Winfried

Hello,

Denmark's BellaBike trikes are unusual with their two front wheel-drive, and the rear wheel that steers.

Empty, the bike weighs about 40 kg/80 lbs. It comes with a Nexus 7 gear hub.

Out of curiosity, do you think it takes more effort to move that bike compared to regular trikes because of the two wheel-drives in the front instead of one in the rear as usual?

Thank you.

thumpism 

Interesting configuration. I suspect turning both those drive wheels isn't significantly more difficult than turning one of them and there might be benefits to the setup.

Winfried

Rather than steering, I'm concerned about the effort required to spin the two front wheels (instead of just one).

Or maybe with "turning", you meant what I just wrote :-p

andrewclaus

The added weight and extra work on turns is probably negligible. I wonder what the added cost is, how reliable the differential is, and if there are any servicing issues.

dsbrantjr

I would think that the 2 front wheel "tadpole" design would be safer against overturning when braking during turns than the 1 front wheel "delta" design.

dsbrantjr

I do not see a differential in the photo, I wonder if both wheels are driven or just one. That silver cylinder is the multispeed hub.

HillRider

I didn't see one either and, yes, that is the Nexus hub. It does seem to be an awkward and excessively complex design. Front steering, even if it has two front wheels and requires Ackerman linkage, and rear drive makes more sense.

JohnDThompson 

I don't see one, either. Without a differential, one of the driven wheels must lose traction in corners. A differential will prevent that, but at the cost of additional weight and mechanical friction.

andrewclaus

The differential is shown farther down the technical specs in the website: Differentialen er vigtigt for en stabil kørsel, standard hos os

70sSanO

The steering (turning) aspect aside, the pedaling effort of two wheels vs. one can probably be realized by comparing a bicycle to a rear drive tricycle.

Rear drive tricycles have been around for a long time and the additional dual wheel weight and if any more effort is needed can give that answer.

John

icemilkcoffee 

Why would they even need a differential? Bicycles have freewheels!

HillRider

If both wheels are driven, the freewheel only allows both to freewheel while coasting but, if it has a solid axle, that would not allow one wheel to rotate at a different speed than the other. Each wheel would require its own freewheel and a separate drive.

In this case the differential seems to be small mechanism just above the brake rotor and driven by the short chain.

Winfried

How does the differential work? Is the magic all into that part?

Is a rear drive trike (delta) harder to move than a front drive (tadpole)?

HillRider

Why are you so fixated on which is harder to move? Given the weight and extra drag I have to think neither style would make any difference.

A differential allows one driven wheel to rotate at a different speed than the other. When going around a corner, the outside wheel has to travel further than the inside wheel so it has to rotate faster. A differential allows this to happen.

Camilo

Tadpole recumbents are generally (single) rear wheel drive and (dual) front wheel steering and braking. The crank goes through a long chain w/ idler to the rear derailleur and cassette. On my tadpole, the drive train, with the exception of the incredibly long chain run, had a common triple crank with derailleur and 9 speed cassette on the rear hub with long cage derailleur.

AeroGut

To answer the original question, the effort required to pedal a bike is almost all due to the total weight and what gear you are in relative to how fast you are trying to go, with a little contribution from wind resistance and rolling resistance. So whether you are driving one or two wheels really doesn’t matter. I presume a cargo trike like that is pretty heavy, though, so it’ll be slow to get moving and tough to go uphill, but that has little to do with driving two wheels vs one.

JohnDThompson 

When rounding a corner, the inner wheel travels a shorter path (smaller radius turn) than the outer wheel, so the outer wheel must be allowed to rotate faster than the inner wheel. A solid axle driving both wheels will not allow that, so the outer wheel will lose traction (skid) in corners. A differential prevents this by allowing the wheels to rotate at different speeds while still transmitting power to both wheels.

JohnDThompson 

Here's a video on how a differential works. It's showing an automobile differential, but the principle is the same: