All the danger of a Penny Farthing, with none of the authenticity. Well in this design of Penny Fakething, there is the advantage that you can dismount forwards, avoiding the 'header' type accidents common with a traditional Penny Farthing.
A modern take on that classic bicycle design.
Step 1: Starting the frame
Select a scrap frame & forks. Cheap 'gaspipe' MTB frames are easy to weld. Remove the forks and assess how it will go together.
Step 2: Bending the forks
The forks will have to be bent to match the frame. Forks are tough, so use levers to bend them.
IMPORTANT: Unless you are tall (like me) you may need to bend the top-tube and down-tube of the frame in to make it smaller - in this case you will have to cut the frame first.
Step 3: Cutting the frame and forks
The frame & forks can be cut so that they fit together. A normal hacksaw can be used, or a pipe cutter.
Step 4: Joining the frame
If the sizes of tubes that are to be joined are a match, then a short piece of smaller tube can be used inside them as a ferrule to help line the joint up and add strength. If the sizes don't match, then one tube can be welded inside the other. This will make a less attractive weld, but, so long as the weld is strong, you can fair the shapes with car body-filler (bondo).
Step 5: The Armature
The armarture, or spine, will need to be made from strong tubeing. I used 40mm ERW steel tube - this is probably the minimum that you could get away with.
It was bent using a hydraulic tube bender. If you are lucky, you may find some scrap that is already bent to a suitable shape.
I welded the headtube in before I did the second bend, so that I could assess the shape more easily.