jharley

Perhaps this is a no-brainer for most of you, but I am new to this, so help me out!

I am designing my second frame, a commuter/tourer/cross country bike, with the following desired characteristics:
1) 450mm chainstays
2) 80mm drop
3) room for 2" tires and fenders on 700c wheels
4) a plate for a kickstand mount
4) Conforming to the following lugset and bottom bracket angles that I have:

https://www.cycle-frames.com/bicycle-...L-SOCKETS.html
https://www.cycle-frames.com/bicycle-...E-SOCKETS.html


As you can see, these have are standard road angles. The angle between the chainstays is ~7 degrees or so. I've got a frame drawn up that fits all the angles perfectly, EXCEPT the tire clearance.

Even with 450mm chainstays there is not enough room. So obviously I need to run bent chainstays, right? But this shell needs 22mm round stays, and as I see it I would need to put two bends relatively close together since I can't really change the angle of these chainstay sockets (i.e. an outward bend close to the socket followed by an inward bend further back.)

So option number 1 would be to get some plain round chainstays and bend em, but I don't think I will be able to put these bends in so close together without deforming the stays quite a bit and weakening them?

I considered grinding off the sockets on the BB shell and brazing on essentially a piece of angle iron, then brazing single bend round chainstays (which are available to buy) to that. The angle iron could serve as a kickstand plate as well (pardon my MS paint mockup):


How about Jimmy rigging some kind of other flat plate solution like this (except on both stays):


Or cutting a piece of 4 inch steel pipe and making something like this (except instead of the oval monostay I would have two very short round stays going to it):


Or something I haven't thought of?

Thanks!!!!

jharley

Well shizz, check this thing out:




Custom machined by some dude I stumbled across on the web.

unterhausen

I always wondered who they were going to sell those lugs to. If you are getting them because you think it is easier to braze them, I don't think you will find that to be the case.

Nova has a standard MTB BB shell that will probably work better angle-wise. But they also sell s-bend stays that will fit in a standard bb shell that I think will probably give you enough space. Of course, you need to go with an oval bb socket. Those fairly radical solutions you show above are for 29er frames with much larger tires than you propose and very tight clearance with the frame. Not sure you need that. You can also go with a 7/8 tube and get it bent in an s bend

ftwelder

Ditch the lugs and make your own. 29X2.5 on 17" chainstay/standard MTB rings.


29 277 by frankthewelder, on Flickr


29 310 by frankthewelder, on Flickr

jharley

Thanks guys for the thoughts. As to the lugset, I chose it b/c I like the look but am not confident yet in my ability to do a good fillet braze. Ditto for the bottom bracket, although if you want to come over and weld that up for me ftwelder it looks like exactly what I need! :

I did mess around with the angles of that MTB BB they have at Nova in rattleCAD but I can't get anywhere close to the drop I am looking for with that 67 degree ST-CS angle. Even getting an 80mm drop on the road BB is going to require about 2 degrees of massaging.

Time to expand my brazing skills I guess.

ftwelder

I am still on the learning curve on the brazing also although I am more confident in my fillet skills than I would be with a BB lug I think.

Mos6502

How about instead of having two separate stays welded to a flat bridge, you just use one really long stay bent into a U shape?

ftwelder

When tube is bent, the wall gets very thin on the outside of the bend. We did Yeti's that way "back in the day" and I had to fix a lot of them with gussets. thick tubing is fine but the real issue would be finding someone with the correct bend radi.

depending on where you look..

Mos6502

Maybe something like the old fashioned Raleigh crown would work:


I'm not sure if it is, but from some reason attaching chain stays to a flat piece of bar just seems wrong to me. 0:

Wulf

A simple indent should accomodate up to 700x32 or even 35.

Mos6502

That wouldn't be as cool though.

