What is going on here?

Discussion in 'All Things Schwinn' started by ballooney, Dec 17, 2017.

  1. #1 Posted Dec 17, 2017

    Finally riding a big boys bike

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    Bike: '49 B6

    Problem: crank arm will not clear the chain guard.

    Outer Measurements between chain stays taken at the drop out (5") and just after the kickstand housing (4 1/4") are the same as another B6. So there doesn't appear to be a bend in the frame after the bottom bracket.

    Crank that came on the bike appeared bent so I replaced it with the crank that works fine on another B6. Here is the crank that came on the bike...looks to be a 1" flare when using two straight edges:
    bb6671bd58d2121da90e4fe3cff48b33.jpg

    Here is a crank that is straight for comparison. Looks to have a 3/4" flare:
    ad9b18c175242c82c15f4b59456a01dc.jpg

    With a straight crank on the bike in question, here are my clearances:
    d6e62779f5f09345295b667805652313.jpg
    e091884a4c496b53b65b95f00f60b0e0.jpg

    Compared to a B6 with no issues:
    9b7b26a2bdfb8d8bd60086619bb59215.jpg
    849ab4f6ae8cbfacf46693229af82392.jpg

    The B6 with the clearance issue seems shifted in that there is plenty of clearance on the non-drive side but almost no clearance in the drive side. Just the opposite of the good B6.

    What got me here? The bike rode oddly under feet like a bent shaft on a pedal. So I started pulling it apart...pedal shaft was straight. Pulled the crank and noticed it was bent...ah ha! Picked up a straight crank and boom, clearance issues. Must be a bent frame in which the original crank was bent out to accommodate the clearance issue but the measurements on the chain stats match a good bike. So what gives?


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  2. #2 Posted Dec 17, 2017

    Riding a '38 Autocycle Deluxe

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    maybe the triangle is out of alignment? Had the same issue with a 48 DX.
     
  3. #3 Posted Dec 17, 2017

    Riding a '38 Autocycle Deluxe

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  4. #4 Posted Dec 17, 2017

    Finally riding a big boys bike

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  5. #5 Posted Dec 17, 2017

    Look Ma, No Hands!

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    Install your peddles. If the crank arm/arms are bent you should be able to tell by the angle of the peddles. Is it the original chain guard? Maybe the chain guard is tweaked? Try moving the guard as far forward as possible. If that doesn't work, try going aft. Position it where the interference is the least. Then gently persuade the guard away from the arm.
     
  6. #6 Posted Dec 17, 2017

    Riding a '38 Autocycle Deluxe

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    Sure did. I was able to correct it by doing the 2x4 trick. Somewhere there’s a thread on re-aligning the rear triangle. Mine was out of alignment on the drive side causing the crank arm to hit the frame. I’ll see if I can find the thread.
     
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  7. #7 Posted Dec 17, 2017

    Finally riding a big boys bike

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    String test shows rear triangle to be evenly spaced in relation to the seat tube...if I did this correctly?
    e257a2ed6db11d8dd35fb6807e9c95ae.jpg

    40e08c42853d3808988ee8047595f569.jpg

    bdf05f3a651d66b18ead2cee80e9ca77.jpg



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  8. #8 Posted Dec 17, 2017

    Look Ma, No Hands!

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    Here are a few pictures of my 48 DX. As you can see there is not much clearance between the crank arm and the chainguard. How hard is your crank hitting your guard? DSC_0586.JPG DSC_0587.JPG DSC_0588.JPG DSC_0589.JPG
     
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  9. #9 Posted Dec 17, 2017

    Look Ma, No Hands!

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    One more picture. DSC_0590.JPG
     
  10. #10 Posted Dec 17, 2017

    Finally riding a big boys bike

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    The crank is completely blocked by the guard.
     
  11. #11 Posted Dec 17, 2017

    Wore out three sets of tires already!

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    i.d. like to add . The chainguard can be mounted in inside of frametab or outside. Depending on clearance requirements.. I thought I saw maybe fender didn't have relief for chainguard to tuck in. Been a long time since I built this 48. Barely clearing on non drive side. The bearing cone - all diff size so I had to choose a good 1 And cups were worn etc. I hope you have plenty of spare parts for this build.

    uploadfromtaptalk1513547506646.jpg

    uploadfromtaptalk1513547529606.jpg

    uploadfromtaptalk1513547743529.jpg
     
  12. #12 Posted Dec 17, 2017

    Riding a '38 Autocycle Deluxe

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    The 48 catalog shows the guard mounted on the inside of the mounting tab.

    1948_schwinn_3.jpg
     
  13. #13 Posted Dec 17, 2017

    Cruisin' on my Bluebird

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    What hardware are you using....
     
  14. #14 Posted Dec 17, 2017

    Cruisin' on my Bluebird

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    Theres a jig to check the trueness of the frame
     
  15. #15 Posted Dec 17, 2017

    Cruisin' on my Bluebird

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    One photo shows the front tube angled at a odd angle....
     
  16. #16 Posted Dec 17, 2017

    Finally riding a big boys bike

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    Thanks for your input. The chain guard is original. I have mounted the guard on the inside of mounting tab and outside...no luck with clearance.
     
  17. #17 Posted Dec 17, 2017

    Finally riding a big boys bike

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    I have just the opposite for clearances...plenty of clearance on the non-drive side but barely clears on the drive side. Yet, with the string test, the rear triangle appears true. Strange.
     
  18. #18 Posted Dec 17, 2017

    Finally riding a big boys bike

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    I used a string from rear-drop outs, around head tube and back around. Measuring seat tube to string appears to be the same for both sides concluding the rear triangle is in alignment. Could the bottom bracket be off? Puzzling!
     
  19. #19 Posted Dec 17, 2017

    Wore out three sets of tires already!

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    Just looked at pic showing "straight. crank in frame. .Definitely too many threads exposed on non sprocket side. So lets move it (crank) over with intent of clearing frame. When I work on bikes lately I'm limited to parts that are usable. Schwinn stuff is common but older parts from 10 spd. would work? What I would look for are adj. Cones of diff. Thicknesses. All I have left now are repro anniversary BB cups. threw all worn out cups+cones away. Looking at BB on mine you see thicker cups.
     
  20. #20 Posted Dec 17, 2017

    Finally riding a big boys bike

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    Great suggestions. I’ll check the cups and compare with another B6 and try to work the crank threads over giving more clearance on the drive side. I will also expirement with mounting the guard on different sides of the mounting bracket one more time.