So I've got a friendly challenge going with my brother to see who can make a top that spins the longest.

My brother recently got a job with a 3d Printing company which is how this challenge came about. He will be drawing up his top and printing it, while I'll be making a wooden top on the lathe.

I was curious if anyone here had any design tips for a long spinning top? I've only made one piece tops so far, but was considering a 2 piece top using some of the densest wood I've got.

Some limitations to the design, it can only be 4 inches in diameter at the widest and a holding device with a string can be used to propel the top.