and bog.

    A slider is nice and consistent but engages from a low rpm,so takes a big engine or juice. This is why the high rpm NA Pro Stocks have a lock-up and not a slider. They can also have the cam timing to really favor high rpm power because the clutch never pulls it down.

    All in all this clutch control is what made all the difference in ET's.

    Never had the opportunity to use a Karata Glide, but I'm assuming it's lockup hat/arms are bolted to the clutch hub just as the MRE, correct me if wrong about that.

    The consistency is attained by the same static pressure (spring pressure) being applied each time and the same increasing dynamic pressure (lockup arms/weight) being applied each time. Wink Remember the lockup arms/weight are doing nothing without some wheel speed.

    The amount of force engaging the clutch is coming from two places, 1. spring pressure (which is normally set to allow more slippage than the stock springs would) and 2. lockup arm weight (which does not come into play until at least some wheel speed is attained) This of course is because the clutch hub to which the lockup hat attaches is connected to the rear wheel. No movement of the rear wheel equals no movement of the clutch hub, no movement of the clutch hub equals no pressure applied by the lockup arms/weight.

    Don't hold me to this, because I don't have the graphs in front of me right now, but I'm thinking that we're normally seeing probably 8/10ths of a sec or so from the time we make the hit until full lockup is attained. At that time, the clutch hub and basket are turning the same rpm with zero slippage as you'd mentioned earlier.

    I will say too that if I were going by a "seat of the pants" assessment of slippage, I would never dream that the clutch was slipping for that long of time.

    Theoretically, you could take a bike that exerted X pounds of force on the clutch pack going through the traps at 150mph, change nothing else but remove the crankshaft, rods, pistons block and head and then tow it through the traps at 150mph, the clutch pack would be subject to the same X pounds of force, thus proving that crankshaft/engine rpm plays no role in the application of the lockup arms.

    Doubt anybody's gonna try that tho
































    Crazy people don't know they're crazy, I know I'm crazy therefore I'm not crazy, isn't that crazy.....

  • #2
    Nice write up. How about some pictures of the different setups.

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    • #3
      but there is a difrence twixt a purely centrifugal clutch an a spring pressurized centrifugally assisted clutch.
      THE NEGATIVE ONE no better don't click
      https://www.youtube.com/watch?x-yt-c...-ts=1422579428
      How's my Spelin, CALL 1-800-BOSS to report my bad spelizin

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      • #4
        Originally posted by RoadKing View Post
        Nice write up. How about some pictures of the different setups.
        I can post some data with ET's ,HP rating and over all weight.
        Crazy people don't know they're crazy, I know I'm crazy therefore I'm not crazy, isn't that crazy.....

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        • #5
          My best set up yielded an 8.81 at 157.05 mph. bike and rider 725lbs. stock Vrod Destroyer chassis. 200+hp. I had red medium static springs, set at .780 made it 4800-5000 clutch engagement. no shims just springs, and 22 grams on the dynamic arms.. the spring pressure works against the arms and weight isn't helping, but it run a 8.81, 65 year old rookie never done it in his life.
          It was a shitty goodyear tire. Mickey's are the way to go now.

          Crazy people don't know they're crazy, I know I'm crazy therefore I'm not crazy, isn't that crazy.....

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          • #6
            thats some interesting stuff
            Expectations managed for free

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            • #7
              had mtc make me up a slidder for my destroyer with 1550 motor. need your knowledge on initial setup. appreciate any help you can send my way. jerry

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              • #8
                Originally posted by jerryk4789 View Post
                had mtc make me up a slidder for my destroyer with 1550 motor. need your knowledge on initial setup. appreciate any help you can send my way. jerry
                Jerry, welcome to the forum. Find the intro thread and introduce yourself. You are asking a question on a 4 year old thread.
                Mark

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                • #9
                  can not seem to find it

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                  • #10
                    Originally posted by jerryk4789 View Post
                    can not seem to find it
                    Here you go. Click on the link below and then create a new topic..

                    https://www.hdherd.com/forum/main-ca...-our-community
                    .
                    2010 FLHX - Street Glide
                    HERD MEMBER #00003

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                    • #11
                      Copied from my response to your Welcome thread:

                      Welcome from NE PA Jerry. If you're running V-Rod Destroyers I trust you know of Rich and Ray Vreeland or Vreelands HD, in Bloomsburg PA. If you have not heard of Ray, got to their website, here is a link to their V-Rod racing page http://www.vreelandsharley.com/v-rod-racing . If you don't see what you need, give Ray a call and I am sure he can hook you up with a source.
                      Mark

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