Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
Outside the bag the box came in.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.



Complicated De-synchronised Tandem

independant tandem pedaling
  (+5, -1)
(+5, -1)
  [vote for,

Most (all? tandems) share a drive chain and synchronised pedals. This has advantages, but also means that both riders have to adopt the same pedaling rhythm and action. Complicated De- synchronised Tandem allows each cyclist to pedal independently, using their own preferred gear and rate of pedaling, both driving forces being added together via a complicated differential style gear box at the rear hub. (hence the complicated part of the title) This means that one of the pair of cyclists may prefer to use a low gear with rapid leg motion to climb a hill, whilst the other wants to use a higher gear, with less movement. Simultaneous cycling action is no longer required.
xenzag, May 30 2016

Tandemonium http://www.popsci.c...1&query=tandemonium
Back in 1992. [neutrinos_shadow, May 30 2016]

hydraulic bicycle (could be multiperson) https://en.wikipedi...i/Hydraulic_bicycle
[beanangel, Jun 04 2016]

Intermediate drive shaft prior art http://www.davincit...om/drivetrain-info/
Different to what you describe but achieves the same result [EnochLives, May 28 2019]


       A dual generator/battery/motor system would be much more flexible.
8th of 7, May 30 2016

       A quick Google search failed to get a useful hit, but I remember seeing a tandem race bike in a magazine many moons ago, featuring shaft drives and a differential to combine them.
A differential is hardly "complicated", considering all the gearing and gubbins that's on a bike anyway. It would fit neatly inside the rear wheel hub.

       (Later...) Ah-ha! Found it at the Popular Science Magazine Archive. There doesn't seem to be a mention of a diff, so maybe I remembered it wrong (or read about it somewhere else as well).
neutrinos_shadow, May 30 2016

       The main problem, of course, is decoupling one set of pedals from the other, whilst still allowing each to contribute to propulsion, and without wasting any of the power.   

       One solution is simply to have two rear wheels - one for each peddler. For aerodynamic reasons, it would be better to implement this as three-in-a- row rather than as a tricycle. This also has the advantage that each rider can sit directly over a wheel, which will allow the frame to be slightly lighter in construction.   

       However, a three-wheeled in-line bike would be quite difficult to steer. A hinge between the front two-thirds of the frame and the trailing third (with its third wheel) would solve this problem, but of course the hinge mechanism will add weight.   

       An even better solution, therefore, would be to have the front and rear parts of the frame independently mobile, but then of course the rearmost cyclist would be riding a unicycle - a skill so difficult that only idiots can truly master it. Fortunately, it would be a simple matter to add an additional front wheel to the rear section of the bike, giving a total of two front wheels, two rear wheels, two frames, two sets of pedals and two seats. Since there are two riders, the advantages of this system are obvious.
MaxwellBuchanan, May 30 2016

       Or the front rider could drive the front whel via a shaft drive, and the rear could use a conventional chain and gears (altho changing gears would be interesting).
8th of 7, May 30 2016

       hub gears, in the pedal sprocket instead of the wheel hub.   

       That's actually a good idea in a regular bike as well.
FlyingToaster, May 30 2016

       Here's a possibly simpler mechanism:   

       Each cyclist's pedals connect to a gearbox (aka an Internal Gear Hub), which connects to a freewheel, which connects to a chain. There's one chain for the bicycle, not one per cyclist   

       The chain then drives the rear wheel.   

       Each cyclist can of course choose whatever gear he desires, and if he chooses to take a break and not pedal, the freewheel will prevent his gearbox and pedals from being forcefully spun by the chain.   

       This can scale up to arbitrarily many cyclists.   

       Also, the chain could be replaced by a drive belt or drive shaft, if the designer so chooses.
goldbb, May 30 2016

       You're over complicating this. You just need a rear tire with a standard derailleur on one side and a mirror image derailleur on the other. One has the chain to the front pedals. The other has the chain to the rear pedals.   

       // hub gears, in the pedal sprocket instead of the wheel hub. // .... // which connects to a freewheel, which connects to a chain //   

       No, the chain MUST be connected to the rear wheel through a freewheel gear. Otherwise if something gets stuck in the chain or it derails, either the tire will lock up and skid or something else will break.
scad mientist, Jun 02 2016

       I like the idea of this idea.   

       hmm, couldn't you use something like an old fashioned steam train governor to allow either pedaler to contribute to the flywheel while only one cyclist controls the speed?   

       Err, two separate bicycles, or would that just be too easy?
not_morrison_rm, Jun 04 2016

       A tandem is always going to be more energetically efficient, because of air resistance, and like for like a tandem weighs less than two bikes - not by much, but it does.   

       // old fashioned steam train governor //   

       Steam locomotives generally don't have governors. Steam traction engines, used to drive generators and threshing machines, do have governors - but they operate by throttling the steam supply, and are engaged only when the engine is stationary.   

       A Watts or a "centrifugal" governor would also have gyroscopic properties, and the mechanism would need to be guarded.   

       A governor like that could be used but it would need a CVT for each power input.
8th of 7, Jun 04 2016

       thinking polymers and fluids, could two people drive as many hydraulic tubes ( squinchers that raise fluid force at one reservoir)) as they like while the drive wheel is motioned from the squinched fluid reservoir?
beanangel, Jun 04 2016

       Yes, but on the scale of a bicycle where the power is no more than a few hundred watts, the losses in a hydraulic system are huge compared to a simple mechanical one.   

       Bicycle transmissions easily achieve 95% efficiency, compared to 85% for the best automotive units; but they are handling 30kW, not 300W, so require oil-bath lubrication.
8th of 7, Jun 04 2016

       //two separate bicycles// [nmrm], make it two bikes with a cabled, articulated linkage between the frame heads - and each set of handlebars steers the other bike.
lurch, Jun 04 2016

       Planetary gear system. Two degrees of freedom. One input drives the planet carrier, one drives the sun or ring gear.   

       Or pneumatic power. Forget hydraulic.
RayfordSteele, Jun 05 2016

       Would pedaling out of sync with the passenger make it harder to balance?
RayfordSteele, Jun 05 2016

       Other than an electron interface, each is going to feel the others input, no matter what mechanical system.   

       I'm for two chains, derailleurs with personal gear ratios to each rider. Two derailleurs makes a sort of double clutch system through the rear bicycle wheel between riders. The rear set, of course, has free wheeling when not driving. And one chain would be longer than the other.
wjt, May 28 2019


back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle