Dylansbob 

I know there was a similar thread earlier, but I couldn't find it.

So I've been kicking this idea for several years and just curious as to thoughts. Several years ago there was company called Willow that offered a triplizer ring in a 46t for 130bcd cranks. A quick and simple way to create a 46/30 crank out of a fairly common sized crank. What I want is the same in a 144bcd pattern. Both for classic NR cranks, but also all of those relatively-decent fixie fad cranks. Every time I go to the co-op, I see one or two and think it's such a waste of a short crankset.

I've heard Vuelta will do custom, I"m guessing their minimum is fairly high or someone else would have done it by now. With modern CAD/CAM/CNC, I wish there was a way to scan in my extra Willow, alter the bcd, and cut a few hundred new ones.

Roger M

Not a 46t, but same idea in a 42t.

https://www.redclovercomponents.com/..._42_Teeth.html

Big Block

"do it"
That is what a mate of mine told me nine years ago.
So I did by using the method I set out here, I was able to have a custom stainless steel chainring manufactured with five crowns with light engraving for a project.
here it is fitted during the mockup for the chain guard fitting. It was before I filed the leading edges of the teeth and gave it a polish.


and the finished bike


The chainring was one of the most straightforward tasks in the build.

dedhed

"Flexibility: For the time being, at least, the 144 triplizer will be available only in the 42-tooth size. That should work for most users, but those who want a 44-, 46- or 47-tooth triplizer ring for an old-school half-step-and-granny setup are out of luck, at least for now. I may add rings in those or other sizes later if there’s enough demand."

​​​​​​https://www.redclovercomponents.com/...two-ways-to-go

scarlson 

I'm interested in some of the specifics of how you did the chainring. What did you end up using for a roller diameter? I have done a couple of custom rings for my René Herse project, but although they work fine running a chain, they don't quite look like normal chainrings - the teeth look a little thick!




I used a roller diameter of 0.306" (like ANSI 41) but after making a couple, I feel like the roller diameter used to make derailleur chainrings is slightly bigger (like maybe ANSI 40, 0.3125" roller diameter). I know they'll work for singlespeed, which is what you've got going on there as well, so maybe you don't know the answer, but I know that roller diameter doesn't matter as much as other parameters for the sprocket and a slight diameter mismatch may make the chain easier to derail, for shifting's sake. Any thoughts would be appreciated! Did you just use "bicycle" chain specs as listed on Sprocketeer?

Erzulis Boat 

I do my own sprockets for my MC's. I go through Rebel Gears and get get any size/pitch blank I want. I bet that they can provide proper blanks for a bicycle chain. I just bolt them to a plate and CNC the bolt holes and lightening cuts etc. I believe that a bicycle is a #40 size.

Here I am making a 530 series chain go on to a Marchesini wheel.

Big Block

buried in there you have the answer, beyond my knowledge.
Can't you take measurements from an unused chainring?

In Australia you could contact Bespoke Chainrings (they do post worldwide).
my version was for looks first, function second.

scarlson 

Thanks for the confirmation on ANSI 40. I appreciate that at least one other person thinks it might be that size! And, nice, I have a little '69 Honda CB350 motorcycle myself - I should have thought about that! Usually these motorcycle guys have more access to the serious tools, and the custom scene means there's lots of people who will think outside the box. Randonneur bike restoration is, well, a little stodgy - more Pebble Beach concours d'élégance than Sturgis rally, if you know what I mean.

I did mine myself, on the waterjet cutter at work, and then finished them on the lathe. It's some trial-and-error, but I'm having fun and learning something!

It's pretty hard to get the exact measurement of roller diameter by measuring between the teeth. A nice, exacting way to do it would be to turn a piece of metal on the lathe and keep trying to fit it until it fits in between the teeth all the way, and then measuring that diameter with a micrometer. I have done with a chain roller from a chain I took apart, and did find that the roller has some play on a new chainring, which means it's probably ANSI 40 like Erzulis Boat says.

But does yours function nicely? That's the proof in the pudding!

unworthy1

FIFY:
That's the proof in of the pudding!
"The proof" is "the test" in this sense, and it's "in the eating".

unless you are making that time-worn pun that has become so widely used it has eclipsed the original saying:
"The proof (meaning the alcohol: brandy, rum, whiskey) is IN the pudding"
Which is just a joke for drinkers to appreciate...

Guess that's another "exception that proves the rule"...but don't get me started!

scarlson 

I know the right way to say it. More common in Britain though, where half of all food is called a pudding. The above is an homage to my working-class roots, particularly my grandparents, who said it this way - and yes, they did drink a lot.

But here's the big question. Do you have any opinion on chainring-chain roller diameter mismatch?!