DIY tonearm, the US Patent Office has many tonearm

Before you re-invent another great tonearm, check with the US Patent Office. The famous Graham, linear air bearing , and magnetic damping tonearms are in there. Many of these patents published in the late 70s and 80s. They are expired and available for public use. The principle of tonearm designs are simple but workmanship and tuning are critical. Make use of your tax money. Unipivot tonearm is simple to make, you can come up with your own tonearm balancing schemes. Have fun
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2Fsearch-bool.html&r=0&f=S&l=50&TERM1=tonearm&FIELD1=&co1=AND&TERM2=&FIELD2=&d=ptxt