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  1. #1
    Senior Member southpawboston's Avatar
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    Drilling into an existing frameset: structural concerns?

    i'll be soon receiving a beat up but intact vintage frameset, which i expect to send off to get powder coated while i work out the details of my next vintage build. before i send it off, i'd like to drill the frame and fork for internal dyno wiring. i know frame builders drill into frames all the time, such as when they add bottle mounts, rack mounts, etc. plus, fork blades and stays often have pre-drilled holes for water drainage and breathing. so, my instinct tells me that introducing a few holes here and there shouldn't significantly affect the frame strength, but i am a little concerned about specifics:

    1) i was wondering what's the maximum hole size i should drill before i have to worry about compromising the tubing, structurally (i plan to use rubber grommets, so the holes will be larger than the wiring itself will require). for you frame builders who routinely do this, what size holes would you drill?

    2) are there critical areas of the frame/fork i should specifically avoid? for the fork blade, i was thinking about two holes, near the bottom and top, on the inside face of the blade (the top of the blade is sealed with the crown, so i can't route the wire out through the top of the fork blade). the blades each already have two small holes for breathing/drainage. for the frame, i was planning on two holes, one near the top of the downtube, on the underside, and the other on the left chainstay, inside face, near where the fender meets the stay.

    in case it matters, the frameset is a touring-grade frameset made with tange 2 DB chromoly main tubes, and tange 5 chromoly straight-gauge stays and fork blades.

    thoughts? should i not do it? or am i worrying about nothing?
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  2. #2
    Senior Member southpawboston's Avatar
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    no opinions?
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  3. #3
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    Framebuilders is a little slow tonight.
    Give it time and they'll chime in.

  4. #4
    Randomhead
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    I want to do this, but I haven't convinced myself to do it yet. When I do, every hole will be reinforced. I know there are framebuilders that have a policy not to drill holes. Some people drill lots of holes.


    Where is the wire going from the hole in the chainstay? That seems like a strange place to get the wire out. This one needs a reinforcement, there is a lot of flexing here.

    The small holes are actually vents; they are the vestiges of construction, they probably are a bad thing on a bike in use.

    Just as a point of reference, water bottle bosses are 1/4" holes.

  5. #5
    Senior Member southpawboston's Avatar
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    the wire will exit the chainstay at the bottom of the fender, then run along the inside edge of the fender to the taillight.

    i doubt the small holes are vestiges of construction... i've always been told they are critical to allow water to drain from tubes, and that this is why seatstays, chainstays and fork blades have those small holes. but, i could be wrong...

    since the powder coater that i am going to be using is also a frame builder, i wonder if i should have him reinforce the holes by brazing some sort of reinforcing collar around them?
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  6. #6
    Randomhead
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    the small holes in the fork blades and seat stays are vent holes, ask any competent framebuilder. The only ones you need to keep open are internal and a bb drain.
    I have no idea why people used to drill vent holes in chain stays, it's silly. Don't think you see any on a recent frame. Many framebuilders close off the vent holds in forks and seat stays after the bulk of the brazing is done. Peter Weigle is the most prominent builder I can think of that does this.

    You will crack your chainstays eventually without a reinforcement, I'm pretty sure of that. I wouldn't be happy with an unreinforced 1/4" hole at my fork dropouts. The hole at the top is a different matter. If there is a crown tab, you could use that as the reinforcement.

  7. #7
    tuz
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    I've been thinking about that since I'll soon install internal wiring on my frame. I've yet to see what cables and grommets I'll have but I'd say a 1/4'' hole sounds a bit big, especially if you're grounding one terminal to the frame? So for a small hole you might get away without reinforcements, but I agree they are better. For big holes I've seen water bottle bosses or water bottle reinforcers. For the fork it's also common to braze guides instead of routing internally (I'll go this way). You could also change your routing scheme by exiting the cable higher on the ST where it is close to the fender, and then route inside the fender.
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  8. #8
    Randomhead
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    the frame really stinks as a ground plane, but using it does cut down on the size of the hole you would need. Seems like you would have to connect the fork to the frame if both needed to be connected.

  9. #9
    tuz
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    Hmm well my unpainted frame seems to conduct current fine, even between the fork and frame. But yes you have to watch out the contact points after paint.
    homebuilt commuter, mixte, road and track (+ Ryffranck road)
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  10. #10
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by unterhausen View Post
    the frame really stinks as a ground plane, but using it does cut down on the size of the hole you would need.
    I haven't experienced any problems using the frame as the ground. I have 4 bikes set up this way; two of the even have tail lights mounted on bolt-on rear racks using the rack and frame for ground.

  11. #11
    Randomhead
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    do you use the traditional grub screw to make ground contact?

    a steel frame works as a ground plane, no doubt about that, dyno lights never had a ground wire in the past, they just had a sharp screw that you would drive through the paint. It's just that making that connection and keeping it a good connection is problematic.
    Last edited by unterhausen; 09-26-10 at 01:01 PM.

  12. #12
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    I don't think little holes that are off the main load planes are a big deal. I tend to thing holes can be good for reducing corrosion. It is hard to totally seal stuff against water, and no holes means vapour is contained. But if one is completely sure no vestige of water can get in then that should be better. The insides of tubes like the stays and the blades shouldn't be heavily loaded. Sealing holes with braze or weld does not sound like a repair to me, grometing them with some metal would be better. I am assuming pretty small holes though, 1/4 is a big hole.

