Stacked N20 geared motor

2021/11/27 Several weeks ago I DIY the N20 type geared motor in serial connection. I expected that the output speed will increase without decreasing the torque. Unfortunately, the result is not as I expected. The speed increased as I expected but the torque decreased (I didn't know what happened at that time). What is the additional power of the second geared motor that goes on? Now I know it may be caused that when connected as serial configuration when rotating the second geared motor worked as a power generator. They will generate the power against the first geared motor. It means that half of the additional power is wasted on keeping the second geared motor rotate at the same speed. Today I will try to connect the geared motor as a parallel configuration. It works very well. The mini N20 type geared motor can provide very powerful output torque. It can be used in daily life at a very low cost. Hope it will give you some idea or help.Please like and share with your friend. Thanks a lot. Have a nice day. https://youtu.be/XoGdlUatrAw