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  • R & R 52T Rear Sprocket

    From: http://www.hydra-glide.net
    : VintageTwin
    Senior Member
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    Re: belt or chain primary
    « Reply #6 on: Oct 31st, 2003, 2:43pm »
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    I talked to PRIMO in the past about different size motor pulleys. He told me they had no plans of making a 24 tooth motor pulley equivalent. I went to BDL and he told me that attempts to make any motor pulley other than the 23 tooth equivalent lead to belt destruction. Whatever combination PRIMO, BDL or KARATA use is what mathmatically "works" sucessfully on the machines. The biggest bane to me is having a motor that sounds and feels like it wants another gear at 65 mph. That ****s, but I'm making my machines 1-1/2", 11 mm., under OE tin, (non- vented, stock inner and outer primary covers) belt drives anyway.
    « Last Edit: Oct 31st, 2003, 2:45pm by VintageTwin » Logged
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    Dereborn
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    '62 FLH rigid bobber(slightly in the ratbike-area...)




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    Re: belt or chain primary
    « Reply #7 on: Oct 31st, 2003, 9:42pm »
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    Never saw a welded rear sprocket! Wonder if tradition differs in different parts of the world... Riveted of course, but also bolted. I had to change mine the other year, and was adviced to bolt it, did so and hav had no problems at all. I have standard stroke, compression and bore, SU carb and no dragracing ambitions, so I guess I don't stress it a lot. 6mm bolts with nyloc nuts anyway does the trick for me! I think it's 52 teeth now, right? how much do you guys think I have to lower that to notice any difference? 50? 48?
    Cheers
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    DuoDave
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    Re: belt or chain primary
    « Reply #8 on: Today at 12:33pm »
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    A word of warning if you are dealing with a riveted rear sprocket. I had to replace mine, so I ground the heads off the rivets and went round the drum tapping them out. The last one(!) was distorted and jammed, so I gave it a slightly harder tap and an inch sqare section of the drum broke clean off. I should have remembered from past experience how brittle cast iron is. I had to buy a new drum and it was pretty nerve wracking peening the heads of the new rivets.
    As dereborn says.....learn by doing.
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    VintageTwin
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    Re: belt or chain primary
    « Reply #9 on: Today at 3:20pm »
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    Anyone know of a jig (OE or homemade) that will work for replacing rear sprockets. The '36-57 Big Twins used rivets, maybe the '58 did too, but the '59 up uses rivets and dowels pins (like a rivet but bigger or vice-versa, I don't know, I'm not looking at the book). I had a chapter going on it in 2000, but I explained and sent a '63 rear drum to USATCO (U.S. Air Tool). He sent me back a rivet air gun and bucking bar (you place this steel slug on the shank) and you put the cupped end of the rivet gun on the head of the rivet and ...rat-a-tat-tat...whilst you hold the buck bar against the shank. The amazing thing that happens is that the rivet shank sticking out from the sprocket surface squashes down into a short-stacked barrel of solid steel. Mike W. at USATCO did a few trial rivets on the '63 sprocket and drum I sent him. The barrels squashed in perfect symmetry, like a machine squashed them. I tried it on the '63 drum with my new rivet gun and backing bar next to his perfect ones and my rivet barrel squashed OK, but was kinda lopsided, but the rivet was tight and I could tell, that with practice I could do better. Problem is, that when I went to Kennedy's (in Oceanside) to find a drum in their graveyard, the only drum and sprocket I could find was this '63 that had the sprocket bolted to the drum (like Dereborn mentioned). I figured it would work and be easy to remove the sprocket from the drum for my experiment. Anyway...I did all this work, and didn't realize until I had the '63 sprocket back from USATCO, that the years I am concerned with '36-59 all have separate dust rings in front of the sprocket. '63-up has a cast dust-ring on the drum!! Awww...man!! Bum-kick!. I went back on the phone to Mike W, and he said..."Oh yeah, that does make a difference". So, if you read the Palmer resto book, he talks about needing a hollow drift. OK, but I think you need a hollow drift that has a bottom in the hollow drift's shank. The bottom in the hollow shank will act like a bucking bar. The hollow will allow you to press the dust ring tight against the drum, right? And when you hit the rivet head with the gun, it will cause the rivet shank to hit the "bottom-out" of the hollow drift and cause the rivet to squash. The drift and the hollow needs to be a somewhat bigger diameter than the rivet shank diameter, so that the shank can squash and form a barrel. I think that with the new rivets tight in the holes of the drum and sprocket (even if you have to re-drill holes because the old ones are too slopped-out), that a hand held air rivet gun and a hollow drift with a bottom in the hollow would work on a dust-ring rear drum and sprocket.
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    49oldschool
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    Re: belt or chain primary
    « Reply #10 on: Today at 3:49pm »
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    huh?

  • #2
    Rear Sprocket Rivet Gun

    Here's tha gun and anvils I got from USATCO. There's one anvil for dowel pin heads and one for rivet heads. You hold the bucking-bar on top of the rivet shank (this is where we need a hollow drift with a exacting bottom-depth) and not a bucking bar. Bucking Bar is for '63-up drums with the cast dust ring. Not for '36-'62 machines. Make that hollow drift of substantial weight too! That rivet gun is aircraft quality. Packs a whallop. You can use a Chinese rivet gun too Harbor freight has them for 20-50 bucks.
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    • #3
      http://www.flatheadpower.com/ -reply

      Chris Olsen
      Member posted 05 November 2003 11:48            
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      So what's the question?

      This whole thing strikes me as a bunch of work for very little.

      For one thing, the way to vary the ratio with a belt drive is to change the Trans Sprocket, not the Wheel Sprocket. I'm running a Primo 8mm 1 1/2" Kevlar enclosed belt on my 80" Knuckle with a 23 tooth Trans Sprocket and it cruises at 70 mph plus, very nicely. Trans Sprockets are available from 20 to 26 teeth, I've even heard of 28.

