A few years ago, I had seen Trevor Blackwell's page on building a vehicle inspired by the segway™, which he subsequently followed up with an updated version. I was very impressed but not inspired to build my own just yet.
I went on holiday to Jersey and had a go on a segway there, and I just knew I had to have/build one.
The basic plan:
Build from steel box section, using a minimal amount to maximum effectiveness. Can not use aluminium as cannot weld this myself, but I can use a MIG welder to weld a steel frame together.
Use 20" bicycle wheel with disc brake mount hubs. This allows me to bolt on a sprocket to the standard 6 bolt disc brake mount.
Use 750W motors for upto 1HP rated operation. Use 1:5.4 chain drive reduction ratio to bring 2800RPM down to 520RPM for an approximate top speed of 31MPH.
Use OSMC H-Bridge to drive the motors at upto 160A continuous if needed. Use Arduino to control OSMC and keep the balance by reading a gyro and an accelerometer.