Flanged/hooded/Breeze-style dropouts

I need help figuring out how to better miter chainstays for hooded dropouts. Wow, it took way longer than i’m going to admit in writing.  My chainstays are also 1mm shorter than i planned because of the file/check/repeat process not going as smoothly as it could have.

Do others that use hooded dropouts file the chainstays to fit or do you have some whacky fixture to use on the mill? Do you just use some custom tube block to hold in a milling vise and do it that way? I’m really curious what others do as this was harder than doing seatstays! I can’t figure out the geometry, honestly.  How do you calculate what the miter angles need to be for this setup? I know the next time of filing it’ll be faster, but I would love to get advice if there’s a better method.

The reason they’re so hard (in my opinion) is that you need the miter to be tight and with my chainstay fixture you miter for the BB before connecting the CS’s to the dropouts (Sputnik, not Anvil which I believe you can cope for the BB after you weld on the dropouts…?).  With slotted chainstays/plate-style dropouts, you can have a little wiggle room and also slide them forward a little if needed since the brass will fill’er up.  I’ve not TIG’d plate-style dropouts but I imagine you can cinch down (lightly hammer) on the chainstay to make a better fit just like when brazing.

These dropouts are pretty interesting too (Part#: DS1001).  I have been saving them for this bike since they cost so damn much.  They’re Paragon flanged sliders made for Rohloff hubs so they have no derailleur hanger and instead have a long vertical dropout slot on the non-driveside to fit the part of the hub that stops it from twisting around its axis when shifting. These are 2x the price of the plate-style sliders, so it’s no wonder you don’t see them very often.  Or is it because they’re a bitch to miter for? They have different radii flanges — neither of which is perfectly fit for a half-round file it seems — the chainstay is a 1.75″ radius and the seatstay is 1.375″ radius. They have to be filed at an angle and offset from the chainstay’s centerline so similar to the seatstays/seat tube miter.

Anyways…tonight I tacked them up in the fixture, and hopefully I’ll weld them tomorrow out of the fixture.  Then after some touch up the BB miter I can attach the chainstays to the BB and get on with it.  I’m curious how my alignment is on this frame so far as I’ve not checked.  I am trying to follow “The Anvil Way” of building a frame to see how it goes…

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