A P180 Pilot executed a go around after hearing a scrapping sound in the flare. The landing gear had not been lowered.

Narrative

I was flying a Piaggio to a nearby airport for maintenance. Upon taking off I realized I had a primary trim failure; I then selected secondary trim and continued my flight. When handed off by Center to Approach; they gave me vectors for Runway 23. I was having trouble locating my traffic on final. When I went to lower the gear I noticed my speed was a little high. I then went back to find my traffic. I spotted it on short final. With the trim in secondary you have a split switch on the pedestal. So I continued working the trim and turned final. In the flair; I heard an unusual noise like something scrapping. I elected to go-around and notified the tower. I then noticed I had failed to lower the gear. I then lowered the gear and returned for landing and taxied to FBO. I believe that being distracted by the secondary trim; which is half the speed of the primary trim and not being able to find my traffic contributed to my oversight of the gear. Checklist; checklist. I've been flying for many years you would think that you would not fall into an error chain.