How do I calculate the forces on a guitar stand (Tripod type)

[Xeno777]

I want to build a bass guitar stand for my guitar using wood, I'm modelling it after the image shown. The alterations I'm making are to increase the height of the legs , to place an attachable weight below the stand . This will allow the stand to have a lower center of mass and will greatly reduce the stand from falling over when pushed.

 

[jrmichler]

Calculating forces on a guitar stand is overthinking the problem. The real design criteria is not the weight of the guitar, but:
1) It should not fall over if somebody lightly bumps it.
2) It should not collapse if somebody lightly leans on it.
3) It should not sway back and forth too much if somebody touches it.
4) The guitar should not fall off if it is lightly bumped.
5) etc.

In any case, start with a sketch showing what you want it to look like. Analysis needs a starting point. In this case, the sketch is your starting point.

 

[CWatters]

If the base is an equilateral triangle I would suggest the force on each leg should be the same (eg a third of the weight on each leg). If not that would imply the centre of gravity wasn't in the centre. If the centre of gravity/mass isn't in the centre it's more likely to fall in one direction.