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Line-Shaft Clutch

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  • Line-Shaft Clutch

    After doing a bit of research on line shaft style clutches, with a manually operated swing lever to actuate them, I've decided to build one, "Just to see if I can!!" (This train of thought was brought about by John who is building the 19th century machine shop diorama on Model Engine Maker). A bit of research yesterday showed me that the smallest I can possibly make this clutch is 1.75" outer diameter, to work on a 1/4" diameter shaft. There are a few parts to this "expanding shoe" style of clutch that become too small for me to make if I try to make the clutch smaller in diameter. I have made use of a keyslot cutter in a very unorthodox manner to get started on this, and since I'm doing this in "real time" I will keep you posted of my progress.---Brian

    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

  • #2
    This is the center hub of the clutch. It is fixed to the line-shaft. The expanding shoes which transmit torque to the outer hub slide in the miniature T slot which was cut thru with the keyway cutter.
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

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    • #3
      Seems like the mass of the radial sliding parts would be affected by centrifugal force. How will it disengage?

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      • #4
        Some of the older mechanical power hammers and punch presses have tapered cones that are pulled in by a lever acting on a spider that spins freely on the shaft. When the lever is pulled in, the tapered cones engage when enough friction is available to overcome the inertia of the related parts; then the cones release when the lever is moved the other way. Little Giant power hammers had this type or drive in a couple of configurations. They typically used wood against iron for the drive surfaces but I have also seen brass against iron.

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        • #5
          This is going to be interesting! Looking forward to watching this build.

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          • #6
            Originally posted by Forrest Addy View Post
            Seems like the mass of the radial sliding parts would be affected by centrifugal force. How will it disengage?
            I presume in the real world the rpm is so slow that centrifugal force can't carry any torque to speak of.
            .
            "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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            • #7
              Some very close (fiddly) work here. First picture shows cutting a 1/16" slot into one side of the sliding pressure shoe. Second picture shows the sliding pressure shoe profiled for a sliding fit into the brass part. That slitting saw blade is 1/16" wide!! Next step will be to separate the sliding shoe into two pieces, one to bit on each side of the center of the brass.

              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

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              • #8
                Originally posted by Forrest Addy View Post
                Seems like the mass of the radial sliding parts would be affected by centrifugal force. How will it disengage?
                Line shafts didn't turn fast enough to have a problem with centrifugal force acting on the clutch shoes.
                Brian Rupnow
                Design engineer
                Barrie, Ontario, Canada

                Comment


                • #9
                  This just about reaches my limit for "small stuff". The "sliding pressure shoes" are finished. the side where you can see the heads of the socket head capscrews faces inward towards the clutch drum. The side where you see the slots and the shanks of the #40 shcs faces out. The dark blue "actuator arms" (as per the solid model) fit thru the slots in the brass part and bolt to the "sliding pressure shoes". There is a full 8 hours in what you see here.

                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

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                  • #10
                    Nice work!!

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                    • #11
                      Originally posted by TGTool View Post
                      I presume in the real world the rpm is so slow that centrifugal force can't carry any torque to speak of.
                      Sort of. I've worked on and operated line shaft gear, and one of my earlier mechanical jobs was repair of the drive for a lathe (mid size--- 56"X120 between centers) from overhead countershaft. This section was in place only for the lathe and had, at the time, a 10HP motor mounted to drive the section, but it was not operational yet.

                      In this set up, which was as it had been installed in roughly 1900, the drum was the drive side, and the shoes were the load side. The shoes were sprung, but still had some drag at line shaft speed. The intent, by the book, was that the machine load would be enough to break static friction so the load could slow, and the release would be gradual, over a couple seconds. The driven machine would coast for 20 sec or more, so it made no difference in safety. You got hung up, you were going for a ride. A long ride. A long, painful, and soon to be wet ride.

                      I think the idea was that this allowed the operator to be able to bring the machine to speed smoothly without burning the shoes, rather than have to fight the springs and wear it, or slam it in and either jump belts or snap shafts. Yes, it is REALLY scary when a shaft snaps.

                      Other fun with this was lining the shaft bearings, repouring the shot ones, shifting pulleys on the shaft to line the belts (the original line didn't match without the rest of the shaft), and dealing with a foreskin... foreman, sorry... that couldn't understand what the oil lifting rings were for, and swore the book I showed him was wrong. He never did get the safety cages in around that belt. Probably still aren't there, and I'd bet the machine still gets use.

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                      • #12
                        This is a "real" line-shaft clutch set-up, and it is what serves as the basis for my design. One thing that the "real" one has and my model doesn't (because of scale/space restrictions) is individual adjustments for the tapered surfaces on the arms that the sliding cone interacts with. That would serve to adjust the sliding pressure pads on each side to contact the inside of the drum equally. At the scale I am working, there simply isn't room for threaded adjusters, so I will have to resort to grinding the angled contact surfaces on the dark blue "arms" to get equal travel/pressure on both pressure pads.
                        Brian Rupnow
                        Design engineer
                        Barrie, Ontario, Canada

                        Comment


                        • #13
                          I don't THINK that there were any springs in there to retract the shoes and disengage the clutch, but I really don't know. That picture is one I downloaded off the internet. I have never seen one of these clutches in "real life". If anyone has info to the contrary, please let me know.---Brian
                          Brian Rupnow
                          Design engineer
                          Barrie, Ontario, Canada

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                          • #14
                            I'm going to make a small change to the pulley drum. Since most of the machinery I drive use 1/8" diameter rubber O-rings as drive belts, and we will want to actually "field test" this clutch, I have put a groove in the green drum to keep the o-ring in place.
                            Brian Rupnow
                            Design engineer
                            Barrie, Ontario, Canada

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                            • #15
                              That looks like the same type of clutch that engages the carriage feed on my friends antique shingle mill.

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