jahbikes

Hey All,

Just picked up a tandem frame from my shop's bike-hoarding mechanic for free, which was neat of him given that it looks to be in great shape, has got some nice guts to it and has a fresh paint job. The part that isn't so neat is the helluva time I've had sourcing parts for a build.

Namely, while the stoker portion of the frame resembles a 1970's Atala step thru and will be no problem sourcing parts, the captain's got perhaps the most bizarre bottom bracket shell I've seen to date - threadless and eccentric in appearance, 43mm inner diameter and 58mm shell width.

I'm tempted to assume the captain, like the stoker, is also Atala (and that this isn't a freshly-painted Frankenstein bike) but my thinking hasn't been supported anywhere online in my hours of searching.

So that I can find info on its original build spec or figure out a solution to hang some cranks from this thing, here's my question, no further ado:

Who made this bike? Year, make, model - possible solution to a very rare BB standard so I can ride this thing?

Thank you for the read and I appreciate your contribution.

SJX426 

@jahbikes - Welcome to C&V!
You need to provide pictures of the frame details, bottom bracket, seat clusters, head tubes, fork crown, drop outs, brake bridge, etc. You may also want to visit the Tandem forum.

The front BB looks like it takes an eccentric BB that is common for Tandems. It allows for adjustment of the left side chain.

[IMG]P1010345, on Flickr[/IMG]

T-Mar

It does look like it could be manufactured by Rizzato, who owned the Atala brand. If so, the serial number will be located at the top of the seat and be format Fyyxxxxx, where F is an alpha character indicating the fortnight and yy are numerals designating the year.

+1 to the eccentric bottom bracket., which is very common on tandems.

Bianchigirll 

Does that seatpost come out?

romperrr 

Nothing to be add besides that I'm excited to see this built up.

KonAaron Snake 

So I'm sure that this isn't what you want to hear, but if your goal is to build up a tandem to ride and enjoy, I'd start over. If it's something to be a talking piece and ride it for a few miles, that's another story and you might enjoy it. It's not a tandem I'd put any serious money in to.

The things with tandems is that they're also black holes...they require a lot of parts, but they also aren't worth very much most of the time. This one won't be, almost regardless of how built (I'm trying to be honest and helpful...I know it's coming across negative). I'd recommend buying tandems complete and built as you want from the beginning...there are far more of them out there than you might think and they usually do go for short money.

I know this project seems really cool, but the reality is that it's not going to be a very good tandem for riding and it's going to cost a lot in parts unless you build it up with budget bits and spare stuff in the basement.

due ruote 

Also, I have to agree with the previous post. It's going to take a lot to get it rolling, and I would guess you are going to feel lots of flex in that frame during anything more than puttering about.

corrado33

Here's sheldon's article on tandem sync chain adjustment, including the different types of eccentric BBs.

I'd start there.

Tandem Bicycle Synch Chains

SJX426 

I agree with the others about the ROI. What would be really cool is if he gave you all the unique parts!

As I think of the list, it is hard to come up with nearly anything, other than those things you are in contact with when riding, that are not unique.... OK the RD, FD, rear block and rings. Oh and the front brake cable! Maybe brakes.

When you design for two people on one bike, the design is deceptively different for nearly every part.

jimmuller 

Re the BB, do you have the insert (called the eccentric) or do you see just the shell in the frame? The shell typically wouldn't have threads. It holds the eccentric in place with some sort of clamping mechanism, either a few set screws like SJX426's above or with two bolts which squeeze together a split underneath. The eccentric would typically be threaded for a conventional BB; on our Peugeot both BB's are French. I don't know if eccentrics have standard sizes so finding one could be tough. One nice thing about having an eccentric is that in addition to rotating it to adjust timing chain tension you can also move it side to side some small amount to improve chain line for the timing chain.

Most but not all other parts are generally common with solo bikes. The steerer tube may require a different stem diameter. Fork and HT races will be different. The other tough part could be stem for the stoker which typically clamps to the captain's seatpost. Rear spacing will, be whatever it is but that's easy enough to solve in most cases. I'd suggest touring wheels because they can carry a load.

Be aware that the timing chain typically goes on the left. So you need a captain's crank with spider on the left and a stoker's crank with spiders on both sides. You could just reverse a conventional crank but the pedal threads would be backwards which may lead to them backing out. Check out Bikesmith Design for having cranks made for you.

noglider 

Aaron is probably right. Most tandems don't ride very well because they flex a lot. This appears to have no reinforcements to mitigate that. My tandem is whippy, but we live with it. This looks potentially awful. You should test ride a few to get an idea of what you like.

How does your significant other feel about tandeming? Mine was pissed when I bought it, but she has come to like it. We started riding it last year. We took our first ride of the season on Sunday and had a short and intense ride, which was fun.

KonAaron Snake 

Your tandem is still much better designed, with thicker tubes and more rear space, than this one. It could be fun to ride very casually though.

Darth Lefty 

I'm with @KonAaron Snake. If I wanted to build up a frame like this to ride, I'd use as many classy-looking but modern parts as possible. Tandems benefit more than solos from modern conveniences. It still might come out noodly, and short for the stoker.

gugie 

Burley made their eccentrics threadless, and used locktite to fix sealed bearings into them.

