I just got this weight driven banjo clock on eBay. Seller warned me that it ran a little bit fast. So I've got the bob as low as possible on the pendulum that came with the clock. He was right... It gains about 5 minutes after about 4 or 5 days. I know there is some mathematical formula (which I'd rather avoid...) for determining the correct pendulum length for a specific clock movement. I was just wondering if there was anything else I could try "short" of getting a "longer" pendulum rod... The clock case could accommodate a slightly longer pendulum rod. Does the weight of the bob have any impact? Probably not... The clock has not stopped running since I hung it up a about a month ago. So everything else seems fine. Thanks.