A number of plans for building a pole lathe exist. Most folks adapt the designs they see to suit the materials and circumstances they have to hand.
The beauty of making a lathe from wood is that it is easy to modify or otherwise chop lumps off it. Trying out a new idea can consist of sawing up an old floorboard as a prototype and then making a nice looking version without the mistakes in it. Be warned though, I made what I called my racing donkey to replace a broken shavehorse the night before setting off for an AGM. This cobbled together device lasted over four years before being replaced by mark two lightweight shavehorse. If you have any questions about the construction of any of these things try asking on our Ask & Answer where either myself or others will attempt to help.