Tandem Bottom Bracket Shells

[Amir Avitzur]

Did anybody ever make lugged tandem bottom bracket shells?

These would be oversized to accept an eccentric?

Anybody know the dimensions of modern steel tandem bottom bracket shells?

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Amir Avitzur
R"G Israel

[M-gineering]

On 7/11/2017 9:20 AM, Amir Avitzur wrote:
> Did anybody ever make lugged tandem bottom bracket shells?
> These would be oversized to accept an eccentric?

Only the front would be excentric, rear would be standard with
horizontal DO's or ea derailleur

>
> Anybody know the dimensions of modern steel tandem bottom bracket shells?
>

come on, Amir, you've been around long enough to know there will not
ever be 'a standard' but that you should ask for the current 10 most
popular ones


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mvg

Marten Gerritsen
Kiel Windeweer
Netherlands

Tel: +31 598 491865


www.m-gineering.nl

[walawalaoxenfree]

OK Marten

What are the current 10 most popular tandem bottom bracket shells for the front (eccentric side) .

Looking for sources and the dimensions of the shell(s).

Amir

[Alex Wetmore]

If you don't count proprietary ones there probably aren't 10 available.

The 2 most popular are the Easton insert and the Bushnell insert.  Nova sells both and they wouldn't fit into the same lug.  I think you need to pick one and go with it.

http://www.cycle-frames.com/bicycle-frame-tubing/TANDEM-and-SINGLE-SPEED-SHELLS/

A tandem lug seems like an odd thing to make, there are so many variables that you eliminate.

alex

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From: frameb...@googlegroups.com <frameb...@googlegroups.com> on behalf of walawalaoxenfree <walawala...@gmail.com>
Sent: Tuesday, July 11, 2017 12:57:15 AM
To: Framebuilders
Subject: Re: [Frame] Tandem Bottom Bracket Shells

 

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[Mark Bulgier]

Haden made lugged BB shells for tandem (click the last link on this page http://www.equusbicycle.com/bike/haden/), but only for 1-1/8” ST & DT (annoyingly small tubes for a tandem).

Also, beware Haden eccentrics, whether lugged or lugless, their eccentricity (“E”) is less than 1/4”, so they don’t work with some lengths of bottom (keel) tube, without resorting to timing rings with an odd number of teeth. With E greater than 1/4”, any keel tube length works with even-numbered teeth on timing rings. All modern eccentrics have E > 1/4”, I believe. An eccentric that isn’t eccentric enough is a very stupid thing. Haden shells had a large enough ID for the insert to have E > 1/4”, but they just didn’t put the English-thread hole off-center enough in the aluminum insert. It’s almost like they didn’t know what they were doing! Yes, shocking, I know.

I vaguely recall there was an Italian set also, probably also for 1-1/8” tubes, i.e. stupid & useless.

Plenty of people have made their own. Tom Kellogg for example, famous for the “Miami Vice” tandem featured in Bicycle Guide magazine (‘90s I think). Here’s a set some guy named rykrisp made:
http://photobucket.com/gallery/user/rykrisp/media/cGF0aDovbXl0YW5sdWdzLmpwZw

Making a tandem lugset can be about as much work as making a whole frame, so you have to be a little nuts.

There is a tale that gets told now and then (probably apocryphal), that Pogliaghi made lugged tandems by building an entire tandem frame from OS tubing, then cutting the middles of the tubes out to get the “lugs”. Hopefully Signor Pogliaghi was not that stupid. (His tandems are pretty dumb though, so maybe...)

Mark Bulgier
Seattle

[dbohemian]

I have a set of lugged BB shells with eccentric  for a tandem that is 35mm DT 28.6mm ST's and 44mm Boom.  With 25mm chainstays (which I have) that I would be interested in selling.

Dave Bohm