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Rockerblock I.C.--Something a little different-

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  • #61
    Hey---I'm not just a pretty face!! Sometimes I do real work too. Saturday I made gears. Sunday a customer came by on his way up to the Blue Mountain ski area and left me the smallest arbor press in the world to make some modified tooling for it. It is used for a punching/staking operation which he was previously doing in his vice.
    Brian Rupnow

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    • #62
      Originally posted by brian Rupnow View Post
      Sunday a customer came by on his way up to the Blue Mountain ski area and left me the smallest arbor press in the world to make some modified tooling for it.
      You know you say that, but:

      from the shopmade tools thread here:
      http://bbs.homeshopmachinist.net/thr...86#post1106886
      Location: Long Island, N.Y.

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      • #63
        How about this for the crank assembly.
        * Make the crankpin and crankshaft rod with integral "guide" portions of lesser diameter; that is, guide portions and "real" portions are one shaft.
        * Make 3 doughnut washers with holes the size of the crankshaft and with length the width of the space between the throws.
        * Face the washers to be the same length; maybe do them all in one pass in the milling vice.
        * One washer goes over crankshaft main shaft and will be milled out later.
        * The conrod is a single assembly (with bored hole) and is assembled over the crank pin prior to pressing.
        * The other two doughnut washers sit between the throws to keep the throws parallel.
        * With the guide shafts and doughnuts in place the throws are clamped together to stop them moving during pressing.
        * The clamps could be a bolt goes thru the loose doughnuts and is a drill and tap into one of the crank throws.

        Norman

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        • #64
          RichR---Okay, I admit it. Yours is smaller than mine. Ha Ha Ha Ha
          Brian Rupnow

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          • #65
            Originally posted by brian Rupnow View Post
            RichR---Okay, I admit it. Yours is smaller than mine. Ha Ha Ha Ha
            Funny comeback, but I'm afraid I can't take credit for that work of art. It was made by forum member jimmyj.
            Location: Long Island, N.Y.

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            • #66
              Okay--Back to business. Immediately after I had machined the gears my phone rang about 5 times in a row, each time with a customer I couldn't turn down, and each customer wanted to be looked after "right now". Being a slave to my bank balance, I said yes to all of them, and haven't had time to play "small engine" since. I have discovered one thing, and I'm not sure yet whether it is really a problem or not. When I make built up crankshafts from 3/8" diameter stock, I ream the holes which I am pressing shafts into with a 0.3735" reamer. I use 3/8" drill rod for the shafts, which always seems to come in at .0005" oversize. This gives a VERY hard press fit, with .002" interference, and I have never had one "slip" after the fact. I don't use 3/8" cold rolled steel because it comes in at about .0005 to .0001" undersize, and though it does give a press fit, it is quite a light press fit, and it WILL slip after the fact. Last year I purchased a 0.4985" diameter reamer in case I wanted to make a crankshaft using 1/2" nominal shafting. The problem is, that I just stopped at my metal supplier today and micrometer measured all of their "01" drill rod, and it all comes in exactly at 0.500" diameter. So--I will only achieve a .0015" interference fit. I have to think on this a bit before I proceed. ---Brian
              Brian Rupnow

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              • #67
                The larger diameter of the shaft will compensate some. The friction acts at a larger radius giving more torque resistance. Just need to check the stresses and make sure the outer part is thick enough that you get the bore pressure you need.

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                • #68
                  What to do--What to do??--Well, we'll make a little test. I drilled and reamed a 0.4985 hole in a piece of 3/8" mild steel, and I turned a very slight "lead" on the end of a piece of 1/2" drill rod, and I pressed it to see what happens. This type of pressing can not be done on a manual arbor press. It gets done in my vice. This was tight, but not "Oh my God, I've just given myself a hernia" tight. (That's the way it is with a .002" interference.) So, to farther quantify the results (We're getting really scientific here), I put the piece of plate in the vice, clamped my vice grips on the 1/2" round stock, and gave it the old "Reef your guts out" test.--And it slipped---Just like I thought might happen. The fit is tight enough to withstand moderate abuse, but not exceptional abuse such as backfire, pre-ignition, or nuclear Armageddon. I do however, think it would work fine if the components were cross drilled and pinned. Probably with .094" (3/32") dowel pins.

                  Last edited by brian Rupnow; 04-12-2017, 09:27 PM.
                  Brian Rupnow

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                  • #69
                    How about using a scotttish key to lock them together?

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                    • #70
                      or would a smidgeon of loctite help?

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                      • #71
                        Originally posted by OKChipmaker View Post
                        How about using a scotttish key to lock them together?
                        What is this?
                        Something akin to Russian axial thread?

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                        • #72
                          I have no idea what a Scottish key is, and yes, I always use a bit of Loctite.---Brian
                          Brian Rupnow

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                          • #73
                            I believe a Scotch key is where you drill and tap for a setscrew so the center of the screw is on the boundary line between parts. It's actually a very good thing to do in some cases. The round portion keeps the parts in radial alignment and the threads keep the parts in axial alignment.
                            Last edited by Toolguy; 04-13-2017, 07:21 PM.

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                            • #74
                              scottish key is as toolguy said,hole drilled in the boundary line,half of the hole in the each part.then thread and use a screw, or use a over size pin pressed into unthreaded hole.

                              Some roots type superchargers and vacuum pumps use this system to lock the gears to thar shafts.

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                              • #75
                                Thank you for the explanation guys.---Brian
                                Brian Rupnow

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