I used to like riding my bike in top gear everywhere, including up steep hills. After a few years of this I thought I needed a higher gear. I picked up a second hand bike and used it to create my superbike. This had one fixed gear. The largest chainring on the crankset with the pedals was attached to the smallest chainring on the extra crankset. The second chain connected the larger chainring on the extra crankset to the smallest sprocket on the rear cassette.