11

Many two wheel drive mountain bikes exist. Here's one article advertising a new one: There’s been no shortage of attempts to build a workable two wheel drive bicycle over the years, but this latest effort from Double of Japan looks like one of the most compelling yet. https://www.bikeradar.com/news/this-is-a-two-wheel-drive-bike-done-right-sort-of/ They do ...


10

According to Wikipedia, Gold has an "ultimate tensile strength" of 100 MPa, while steel runs from 400 to 5000. (Carbon fiber laminate is 1600.) Gold has a specific gravity of about 19, while steel has a specific gravity of about 7.8. So it would take about 4 times as much pure gold by volume, or about 9.7 times as much gold by weight. A 15 pound steel ...


7

No, no, no. Just no. Two kilometers is only a half-hour walk. That's hardly a big deal. Why risk injuring or even killing yourself to save what can't be more than 15 minutes by the time you've called your friend and they've come to get you. Alternatively, fixing a puncture "in the wild" just needs a spare inner tube, tyre levers and a pump. That takes up ...


7

Trivially: yes, of course you can. You almost certainly won't be able to ride that bike, though. The problem is not the weight of the frame, it's the weight of the rider compared to the strength of the gold. Essentially you have an 80kg rider on a frame that might weigh 20kg if made of gold rather than 5kg in steel. The dominant mass is still the rider. ...


7

Seems like a lot of work for little gain. You'd be able to lighten by the weight of 7 cogs, but the shifting action will suffer. My early megarange was quite bad at the last change, which was 26 or 27 up to 34 You'll also need to install 7 cogs worth of spacers to hold the remaining three in a fixed place on the freehub. And I politely challenge the "I ...


7

The closest to that is the Sachs DD3 "dual drive" hubs that are a 3 speed IGH with a standard cassette mount, available in 8,9 or 10 speed cassette versions. According to this site the ratios in the hub are 0.73,1,1.36 giving 1.86 between high and low gears. That's wider than a double chainring setup but narrower than most triples (a 20/30/40T triple has a ...


6

I take it KERS is "Kinetic Energy Recovery System" which takes energy from your momentum and stores it temporarily, also offering a braking effect. With the intention to use this stored energy for subsequent acceleration. A spinning flywheel on the front wheel may have significant precession effects when spun up. If the rider tries to turn left or right, ...


6

Interesting idea but the front axle (whether is be a 15mm through-axle or a 9mm QR axle) does not rotate, the hub-body and by extension the rest of the wheel rotates about the axel via the bearings. Making such a system where the axel does rotate (e.g. unicycle fork) would require creating a capture system (which is the current function of the QR) to secure ...


6

It would most likely not work without a bunch of expensive finagling. Most inexpensive cassettes come on carriers, meaning removing individual gears is not really that possible. You can still buy individual gears, but they are a more specialty item and very expensive. After you messed with all that, you would likely find that the lower gears tore through ...


5

There have been front drive designs, but all variations I've seen are either impractical, structurally inferior, or both. There is no real benefit to having both wheels deliver power, and that would add a gigantic amount of weight and likely be quite problematic. Imagine needing two separate drive trains that involve separate chains, cassettes, derailleurs, ...


5

But to compare 24 carat gold is just not fair. Bicycles are made of hardened alloys: Aluminium alloy 6061-T6 that is commonly used in bicycles is 6 times as strong as pure annealed aluminium. Steel 1090 alloy is 80 times a strong as iron. Hardened alloys go back to medieval times. Hardened 18 carat gold is about the same strength of Steel 1090. So ...


5

I Designed wire and cable machines for about 10-years and a previous life and have indeed seen your setup many times as a system for maintaining tension on a cable; For that purpose it works great. If all you were trying to do was maintain chain tension at varying lengths, you would have something. But as Carel points out in the comments (and I've spent ...


4

It could be done but would be expensive because you'd need torque sensing cranks. These exist for power monitoring but are priced as a tool for serious athletes. They would give you cadence as well. Then you'd need electronic shifting - also expensive. The actual control could be implemented in any microcontroller of your choice, but you'd need to consider ...


4

As long as you can transmit the force you want to the terrain through one wheel, there is no advantage to driving the second one. As a road biker, I have no problem here. I cannot generate enough torque to break the rear wheel free, so it wouldn't help me at all to drive both wheels. The reason off-road drivers want four wheel drive is that one or both ...


