Solid shaft or hollow???

Okay.... picked up an LXD 650 mount and completely disassembled it to see how it works and to see the quality of the mount... Anyways... One thing I thought of doing to help the stability of the the mount, is to replace the hollow shaft; which allows the counter weight bar to slide into it, with a solid shaft and have the counter weight bar thread onto the shaft not into it. Would this benifit me at all or is this just a waste of time.... Any help on this would be great....
Thanks,
DAN

I'm no engineer so take what I say with a grain of salt - the Losmandy mounts are hollow shafted while the Celestron CI-700/CGE are solid shafted. All are very stable so in an of itself I don't think Solid shafts necessarily get you a more stable mount. I recall 6 or 7 years ago when Celestron first came out with the CI-700 as a replacement for the Losmandy CG-11 mount, Scott Losmandy (pretty sure it was him...) wrote a piece explaining that with the stresses that a GEM gets, Solid shafts offer no increase in strength. Then again, if you have the capabilities, why not try it and see?

>>>One thing I thought of doing to help the stability of the the mount, is to replace the hollow shaft; which allows the counter weight bar to slide into it, with a solid shaft and have the counter weight bar thread onto the shaft not into it. Would this benifit me at all or is this just a waste of time.... Any help on this would be great....
Thanks,
DAN
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Personally I think it would be a complete waste of time and even possibly counter-productive.

The important thing here is the stiffness in bending and possibly torsion. The stiffness of a tube in both bending and torsion is related to the 4th power of it's diameter. The outside section is the important region, the center does essentially nothing. That is why the shaft is probably hollow, it costs more to make that shaft hollow after all. A 1.5 inch shaft with a 1 inch hole in it has 80% the stiffness of a solid shaft whereas it only requires removal of just 0.080 inches from the diameter, for that 80% stiffness...

In my experience, the shaft stiffness is not the problem that causes an unstable mount, rather it is normally a undersized tripod.

Jon

You would see a slight increase in stiffness with a significan increase in weight. But the thing I would be careful of is the change in the mount's resonant frequency: replacing the hollow shafts with solid might change the vibrational frequency into a range that might be annoying, or that might resonate with guide motors, wind, etc. Probably not, but it's something to consider before you make the change permanent.

Tim Iafolla