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Donut Lab's next-generation in-wheel motors

donutlab.com

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Re: Donut Lab's next-generation in-wheel motors

#21

Post by Neywiny »

exabrial wrote: post #18

There's a concept called "unsprung mass", which basically destroys handling of all vehicles from race cars to trucks. Basically the greater the unsprung mass, the harder it is to damp the input into the suspension because of the inertia of the moving suspension components themselves. An ideal suspension has zero undamped mass, and all input to the suspension is a direct result of contact with the surface the vehicle…

There's also the inertia problem where it's harder to accelerate mass that's further away from you. The classic spinning ice skater demo. This feels physically disadvantageous. Hopefully I'm wrong though, the more competition in spaces the better.

Re: Donut Lab's next-generation in-wheel motors

#22

Post by anamax »

vlachen wrote: post #6

I spent a number of years designing outer-runner direct drive permanent magnet motors for industrial equipment and I've got some questions. Cheifly, bearings. They're not shown in any of the oh-wow images, but these will likely be the most expensive component of each motor. Big bearings are expensive, and to accept the loading of normal wheel operation, these will have to be pretty beefy. That's not even discussing o…

Does "suck up huge amounts of power" for a seal imply "generate lots of heat"?

If so, is that heat another issue or is it a "don't care" because the heat is over a large enough surface?

Re: Donut Lab's next-generation in-wheel motors

#23

Post by vlachen »

anamax wrote: post #22
vlachen wrote: post #6

I spent a number of years designing outer-runner direct drive permanent magnet motors for industrial equipment and I've got some questions. Cheifly, bearings. They're not shown in any of the oh-wow images, but these will likely be the most expensive component of each motor. Big bearings are expensive, and to accept the loading of normal wheel operation, these will have to be pretty beefy. That's not even discussing o…

Does "suck up huge amounts of power" for a seal imply "generate lots of heat"? If so, is that heat another issue or is it a "don't care" because the heat is over a large enough surface?

It absolutely matters. Every Watt of energy that doesn't become torque at a rotational velocity is just heat.

Contact seals work by contact and friction, friction generates heat proportional to linear velocity and linear velocity goes up proportionally with radius.

The motors I designed were intended for food production washdown areas, and if I were designing large motors for use in road environments, I would use a lot of similar methods, including high quality contact seals.

Teflon seals would probably have the required capabilities, but they will get destroyed by dust and grit. Nitrile seals would do it too with the detraction of a huge power loss at the seal. I wouldn't trust a plain labyrinth seal to do the job.

Re: Donut Lab's next-generation in-wheel motors

#25

Post by m463 »

lelanthran wrote: post #17
notjulianjaynes wrote: post #9

Earlier quoted context omitted.

If the weights are listed on the are to be believed, this shouldn't be an issue. It says 40 kg for a 21" wheel. A quick Google is telling me that a regular old steel wheel from a truck of the same size is around 50 to 80 lbs (23-36 kg). That said, I was already thinking 630 kw per wheel was a pretty incredible claim before I realized these are apparently not much heavier than a non-mptorized wheel. These have to be s…

> If the weights are listed on the are to be believed, this shouldn't be an issue. It says 40 kg for a 21" wheel. A quick Google is telling me that a regular old steel wheel from a truck of the same size is around 50 to 80 lbs (23-36 kg). I'm skeptical; They say 40kg, but I think that's just for the motor, not the entire wheel. I working off the (maybe incorrect)[1] assumption that the 40kg doesn't include the steel/…

A regular wheel is about 12kg bringing wheel+tire to ~25kg

At these weights, I suspect the vehicle won't handle as well as a vehicle with the motor offboard.

Re: Donut Lab's next-generation in-wheel motors

#26

Post by ajb »

More on their design can be found in their patents, https://patents.google.com/?assignee=verge+motorcycles&oq=as... Although that may not be their most recent work due to how long patents take to get published.

NB reminder that your employers legal policy may be to never look at patents.

Re: Donut Lab's next-generation in-wheel motors

#28

Post by esperent »

vlachen wrote: post #23
anamax wrote: post #22

Earlier quoted context omitted.

Does "suck up huge amounts of power" for a seal imply "generate lots of heat"? If so, is that heat another issue or is it a "don't care" because the heat is over a large enough surface?

It absolutely matters. Every Watt of energy that doesn't become torque at a rotational velocity is just heat. Contact seals work by contact and friction, friction generates heat proportional to linear velocity and linear velocity goes up proportionally with radius. The motors I designed were intended for food production washdown areas, and if I were designing large motors for use in road environments, I would use a l…

> Every Watt of energy that doesn't become torque at a rotational velocity is just heat.

Do you have any rough numbers to put on this? If there was 1000w of electrical power going to a wheel like this, what kind of heat loss are we talking? 5%, 10%, 30%?

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