DSC Encoder mounting

I am wondering how many here have encountered encoder errors due to the arm type that was used to mount them. I have recently had to replace the AZ arm that came with my scope. It was a metal arm that had two angles and a hole for a screw to hold it. I think it was Astrosystems but not certain. The strain from the mounting caused errors of about .5° when slewing. I made a new one from 1/16" ABS and used the slotted mount type and now the errors are corrected.
The reason for this query is that I also received an email from someone concerning errors and I replied to him with this explanation. Anyone else see this happen?

Hi Floyd,
How did you know it was the mounting arm and how does the mounting arm cause errors? I've never given much thought to my mounting arms.
Thanks,
Bruce Rodgers

Floyd,
I haven't encountered any encoder errors due to the Altitude mounting arm on my astrosystems scope. I have read of encoder errors that occur because of the method of attaching the encoder at the end of the mounting arm to the box. I use a mounting block to receive the shaft of the encoder and unless the mounting block isn't positioned properly on the box, errors in altitude may occur. The mounting block is itself attached with adhesive and has occasionlly loosened with temperature extremes and I make sure I re-mount the block so the scope remains orthogonal.
It's possible the slot in a mounting arm may have to be "notched-out" more for a specific scope so that it does it's job but I haven't seen a case where the arm itself is the cause of an encoder error.
As far as the AZ arm goes, I haven't encountered any problems with the bar itself and I haven't read of any to date. Problems with an AZ nut loosening are not uncommon and can be remedied with a locking nut/bolt combo and vendors sell them in their kits. It seems you were unfortunate enough to encounter an unusual problem with your set-up but it seems you've remedied it.

I attach the encoder to a short aluminum strap, which is held against a screw on the floor of the rocker box by means of a weak coiled spring. The encoder shaft is held by a set screw in a 1/4" hole drilled in the central pivot bolt of the rocker box, which is fixed to the ground table. No plastic, no slot, no errors.

Ya know, Floyd, if you slap a rubber band arond the screw and one tongue or the other around that slot, you'll have the same effect as my spring.

Ya know, Floyd, if you slap a rubber band arond the screw and one tongue or the other around that slot, you'll have the same effect as my spring.