[bobbotron]

Hi all,

I've spent some time pouring over the archives here and on the now defunct frameforums, looking for info on how to prep a chainstay for a tabbed dropout. I tried to start tackling my first rear triangle last night (with a lugged BB), starting with the chain stays. I was aiming for a simple slot filed into a dome, which I'll then be brazing/filling with brass. I cut the stays to length, and then started to slot one with a hack saw and file (mostly file) and then realized I had way too many q's in my head to continue. (That, and it was a sweat shop in my shed last night.)

The Paterek manual says to slot them 6mm deep, and that the notch should in line with the ovalized section of the tube. However... I started doing this, making the notch parallel to the chain stay. When I fit the dropout in the stay, and placed it in the BB, things didn't look right. The face of the dropout didn't look parallel to the center of the bike. Is the usual method to correct for this to slot the chain stay at an angle (that will be "fun" to get :arf: that will be a good test of my level of precision at this point) or does one braze it in and then bend it (sounds gross and can't be good for the joint, but possibly ok?) or....? I am open to suggestions. I imagine this is one of the very many "there are a thousand different ways to do it, most of which all work well, and some which are notoriously bad but often tried" parts of frame building.

Interestingly, the dropout's tabs have a light bend in them, which helps bring them closer to parallel. I suppose I could also try bending them in a metal working vise before brazing.

 

[dbohemian]

Interestingly, the dropout's tabs have a light bend in them, which helps bring them closer to parallel. I suppose I could also try bending them in a metal working vise before brazing.

We call them "cranked or precranked" dropouts. Many older styles of drops were provided this way. The newer ones from paragon and the like are not cranked or bent.

Depending on your design you need to bend them more before doing the final brazing. Everything should be money in your fixture before you braze them. A bit of after braze bending won't hurt anything but I like to get them very close before hand.

Are you really going for a dome? or just a typical beveled end? Domes are harder. You slot, squish the end in your vise, open slot again, re-squish, etc, etc until you have a dome. Then you fit up your drop and braze.

It is also totally reasonable to cut your slot at an angle dependent on your design and not crank the drop-out which can be preferable when working with MTB designs that require more angle, it just gets to be too much to bend without distorting the disc tab and the like.

Small pitch. I really don't know how you guys go about doing this with all your knowledge from the interweb.....It may seem very simple but I must spend 3-4 hours discussing different types of chainstay ends and the necessary abbreviations (have you considered cog clearance in your design?) I could have never been where I am without personal instruction.

 

[bobbotron]

We call them "cranked or precranked" dropouts. Many older styles of drops were provided this way. The newer ones from paragon and the like are not cranked or bent.

Depending on your design you need to bend them more before doing the final brazing. Everything should be money in your fixture before you braze them. A bit of after braze bending won't hurt anything but I like to get them very close before hand.

Are you really going for a dome? or just a typical beveled end? Domes are harder. You slot, squish the end in your vise, open slot again, re-squish, etc, etc until you have a dome. Then you fit up your drop and braze.

It is also totally reasonable to cut your slot at an angle dependent on your design and not crank the drop-out which can be preferable when working with MTB designs that require more angle, it just gets to be too much to bend without distorting the disc tab and the like.

Small pitch. I really don't know how you guys go about doing this with all your knowledge from the interweb.....It may seem very simple but I must spend 3-4 hours discussing different types of chainstay ends and the necessary abbreviations (have you considered cog clearance in your design?) I could have never been where I am without personal instruction.

Thanks for the info Dave!

Oh goodness, I meant beveled, I'm trying to keep it easy.

Great to know about bending the tabs - this one really wouldn't need to be bent too much from its current position. No disc tabs involved either, it's just a simple horizontal dropout.

To be honest, I need to think about the cog clearance. I was pretty sure it would "just work", but could be wrong. (I am building it up for a 3 speed IGH.)

Heh, we "web trained" go about it much slower, with much second guessing and likely less accurately than those with trained real world teaching.. :arf: I'm not completely without ears to pick; I have a frame building friend in Montreal (I'm in Ottawa) who I bug about building from time to time, and there are some people in town I know who are useful resources including my friend who's made his way through one frame who is a great help. That said, if there was a class in town, I would take it, there is so much to learn, and it's so much easier to do so with a experienced teacher.

 

[Smokebikes]

To bend the DO's.........a large cresent wrench and a vise works well...........just remember to bend them so that they bend towards each other. If you postion both of them at the same time in the vise and bend them equally in the same direction :nono: then one will point out while the other one points in....:madman: