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Another thought provoking and interesting thread Peter (Brendan & others....)
I've often thought myself, that it was a little strange there is SOOOO much concrete and stiffening in the pier with Xmm thickness steel and gussets etc etc and then there are 4 piddly bolts holding up a steel plate with 20-40Kgs of spread load (especially at Zenith when say a newt reflector is horizontal and the counterweights and tube are at opposite ends of what essentially looks like a see saw at rest)?
It seemed to defeat the purpose of all that mass and rigidity to then introduce a point of (my initial thoughts) weakness simply for what I thought was ease of mounting and perhaps clearance for the base of the EQ mount.....
I know it is more complicated than this, but as a few have said and Jason has mentioned recently, as the EQ base is inherently adjustable, I didnt see the point of having so much air gap and "unsupported" load simply resting on the compression properties and rigidity of some bolts sticking out of some concrete or steel?
I suppose its all relative, based on how accurate and tolerant the system is to vibrations induced by walking, motors, resonant frequencies, torque introduced by the optics and mount etc etc. so I suspect for most amateurs who simply want the convenience of a mount that can be left set up and is more stable than a tripod (ME) and dont need the accuracy to image above 1000-1500mm FL, a simple pier without an adjustable top plate/rat cage, would probably do?
Based on my limited Engineering Science knowledge from High School, I would assume that the vertical bolts that hold up the pier plate, would benefit from some sort of structural truss design that "tied" them together, a bit like a bridge truss where the triangle is stronger than the individual girders and can handle more compression and bending stresses induced on them?
I wonder if this would produce any more rigidity in the system than simply four bolts pointing vertical? At least the plate could still be there for adjustment (or whatever its needed for) and the assumed weak points could be reinforced?
Or have I got this all wrong? Is the system as it stands with the EQ mount on top all centred and balanced about the vertical axis of the pier and therefore, any bending moment or stress induced into the base would be evenly distributed down into the structure and not transverse to the mount and pier?
I think I confused myself more....oh well, it may be a while before I get around to a pier, so I shall read on with interest in the meantime....
Cheers
Chris
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