I know it’s just a rendering but those planetary gears look really tiny to be transmitting that much torque. And the test vehicle has only gotten up to speeds of 120kph, or 75mph. That’s basically the minimum speed on my local highways
Sure they do. That’s cause they’re not transmitting much torque at all. They don’t have to. You don’t have a lot of torque anywhere except at the ring gear - and not on the gears driving it. You’re thinking based on traditional drivetrain heuristics, where you might easily be putting upwards of 8000lbft through the axles. But as this eliminates the need for most or all pre-reduction, even direct driving off an enormous electric motor, it’s a way, way less torque than you’d see even on the cv joints of a geo metro.
They didn’t test it to a particularly high torque. The video embedded in the article claims they tested it to 1200nm wheel torque. A Civic type R makes more at each of its front wheels in first, second and third gear assuming maximum engine torque. Not only that but they also claim a 6.241 ratio on the thing so it’s still going to need a fairly substantial input torque. With the specs they posted, it would make for a car that goes down the road just fine, but probably isn’t going to be in any of the fastest categories.
torque is the same across the system of gears, regardless of the lever, that’s why its Newton-meters. In engineering terms, you’re primarily concerned with the shear load on the axles or gears at their specific loading in the power transmission chain. Even with the CV joint or this uni-wheel, the force of engine braking and acceleration is going to put similar shear loads. In fact, I would think other similarly sized gears are subjected to similar loading in differential gearboxes and the actual transmission of most ICE engines. Making gears tough enough is easy. Even in the insane shock-loading they will see as a unsprung wheel assembly.
the whole point of this design is expressed in the video: efficiency.
It doesn’t matter what the longevity or durability of either design is, the problem is that a short axle produces high angles on a CV joint and lowers the power transmission efficiency of the CV joint dramatically. in order to pack the motors close to the wheel, and maintain a suspension system with enough travel, they have to use a different design to maintain the range and performance.
I know it’s just a rendering but those planetary gears look really tiny to be transmitting that much torque. And the test vehicle has only gotten up to speeds of 120kph, or 75mph. That’s basically the minimum speed on my local highways
Sure they do. That’s cause they’re not transmitting much torque at all. They don’t have to. You don’t have a lot of torque anywhere except at the ring gear - and not on the gears driving it. You’re thinking based on traditional drivetrain heuristics, where you might easily be putting upwards of 8000lbft through the axles. But as this eliminates the need for most or all pre-reduction, even direct driving off an enormous electric motor, it’s a way, way less torque than you’d see even on the cv joints of a geo metro.
They didn’t test it to a particularly high torque. The video embedded in the article claims they tested it to 1200nm wheel torque. A Civic type R makes more at each of its front wheels in first, second and third gear assuming maximum engine torque. Not only that but they also claim a 6.241 ratio on the thing so it’s still going to need a fairly substantial input torque. With the specs they posted, it would make for a car that goes down the road just fine, but probably isn’t going to be in any of the fastest categories.
torque is the same across the system of gears, regardless of the lever, that’s why its Newton-meters. In engineering terms, you’re primarily concerned with the shear load on the axles or gears at their specific loading in the power transmission chain. Even with the CV joint or this uni-wheel, the force of engine braking and acceleration is going to put similar shear loads. In fact, I would think other similarly sized gears are subjected to similar loading in differential gearboxes and the actual transmission of most ICE engines. Making gears tough enough is easy. Even in the insane shock-loading they will see as a unsprung wheel assembly.
the whole point of this design is expressed in the video: efficiency.
It doesn’t matter what the longevity or durability of either design is, the problem is that a short axle produces high angles on a CV joint and lowers the power transmission efficiency of the CV joint dramatically. in order to pack the motors close to the wheel, and maintain a suspension system with enough travel, they have to use a different design to maintain the range and performance.