Very interesting, Nghiep, how do you make the pivot point for the tonearm? I have read elsewhere that the best material for a DIY tonearm is a carbon-fibre tube for an arrow at $5! I've been toying with either imitating the Well-Tempered design or building a unipivot for a long time. Good post!
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
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