Taught/loose chain issue:'63 Raleigh Sports

Discussion in 'Vintage Lightweight Bicycles' started by slowride, Apr 16, 2018.

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  1. #1 Posted Apr 16, 2018

    'Lil Knee Scuffer

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    Hello Cabers!

    Here's a good mystery for you experts!

    Finishing up on of my '63 sports and am having an issue where chain is tight/loose depending on crank sprocket rotation. When you rotate the crank the chain tightens and loosens depending on the angle of the crank arm. On the drive side, when crank arm is at 9-o-clock there is 7/8" deflection but at 3-o-clock less than 1/4". With this adjustment the chain binds. Please see the pictures. I have another '63 sports that does not have this problem so in order to try to isolate the problem I did the following one at a time:

    1) Swapped out chain,
    2) Swapped out bottom bracket axle
    3) Swapped out bottom bracket adjustable cup
    4) Swapped out bottom bracket crank
    5) Swapped out entire rear wheel.

    Also of note, I put all new bearings in bottom bracket but I did not swap out BB fixed cup. I used the friction method to remove the fixed cup on another bike but since then I heard you can damage it this way so did not on this bike. Based on everything, I think maybe the BB fixed cup is worn. The BB was definately not serviced since 1963 as it was bone dry and did not rotate freely prior to opeing it. Please see pictures of original adjustable cup as reference/clue of what fixed cup wear may look like.

    Lastly just FYI, I used a method found online to check for proper chainline whereby you take string and tie one end on non-drive side rear drop out loop around head tube then back to drive side rear drop out then measure distance from string on both sides as it passes seat tube ; using this admitidly crude method the frame seems very straight. From there you then measure from crank sproket to center of seat tube and use this as guide for building the rear hub( OLD (over locknut dimension) )in order to ensure the rear sprocket is in line with the crank sprocket. I did this because the hub appeared to to have been serviced at one time and based on other work on the bike I did not trust it to have been properly re-assembled.

    In conclusion, if I adjust the chain tightness so there is 1/2" deflection at the tightest point in the crank rotation (3-o-clock) , the loosest deflection is 1" (at 9-o-clock). For just casual riding this will probably not be an issue but I've spent so much time totally refurbishing this bike I want it to be right! Thanks for you're expertise everyone!

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  2. #2 Posted Apr 16, 2018

    Wore out three sets of tires already!

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    Good loo
    Good looking bike!! This may not be the answer, but this is what I have learned about sprocket roundness. They aren't.
    On a chain drive unicycle, any slop feels scary. I did what you have done to eliminate it. No luck either. With a unicycle the sprockets are the same size. I realized that the sprockets are usually out of round, much like the ergonomic chainrings, but not visibly. By "timing" the two sprockets to be eccentric at the same time, I could eliminate the slop and tightness of the chain. This won't work with different sized sprockets. My suggestion is to live with it, or replace the egg shaped eccentric sprocket. The front is probably the culprit due to its size.
     
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  3. #3 Posted Apr 16, 2018

    Riding a '38 Autocycle Deluxe

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    Bent chainring?
     
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  4. #4 Posted Apr 16, 2018

    Look Ma, No Hands!

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    Agree with previous posters. Chainring or rear sprocket aren't round.
     
  5. #5 Posted Apr 16, 2018

    I live for the CABE

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    Check every tooth of the Raleigh bird chain ring. Look close.
     
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  6. #6 Posted Apr 16, 2018

    Finally riding a big boys bike

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    Take the chain off and spin the front crank fast to see if the Ring is out of round. Watch it closely while it spins free...sometimes you can mess with the ring, but usually not.
    This loose/tight scenario happens a lot with old fixed 1"-pitch chains and rings, which when worn out together are all over the place. If you piece together a skip-tooth(1" pitch) chain with worn sections from other chains, it really gets bad.
     
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  7. #7 Posted Apr 16, 2018

    'Lil Knee Scuffer

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    Hi everyone, thanks for taking time to give advice. The very odd thing is I swapped out chain ring and entire wheel from my other '63 sports (black step through) that I was refurbishing at the same time and it didn't make any difference on the red bike. Again I Swapped chain, chain ring, bb axle, adjustable cup; nothing made any difference...

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  8. #8 Posted Apr 16, 2018

    Finally riding a big boys bike

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    I hope you can make it work. Those are beautiful bikes. Really love em!
    Additionally. I really like this fixed cup tool. Works like a charm. Their cotter pin tool is also great.

    http://www.bikesmithdesign.com/BBTool/
     
    #8 3-speeder, Apr 16, 2018
    Last edited: Apr 16, 2018
  9. #9 Posted Apr 16, 2018

    Wore out three sets of tires already!