      As for mounting rear sprockets, They should all be rivited. The so called "Dowls" are just 4 slightly larger rivits that fit in the slightly larger holes which are possitioned at 12,3,6 and 9 O'clock from each other around the circumference of the drum.

      Welding a rear sprocket is a Slob Trick if ever I heard one. Usually when a sprocket gets loose, it's because the chain was not cared for (greased and adjusted and or the oiler was turned off because the fool didn't like a dirty rear rim), the sprocket wore because the chain was not cared for. The whole mess started vibrating like hell and so the rivits got loose.

      If you want your sprockets to stay rivited, keep your chain in good shape. End of story.

      Just one other thing, if you forget the dust cover, it's not the end of the freakin world.


      Plumber
      Junior Member posted 05 November 2003 00:15            
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      Wow, a 23 tooth trans sprocket is low. I've always run a 25 tooth. Someone on this post runs a 26, but doesn't see much change in a lower back wheel rpm. I haven't seen a 28 tooth trans sprocket advertised. I will try a 26 tooth trans sprocket. It's getting pretty tight in there with a 26 tooth, 28 T?? I don't know about that. I'll look through my catalogs. As far as welding rear sprockets to rear drums. Some of us live in europe and areas where Harley dealer expertise is not available, and maybe they want to get on the road and not dick with trying to replace a bunch of rivets and not having the tools to do it with. The Harley manuals don't tell you what actual tools to use, you know? Maybe if they find nuts and bolts to use, it gets the job done for them. So what the hey, you know? One of my questions is how to rivet the rear sprocket on the drum using the dust ring, and how a hollow drift with a bottom will cause the rivet to squash. Any comments on the hollow drift? I will post a pix of the rivet gun on the AMCA site under "Panhead". The gun I got. I found the gun O.K.?? Now we need to have someone make a hollow-end drift with a bottom at the correct depth. The rivet gun works. Hands down. Done deal. Get us a drift. Check out the gun at http://www.antiquemotorcycle.org/
      >Panheads>R&R Rear Sprocket
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      Chris Olsen
      Member posted 06 November 2003 05:13            
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      The correct technique for riviting is as mentioned in your 1st message. The rivit has a round head. This side goes to the back of the Drum with the flat end sticking out through the Dust Cover. It is the round side which you drive with the rivit gun using a concave headed "Die" as they are called, of the correct size (same Hieght and diam of the rivit head)fitted in the end of the gun. These dies can be purchased from the same outfit that makes the gun or of nearly any other manufacturer as they are all pretty much standardized, no need to go making "hollow punches". A Flat Faced Bucking Bar (any substantial block of steel weighing a couple of pounds or more) is held tight against the flat end of the rivit while driving the round side with the gun, (Yes, it sounds a little reversed from what you might think). The work is best done with 2 people; 1 to hold the Bucking Bar while the drum is secured in a vise and the other person to run the gun. The idea is to hold the Bar very tight and squarely against the rivit end while watching the rivit squash out evenly. The gun opperater must also hold the gun very tightly and squarely against the rivet while working. You do not want the swelled out area to get thin. this would be a weakened rivit. Keep the height of the worked metal no thiner then the diam. of the rivit itself and just swelled out to 1/3 to 1/2 larger then the original diam. It is also not nessisary to duplicate the round head on this side, flat is fine. A typical drive takes only about 2 to 3 seconds to occur when done by an experienced riviter, actually about 1 second once you get really good.

      As for the Dust Ring, just hold the head of the Bucking Bar clear of the raised inner lip on the Dust Ring so you don't crush it. You might need to sand the sides and or corners of the bar to clear the raised lip and still get full coverage over the rivit end.

      You shouldn't need any more air preasure then is normally found on shop compressors; 70 or 80 psi is fine. I certanly wouldn't go past 100.

      Note: the biggist cause of damage or breakage to the surrounding area is a bouncing rivit gun. Put your shoulder into it.


      I have driven millions of rivits while working at Boeing Military and Commercial Aircraft Co. here in Seattle, WA. so I know what I'm talking about. Good luck.


      Plumber
      Junior Member posted 06 November 2003 05:19            
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      You need to hold the dust ring against the sprocket while all this riveting is going on. Unless you vise-grip the dust ring to the sprocket. Guess that could be done. You can't let the dust ring flap around and hope it sticks next to the sprocket. No need to get all tight-jawed about it. It's all hobby stuff. Nobody does this for a living. And I've never met anyone that knows everything about Knuck & Pan, none that are still alive today at any rate. Thanks for the tips.

      Comment


      • #4
        Cure For Belt Primary/ Low-end Final Drive Ba-Lues

        zooma
        Junior Member posted 08 November 2003 20:47         
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        I think that the rivets are going to work better in the long run than the treaded fasteners because the rivits as they are peened in are going to conform to the holes in the drum and sprocket and fill up all the space and handle more torque. I.ve seen some special tools in the past like a piece of 1/4 wall tubing that is the right diameter to back up all of the rivet heads at the same time and you just drop the drum in with the rivets up and fire away but never been that prepaired myself for a job that only gets done once every couple of years.Also the way that i've always changed final gearing with the belt drive primary is whith the tranny sprocket. Running a 26t with a 93ci and seems about right.


        Plumber
        Junior Member posted 09 November 2003 02:24            
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        Yeah..yeah!! Cured the high-end-want- another-gear, annoying, distracting, pestering, trip *******-ing, whining blues that I was setting myself up for. Cured it with a 26 tooth transmission sprocket change-out. Motor-freakin-scooter! You made my week. Thank you for your report. 26 tooth tranny sprocket here I come.

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