Bought a HG-1 early this year and have been working on how to motorize it. Here it is after few months working and it is really close to what I want and what I want it to look like.
Added two holders to hold the motor in the case with real time rpm display and changeable speed from 15rpm to 80rpm. Easy to install and no any damage or change the factory alignment during installation.
Recently see a topic in socraticcoffee investigating relationship of rpm on ground distribution. Seems like changing rpm can be one of the playable parameter in making espresso, will try to do some simple test in the future as I don't have those equipment to test it in professional way, and the range of my machine now is a bit narrow from 15 to 80rpm. But I think as HG-1 is designed for hand grinding so even in the future I will at most slightly increase the range up to 100rpm or 120rpm. Now I mainly stick to 40 to 50rpm when making espresso and everything just looks so great!
Just to share how lovely it is, now it is with 120w motor, in 220v providing constant torque on any rpm.