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Drive side chain stay dropout question

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Drive side chain stay dropout question

Old 04-30-20, 11:10 AM
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Roger Bloom
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Drive side chain stay dropout question

I致e completed the front triangle on my first frame and I知 about to do the stays and the dropouts. I知 using Columbus horizontal dropouts and I知 wondering about the placement of the drive side dropout. My concern is about chain rub in the highest gear. I saw a Chapman video on Instagram where his just puts it off center of the stay favoring the inside to compensate.
I致e looked at the steel frames I own and one (Serotta) looks like it was machined or filed down with the dropout still centered. Another (nishiki Olympic) the dropout again looks centered and both the chain and seat stays look almost flattened. I looked through my copy of the patereck manual and he just centered the dropout. Probably because it was all 6 speed back then and lots more room. Thanks in advance for your help.
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Old 04-30-20, 11:26 AM
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You can cut them back on the inside. The angle of most chain stays means that it's probably going to be in the way in the front.
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Old 04-30-20, 08:42 PM
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And don't forget about the chain's kick up off the small cog when shifting that can catch the lower inner end of the seat stay. I use to scallop the chain and seat stays a lot on their insides. At times needing to add material to the drop out's tabs to allow the filing back of relief. But with today's 11t cogs being so common less scalloping seems to be needed. Do find this out prior to painting. Andy
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Old 04-30-20, 09:59 PM
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The chain doesn't touch the chainstay. What you need clearance for is the freewheel teeth, and only when removing/installing the wheel.

The seatstay does come close to the chain, on a properly dish-optimized wheel. So the seatstay needs a deeper clearance, while the chainstay needs a longer one (with horizontal dropouts anyway).

If you center the stay on the dropout, then the best way IMHO is to flatten the inner side of the stay before brazing, turning the cross-section into a "D". This is best done with a specially shaped die, not just hammering. Making the die is too time-consuming for most hobbyists, so I'm not actually recommending this method to you. But here's how it looks finished. Old used-and-abused bike, but the paint is relatively unscathed from contact with the cogs or chain:

Brief history lesson: This localized D-section is the way that better Italian frames have been made since the '50s, maybe earlier. For decades, vintage French and British builders stubbornly hung onto domes or other shapes that forced people with Campy (or other dish-optimized hubs) to add a spacer to the right side rear axle, which is lame because it adds to the wheel dish. And some hubs (e.g. Phil Wood) don't even let you add a spacer. Your other alternative was just let the chain grind it's own clearance over time... French hubs just came with more space there, so their wheels gave up dish for no good reason.

If you make that shape by removing metal only, not smooshing the tubes into a D-shape first, then you'll break through to the inside of the stay. This can be dealt with by filling the stay with brass in those areas. Not my favorite way, but good enough if you're sure to add enough brass. Remember it has to come pretty far forward on the chainstay with horizontal DOs, that is a lot of brass.

Better alternative to that is offsetting the slots, so the stay is mostly off to the right, on the right-side DO. This requires filing the tabs of the DO, that go inside the stay, into a half-moon shape before assembly. If you file the tab carefully to match the shape of the inside of the stay, you get a large area of contact for brazing, and much less metal needs to be removed afterward for cog and chain clearance.

Some DOs have been made with the tabs already made in the half-moon shape. Ritchey DOs, the old forged ones, not cast or hooded style, were the first to come pre-made like that, but then a lot of knock-offs started using that idea too. I doubt your Columbus DOs have it, but it's quick'n'easy to make the shape yourself, a few strokes with a file.

Here's a pic I found on the web, probably a Ritchey or a knock-off, showing the shape I mean:

That's good enough for jazz, but I would still improve that a little with a file if it were my frame.

Mark B in Seattle
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Old 05-01-20, 06:49 AM
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Thanks for both the history lesson and the tip on shifting the dropout. I’m definitely going to put this to use.
I was a bike mechanic from the late 80’s through the 90’s till I had to get a job that paid well enough to raise a family. As I build this frame it is connecting so many dots between components and frames that like you said were work arounds or modifications that had to be made.
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Old 05-01-20, 10:45 AM
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Unterhausen,do you live in state college? That’s my hometown I lived there until 1990 when I moved to the Lehigh valley to be closer to the velodrome.
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