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  1. #1
    I just wanna ride stryper's Avatar
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    Drilled crank arms

    So I've seen drillings in chain rings plenty, both for weight and aesthetics. Seen it in lots of hubs too. When I took a look around though there was only one crank I found:


    I just picked up a pair of similar Sugino Mighty Competition cranks below:


    I'd like to replicate the drilling down the flute of the arms, and a few holes in the flutes of the spider too. I think small holes like that just in those fluted areas should be safe. I know later models of the Sugino Mighty cranks had those spiders bored completely out, so some holes should be nothing compared to that, and as far as this design goes, I found nothing about these cranks breaking or having weakness in the arms, so I'm having trouble imaging I'd be in any trouble there. I'm only 150lbs, and although I'm strong I'm no 200lb 6'4 racer, nor am I racing the bike at all.

    I'm just kind of looking for opinions. I know most people will say it's a bad idea and what's the point and bla bla bla, but I like how it looks, the detail of it, and would like somebody to either affirm that it's not significant enough to harm the integrity of the cranks, or that for sure I'd end up breaking them because here are 10 pictures of vintage fluted cranks that all broke down the arm.

    Just to make sure it's clear, I wouldn't be drilling around the pedal holes at all, nor anywhere that isn't already fluted. And the holes would be small, just like in that Campy crank

  2. #2
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    from experience in drilling holes in motorcycles - anything between the "webs" of a casting holds very little strength.
    I would be happy to do it. Counter sink the holes for a smooth edge/slightly more weight shavings

  3. #3
    bike whisperer Kimmo's Avatar
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    Hey, why not? As long as you have the skills to do it accurately enough...

    I'd use bigger holes. The diameter of the flat area of the thin sections.

  4. #4
    Senior Member Homebrew01's Avatar
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    Should be fine .... but making it look good can be tricky.
    Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike

  5. #5
    Senior Member the_tool_man's Avatar
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    There should be no major issue with drilling the arms in the web area, provided you don't go crazy. It's a balancing act, of sorts. As the holes get bigger, you remove material from the cross-section, which weakens the arm. Taken too far, the arm loses rigidity. Taken further, it breaks. However, as the holes get smaller, they cause stress concentrations which increase the liklihood of stress cracking. Aluminum is especially prone to this, so you shouldn't go any smaller than the small holes in the example you provided. The main thing is to chamfer the holes with a coutersink, and make sure there are no rough edges inside the holes. Ideally, you should drill them slightly undersize and ream them to get a smooth surface finish. If you could polish the holes, that would be even better. Good luck. Post pics when you're done.
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  6. #6
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    Holes in the web area of the crank arms should be safe enough but I'd be VERY leery of drilling holes around the pedal eye if for no other reason than the drilled crank you show seems to have a lot more metal around the pedal eye than the Suguino crank you propose to modify.

    Interesting to see the return of "Drillium".

  7. #7
    Senior Member Grand Bois's Avatar
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    Quote Originally Posted by HillRider View Post
    Interesting to see the return of "Drillium".
    Lots of people are still doing drillium. You can see some examples and even some instructions by searching posts by "Drillium Dude" in C&V.

  8. #8
    Senior Member rydabent's Avatar
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    Back in the Middle 80s a light weight craze swept cyclist. They were drilling out everthing!!! Then parts began to fail. They came to the amazing conclusion that for the price of a few grams they were rewarded with a broken bike.

    Really people eat a couple less cookies and take pound off. It is all the same, and the bike will finish the ride or race.

  9. #9
    Senior Member Grand Bois's Avatar
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    It doesn't save a significant amount of weight. It's mainly for looks.

  10. #10
    Old fart JohnDThompson's Avatar
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    Zeus 2000 had drillium arms and rings from the factory:


  11. #11
    Retro Grouch onespeedbiker's Avatar
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    It's interesting to note that on several web sites they describe the old Campagnolo Super Record and Victory brake levers as being drilled for weight. The levers were not drilled but manufactured that way, so in reality both levers weighed more than the available none drilled levers (Record and Triomphe); the Campagnolo reason was to keep ones hands dry so they wouldn't slip on the smooth levers.

    allez5.JPG
    Last edited by onespeedbiker; 08-29-12 at 11:21 PM.

