2.- since the board can only get 5v max,
Motors do not deliver force, they deliver torque.
my purpose would be have a motor with a torque able to pull 15kg
You need to factor on the friction it will take to move your load. If your 15kg is sitting on a good skataboard on level smooth pavement, then a linear force of .1 kg might be needed. If the 15kg is mounted on a rubber mat, a linear force of 20kg might be required to make it start moving. If you are lifting the weight, then you would need a motor that would develop more than 15kg-cm while winding a lifting cord being wound on a 2cm diameter shaft.
yes horizontal and wooden surface, without much atrict/friction, just normal floor.The wheels, just normal rubber wheels, that you find in most robots, the plataform itself gonna be a cube with less than 50cm.
Do you realize that the second sentence above adds entirely new information. Before that people had been assuming that your 15kg load would be sliding along the surface with all of the friction that that entails.In your second sentence you tell us that there will be wheels which should reduce the friction enormously.
yes horizontal and wooden surface, without much atrict/friction, just normal floor.The wheels, just normal rubber wheels, that you find in most robots, the plataform itself gonna be a cube with less than 50cm.EDIT: its only a plataform that moves forward, backwards, or sides, tranposrting a bucket on top.
precisely for this I added that info. and that's all,