Ok, I said that I'd look at a centre of gravity / front of centre calculation at some time which, given that there are two gauges supporting the arrow, ought to be easy.
Intuitively, the centre of gravity position ought to be a simple calculation based on the ratio of the weights, but I couldn't justify to myself why, or exactly what the formula to use would be. So, I tried to work it out. My wife saw what I was doing, and pitched in to help. This led to a bit of colourful language as, being a civil engineer she insisted on thinking of the problem in terms of the reactions upwards at the supports whereas I, being a normal human being, wanted to think in terms of downward forces on the gauges. Once we sorted that out we figured out the sums:
This sorted things out in my head plus gave a nice formula for plugging values into. Giving this:
Yay! The centre of gravity is 455mm in front of support 1. That's good, isn't it?
Well no, not really. You can find the centre of gravity of an arrow by balancing it on a finger. What you really want to know is the front of centre position as a percentage of total arrow length, which is what all the recommendations for good arrow flight are in terms of.
This is in theory a simple calculation; in fact trivial for the microprocessor. However it involves knowing the arrow length plus its relative position on the supports. This is data that's not easy to enter on a device without a keyboard. And the data input can't be more trouble than it's worth.
This will need some thought...
Intuitively, the centre of gravity position ought to be a simple calculation based on the ratio of the weights, but I couldn't justify to myself why, or exactly what the formula to use would be. So, I tried to work it out. My wife saw what I was doing, and pitched in to help. This led to a bit of colourful language as, being a civil engineer she insisted on thinking of the problem in terms of the reactions upwards at the supports whereas I, being a normal human being, wanted to think in terms of downward forces on the gauges. Once we sorted that out we figured out the sums:
This sorted things out in my head plus gave a nice formula for plugging values into. Giving this:
Yay! The centre of gravity is 455mm in front of support 1. That's good, isn't it?
Well no, not really. You can find the centre of gravity of an arrow by balancing it on a finger. What you really want to know is the front of centre position as a percentage of total arrow length, which is what all the recommendations for good arrow flight are in terms of.
This is in theory a simple calculation; in fact trivial for the microprocessor. However it involves knowing the arrow length plus its relative position on the supports. This is data that's not easy to enter on a device without a keyboard. And the data input can't be more trouble than it's worth.
This will need some thought...