The old three-bolt cottered cranksets found on lower-end Raleigh "ten-speeds" like the Record and Grand Prix used what, a 116 BCD? Most bikes came with a 52-40 rings or thereabouts, as I recall. Does anyone know what the smallest available ring would have been? I'm guessing at least a 38, and maybe a 36. Can anyone suggest a source for a ring of that size?

Ebay.

I'm not sure, but I think the cranks in question are copied from Williams C34 and C1000. Earlier ones have small, threaded bolt holes; later ones have large smooth bolt holes. The Williams chain rings were made in both 1/8" and 3/32" widths, and as small as 32T.


This photo is of my Norman Rapide, from 1950. The bolts have a square head and thread into the ring from the other side.

I'm pretty sure I have a 34T and a 38T that I'm not currently using; I'd have to check exactly what they are.

See here for more detail.

Sheldon's crib sheet is a great place to start to get a handle on the smallest ring for a given BCD.

True enough--I've referred to it often over the years. It's too bad he doesn't list any three-bolt chainrings.

A circle is a circle, right? Once you determine the BCD of your crank you know what to look for.

Thanks--you are correct. I should have thought of that.
It looks like the obsolete Campy 116 (a 5-bolt) ring went down to 35 teeth. So I would guess that maybe the 3-pin steel ones came in at least a 36, maybe a tooth or two smaller.

^ That would make sense to me. You can either have one made (CNC aluminum) for $50-70 or just wait for what you want to pop up on eBay.

You can drill out an old freewheel cog;

I like that. Does it work as expected?

It comes close. It's kind of a cheap crankset to start with and the arms were a little bent and the 2 and 3 chainrings weren't exactly straight, then there's the worn out POS derailler.
If I'd started with good parts it would have been fine.
Oh, the acorn nuts on the oversized bolts will really tangle the chain if it comes off on the outside, then it wedges itself between the outside ring and the cranks and screws up the chainring that you just spent a bunch of time getting straight.
It comes close.

Wow, that's quite a freewheel cog! It looks to be around 36 teeth? How'd you lay it out? Then you just drilled it out with a drill press, or what?

It's a 34. I think smaller would be better for my needs but this is what I had.
I laid out a circle the size of the cog on a piece of wood with a compass. I set the cog in place and locked it down with a couple of wood screws between the teeth. I got the BCD off Sheldon's site and drew a circle on the cog of that diameter, using the center that I'd drawn on the wood. Then using that diameter and the compass, I divided the circumference into 6 and punched a dimple on 3 of those marks. Then I drilled a little pilot hole and followed it with a big bit the size I wanted. I should have waited till I could go use the drill press at the shop but I got anxious and just used a hand drill.
I replaced the whole thing a month or two ago with an alloy cotterless setup just cause I finally found a spindle that works with this bottom bracket but I might go back, just cause this bike looks better with chrome and I think most of the troubles I was having were more to do with a worn derailler and chain. I can't believe I've put enough miles on this bike to wear out a chain already.

Jon,
You might contact these guys, they can make you what you want!
https://www.cycleunderground.com.au/chainringdesigns.htm

According to Sheldon, the way to determine the BCD on a three pin crank is to measure the center to center distance between the holes and multiply that by 1.155 .

Look at me, I don't even have the bike yet and I'm already working on it.... Thanks, Eben.
I'll check with the Australians, but I think they only work in aluminum, not steel.
JV