  12. #12
    I just wanna ride stryper's Avatar
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    Quote Originally Posted by Kimmo View Post
    Hey, why not? As long as you have the skills to do it accurately enough...
    Well I have a drill press, brand new drill bits, and some clamps. Hopefully I can be accurate, we'll see

    Quote Originally Posted by Homebrew01 View Post
    Should be fine .... but making it look good can be tricky.
    I'll mock up some versions in photoshop to see what I think looks best first, how many holes, what size, where exactly.

    Quote Originally Posted by the_tool_man View Post
    There should be no major issue with drilling the arms in the web area, provided you don't go crazy. It's a balancing act, of sorts. As the holes get bigger, you remove material from the cross-section, which weakens the arm. Taken too far, the arm loses rigidity. Taken further, it breaks. However, as the holes get smaller, they cause stress concentrations which increase the likelihood of stress cracking. Aluminum is especially prone to this, so you shouldn't go any smaller than the small holes in the example you provided. The main thing is to chamfer the holes with a coutersink, and make sure there are no rough edges inside the holes. Ideally, you should drill them slightly undersize and ream them to get a smooth surface finish. If you could polish the holes, that would be even better. Good luck. Post pics when you're done.
    Good information, thanks. I might need to pick up a ream set so I can do that. And I'd think maybe a pipe cleaner and some polish would be the best way to actually get in the holes depending on how small they are?

    Quote Originally Posted by HillRider View Post
    ...I'd be VERY leery of drilling holes around the pedal eye if for no other reason than the drilled crank you show seems to have a lot more metal around the pedal eye than the Suguino crank you propose to modify.
    I posted in the OP I won't be putting any holes around the pedal eye. From what I've seen of broken cranks that seems to be the most common area to break, I wouldn't want to risk anything.

    Quote Originally Posted by rydabent View Post
    Back in the Middle 80s a light weight craze swept cyclist. They were drilling out everthing!!! Then parts began to fail. They came to the amazing conclusion that for the price of a few grams they were rewarded with a broken bike.

    Really people eat a couple less cookies and take pound off. It is all the same, and the bike will finish the ride or race.
    If weight was the issue I would stick with my current Miche cranks that are 495g for the set w/o bolts. Just the drive side arm of these sugino cranks weighs almost that much. I like the more classic look and I think well placed/executed drillings just add to the look, nothing more. I have an aunt in-law not too far away in the bay area who's a jewelry maker and I'm considering asking if she'd engrave the cranks too, but that might be too much.


  13. #13
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    Sorry about missing your disclaimer that you weren't thinking about drilling the pedal eye area. As to the engraving, during the "drillium" era there was also a fad of "pantographing" components, i.e. engraving designs, logos, the maker's name, etc. and filling the engraved lines with contrasting colored paint. It made for a striking appearance but also led to a lot of broken parts (can you say "stress raiser"?) and quickly went out of fashion.

  14. #14
    Senior Member Kactus's Avatar
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    Quote Originally Posted by stryper View Post
    I have an aunt in-law not too far away in the bay area who's a jewelry maker and I'm considering asking if she'd engrave the cranks too, but that might be too much.

    THAT is gorgeous!

  15. #15
    I just wanna ride stryper's Avatar
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    Quote Originally Posted by HillRider View Post
    Sorry about missing your disclaimer that you weren't thinking about drilling the pedal eye area. As to the engraving, during the "drillium" era there was also a fad of "pantographing" components, i.e. engraving designs, logos, the maker's name, etc. and filling the engraved lines with contrasting colored paint. It made for a striking appearance but also led to a lot of broken parts (can you say "stress raiser"?) and quickly went out of fashion.
    No worries.

    And I didn't know it was ever a fad and caused issues. Perhaps then I won't be engraving and drilling the same crankset lol. Maybe another project for another time.

    It's funny the longer I ride bikes the more I realise sometimes you end up with more than one bike that serves the same purpose, you just have so many components you really like how can you choose between them all.

  16. #16
    bike whisperer Kimmo's Avatar
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    Quote Originally Posted by Kactus View Post
    THAT is gorgeous!
    Definitely +1... really impressive, and works quite well with the more modern crank...

    I have Mirage cranks on my bike, and they use a hell of a lot more metal than old-school cranks... I keep thinking about carving about a quarter of it off.

  17. #17
    Senior Member the_tool_man's Avatar
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    Links on this page to drillium articles from the era:

    http://www.tearsforgears.com/2005/09/drillium-info.html

    Fun to read.

