ron van sommeren wrote:Single strand gives you a better copper fill factor.
Which leads to higher efficiency
Higher efficiency does not only mean that the motor makes better use of the batteries' power, it also means the motor is able to handle a higher power input before hitting its maximum temperature mark i.e. a the power/weight ratio will be higher.
Say the motor has an efficiency of 70% and it can handle 500Watt input. That means it can get rid off 30%*500=150Watt excess heat. Now, by cramming in thicker wire (and/or using better stator-iron, segmented magnets), efficiency increases to say 75% (I'm a bit optimistic here). The motor's ability to loose those 150Watts has not changed (by radiation, convection and conduction). This means the motor now can handle 600Watt before it hits the 150Watt (25%*600Watt) losses mark. An efficiency increase of 5% gives an increase in the power to weight ratio of 20% (from 500Watt to 600Watt). That's why efficiency plays such an important role, in any motor design: efficiency governs maximum power. The motors weight may have increased a bit due to more copper.
If you increase efficiency of a 80% efficient motor to 90%, specific power would increase by factor 2, i.e. 100%more.