How to calculate and what are the parameters of an electric motor for a bicycle / skateboard?

Question

Electronics

Good afternoon.
I got excited about the idea of ​​​​assembling an electric skateboard (more precisely, a mountainboard), since it’s 7 km to work, partly along forest paths, partly around the city.
I dug for almost a month with the board / wheels itself, the device is assembled, now you need to make the actual electronics.
As far as I understand, I have three items that I need to purchase and combine into a single whole. These are: an electric motor (I want to make two, for both rear wheels), a controller and batteries.
The main problem arises with the engine, since there is not a lot of material on this topic, and there are 100500 options on hobbyking, often not differing in performance characteristics, but differing in price and size.
I would like to get an answer on the materiel, and not just, "I use this."

Answer 1

Let me insert a photo for you
On the topic - buy on Avita with a dead battery and twist the necessary details
www.avito.ru/rossiya/transport?s=1&q=%D1%8D%D0%BB%...
www.avito.ru /rossiya/mototsikly_i_mototehnika?s=1&... After reading
what is available, you can also understand what motor is needed for your weight - the required speed, etc.