4

As anyone can easily conclude, having a driving front wheel on a traditional bicycle would be mechanically more complex than achieving the same result with the rear wheel. The front wheel is primarily used for steering, that is it rotates around a vertical (almost) axle. Relegating the steering to somewhere else (i.e. to the back wheel) is not an option as ...


4

While I'm aware of the fact the link-only answers are frowned upon in this community, I'd just leave this here. I'm not too sure, but I guess you might as well be able to buy one if you so wish. https://twicycle.com/


3

I don't believe such a device currently exists that you can mount on a bicycle, but there are devices that have characteristics similar to what you seek that you can mount a bicycle onto. They are specific types of bicycle trainers. The explanation is a bit long but if you understand how trainers work and how they compare to the work you do to move your bike ...


3

If you really want that wide a ratio, the widest ratio chainset combined with the widest ratio cassette commercially available would get you very close. There are crank sets that can take chain rings from 22 to 50 teeth (finding a front derailleur that could do this range might be hard), and an 11-40 cassette. Cross-chaining would be a bad thing given how ...


3

Shimano's Alfine Di2 electronic shifting system for hybrids has some ability to shift automatically, although I don't know if it is load adjustable.


2

Say you can keep a 30 kph pace on a flat straightaway. On a hill, that can drop to 10 kph or even less depending on the grade you have to climb. Call it 1/3 of your flat pace. Say that half your run is uphill and the other half downhill, and let's also say that the total run is 30 km. If you run on the flat at your regular pace, it takes one hour to do that ...


2

I think you could do this with a continuously variable transmission and some way to measure the load. You could DIY some pedals to measure with how much force the rider is pushing. The pedals would probably have to wirelessly transmit the data to a microcontroller so that you could adjust the gear ratio, since there isn't really a good way to run wires from ...


2

CVT transmissions using conical pulleys and a V-belt are common on mopeds, scooters, and very small engined cars. One of the advantages is in the name: a continuously variable transmission with literally an infinite combination of gear ratios. Why wouldn't you want this on a bicycle? At least the system on mopeds uses centrifugal linkages to provide the "...


2

If you remove the front fixed pulley the remaining two look a lot like a derailleur mounted upside down. Your rear "fixed pulley" has to be the one that does the shifts, so has to move in an out. The vertically sprung pulley could be that or could be a standard jockey pulley that moves fore and aft to take up the chain slack. Perhaps you should try to ...


2

If the only contact allowed is your feet on the pedals, I do not think it is possible to balance for any sustained amount of time. It only becomes possible when you allow a third point of contact to leverage against, such as a thigh against the top tube. This is because the pedals are offset somewhat from the center of the bike, so you will not be able to ...


2

It's possible, for those who can do the seemingly impossible, at least if you allow the rider to do a wheelie at the smae time. Artistic cycling (YouTube link) seems to be a big thing in Slovakia, and merely riding standing with no hands would be a bit basic for these people, but they do pass through that position a few times (and fixies mean they must be ...


2

It’s possible to stand and roll, I’ve done it, but with knees touching saddle for stability, which is currently against the rules. See YouTube for similar. I wouldn’t rule out someone more athletic than me being able to comply with the rules after practise, for rolling at least. As Daniel points out, the bike must be cooperative, so stable and balanced. ...


2

I have seen that done with monocycles, but I am afraid that doing it with a bicycle is going to be more difficult if not impossible. The reason I think so is that when you stand up and pedal you are also unbalancing your bike right and left. If you do it while holding the bar, you can compensate it in a certain way. (think cyclist standing while going ...


2

4 chainrings seems to be the feasible limit: http://abundantadventures.com/quads.html However if you add an internal planetary gear setup, A 100 speed might be possible if not practical. Here's a 63 speed bike. https://sheldonbrown.com/org/otb.html There are internally geared 2speed front axles. https://www.alphabent.com/internally-geared-cranksets ...


1

Front chainrings are limited to 3, practically by the width. Remember the chain is under tension as it arrives onto the chainring, whereas its under tension when leaving the rear cassette. So its much more sensitive to arrival angles on the front. I've ridden a bike with quad chainring, and it was very bad at front shifting, to the point friction shift was ...


1

When done by a rider on a bike moving a second bicycle, this is called ghost riding and it can be easy or very hard depending on the two bikes and their riding characteristics. Normally the rider would steer, brake and perhaps gear change with one hand, and have their other hand on the middle of the tow-bike's handlebars. Braking is done slowly and gently. ...


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