Cha1nsaw

I'm investigating the possibility of changing a steel frame 10 speed to a 3 speed Sturmey Archer rear hub but will need to cold set the rear triangle to close the gap between dropouts. How much can the frame safely be changed without compromising the integrity of the tubes? The frame in question is a mid 80's Schwinn World.

Thanks,

Chainsaw

HillRider

Is the frame currently a 10-speed in the modern sense (2 or 3x10, 130 mm OLD) or a 10-speed in the 1980's sense (2x5, 120 mm OLD)? If it now has 130 mm spacing it was probably cold set to it from 120 or 126 mm so you are going back somewhat anyway. Making it narrower should be ok particularly since narrowing won't stress the chainstay bridge.

hueyhoolihan

just to give you some perspective, i've recently installed a 130mm coaster brake hub in an old ('97) Gary Fisher rigid MTB steel frame wih 135mm dropouts. i used moderate hand force to squeeze the rear triangle together.

i took the wheel off the other day and found that the frame kind of "got the idea". decidedly less pressure was necessary to squeeze everything together now, but i don't expect much more improvement.

FBinNY 

You won't be coming anywhere close to the limit. Odd are you could probably bring the en until they touch, or at least very close.

The real issue is that as you bring the ends in the angles change, so the dropouts are no longer parallel. The amount of the error can be trivial or meaningfull depending on how much things change.

When your finished you can test for the issue as follows. Mount the wheel without the chain on. Tighten one side, then the other in sequence. Now loosen the first side and note if and how far the axle moves. If it moves about 1/4" or more I suggest you correct (or have a shop correct) the dropouts for parallelism.

fietsbob

3 speed sturmey archer hubs are made with a variety of different axle lengths with the - sun gears , the one in My Brompton is for a 117mm dropout X-RD3/BSR

modify the Hub or buy the right one from the Get Go for your wheel Build..

https://www.sturmey-archer.com/files/...EED%20HUBS.pdf

JohnDThompson 

Before you go to the bother of cold-setting, see if a couple spacers on the axle will take up the slack instead.

Cha1nsaw

I'll check the spacer idea first to check feasibility but don't want to use more than 2 on the finished product. I want the change to look factory. The gears are 2X5 (or 6) but I don't know the width yet. I'll have to figure how to route the shifter cable (gonna need some pulleys), relace the original 27" rim to the new hub, take off the 52 tooth crankring and line everything up. I was looking at the bike the other day (before the snow) and noticed the rear dropouts aren't machined to the full depth, only about halfway. Looks like there will probably need to be some filing to get the chain length right. Joy, joy; metal filings!

Thanks for the input! I feel better about bending my frame now. :-)

Chainsaw

nfmisso

That is SCARY. Drop outs are not machined, they are stamped or forged, with just a quick clean up operation afterwards on a sander. Are they vertical dropouts or semi-horizontal? It is not practical to change vertical dropout to semi-horizontal. This may not be the frame for your project.

Are also going want a "narrow wide" chainring to reduce the risk of derailments.

It sounds like you need to do a LOT more research and measuring before you change anything.

Andrew R Stewart 

Many bikes have rear drop outs with what seems to be a partially produced slot. It is an attempt to emulate the forged with positioning screws style. Andy.

Cha1nsaw

The dropouts are semi-horizontal. They appear to be stamped but of higher quality than a department store sheet metal dropout. They actually are fairly heavy duty.

Chainsaw

Gresp15C

I have a 1982 World Tourist, which I converted to 3 speed Sturmey Archer AW hub. I'd be shocked if your World is not the same frame, made by Giant in Taiwan. I nudged the drop-outs closer together with no problems.

Is it an old Sturmey, or new? I have two AW hubs, both from the early 1960s. They made two different axle lengths, as noted in the parts list:

https://sheldonbrown.com/sutherland/CB-IGH-4-aw.pdf

I have one of each. The longer one is on my Trek, which I didn't want to bend quite so much, so it's mounted on the bike with spacers. The older is on the Schwinn with no spacers.

The other thing to note is that there are a few different styles of anti rotation washers, but you have to get the ones for your dropout slots, which are larger than the slots on the old Raleigh frames.

Tomorrow, I'll take a picture of how I did the cable routing, which I think works pretty well. The dropout slots are not particularly long, but they are definitely horizontal or semi. This is a good frame for adapting to fixed or IGH. As for getting the chain length right, rather than filing the dropouts, I'd add or subtract one tooth from the rear cog. That changes the position of the axle in the slot by 1/4 inch, plus or minus. Then you can also move the axle plus or minus 1/2 inch by adding or removing a chain link. You can get 3/32 width cogs from Niagara Cycle.

Gresp15C

@Cha1nsaw, as promised, pictures:



Click on them for better detail. On the brown Schwinn, the cable goes through the two braze-ons that are in the top tube, down the seatstay. The fulcrum clip, or whatever it's called, is attached to the seat stay with a hose clamp, and some innertube rubber between the clamp and the stay. It has stayed put since 1998.

The chainguard is from an old Huffy, trimmed with a tin snips, and painted with touch up paint that was left over from my first car. The color match is dumb luck.

On the blue Trek, the cable routing goes down the down tube. During that era, derailer cables were routed with these steel clips. I turned two of them into cable guides at the top and bottom of the down tube, so the cable comes out the chainstay. It is held on with just some innertube rubber and a nylon cable tie. As makeshift as it looks, there's not much force on it, and it's also been reliable. Both of these bikes shift smoothly and accurately.

Also, you can see the semi-horizontality of the dropouts.

Cha1nsaw

Thanks for the pictures Gresp! I'm just getting back into cycling and have only been riding the Giant or a clunky box store tandem with my wife lately. It's amazing how light the "heavy" steel Schwinn feels now!!

Chainsaw