    The engraving is beautiful. But I can think of no better way to initiate a fatigue crack in aluminum. If you have your cranks engraved, hang them on the wall. Don't ride them.
    Optimist: The glass is half-full.
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  18. #18
    Senior Member Garfield Cat's Avatar
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    How about the drilled crank arms like the Rotor system?

    http://www.rotorbikeusa.com/3d_road_cranks.html

  19. #19
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    Most crank arms come with 2 big holes in them from the factory,they don't seem to crack real often.....go for it.

    Make sure to break the edge on everything.Just don't go crazy,it'll be fine.

    I like the way it looks,if I was more OCD,I'd do it to everything I own.
    Everything should be as simple as possible...But not more so.---Albert Einstein

  20. #20
    Ride, Wrench, Swap, Race dddd's Avatar
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    Quote Originally Posted by the_tool_man View Post
    ...As the holes get bigger, you remove material from the cross-section, which weakens the arm. Taken too far, the arm loses rigidity. Taken further, it breaks. However, as the holes get smaller, they cause stress concentrations which increase the liklihood of stress cracking. Aluminum is especially prone to this...

    Please OP, read the above twice.

    I'm a mechanical engineer, and from what I know about metals and stress distruibution, I will tell you that without actually testing your modifications, you'll likely see a very serious decline in the part's structural integrity which might give no clue to when a catastrophic failure will occur. Ask yourself, "how much do I know about the grain structure's orientation in this forging".

    The bigger holes induce the very flex which can cause rapid failure, and the small holes create the highest stress concentrations.
    Pick your poison!

    This drillium activity should really be only for display parts, not riding.

    This reminds me of the guys in the cities who ride their bikes with no brakes, and so I must question the definition of "cool".

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    Holes in frames and bike parts is real dangerous: Don't do it.....Mom always said I would kill myself......



    Delta Sports Frame......looks like an accident waiting to happen......they're so bad their only making 200 of them.....

    Like everything in life,there's a risk,whether you drill it or not.How many people you know or have heard about being injured from drilling their bike parts?

    If you weight 300-400 pounds,are a body builder,use your bike to jump off of cliffs,race down the side of volcanos....you might not want to drill your parts.

    If your like me and tour on your bike,ride around the city and go to the beach....drill away,just don't go crazy.If you can't sleep at night,don't drill it all the way through,it will still look nice.
    Last edited by Booger1; 08-29-12 at 12:51 PM.
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  22. #22
    Ride, Wrench, Swap, Race dddd's Avatar
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    Parts like the frame above are tested before going into production.
    Yours is a lousy point. But, since it's not your bike being drilled, I guess it doesn't matter?
    The point I made, that you refer to, is that without testing of the drilled parts, they are upteen times more-likely to fail.

    Another point to consider is that none of us will live forever. Death could come at any time!
    So, if your posessions/estate were sold off, do you really want some un-knowledgeable new owner having to pay the consequences of your hapless re-engineering of a crankarm or handlebar clamp?
    These modifcations are like sabotage imo.
    Last edited by dddd; 08-29-12 at 01:42 PM.

  23. #23
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    I'm pretty sure the crank shown in the original post is not actually drilled through. I think Jeff has just done small stopped holes and filled them with paint. At least that's what looks like in that photo. He's forum member "drillium dude" so you can ask him if you want.

    Italvega used Record cranks with large holes drilled down the center of the cranks on their Superlight model, as well as many drilled components. I always thought the holes down the center of the crank were a really bad idea and did not look really look good either. But the work on the rest of the bike was very cool.

  24. #24
    Retro Grouch onespeedbiker's Avatar
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    The Italvega Superlight probably had the most OEM drillium http://s183.photobucket.com/albums/x...%20Superlight/ unless you count Affinity Cycles Drillium http://prollyisnotprobably.com/2010/...-drillium-212/
    Last edited by onespeedbiker; 08-29-12 at 11:46 PM.

  25. #25
    Senior Member the_tool_man's Avatar
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    Quote Originally Posted by onespeedbiker View Post
    It's interesting to note that on several web sites they describe the old Campagnolo Super Record and Victory brake levers as being drilled for weight. The levers were not drilled but manufactured that way, so in reality both levers weighed more than the available none drilled levers (Record and Triomphe); the Campagnolo reason was to keep ones hands dry so they wouldn't slip on the smooth levers.
    This was quite common then, and not restricted to high-end stuff. The mid-level Dia-Compe brake levers on my Fuji are made this way. I remember the bike shop guy making a big deal of the weight savings, but you're right. It's for traction.
    Optimist: The glass is half-full.
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