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  1. #1
    650b me
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    Forgot to drill vent holes

    I tacked the chainstays to the BB shell, then realized I hadn't drilled vent holes. I also brazed the tab-style dropouts on the other end of the chainstays. I did remember to drill vent holes at that end.

    What's my best option? De-tack the stays from the BB shell, clean up, drill holes and re-tack? What's the risk if I don't drill vent holes and complete the brass fillet? Any trick way to drill the holes after the fact, coming in from inside the BB shell? Such a noob...

  2. #2
    Nemophilist
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    Hey;

    Vented is vented. If the tube has a hole in it, you should be fine. You can tune the pitch of the note if it whistles by drilling it different sizes, if you want to get that technical. Minor chords might be a harbinger of bad times ahead, hence the suggestion.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  3. #3
    650b me
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    Not sure I follow you, Trailmaker. To be clear, I have no vent holes at the chainstay/BB shell junction. Obviously, a hole in the BB shell is the preferred method, but since it's already tacked, what if I drilled a small hole in the chainstay before filleting?

  4. #4
    AZ
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    Quote Originally Posted by golden boy View Post
    Not sure I follow you, Trailmaker. To be clear, I have no vent holes at the chainstay/BB shell junction. Obviously, a hole in the BB shell is the preferred method, but since it's already tacked, what if I drilled a small hole in the chainstay before filleting?



    If you drilled holes at the dropout end you should be okay.

  5. #5
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    I'd think you could pop in a small vent hole from the BB side. The one you already have should be fine for keeping the hot air in the chainstay from blowing out your puddle. Adding a second just makes it easier to soak the flux out with water by giving you one hole to let air out when water flows into the other.

  6. #6
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    Hey, TM is teasing you a bit. Like making a musical sound by having 2 holes of various sizes and blowing air through, lol.

    Ok, back to your scenario. No big deal. If you ride the bike in dry conditions, no water will migrate in there. Unlike seatstays, water will run towards the BB if it enters the chainstays at the drop-outs. Those BB holes will then allow water to sit in the BB shell until you service the BB and wonder how so much water got in there. If you adventure ride and travel through rivers and submerge the bike, well, you get the idea. In constructing the frame, you have a vent already and only 1 is needed to stop pressure. If
    you stand your bike so it hangs from the front wheel after wet riding, the chainstays will drain-off, sitting water will rust the chainstay out at the BB junction. What can you live with?

    Eric
    If I don't make an attempt, how will I know if it will work?

  7. #7
    Nemophilist
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    Ummm...

    Vented is vented? No air will be trapped in the BB housing, right? Certainly none in the DOs. You vented the CSs when you welded on the DOs, right? Since it is the CS that need to breath, vented is vented!

    Now, the good Doctor brings up a point that I would not have considered, not being a brazer. Soaking off flux would indeed be far easier, or getting the frame to dry out at all, with vent holes in the BB. So too would it be better for getting some rust inhibitor in there with BB holes. Still, it will not kill the bike. I did the same thing on my first frame, and it survived just fine.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  8. #8
    650b me
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    Sorry, Trailmaker. Once I read Dirty Sanchez's comment I immediately understood what you were saying. One hole is enough. I learned at UBI, and we drilled a hole at each end. One thing I like about doing this, as you mentioned, is that it makes it easier to get rust inhibitor inside.

    I think I will definitely un-tack the non-drive-side stay because it is positioned too far outboard right now and the asymmetry is bugging me. So while I'm at it, I'll go ahead and drill a hole in the BB shell. Drive side? Haven't decided yet.

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