Here is a video of me riding Skippii’s geared giraffe in front of my house today. It shows my method of mounting it, and an example of some of the speed you can get with it.
My old boss had a giraffe like that, it was insane to ride. I’m no good with numbers, but it was one pedal revolution = 3 turns of a 20" wheel, someone with some brains can work that out It was impossible to mount alone, you had to be pushed until you got up some speed