Re: [CR]Quadruple Chainrings

(Example: Framebuilders:Dario Pegoretti)

In-Reply-To: <5.1.0.14.0.20050212082555.03047a48@pop.earthlink.net>
References: <000c01c510c9$294fe560$6601a8c0@Balboa>
Date: Sat, 12 Feb 2005 07:28:15 -0800
To: Mark Stonich <mark@bikesmithdesign.com>
From: "Jan Heine" <heine93@earthlink.net>
Subject: Re: [CR]Quadruple Chainrings
cc: classicrendezvous@bikelist.org

>At 2/12/2005 05:37 AM -0800, Jan Heine wrote:
>>The drawings show cross-over gearing. From memory, it may have been
>>50-44-36-26 or something like that.
>
>I remember from a photo in the early '70s that spacing was even,
>suggesting 26-34-42-50 or 26-36-46-56, probably the former. FD
>looked like a one-off.

Yes. Singer front derailleur, but not the superlight version. It used a Simplex (?) cage, as far as I remember E. Csuka, the maker, telling me. They used those on triples and maybe doubles, too.
>Don't know what they did for a BB spindle.

Custom? They had their own spindles machined for their proprietary BBs. It should not be too hard to tell their machine-shop guy to make one that was longer.
>>If VBQ had an April 1 issue, I might include a techical article on
>>"double half-step" - half-step is nice, but with a granny, you get
>>very large steps in the smallest gear. By using four rings, you
>>could use a 50-47-28-25 or so, and get half-step the second time
>>around!
>
>Have you actually done this?

No. I prefer two well-chosen chainrings, like a 46-30. That gives me all the gears I need these days.

I can see that recumbents might need more gears, as many (but not all!) of them are very fast downhill and very slow uphill.

Like most April Fool's jokes (note the date on the proposed issue!), I hadn't thought this through. Of course, you'd need a constant percentage difference between chainrings, not constant-tooth. How about 50-45 (ca. 10%) and 28-25 (ca. 10%)? Or maybe, to take the joke one further, how about half-tooth chainrings, like 25 1/2? A capable metalworker should be able to machine one for me! (In fact, the only solution is going with shorter pitch. If you make the teeth half as big, you can get the elusive 25.5-tooth ring by making it a 56-51. Just need a new chain, too. Shimano has been there with their 10 mm (?) pitch components, they just weren't radical enough!)
> Based on my experience, I don't think you would be able to shift
>from the 25 to the 28 without first going to the 47 and dropping
>back down. Not a big deal with even chainring steps and a close
>ratio FW. But I think it would make 1/2 step impractical. I'm not
>even sure you would be able to make the 28-25 shift.

I am sure that would be a problem. So much for the royalties from my envisioned "double-halfstep" patent. ;-)
>Mark Stonich;
> Minneapolis "It's going to be almost 50 today!" Minnesota
> http://mnhpva.org
> http://bikesmithdesign.com

--
Jan Heine, Seattle
Editor/Publisher
Vintage Bicycle Quarterly
c/o Il Vecchio Bicycles
140 Lakeside Ave, Ste. C
Seattle WA 98122
http://www.mindspring.com/~heine/bikesite/bikesite/