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    Two thoughts.
    1. Are you saying that you've moved all drive train components from one bike to the other, and they don't have play on one bike but do on the other?
    2. I looked at one of my bikes, and I have the chain set to just right at the tight spot, and at the loose spot I've got nearly an inch of play. It rides like a dream.
     
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  10. #10 Posted Apr 16, 2018

    Cruisin' on my Bluebird

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    sounds like the one place you have left to look is the drive sprocket and drive bearing on the SA hub.
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    If the hub driver bearing was highly worn or the the drive sprocket somehow not properly seated, it could be eccentric on the axle, and might give you the same symptom.
    - oops, never mind on this - you did swap out the wheel

    If it always appears at the same phase of the crank, seems like the eccentricity would have to be in the crank/BB.

    If it's related to pedaling load, though, you could have something like chainstay flex (produces ghost shifting on a derailleur bike) and you wouldn't be able to identify it with the bike on a work stand.
    back to the crank - it should be easy enough to rig some kind of runout indicator on a work stand to the check the crank and chainset for out-of-roundness - you just need a stick over the crank parallel to the spindle that you can measure the gap to the chainset teeth as you rotate the crank.
    Just throwing out ideas.
     
    #10 bulldog1935, Apr 16, 2018
    Last edited: Apr 16, 2018
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  11. #11 Posted Apr 16, 2018

    Cruisin' on my Bluebird

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    roll the crank pin on a flat surface... you'll find the problem
     
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  12. #12 Posted Apr 16, 2018

    Riding a '38 Autocycle Deluxe

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    Take the chain off and give the cranks a whirl. I'm guessing you'll see some wobble. It doesn't take much to cause the situation you're describing.
     
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  13. #13 Posted Apr 17, 2018

    Wore out three sets of tires already!

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    Love that red! So, have you had this on the road before all this? Is it possible that the bottom bracket housing (not sure what to call it) was welded on slightly off? Just throwing it out there.....
     
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  14. #14 Posted Apr 17, 2018

    'Lil Knee Scuffer

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    Hello everyone,

    Again , thanks everyone for your time and expertise. Yes I moved all the drive components from one bike to the other and only have this situation on the red bike. Drive components I moved from one bike to the other include entire rear wheel, bb axle/spindle, chain ring, bb adjustable cup (non drive side), chain (red bike has original chain but to eliminate potential root cause I also put a new one on). the red bike functions just fine when I adjust the tight spot to 1/2" (loose spot to 1") so I guess that's what I will do. The only part I did not move from one bike to the other is the bb drive side cup. Was just trying to get it "perfect" but I guess things really never are. Btw regarding the hub I totally disassembled and cleaned and added 5cc of 20w non detergent oil and it shifts and runs like a dream . red bike is AW hub and black tcwIII (coaster brake). Interesting fact Is both bikes have rear hubs from may, 1963.
     
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  15. #15 Posted Apr 17, 2018

    Riding a '38 Autocycle Deluxe

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    You're giving up!? There has to be a relatively simple explanation for this issue. Clearly something is out of round.
     
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  16. #16 Posted Apr 18, 2018

    'Lil Knee Scuffer

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    next thing I am going to try is replace the bb drive side bearing cup; it's the only thing I haven't tried yet. Once I locate ,purchase, and install , I will post an update. Thanks again to all.
     
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  17. #17 Posted Apr 18, 2018

    Cruisin' on my Bluebird

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    did you inspect the chainstay for cracks at either BB or rear dropout?
     
  18. #18 Posted Apr 18, 2018

    I live for the CABE

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    Being a single speed rider I have almost never seen a chain that doesn't tighten and loosen as it goes around. The standard for looseness is 1/4 to 1/2 inch of up and down at its loosest. That is because of the factory tolorences. Roger
     
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  19. #19 Posted Apr 18, 2018

    'Lil Knee Scuffer

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    Hello Bulldog1935: yes I inspected the chain stay, bb, and rear drop outs for cracks and see none. Bike had a very sheltered life. I completely disassembled, inspected, and cleaned. I like your idea of setting up a run out indicator to measure eccentricity of chain wheel but for the moment I don't have the equipment. I will put on my wish list for these situations.

    Does anyone have an opinion on my theory that the drive side bottom bracket bearing fixed cup could be unevenly worn causing a slight wobble of the chain wheel ? Remember that is the only part I have not removed and swapped out . Above I have pictures of the non-drive side bottom bracket adjustable bearing cup. Do the bearing race surfaces always wear evenly as you go around the race or do they wear unevenly since pedaling forces are only applied every half revolution?
     
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  20. #20 Posted Apr 18, 2018

    Cruisin' on my Bluebird

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    usually, the balls go flat, but if you haverace wear it will probably be in phase with mashing loads on the crank - that's where contact stress is highest - and yes, that could produce BB eccentricity. .
     
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