[vlachen]

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.

[esperent]

> 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%?

[vlachen]

Depends on the seal manufacturer. Those numbers are usually provided through their engineering data system. Their data will be fit to a particular tolerance for seal race surface finish, which will be influenced by the reality of manufacturing.

[esperent]

Right, but are we talking closer to 5% or 50%?

[vlachen]

Allow me to embrace my engineer nature and hedge my bets. A contact seal of that size is usually specced for a power transmitting shaft. An (assumed) 20" shaft is going to transmit a huge amount of power. So much that the seal losses will be negligible. Those same losses would exist on any shaft/seal combo of that size, but would take a greater fraction of total motor power, given the size and power constraints given by an internal motor design.