PMK

A one peice all carbon bar, captain seatpost, and stoker stem would be real easy if all the dimensions were finalized.

Carbon post, carbon bar and a short length of carbon tubing. Miter the tube to the proper angle and radius, plus length. Tack it together to verify, then wrap it like a Calfee.

Doing this in aluminum is not a smart idea unless you can accomplish heat treating the aluminum after welding.

PK

zonatandem

Get realistic!!!
The words Beyond/reasonable/ lightest/realistic do not belong in the same sentence!
Even if you work for Bill you'll need to drill holes in that Beyond frame and components to get t under 20 lbs to achieve what you would like.
Back in 1993 when Beyond first came out we were at a tandem rally in Wisconsin when a team showed up with a spanking new Beyond.
Everyone ooohed and aaahed . . . yup, a real nice looking bike!
The Beyond's owner came over and asked 'What are you riding? Can I pick it up?" He picked up our custom c/f Zona tandem and said "Oooh sh*t!! What's this thing weigh?" Told him ' 26 1/2 lbs." That took the smug look of his face!
40,000 miles later we are still riding that 'Ooooh sh*t!' tandem.
Photos attached. Photo #1 : 2003 new Zona @ 26 1/2 lbs. Photo #2 : 40,000 miles . . . (and Smiles!) later.
Good luck with your project!
Pedal on TWogether!
Rudy and Kay/zonatandem

zonatandem

A couple ideas for your uber-lite tandem:
Single chainring (eliminates front der). 48T chainring (smaller/larger to suit your riding style). Believe Sram has an 11x40 mt.bike cassette and proper rear der. Saw a setup like that on an off-road single bike. Can still give you 32-117" range.
Eliminate eccentric; not really necessary. If chain goes slack, replace it.
Smaller crossover chainrings. Have successfully utilized 28T TA rings; lighter than 34s and also requires shorter chain. Did that on our custom 1977 Assenmacher, which at that time weighed a mere 34 1/2 lbs when 'light' tandems were weighing in at 48 lbs.
Grainy photo attached.
Must declare we are a small statured tandem team (sub 250 lbs), 5'7" pilot and 4' 10 3/4" stoker.

Good luck with your project!
Rudy and Kay/zonatandem

LelandJT

The large stock Beyond frame weighs 2930g making it lighter than Calfee or Co-Motion. Paketa is hard to get weights out of but might be a little lighter. My frame has some custom touches that I hope will make it 2700ish grams. That should be the lightest large road tandem frame I've heard of. I think Beyonds were shown in 2004, released in 2005.

Ritterview

Interestingly, I have the unpainted weight of my Size L/M Calfee Dragonfly as 2930 grams as well. When we had ours weighed in the Santana booth in 2010 at Solvang, it was at 25.12 lbs the lightest tandem they'd yet weighed.

I think a Landshark frame would be lighter still, as there is less aluminum in frame and the joints haven't the Calfee's bulbous wrap.



Say NO! to drillium!

zonatandem

LelandJT: I stand corrected on the year of the first beyond. . . . we attended that WI rally in 2003.

fietsbob

same thing .. Carbon Track tandem . Ti, Carbon , Magnesium Beryllium ..& nothing weighs less, than a part Not installed .

LelandJT

That Landshark looks sick. I'd love to fondle one in person but for now I'm gonna peruse their website. As for drillium: sort of...

There are holes in the headtube and both BB shells where the other tubes meet them. They aren't as big as they can be so I had the engineer use a sharpie to outline the largest he thought they could safely be made and I put'em on the mill. Our frames are engineered to stand up to heavy couples with a rack and bags so with that in mind and the fact that we'll be a sub 300lb couple with no bags and only 3 bottles I butted the headtube and increased the butting in the BB shells (again, to the engineer's specs). I shaved the rack eyelets off the dropouts, won't be putting a disc caliper mount on the chainstay, and not installing the upper captain's bottle mounts. I'm using the carbon seat stays that lack V-brake studs* and did some cutting and shaving on the cable guides. I went though the piles of tubing and selected the lightest example of each tube (even though the variations were pretty small it adds up to just enough to be worth it). I'm gonna make the chainstays around 16.3" instead of the usual 17" and finally the seat tubes will be an inch shorter than on a normal large since the carbon seat posts I have are really long.

End result? I'm hoping for sub 2700g which would make it the lightest road tandem frame I've seen that will fit a 6'2" captain and 5'10" stoker. We're gonna be a climbing force! Now if the longshoremen would quit it with their "work slowdown" and get back to their overpaid job of uncrating my chainstay tubing I could get this built before our January Arizona rally. At the very least I'll be riding it and lending it out (to light teams) at our Mississippi River tour in April.

