Tandem bicycle drivetrains

Tandems (bicycles-built-for-two-or-more for the uninitiated) are amazing bits of work. More than anything else, a good tandem is FAST. A tandem is not as heavy as 2 individual bikes, does not have twice the rolling resistance and, most importantly, has essentially the same frontal area as a single bike with two, three or even four times the power driving it. The increase in power without an increase in wind resistance explains the use of trips and quads for pacing (rolling windbreak) on the track before dernys came into the picture.

There are at least four different approaches to getting the power from 2 pairs of legs to the rear wheels.

The crossover front (seems to have been popular with French constructeurs):

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The crossover rear (most common):

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And then the 2 reasons for this post…

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The single side rear (a single side front would be crazy – which means it’s been done somewhere). I found the Paketa V2r by googling racing tandem bicycle; after seeing the bike that ends this post, I was curious about what the current road racing state of the art might look like. I’m not surprised that the timing chain (the link between the captain and the stoker) isn’t a chain at all – belts are popping up in applications where the chainline doesn’t vary – singlespeeds and hub-geared bikes, especially. The biggest advantage that single side rigs have over crossovers has to do with cranksets. On a normal crankset, the left pedal/crankarm is reverse threaded. If it were threaded normally, rotational forces would tend to loosen things up. Since 3 of the crankarms on a crossover drive are on the ‘wrong’ side (both in front and the left on the rear on a crossover rear, for example), you need to purchase special tandem cranksets to get the threading right. On a single-side, the cranks are set up just as they’d be on a solo bike; thus, one can use a super light state-of-the-racing-art set of cranks. You give up the ability to use a triple chainwheel setup, but if racing is the goal, one presumably doesn’t need a super low gear. The folks who make the bike shown below make some other claims about their single side setup regarding torque and bearing stress that I have some trouble getting my head around. It seems to me that the stresses would just switch sides, not somehow balance out. That aside – still a pretty dang cool bicycle.

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Finally, the bike that started me thinking about drivetrains in the first place. This tweet led to this photograph:

P9140375

Which led to me learning about daVinci Design’s drivetrain. I’ll quote their website (I like the sound of jackshaft rather than intermediate shaft – feel free to substitute as you read):

The main component of da Vinci Designs’ ICS is an intermediate drive shaft six inches in front of the rear bottom bracket. The intermediate shaft has two single-speed freewheels on the left side that are independently driven by the cranks at twice the rotating speed and half the torque. On the right side of the shaft, four Hyperglide™ cogs drive the bike. The chain rings are half the size as those on a conventional tandem because of the double rotation of the intermediate shaft. The combination of 12-, 18-, 24-, 30-tooth driving gears equals 24-, 36-, 48-, 60-tooth chain rings. *

Wicked smart! Were I to spring for a tandem (good tandems are NOT cheap), this would be #1 on the list with a bullet. I wonder whether you could get away with eliminating the freewheel body on the rear wheel? After all, the captain and stoker are already decoupled by virtue of the freewheels on the jackshaft and keeping the ‘final drive’ rotating all the time would mean that the captain could shift even when no one’s pedalling. Da Vinci – call me. I’ll sign the idea over in return for just one of your gorgeous machines.

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To finish up, some supplementary material in the form of YouTube videos. First, you didn’t think I’d talk about tandems without embedding this, did you?

Some Paralympic Tandem Pursuit action (the stoker is blind or visually impaired). In pursuit races, opponents start of opposite sides of the velodrome and whichever team closes on the other, wins. In this race, there’s a full-fledged catch (5:35).

No tandems in this one, but it does serve to emphasize the importance of aerodynamics and, dang, team pursuit is just about the most graceful thing in sports.

Wheeeeee!

 

Mangrove tank refresh

Wow. The brackish mangrove tank has been up and running for 3 years! In that time I’ve figured a few things out.

  • Mangrove seedlings really do not like to be planted in deep ( > 4″) water.
  • If you are going to keep the tank temperature close to 80F/26C in a climate controlled building a chiller is not necessary, even if the tank is in a window. The only time the chiller ran was when I fiddled with the controller to test it.
  • In spite of all its good points (weight, etc.) I am still not a fan of acrylic for tank construction.

Over the summer I took it into my head to re-do the mangrove tank. I wanted to move it and swap out the (starting to scare me w/ cracks) acrylic tank for a glass one a friend had given me (thanks, Scott). The original tank was 48x18x18, with an 18″ cube at one end housing the filter (6″) and chiller (12″). The new one is 36x18x18 – exactly the same water volume – and as we did the move we’d be able to rotate it 90 degrees so the 36×18 side would face into the room.

brackish aquarium re-do

Getting things ready. Two black mangroves, the tank, filter foam and a foam fractionator  (aka protein skimmer).

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brackish aquarium re-do

Test fitting the filter foam. I set up a modified Mattenfilter using Poret foam. I can’t recommend this rig highly enough. I have 2 freshwater aquaria set up this way (powerhead just recircs back into the tank – no skimmer) and -knock wood- they both work beautifully.

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brackish aquarium re-do

The roots of 2 black mangroves and the planters both will go into. Mangroves and planters courtesy of Riparium Supply – thanks, Hydrophyte!

