Why ?

also what about salvaging electric motors from cordless powertools? Especially moving into the lawn and garden arena, there's some pretty solid units out there.

15-20

FACTS

Only specs I can see are on the LMT website. In this case that wouldn't make more sense as it would be more inefficient, meaning less sense. I will answer your question and also give advice. Based on my understanding of motors and generators, and also a basic understanding of engineering principles and limited physics knowledge. Electric motors are highly efficient and output is relative to input minus say 10%. This means that regardless of the design of the motors, the output is almost equivalent to input. So for a given motor size/type, a high rpm motor will have less torque but the same power will be consumed when compared to a low rpm high torque motor of the same size/type. 10kw in = 9kw work done. When using electric motors it's important to understand the operating conditions. Eg Don't pick a low rpm motor if you need high rpm. Efficiency is important! Adding gearboxes will substantially reduce efficiency and therefore output. Cost and complexity increases as well as the size of the motor and batteries required. This means weight increases too! Adding gears is inefficient and costly if the motor can be engineered to not need it. The transient spike in power to increase the the speed of a gearbox is also a considerable factor at these rpms. Ie centrifugal mass. For this application the compressor needs to spin at very high rpms. It is very difficult to spin electric motors at high rpms as balancing and centrifugal limitations are reached, as well as other factors. The load the compressor is generating seems substantial also. In the background there was a 3 motor design. I assume this was abandoned due to cost, weight and heat? Questioning the sense of someone's work directly can be confronting. If you intend to attack, I find the best way to undermine someone is to ask questions and let them realise they're wrong. So, when asking questions it's polite to fraise them in a way that shows you want to understand more. Perhaps a better way to ask your question would be, "why have you chosen to not use a gearbox?" or "would a lower rpm / higher torque set up be better? ". This way you can learn or let them learn and everyone wins :)

Rising blue