MassiveD

commuter/tourer/cross country bike

Does CC mean like cycling coast to coast, or across the dessert or mud flats? Cause you don't need anything more than 1.5 tires for what you have on the list in the first case. I respect your desire to do this, but it may be a little much.

jharley

I want to run significantly larger than 35s

unterhausen

curious what 50mm/2" tire you want to use for this purpose? That definitely will take some MTB-like bent chainstays. I really like the Continental Top Contact Winter which I run on my commuter, but that is a 26" bike. I'm scheming to build a new frame around those tires, it is going to be more like a mtb. Currently, I am using a Trek MTB frame.

jharley

True, it is a little much. The specific purpose I have in mind is for closed fireroads/logging roads that are in poor repair but lead to some really awesome places up in the mountains here. These would be overnight trips, 20+ miles. The larger the tires, the cushier I can make the ride without having suspension.

Incidentally, I stumbled across this bike by Hunter Cycles a few days ago which is almost exactly what I was thinking of from a functional standpoint (minus the fancy curved tubes):




Very similar chainstay solution to what's pictured above.

jharley

I'd like to be able to use anything from 29x1.5 slicks up to 29 x 2.5 knobbies if I could figure out how to fit them.

Front end wise, I'm planning on using this crown from ceeway which can fit 68.7mm/2.7inch tires:

unterhausen

what you want to build is generally called a "monster cross." I like the idea, most likely you will have to figure out how to bend tubing.

Live Wire 

[QUOTE=jharley;14240803]I'd like to be able to use anything from 29x1.5 slicks up to 29 x 2.5 knobbies if I could figure out how to fit them.

]
In that case, the fork in your drawing is at least 25mm too short. I think you'll find that when you redraw it, the dt/ht angle will be too far off to work right with those lugs.

jharley

[QUOTE=Live Wire;14241090]Goddamnitttttt! You are totally right.

unterhausen

fillet is the way to go with anything out of the ordinary anyway. Start practicing

jharley

Haha, you are probably right. But I am stubborn! Turns out its not hard to get my angles back going to a 430mm axle to crown fork. (Fairly typical 29er rigid fork.) If I increase the rake to 55 (need to do that to get the right trail with these big tires) and lengthen the top tube by 1cm then I am good.

Anyway, fun conversation, really appreciate the input!

Live Wire 

Yup, you'll have to tweak the ht/bb lug, but it's the chainstay to seat tube angle I'm talking about...there isn't a lugged bb out there that will give you the 80mm drop that you want. The most you can usually get is 60, and that takes some pretty good socket bending.
FWIW, I would try to stay with the 80mm if possible...it's perfect for the type of bike you're building.

Road Fan

I'm not a framebuilder, but I recently bought a used Mike Terraferma frame designed for 42 mm 650b and a fender that is nearly 60 mm wide. The problem I have "mantling" it is that the chainstays are rather wide across their outside. It measures about 108 mm across, where my more conventional bikes (vintage steel Treks or similar) measure more like 92 mm - BIG difference when you're trying to set up Q, chainline, and crankarm clearances. It's proving hard to fine a crankset that provides good triple chainline and minimizes tread (I just like that). What's working is a TA Cyclotourist triple with a 127.5 Shimano BB, and a vintage Avocet Triple crank with an Avocet 4-68 spindle and Avocet cups. I have a 4-70 which is pretty close to right, but the 4-68 would be Right. Both deliver crankarm clearance 5 to 8 mm, and tread 145 to 150 mm.

I know it would not work for me with any Campy or modern Sugino or Sakae cranks. ISO BBs I've found will not deliver the crankarm clearance - Campy just didn't design for a MTB-width frame, in any commonly available components. If I could get a wide-enough ISO BB to make the chainline, I'd have huge Q with a Racing T, and with the widest 115.5 BB, I don't get decent chainline or any crankarm clearance. The TA/Stronglight 49/vintage Avocet style, with straight crankarms, is much better for achieving clearances and alighnment.

I think Mike built up his own BB from steel sheet. They exit the BB shell at quite an angle, similar to Frank's.

Terraferma used a large-ish tube and no dimpling. It's his choice on all his frames. He says it's part of the great pedaling performance. My bike is not finished yet, so I can't say how it rides yet.