I did the math and it looks like using our carbon cranks and Shimano Octalink BBs leaves 520ish grams on the table that a set of Lightnings would take off. However, those Lightnings would have to come out of my pocket so it's probably not gonna happen. I may have to settle for a 22lb tandem that's custom fit and specced for me, first world problems

*The large Beyond frames I weighed (they ranged from 2930 to 2960) all had Ti v-brake stays and disc mounts so I guess the kind of frame weights factories usually claim would be for a medium, carbon stay, non-disc frame. Probably 2750ish?

zonatandem

If you are planning on an eccentric, about 10 years ago we tested a prototype C/F eccentric that weighed then just under 100 grams. However it had some issues during our testing and the project was shelved. Not so an adjustable stoker stem and stoker handrests that saw limited production.
If you are willing to spend extra $$ anything can be done.
Heard of a local guy that had a cassette made of carbon fiber. Lighter, sure; but did it hold up?
We prefer/design our tandems for every day usage and have had fun riding TWOgether for 240,000 miles.
Pedal on !
Rudy and Kay/zonatandem

LelandJT

I've got a prototype magnesium eccentric, 101g. It's got a cool coating on it to prevent corrosion that is supposed to be able to handle the set screws digging in but I'll be keeping an eye on it. For reference the regular Santana eccentric weighs 124g plus the two small steel set screws in the frame.

DubT

Our small/small Calfee Tetra frame weighed 3183 grams, however that included the Enve fork, the Chris King headset, the Bushnell eccentric and the seat post clamps. Somewhere under 2700 grams for the painted frame.

The DaVinci cranks are fairly light and less expensive than the Lightning cranks.

Ritterview

The DaVinci cranks are square taper. The Fairwheel crank review found that in comparison to modern outboard bearing hollow spindle cranks, the square taper 2006 Campy Record to be both the heaviest and flexiest.





If you want an inexpensive square taper tandem crankset, check out the Stronglight Z'Light. Its also better looking than the DaVinci, as seen on this Cherubim.

LelandJT

I'm pretty happy with the used Santana carbon crankset I was able to grab off the shelf for free. Its weight breakdown is:
Capt crank: 183g
Timing cranks: 252g ea
Drive crank: 254g
Bottom brackets: 293g ea
Total: 1,527g

Lightnings weigh 990g, so 1.2lb lighter. This is the only "upgrade" crank I'd consider as I don't think the others provide significant weight savings and are flexier than what I have.

If it helps to compare weights, our 40t timing and 39/53t drive rings with alloy bolts are 267g so 1,794g for a "complete crankset". Also remember to figure in the 73mm shell and wider axle spacing needed for the 160 rear end.

waynesulak

I have found on steel Santana tandems that a wider BB is not needed. I have run square taper BBs from 106 to 126 with daVinci cranks without a serious problem. The chain line and access to smaller cogs in the middle ring is limited with the shorter BBs however it shifts well. Chainline can also be changed a little by using older or newer 160 mm hubs. The newer ones place the cogs a 4-5 mm more outboard than older hubs.

This may be because the steel chainstays are narrower than aluminum or Ti which I have not tried. If anyone reading this has stoker Q-factor issues then there may be options. Crank arm clearance is the limiting factor to narrow BBs.

delcrossv

Ahem:

LelandJT

^And people think riding stoker on a normal tandem requires a high level of trust...

PMK

Agree

PK

PMK

As for cranks and that subject, has anyone ever run Middleburns on a road tandem?

PK

twocicle

The Fairwheel crank test does not appear to directly test or discuss pro/con of square taper axles. They do provide a clear graphic which focuses attention to specific crank arm stess/flex areas and they apply a single plane strain gauge for their testing.

I do believe that historically there were tests done that showed progressive improvement from square taper to isis/octalink to 24mm hollowtech/mega to BB30 and so on, but this particular article does nothing to address that area.

It would be interesting to see data specifically for the daVinci crank stiffness (and whatever current BB options are out there) because those cranks do have some positive characteristics (low q-factor, multiple/swappable spider configurations, low weight, reasonable price point).

LelandJT

After a lifetime of riding and working on bikes I can decisively say that square tapers are inferior. Even though ISIS/Octalink use smaller bearings they at least eliminate the wallowing/oversizing/loosening that often happens to square tapers. If you are a bigger or stronger rider the flex in a square taper BB axle (even a short, solid steel one) is obvious. The 24mm and 30mm spindle external bearing cranks are definitely the best.

colotandem

So what's the verdict?

Inquiring minds want to know.

Bad1

Maybe the reality $$$ of building a sub 20 pound tandem, smacked him in the face?

colotandem

Still no update?

With all the "what does your tandem weigh" thread updates, I have been wondering when we will here from LelandJT and his extralight Santana Beyond...

akexpress 

We had the privilege of riding with (well sort of) Leland and his girlfriend this spring. His bike is light but it doesn't matter as the motors on top are much more impressive. We were riding with the fast group and they would come flying by and drop all of us like flys. I would not want to ride with his full carbon seat either but it works for them. He is a nice guy and they are a nice couple. I had some nice bike discussions with him and he is open minded about all of it.

zonatandem

Back in 2003 had our custom c/f Zona built.
Weighed in at 26.5 lbs ready to ride.
Still riding it 40,000+ miles later.
Have changed some componentry as it wore out.
A Beyond at 20 lbs . . . get real!
Pedal on!

Rudy and Kay/zonatandem