A skilled mountain biker can traverse some extreme terrain, but [The Q] thought there might be room for improvement, so he converted a fat bike into all-wheel drive.

The main challenge here is to transfer pedal power to the front wheels, especially around the earphones. [Q] Solved this problem by effectively constructing a difference from the parts of a very old electric hand drill. Since the front wheel needs to rotate at the same speed as the rear wheel, a long chain is coiled from the rear wheel to the earphone, and is pulled tight by a pair of derailleurs. This front sprocket rotates a series of spur gears and bevel gears arranged around the earphone, and transmits power to the front wheel through another chain.

It will be interesting to feel the bicycle riding on soft sand, mud and rocks. We can see that it has some advantages under these conditions, but it is not certain whether it is enough to offset the weight and complexity loss. The additional chains and gears must seem to be required to capture leaves, clothing, and even skin. However, we suspect that [The Q] is more likely to do so to challenge the construction, and we can certainly appreciate this. With the rise of electric bicycles, adding a hub motor to the front wheel seems to be a simpler option.

Over the years, we have seen several interesting bicycle hacks, including the strandbeest rear end, 3D printed tires, and automatic gear shifters.

good. The main problem will be friction. Riding will be more difficult. You have seen him pedal very hard even on almost level ground.

But it's a good try anyway. Although metal guitar is not my background music choice. Fortunately there is a button. :-)

Yes, interesting build-but definitely some practical problems (not that I have a better solution). Pedaling is not a completely smooth torque transfer-you may (?) struggle with turbulent torque steering, and the harder you push it, the worse it gets. The front tires may want to wash off in the corners-because the spin is not enough to keep up with the rear wheels. It may be suitable for cycling on the beach, but other than that, it seems to have many shortcomings.

Not sure what we can say, there must be additional friction, but we don’t have dynamometers, contrast lenses, etc. Anyway, riding on a soft surface requires more work-this may actually be easier to ride on than previous bikes Riding modifications on a soft surface.

I hope you are right, it's certainly not a system that makes sense on a more ordinary riding surface, but it might actually work better on the annoying soft sand.

You can estimate that each gear contact or chain loses 3-5% efficiency, so if you use two additional chains, two gear contacts, and an additional derailleur, you might see 20-30% Loss or 25-42% of the workload increases through the front-wheel drive power.

This is also a criticism of bicycle hub gears: compared to throwing the chain on different sprockets, the planetary gear contact in the hub will increase the loss-even though the chain does not run in a straight line between two aligned sprockets, it will also increase the loss. , Because it needs a looser chain to allow the tolerance of lateral movement, and it will collect dirt and rub against itself (wear faster).

You can estimate, but is it realistic? As Foldi-One said, we don't have any measurement method, it may still be more effective on soft surfaces.

In fact, I also agree that it may be worse.

We just don't have any way to actually judge, and because the soft sand is too difficult to ride, I hope many of us know this, it seems to be helpful.

I probably shouldn’t say “more effective on soft surfaces”, but “more effective on soft surfaces” may be better. I have never rode a bicycle on the beach (I remember), and the closest thing I have experienced may be snow and ice. I suspect that having a powered front wheel will make handling on ice worse, just because it has been close to the limit of traction. I can imagine that riding a bicycle on dry snow will use the power front wheel much better, pulling the snow a bit and being pushed into the snow, which may be similar to sand.

Jeep built this a long time ago. All gears are driven internally through the frame.

Why not put a brushless motor with a beautiful battery pack on it, just like the old rack at the back, if you can sell a few of them? David Medway

Reopen it at 2:47 to get some sweet sour licks

Rokon has been producing two-wheel drive motorcycles. I want to know how their front wheel mechanism compares with this one. Cool stuff around. Hopefully turning with the power front wheel will not just hit you to the ground with torque steering.

If I were them, I would use a hydraulic motor and connect it to the pump driven by the motor with a hose. This will allow the hydraulic pressure relief valve to limit forces, especially from unmatched tire circumferences when on the road. If two-wheel drive is not required, it also allows the bypass valve to be used to completely bypass it to allow a certain amount of idling.

IIRC This was tried in the conceptual model (20 years ago?), but the resistance loss of the hydraulic fluid is so large that it is impractical. I heard that they are called friction loss, but when we talk about oil in nature, this seems to be a strange choice of words. Shear force, maybe? In any case, the loss is much higher than any chain drive loss.

Some of our mechanical engineering colleagues may be more suitable to elaborate on the exact details of hydraulic loss.

For hydraulic excavators, it is not a big deal to overcome these losses with huge pumps and diesel engines, but for some things that you have to handle by your own strength...

PS: Mainly talking about bicycles, but still may be applicable to motorcycles to a large extent

"Viscous shear and turbulence loss" will not roll off the tongue...

The main challenge is that unless there is a lot of slippage between the front and rear wheels, any difference in tire circumference between the two will put a lot of pressure on the intermediate components.

Indeed, this is equivalent to a 4×4 bicycle, which has been stuck in the 4WD and has a differential-less transfer case. It is a good idea to use a slip clutch on the front drive to ensure safety.