  13. #13
    Senior Member southpawboston's Avatar
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    I'm resurrecting this thread to show the completed project. In the end, only two holes were drilled in the frame: a 7mm hole on the underside of the downtube, near the head tube, reinforced with a 5mm bottle cage boss (with the threads drilled out), and a 4mm non-reinforced hole at the bottom of the BB shell. The decision was made not to drill into the chainstay, but rather have the wiring exit the BB shell and enter the rear fender through a neat little pass-through I devised at the chainstay bridge. So, no structural concerns at all. The frame was then powder coated and built up.

    To run the wiring from the dynamo hub up the fork blade, I made use of the original vent holes at the bottom of the fork blade and at the fork crown (which vents into the steerer tube).

    Here are some photos detailing the wiring:















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  14. #14
    Randomhead
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    pretty slick. I assume you did something inside the fenders to keep the wire off of the tire?

    Is that a triple? Looks like a 52/20 on the front

  15. #15
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    That looks like it will be just fine. Nothing there that builders don't do all the time for other reasons. And it's nice.

  16. #16
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    Great job.

  17. #17
    tuz
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    Well done. Love the through-bolt routing and centerpull brake arm as a light bracket! And I admire your patience in getting the wire through the blade; it must have been a pain?
    homebuilt commuter, mixte, road and track (+ Ryffranck road)
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  18. #18
    Senior Member southpawboston's Avatar
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    Thanks, all!

    Quote Originally Posted by unterhausen View Post
    pretty slick. I assume you did something inside the fenders to keep the wire off of the tire?

    Is that a triple? Looks like a 52/20 on the front
    Every inch of wiring underneath the fenders is glued using "Goop", which I have used for literally hundreds of applications and have always been satisfied with the results. It dries like clear hard rubber.

    The double is 46/26, and coupled with a 12-32T cassette gives me 21-100 gear inches. It's my mountain climber/dirt road rando bike more than routine road bike. Here's a closeup of the drivetrain:



    Quote Originally Posted by tuz View Post
    And I admire your patience in getting the wire through the blade; it must have been a pain?
    You have no idea! I tried about a dozen approaches and came close to giving up and running it externally up to the crown, but then used the vacuum method with a long wire and a short (3") piece of thread glued to the end of it. The wire was able to feed up from the bottom to the crown by pushing because of its own stiffness, and then the vacuum pulled the short piece of thread around the 90 degree bend and out the steerer tube. That did the trick! And, the passage ways inside the blade are very narrow in places. I replaced the single-conductor wiring shown in the first picture with twin-conductor wiring (frame is not used as ground), and if there was a twist in the wiring it wouldn't pull through-- it had to be kept flat and untwisted all the way through the blade and crown.

    Here's the twin-conductor wire routed into the fender from the steerer tube. To accomplish that in spite of a stack of washers and fork crown daruma bolt holding the fender on, I drilled a hole through the stack of washers and into the fender, offset from the center axis where the daruma bolt passes through:




    In this photo you can see the fiber washer stack (necessary because this was a 27" to 650B conversion). the wiring is going right through the stack. You can see the wire hanging down below the fender, as well:


    And lastly, one last gratuitous glamour shot:

    Last edited by southpawboston; 04-13-11 at 09:09 AM.
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  19. #19
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    Sorry for the almost totally off-topic post, but I've been considering switching from a 30-46 to a 26-46. I'm just concerned about shifting. Does your front derailleur have any troubles handling the jump, and what brand/model are you using?

  20. #20
    coprolite fietsbob's Avatar
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    Generally ,The Big upshift is done at the crest of a hill ,
    while there is little pressure on the pedals.

    TA cranks need Period FD's due to the thin space between outer chainring
    and inside face of crank arm.

  21. #21
    Randomhead
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    He has a Huret Jubilee, which I've always considered the best looking front derailleur ever made.

  22. #22
    Senior Member southpawboston's Avatar
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    Quote Originally Posted by Six jours View Post
    Sorry for the almost totally off-topic post, but I've been considering switching from a 30-46 to a 26-46. I'm just concerned about shifting. Does your front derailleur have any troubles handling the jump, and what brand/model are you using?
    Six jours, I have no problems whatsoever with the 20T jump with the Huret Jubilee FD. It handles it with aplomb, and there are no chain-rub issues in either ring, either. And, having a very flat cage, it fits well with the narrow gap between the crank arm and the outer ring. My only gripe is one of cosmetics: the Jubilee cage is shaped for a 50T ring, so it's not perfectly concentric with a 46T ring. It gives the appearance of not being fit properly, but this is strictly a style point, and does not impact the functionality at all. Also, being that the Q factor for this TA double is only 136mm with my chosen BB, the FD cage comes within a couple of mm of the fender when positioned on the inside ring. Again, a non-issue but it could have been had the Q been any narrower or the fender any wider.

    Here's a closeup:



    By the way, I've seen your own bikes, and they are stunning reproductions of some of my favorite bikes of different eras. Top-notch, to say the least. I especially love your 1952 Herse Rando copy. Carefully thought out with all the right details. You've obviously done your homework on these classics.
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  23. #23
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    Thanks for the info, and the kind words. Ebay here I come!

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