At skill around 100 (102 I think) I succeded on the first 2 attempts, so hence I sold a bow while a friend kept the first succes on him.
Haven't been able to do it since, though I haven't tried as many times, nor raised my fletching a lot more.
Agree that the most tedious part is getting the servos, but I've had a lot of luck killing the big clockworks outside mino caves and tracking down the smaller runnaways.
Try shouting to pay for looting them too. Practically wortless if you're not questing with the servos, so many are most willing to give you a loc to loot. Easily made enough for 5 attempts per day while I was here. Although I was hunting them while I still got xp from the bigger ones, so I actually got smoething else out of the killing too.