Rear dropout angles and frame geometry

[theery]

Hello there,
I'm designing my first frame by studying the geometry of my existing frames. My question is about seatstay-chainstay angles (and therefore also rear dropout angles).

In looking at dropouts, it appears there are few common angles, none of which match the angles of those on my current bikes. Can someone explain this? Without building their own dropouts, do builders generally need to design around the available dropout angles? Or are there adjustable ones?

Any help in clearing this up for me would be greatly appreciated.

[e-RICHIE]

All dropouts that have fixed angles are omni-directional enough so that they work outside of the as-cast shapes they are supplied in.

[David Tollefson]

Hooded dropouts are an option...

[Curt Goodrich]

Campagnolo 1010 drops came in one angle and still all frame sizes were a possibility.

[theery]

Thanks, guys. Would you mind elaborating a little bit? I'm still trying to wrap my head around it.

For example, it a dropout is 62 degrees, how would I make it work for a say, 66 degree seatstay-chainstay angle?

[e-RICHIE]

Thanks, guys. Would you mind elaborating a little bit? I'm still trying to wrap my head around it.

For example, it a dropout is 62 degrees, how would I make it work for a say, 66 degree seatstay-chainstay angle?

It depends. If it's a tab dropout, simply orient the two intercepts so that they mate with the pipes as you fixture them. If the part is a plug, you have to be more creative and resourceful; maybe file down the male parts so that they have some play, and let the stays find the sweet spot as you fixture the assembly. Conversely, it's the same with dropouts that have wells that hold the pipes.

[Eric Estlund]

For slotted drop outs you just come in at a different angle. Plugs and sockets have several degrees of wiggle. Beyond that you can grab another part, or do some physical manipulation.

[e-RICHIE]

PS Theery (and others) please add your first and last name to your signature OR have the admins change your screen name to a real first and last name. After April 15, it will be required for all who post anything in the FrameForum.

[theery]

Ah, I see. Thanks for the explanations!

I hadn't realized it was important to mention this until now but I'm making a bamboo frame, so not all of these methods may apply. I'm going to think harder about them and see what might make sense. It make take some experimenting to see what is and isn't doable.

e-RICHIE - I added my name to my signature -- thanks for the heads up.

[Eric Estlund]

You can always make your own, too.

[Doug Fattic]

I'm not sure how this would apply to bamboo bikes but stainless steel Henry James dropouts with plug ends can be bent to fit most angles. i use about an 8" length of 3/4" round stock that has had a hole drilled in each end that matches the OD of the seat stay plug to bend them to my will.

[EricKeller]

I would probably make my own for bamboo, I'm tempted to do that for steel bikes.

Not sure I would be concerned all that much about looks on a bamboo bike, but I've seen some people that let the weird angles of the dropouts ruin the looks of a frame. There are two-part dropouts with adjustable angles available, I think I have seen those on bamboo bikes

[Freddy Salgado]

Sorry chiming in late,

Good thing mentioning the material you would like to build with. Before I get started with method for attaching dropouts I have to ask if you have tested the “crack-ability” of the bamboo material you intend on building with?
If not a quick n easy way to test it is cut a small cross section of bamboo, then split it. If the bamboo snaps back nice and tight you are good to go, if a gap remains when you split the bamboo I wouldn’t use it to build a bike with.
bad boo good boo.jpg bamboo ring test.jpg

The material you choose for dropouts (aluminium or titanium is best for long term reliability)and material you wrap around dropouts to secure them to seat and chain stay is very important. The dropouts I use are 2 piece construction that allow adjustability to set the seat stay where ever I need to place it, one size dropout fits all no bending required.

What material are you lashing the tubes together with?

Ah, I see. Thanks for the explanations!

I hadn't realized it was important to mention this until now but I'm making a bamboo frame, so not all of these methods may apply. I'm going to think harder about them and see what might make sense. It make take some experimenting to see what is and isn't doable.

e-RICHIE - I added my name to my signature -- thanks for the heads up.

[theery]

Thanks, all.

Freddy, I'm using epoxy and hemp fiber.

What dropouts do you use, specifically?

[Freddy Salgado]

Hi Mac,
I get my dropouts from Craig Calfee. I am not sure these are available, worth a shot calling them up I understand calfeedesign is working on some birch wood bike kits to sell for the general public.
I put in a photo of the dropouts hope this helps, like both the Eric’s mention above you can take a stab at making them yourself. Whatever you decide make sure the dropout stud/plug is at least 50mm long. When you tack the dropout to the bamboo make sure one side of the dropout stud/plug is exposed so you can wrap it with the bamboo chain stay.
Plug style drop outs work for steel/carbon frames but not so good for bamboo, there just isn’t enough dropout material inside the bamboo to hold it securely to the chain stay.
bamboo.bike.dropouts.jpg

Thanks, all.

Freddy, I'm using epoxy and hemp fiber.

What dropouts do you use, specifically?

[jaybeeboston]

Reviving this old thread with a Q: I'm building a steel road bike with a CS/SS angle of 65.3 deg, and disc brakes. Without machining my own dropouts, is there any advice on sourcing? The Paragon windowed disc mounts have a 58 deg angle, and while I can make it up with a few degrees of play in the slotting, it would be nice to have a closer angular fit. Which probably means making them myself, since I haven't turned up anything wider than 58 deg in searching the web.

Advice will be gratefully and humbly received.

Jay Borden
Roulez Cycles, Boston (soon Lynn)

[e-RICHIE]

Reviving this old thread with a Q: I'm building a steel road bike with a CS/SS angle of 65.3 deg, and disc brakes. Without machining my own dropouts, is there any advice on sourcing? The Paragon windowed disc mounts have a 58 deg angle, and while I can make it up with a few degrees of play in the slotting, it would be nice to have a closer angular fit. Which probably means making them myself, since I haven't turned up anything wider than 58 deg in searching the web.

Advice will be gratefully and humbly received.

Jay Borden
Roulez Cycles, Boston (soon Lynn)

At times like these, l often add a slight rake to the lower end of the seat stay so that the available d/o angle works for me. Show the stay who's boss according to my opinion. My dropouts are cast in three sizes, and when the frame goes outside the lines of what works/fits, the stay gets a talking to. All it takes is some gentle force and a usable radius, and flowers sent the next afternoon.

[velomann]

This was interesting, since I was wondering the same myself and was guessing it was as it is. (I don't build frames but was curious but afraid to ask)

El Roberto
Fox Alaska

[jaybeeboston]

It will be an interesting bending task, since my client wants hourglass seatstays. I built a pretty nice stay bending fixture with a 10" radius mandrel to do fork blades; it should work for this as well, although I might need to make a smaller radius mandrel to do a decent job with the stay curves. Thanks for the input, Richard.