It actually has one-there is a tensioner on the chain that carries power from back to front. If the force rises, this will cause the chain to skip teeth.

Not what I expected when reading the title... I have been thinking that it might be possible to use a 2WD bicycle with an "electric axle" drive system-these are usually used on ships and are basically electromechanical tuned generator and motor pairs. They are directly connected to each other and transmit power with a fixed "gear ratio". This will be a mechanically simple and not too heavy way to transfer power from the pedals of the bicycle to the front wheels. Of course, in most cases, 2WD bicycles do not have a huge traction advantage over ordinary RWD bicycles... If your traction is exhausted, then you are either in the slippery mud and are at serious risk of falling, or In any case of climbing in this situation, you are more likely to be restricted by wheels or transmission than by traction.

I have ridden a similar 2wd bicycle, made by a man named Jon Lebsak in the 1980s. He seems to have disappeared from the earth, but he once ran a bicycle shop and produced a series of bicycle cycles called Vertebrae. His design wisely uses a straight pull (no derailleur for slack) chain on the tension side. This design with two derailleurs can handle wheel travel deviation and prevent the bicycle transmission system from tangling under tension, but it means that the front wheel cannot withstand a lot of power because it only pulls the derailleur to full extension (And possibly hurt it) before the wheels start to slip. But the interesting thing about a front-wheel-drive bicycle is that you can roll directly onto the curb as high as the wheel. If you drive very slowly, so it won’t bounce back, it will climb straight up. It will climb a set of stairs effortlessly. I have never tried it in severe off-road conditions, but if it behaves there like it does in the parking lot in front of a bike shop, if you are not good at it, it usually stops the work of the bike’s erosion rod Wheel type/manual/hops. I have a paper plan to use a 3-speed rear hub at the front and modify one of the three speeds to open instead of gears. This way you can ride 1wd most of the time. When you encounter a big obstacle, you will switch to the second one, which will be an overdrive and eliminate the slack of the system, and then down to the first one, which will It is 1:1 with the rear wheels and ready to climb. What Jon did, which I think is a better idea, is that he connects the tension wire to the gear on the bearing, where the front edge of the gear is directly aligned with the centerline of the head tube, and he uses profile or mongoose offset struts The front fork, so the chain line can extend directly down the front fork line to the second gear. In this way, the tension line will never change in position during the turning process, but only twists and does not require any length compensation. (Means no front suspension.) The return line has an elastic idler to handle slack changes because it is not a zero-offset chain line.

I also found this link: http://www.ihpva.org/HParchive/PDF/30-v9n2-1991.pdf Please refer to the page starting from 11.

I don't understand the need for a second treatment in terms of tension. The distance from the front sprocket to the rear sprocket will not change, and the amount of chain winding on any gear will not change. There should not be enough changes to be aware of, any excess will be transferred to the slack side.

Technically, they are not derailleurs, because they do not derail the chain from one sprocket to another-they just act as a tensioner.

A large number of exposed sprockets and chains can secure your pants or other parts.

Now I can also grab my shirt with a chain!

In the past, I have made quite a few lawnmower-powered bicycles, and I actually admire the way he arranges the chain so that he uses only a jack and an additional derailleur for steering.

In other words, NOPE. 30 mph on the 10-speed flat road is scary enough, is this monster off-road? There is not enough beer in the world to make it look like a good idea.

He is not building a differential. If he has, it may be okay. When a bicycle turns, the front and rear wheels need to rotate at different speeds. However, this is just a fixed gear set that uses bevel gears to transmit through the head tube. This will not cause the two wheels to spin at different speeds.

But the power-transmitting chain and its tensioning system should allow them to move at different speeds. If it is involved, it will take up some differences in the tensioner, and then if the imbalance continues, the chain will skip.

But because the tires have a small contact area and light weight, I expect it will only wear them faster, and then scrub them on the driving surface in turns.

Bicycles should perform well in the coming ice age

Therefore, when the bicycle turns, the two wheels *must* travel different distances: at the end of the turn, the front wheel turns more than the rear wheel. always.

So what will happen here? Will it tremble and lose grip like a locked differential 4WD?

Think I will cheat and use the electric motor in front. Not very strong, just at the auxiliary level. The spoke sensor at the rear can drive the speed, if the front is only increased a little overspeed. Of course, it will not meet the requirements of competition. Unless the throttle is turned, it can even be set to flywheel. It is recommended to use regenerative braking. The limited-slip clutch can be added to the mechanical version and operated by the hand brake mechanism, which can remain engaged or turn freely again...or pull the lever to engage, because your hand will not pull the brake lever when climbing. You don't always need 2WD. This is a good start... Honor! He has a platform, which can be patched now. The steering can even be achieved through the hinged frame. This may make the drive simpler. Brainstorm, guys--

This is what I expect to see while waiting for the image to load-

It's done, but I still like people doing things for fun.

I am more interested in the effect of steering and suspension forces. The feedback from the road motorcycle world is that it creates a very unnatural feeling and locks the suspension fork in some cases, but definitely improves grip and cornering, more than power loss.

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