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brackish aquarium re-do

Old tank drained and moved, new tank in place. The mechanicals – pump, heater, skimmer – are ready, the red mangrove is planted in some muck scooped from the old tank and the substrate is in place. I saved about 25 gallons of water from the old tank – in it goes, along with enough new water to get us where we want to be.

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Voila!

brackish re-do

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brackish re-do w/ archerfish

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brackish re-do

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brackish re-do

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I’ll update as things settle in, meanwhile, there are more pictures here.

The past is not evenly distributed, either.

The future is already here — it’s just not very evenly distributed. – William Gibson *

Thanks to library digitization, access to the past is becoming much more widely distributed. The title of Paul Sholte’s paper says it all: “Using the past to manage for the future: contributions of early travel literature, free online, to African historical ecology”.  From the Wired Science post that pointed me to the paper,

The writings of early travelers in Africa hold more than just descriptions of adventure and unspoiled wilderness. For conservationists they offer a view that can’t be seen any other way.

“Historical accounts are beginning to unravel our understanding of our environmental past,” said Paul Scholte, director of Kitabi College of Conservation & Environmental Management in Rwanda. “It would be an enormous waste not to use these writings, because we don’t have other sources of information from these periods. They open our mind on a number of issues where we lack the historical perspective.”

These old writings have been overlooked for too long, writes Scholte in an Aug. 26 African Journal of Ecology article. They were once limited to patrons of well-stocked libraries. But now, as digitization projects expand their holdings, anyone who can access the web can read the records of intrepid explorers such as the scholarly Heinrich Barth or the noble Adolf F. A. Heinrich, Duke of Mecklenburg. Sites like openlibrary.org, archive.org, biodiversitylibrary.org and books.google.com, are giving conservationists new opportunities to put the records to use.

It isn’t easy to know what an area looked like and which animals and plants were present 100 to 200 years ago. While pollen sample analysis gives some indication of plant communities, and an area’s oral tradition can be valuable, they are both incomplete pictures.

Compared to oral accounts passed down through generations, historical travel records are generally more detailed, more reliable and easier to date. *

One wonders what surprises might fall out of the intersection of digitization (especially of boring stuff – ledgers and the like), smart reader/translation software and data mining systems. I’m thinking mainly of social history here (Braudel/Annales), but that’s probably just a failure of imagination on my part.

Musical interlude: Not Great Men

 

Dusky Grouper

Another example of mining the past for clues about ecological change: “Ancient art serving marine conservation” in Frontiers in Ecology and the Environment - hidden behind a paywall, but Stanford’s press release give a glimpse:

Fishing scenes were not uncommon sources of inspiration for coastal Mediterranean artists. Micheli and Guidetti found hundreds of Etruscan, Greek and Roman artworks involving sea creatures. Fish depicted in mosaics were often detailed enough to be recognizable as dusky groupers.

But unlike today’s animals, the groupers in Roman mosaics are depicted as being enormous – in one case, large enough to eat a fisherman whole.

Though the researchers pointed out that this example could be a case of artistic license, the depictions imply that groupers were large enough to be considered “sea monsters.” By comparison, groupers in unprotected waters today range from 50-60 centimeters (20-24 inches) in length.

Even more surprising, mosaics show men fishing for groupers with harpoons at the water’s surface. Today, this would be unheard of – modern sport fishermen spearfish groupers in deep water. But writings from the time corroborate this Roman view of the grouper as a shallow-water fish – the Roman writers Pliny and Ovid both describe angling for groupers from shore. *

Interesting – even if you discount some of the size difference as a classic and classical fish story, the behavior/biome change seems to shine through. I’ll keep my eyes peeled for additional examples of this sort of mining…

Bodios IRL

Off I went to the South Shore (I think that’s the correct region name) yesterday for a cookout. Not just any cookout, mind you, but a chance to meet Steve and Libby Bodio in the flesh; Steve and I have been corresponding, exchanging links, etc. for quite a few years. If you know anything  about the Bodios, you know to expect a diverse crowd, viz. a herpetologist who studied elephant seals before going into the building trades, someone who dropped out of law school to sell (fine) carpets (and fly falcons), etc. It was a great get together and more than a bit of a milestone for me – more on that in a moment.

 Steve -on the left- chuckling over an anecdote.

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The back of Libby’s head (sorry – photojournalism wasn’t a priority and the one portraity picture I took is not great) and Eric, Steve’s last Massachusetts apprentice (many years ago).

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Note in both photographs the object sticking out to Steve’s back pocket. There’s a story there; I’ll let Steve tell it, but in the meantime guess away as to it’s identity.

Steve hasn’t been east in many years, so there was a lot of year-totalling-up for him to do with old friends. I’m a newcomer – we’ve known each other on line for 5 years or so – not even the blink of an eye comparatively. That being said, I was thinking this morning about how long I’ve known about him… A Rage for Falcons was the first thing of his I remember reading. I may have read essays or reviews before finding A Rage (in Stroudwater Books when it was in the Pic ‘n Pay Plaza in Portsmouth, for you local old-timers) but the descriptions of falconry in A Rage left a mark and rekindled my desire to fly raptors. I went to the bookshelf and pulled the book, opened it and read ‘copyright 1984′. We’re talking 27 years.

Great conversation (Libby and I talked tazis and teckels – where else could one do that?), great beer (thanks, Throwback), and great hosts (THANKS!, Karen and George). What a day!