|
Gday Mate
Moment is term geek engineers use to measure or quantify bending - it is actually short for bending moment. If you had a force (point load) of say 10 kN acting at a distance of 0.5 metres then the quantification would be a bending moment of 10 x 0.5 = 5 kNm. In a situation like a counterweight bar maximum deflection occurs where the maximum moment is. Its a bit like having a roof beam cantilevering from a house loaded with heavy roofing say - the end of the beam away from the house is going to have the most deflection. So it is a unit of measurement as opposed to the normal use of the word like a moment is an instance or similar.
I dont know the set up on the mount but imagine that forces act vertically in the direction of gravity. Say the gear and worm was between the pivot point and the counterweight (but closer to the pivot point) and the distance from the pivot to the counterweight was say 0.5 m. So if say the counterweight bar is at 45 degrees the horizontal distance (ie D of the moment calc) from the pivot would be 0.5 * cos 45 or 0.7071 * 0.5 = 0.3535 m but if the mount rotates to 30 degrees it becomes 0.5 * cos 30 = 0.433 m. Therefore the lever arm increases as the mount rotates (ie the bending moment becomes larger). this will keep happening until the dec axis is horizontal where the lever arm would be 0.5 (cos 0 = 1) and this is where most bending will occur.
I assume the design of the mount would have some sort of mounted bearings that would limit this effect however, and what I am talking about is simple statics as I said - mechanically it may be all different (and I await being being shot by a mechanical engineer) but it is common sense to minimise all flexure especially in a photographic mount and flexure is usally a result of bending somewhere in the system.
Bolts
|