Like i have said a few times now.
Using M16 bolts and holes that are 18mm is pointless, there is ... to much air
Using M20-24 bolts that have minimal clearance and not setting the top plate too far away (like i do see on on some piers). My opinion is i wouldn't go further than 100mm difference between the plates.
if you spread the bolts sufficiently eg 300mm+ and use a decent plate 12mm or so the top plates are sufficient enough to withstand any forces applied to them and transfer these forces out to the bolts.
Its the same premise why truss tube telescopes work so well. Intentional design putting elements into their strong points eg. Tension and compression. Geometry plays a key point here in putting mass where it is required and taking mass out where it is not.
Like i have said before a pier I designed, fabricated and installed clears the ground by 150mm or so... there are no issues running at 2000mm FL.
On your point of testing your rig to extremes. If you really wanted to do a test that actually has merit not just oh i hit it with a hammer which will never ever ever occure (your test has to be meaningful).
Get a spring weight and hook it onto the top of your pier. Maximdl reports in seconds of arc so you can grab the pier and quickly put 50kgs worth of force at the top of the pier.
Take a reading of the arc second error the guider throws up. upon release measure it again. do that 30 times to gain a good statistical average. That is an extreme case and is measuring your static deflection which is the maximum the pier can move at a said force. This is how I theoretically determine my "vibration" in my normal day to day work by looking at what force produces what deflection.
As for dynamic vibration thats a whole new ball park. It takes into account Natural frequency of the structure, Frequency of the dynamic force, Dampening and a whole host of other things.
Think of a combustion engine sitting on a flat floor with an out of balance crank shaft or even your car the vibration you feel is dynamic it changes with respect to time.
So thats my view point on the dynamics of it and a design that will work.
B. Mitchell
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