rlong

Hello,
My qustion is about modern frame design. Are the top and lateral tubes continuous from front (headtube) to back (stoker seattube), or, are the front and back diamonds built separately. I'm reading from the Paterek Framebuilders Manual (new edition) and the front, back diamonds are built separately, but I'm almost certain that most builders use continuous top and lateral tubes. Sorry if this is the wrong forum for this question, but I know that some of you are more than capable of answering accurately.

Thanks,
rlong

zonatandem

Co-Motion, Burley and some others use the continuous/pierced tube approach which is more labor intensive/expen$ive.
Santana, Raleigh, KHS and many others prefer the less expensive and less labor intensive method of joining tubesets.
We prefer the pierced/continous frame tubes; we feel it gives a much cleaner look and adds a bit more strength in critical areas.
We ride a custom carbon fiber ariZona pierced/continuous/lugged framed tandem.
Your choice . . . all these things are debatable, but after 30+ years of tandeming that's our preference.
Pedal on TWOgether into 2006!
Rudy and Kay/zonatandem

TandemGeek

As Rudy notes, it's a mixed bag as both methods are used and the construction methods / sequence varies as well. So long as the designer selects the right tubing, the person doing the fabrication knows how to weld, and they have the right size jigs and alignment tables, either method can be integrated into their frame designs. After all, it's the combination of the geometry, tubing material (type, thickness, butting), and joining methods that give a frame it's handling and feel.

IMHO, once you start getting into discussions regarding cost, complexity, and which is better or worse you've be drawn in to the marketing. Interestingly enough, even though Santana uses spliced tubes for most of it's tandems, you'll find that it uses a pierced tube on their most popular model of tandem's (i.e., Aluminum Sovereign) top tubes and while Co-Motion uses pierced top and internals on all of its tandems, at least a few years ago I'm pretty sure they were using spliced joints on the top tube's of its uncoupled triplets, quads, quints, etc...

However, that said, like Rudy I prefer the aesthetics of the pierced tubing -- particularly for road tandems which is what is used on our Ericksons -- but don't mind well-executed spliced joints, which is what are used on our Ventana off-road tandem.

rlong

Marketing aside, and I should say that I am not an engineer, I find it curious considering the forces applied by flex in top and lateral tubes, that anything other than a continuous, pierced tube would be as reliable. My question is spurred by my interest in building a lugged steel tandem, impractical as that is, and assumed the fewer joints the better, plus I to prefer the aesthetics of the continuous tubes. I will have to travel around and look at more of the hand built frames available in my area.

Thank you both for your replies.

TandemGeek

Consider if you will, the most highly stressed areas of a tandem frame are the tube junctions at the tandem's headtube, bottom brackets, and top of the stoker's seat mast.... which are all welded using the exact same methods that a tandem builder uses to splice top and internal tubes to the lower-stressed junctions at the captain's seat tube. A proper weld is very strong and does not weaken the integrity of the tubing adjacent to the welds. IMHO, they are really manufacting and aesthetics issues:

1. Would you rather drill a hole in a long top or internal tube held in a jig and lay down two welds or, do you want to use beefier seat tubes, miter two tube ends, and lay down two welds?
2. Do you prefer the clean look of a pieced seat tube or an uninterrupted seat tube?

rlong

Point taken. Ha!Ha! I feel like I'm back in my graduate statistics class, which I loved, but would occasionally make a most foolish statement directly followed by my mentors carefully thrown eraser and joyfull laugh. I can't believe I forgot about the much higher stresses at the bottom bracket and head tube:-)

So, another newby question; You have used the term "piercing" previousily, and in "1." you asked if I would rather drill a hole in the top and lateral tubes. Piercing is not used literally, correct? I mean with continuous long TB and LT the drilled hole is for escaping gasses from the mitered, beefier ST right?

Because I hope to use lugs as much as possible, and twin laterals (which I failed to mention) the clean look of an uninterrupted ST and TT can be achieved (except at the ST clamp, above the TP).

TandemGeek

Here are photos of the pierced top & internal tubes on our road tandems... they are both literally "pierced" by the smaller diameter seat tube. I've also included some spliced joint photos.

For visual reference, the first photo is of fillet-brazed joints and the top tube is ovalized, making it appear larger than it really is. The second photo is of TIG-welded joints which makes it even easier to see how the seat tube passes through the larger diameter internal and top tubes. The last image -- admittedly a poor resolution scan of the '06 Santana catalog -- shows what the spliced joints look like, where separate fore and aft top and internal tube sections are welded to the captain's seatpost. The last image is of the top tube & seat tube junction on our Ventana which, again, is spliced.

rlong

I hardly know what to say or, where to start. I'm stunned! I'm sitting here looking at my Burley Rock n Roll with "pierced" top and lateral tubes and had a completely wrong vision of how they had been constructed. I thought the ST was mitered and brazed in separate sections. I would never have dreamed that you could bore a 1" + hole through a larger TT and LT then slip the entire length of ST through it. Your pictures were like a revelation to me. Thank you for this posting.