Bianchigirll 

Wouldn't that render the idea of a eccentric BB shell pointless then?

due ruote 

I was having a brain cramp when I posted that. As jimmuller pointed out, the BB shell typically has no threads.

gugie 

The bearings go into the off-center hole in the eccentric, the outer race is fixed in place with locktite (green, per Tandems East instructions). The outer shell of the eccentric is free to turn in the BB shell to take up the stoker chain slack, and locks in place in a variety of ways, depending on the manufacturer.

Some of these are threaded, some not:

Bianchigirll 

^ I know how an eccentric BB works but your post gave me the impression that Burley just glued everything down once the tension was set.

Darth Lefty 

And the key:

Eccentrics available from Tandems East
1. Co-Motion Old Style 68x Size 54mm x 68mm
2. Bushnell 54 mm
3. Santana. All Santana’s are 73 mm width x 54.
4. Bilenky 68 x 54mm
5. Trek Old Style 68 x 54mm Large 5mm Socket head
6. Cannondale Eccentric (stock)
7. da Vinci 54mm
8. Schwinn Twin replacement Eccentric (Limited quantity)

SJX426 

[IMG]P1010047, on Flickr[/IMG]

Which is why I didn't remove it! When I paint the frame, it will be masked off. There are circlips incase the bearing get loose but they are also pressed onto the spindle so....$$$$ for replacement.

Standalone 

I will disagree. (or rather agree with KonAaronSnake's final sentence about only being worth it with cheaply sourced parts.)

I love tandems. We have three and once owned another (a cheap modern schwinn 7 speed chinese hunk of junk, which was still fun to ride.), but two came to us with all key parts and one had its BB. Worth it as a back burner project if you're sourcing parts as they appear for cheap. Maybe not as an immediate build and flip for profit.

My son and I put our road Burley together from a bare frame on a Tuesday morning in New Haven, by midday the next day we were well into Massachusetts on it and home the following day. They're not always terrible to work on. If an eleven year old can do it...

Rear hub spacing, a tandem-specific crankset and the eccentric are your main sourcing issues. Other than that, I think this would be a fun bike to build and ride. Keep the fishing line out for a cheap wheelset, an orphaned eccentric, and a tandem crankset and get it out on the road. If the parts don't show up in the next two years, pass it on. I must have held on to that Burley for five or six years before we put it on the road.

Also, I bought a white Atala step through for my mother to match the one I built up for my father. They had Atalas in the '70's and those were my first road bikes... that gas pipe and 70/70 geo has a special place in my heart.

Sometimes an experience building up a bike is a learning experience that will help you better select a more ideal tandem in the future.

An east coast source for many used tandems for your perusal: https://www.bike123.com/

crank_addict

With a free frame and the dirty work of paint done, the OP is off to a good project. Townie, fun rider, rig it with baskets, picnic family outing type whatever. For parts suggest to hunt for an old beat-up tandem and pull what you need. 27" wheelsets can be found for near nothing.

Ps. Don't be afraid to cold set the frame and fork to meet other wheels / hubs. Modify it to your liking.

noglider 

And also a rear stem.

You may need weird things for the rear handlebar, too, such as bar ends. A friend of mine has wooden balls on the ends of her stoker handlebar.

Standalone 

True that. I have beer can cutouts serving as shims on my Extracycle's rear handlebar, but that is an application where they do not need to be super secure.

jahbikes

To all you lovely people,

Thanks for all your input. I do sincerely appreciate the negative comments as they will constructively influence my decisions. I do plan on a spec of classy, modern vintage parts as one of you suggested. 8-speed, rim brake, no drum brake. I've actually found the rear wheel of 126mm width through a distributor. Unsure on number of chainrings I'll run, probably rig it single like I've seen done by Sycip at NAHBS. I may try and score some OG cranks to add to the story this bike tells, but apart from that - simplistic in build and appearance and will probably only be used for casual, around-town sunny day mileage. Something to look good on, enough to convince my SO, who doesn't ride, to tag along for some fun.

Pricing and specifics:
I work at a shop, so sourcing parts and pricing will be (I hope) a breeze and a good deal, respectively. I will also be building the bike and coming up with solutions to problems that come up myself. As for the specifics of the bike, I'm not confused on what an eccentric is or how it works - the eccentric BB shell on this frame is just a VERY bizarre standard. All eccentric BB outer diameters that I can find are 46mm or larger. My eccentric, yes threadless, BB shell is a 43mm inner diameter, 58mm shell width - if that helps. Took my frame to my pal Jeremy at Sycip Cycles (reputable local frame builder of 25+yrs) and he was baffled and suggested I machine down a 46mm eccentric that looks like it has enough purchase for the cinch bolts to still function.

My main question is in regards to the eccentric bottom bracket - whether there're models out there that'll fit a 43mm I.D. BB shell diameter and whether that narrow 58mm shell width will pose any problems. Or, if you know the frame builder or manufacturer responsible, so that I might get in touch with them or at least find some tech docs to point me in the right direction.

Cheers!