The Santana pictures came through just fine and is a method that I am also interested in for a tandem. So many single bike builders seem to have used this method of joining carbon tubes and I think it would also look excellent with carved lugs. I wonder about the labor involved to keep the short tubes aligned well enough to accept the carbon tube inserts. Talk about a LEGO project! Definitly not for the one off builder I would think. But I'm begining to see that my vision is a little limited by my inexperience.

zonatandem

If you are planning to use twin laterals, be sure to put re-inforcing bridges between the two sets of laterals!
Just running the laterals from head tube to pilot seat tube and then to rear bottom bracket and brazing them in place will not be sufficient. Be sure to add at least one or two bridging tubes between the twin laterals as re-inforcement.
Gitane (and a few others) used to build twin lateral tandems and neglected to put in bridging tubes resulting in a bit spongy ride.
If you add some nice lugs to that, you'll come out with a real nice retro-look tandem!

Pedal on!
Rudy and Kay/zonatandem

ElRey

I didn't really notice a

rlong

Right you are Rudy, plus the bridges are the mounts for water bottle bosses, so you really need quite a few of them. I believe this is part of the reason they were discontinued, due to the intense labor involved even when the bridges were mass produced.

dubbelop

But of course the Dutch bicycle wiseguys Koga saw reason in the 2005 model year to 'recontinue' twin laterals ......



And in 2006 livery:


Yes: the top tube is bent

zonatandem

The Dutch tend to be a bit more practical/traditional design-wise on their tandems. However, having said that, the Koga Myata Twinn Traveller is a real exception to this statement!

rlong

Martin:
I went to their website hopeing to see another view of this bike, alas this is it. I had no idea anyone was producing twin laterial tandems anymore. I don't care much for the marathon look with separate sets of laterals in the front and back, but still, pretty amazing bike.

Not to change the subject, but sometime last Spring I recall a rather extensive article about vintage european tandems used for racing, but I can't recall the publication, or, find it now. I get Velo News, Bicycling, RTR, and Adventure Cycling. Does anyone recall this article? There were a number of excellent pictures included.

TandemGeek

It was probably Jan Heine's article in Recumbent & Tandem Rider Magazine (I don't recall which issue) or, perhaps, in his own publication Vintage Bicycle Quarterly (Vol. 2, No. 1 from Autumn 2003) that discussed his use of a restored 1947/8 René Herse tandem for the '03 PBP. He and his partner were the fastest mixed tandem team in '03.



More photos here: https://www.vintagebicyclepress.com/i...ERSETANDEM.jpg

dubbelop

It sure is. For those who don't know this bike, here it is:



This is indeed a different approach! It's very comfortable and quite heavy at 30 kgs, although with all this equipment that's not even too bad a score. Since the 2005 model year it's foldable, that's why the double clamps are in the middle section. I must say they did a smart job of that feature, because the bike now even sports two small 'pulleys' at the left side where one can store the timing chain when the bike is folded. And this foldability solves a problem that people actually have, which is not usual in marketing

Although it's not for us personally (too heavy, cumbersome handling in corners, vulnerable rear suspension) it's a great success in the European tandem market.

galen_52657

Look at the faces! He is busting his butt and she is checking out the scenery!!!

dubbelop

Well, if you get to know Koga it's not too amazing to find they're using this ancient building technique. This company (that builds really fine bikes) sometimes wanders from the 'normal' paths just to be different, if you see what I mean. In my opinion, this twin lateral design offers no substantial advantages, it only looks different. And I personally don't like the slightly bent top tube. But that's just me ..... you can't argue about taste, as they say. Which is good because the 2006 colors are, well, they attract attention
There is only one thing that I really don't understand about this tandem: it's a 26"-wheeled, properly made and reasonably sized and priced tandem, fit for long-distance cycle camping. So why spec a standard XT rear hub, not the tandem variety with threading for the drum brake?

mrfish

You should know that Marten, the Netherlands is flat - no need for serious brakes. No, seriously it seems like a major omission, though it's the sort of thing that most non-tandemists would overlook until too late.

ElRey

God that is one ugly bike.....

rlong

It could be RTR mag. I can't find issue #18, or anything before #17, so it probably got tossed. I don't get Vintage Bicycle Quarterly, so that wasn't it. Dang, I really ment to keep that to. Thanks for looking.

TandemGeek

I'll check when I get home...

gregm

Is that a parking lock on the rear wheel, at about 1:00?

-Greg

rlong

TandemGeek:
I forgot to ask about those beautiful fillet brazed joints on the two pictures. Are they taken from your Ericson's, the most beautiful tandems built, as I believe they are described by the builder. Wow, those are really smooth! Ovalized top tubes are not too common on tandems are they? How would you describe the effect they have on the ride of these bikes?

TandemGeek

It's issue #18, pps 30-33.
A Look Back At Tandem History by Jan Heine

Back Issues of RTR can be obtained for $5 from:
Coyne Publishing
P.O. Box 337
San Dimas, CA 91773

The color photos of the 7 tandems discussed in that article, along photos of 50 other classic French bicycles are included in this book: https://www.vintagebicyclepress.com/goldenage.html