Weird knee servo issue

[Daniel Nolting]

Hello,

I have an interesting problem with two of theVorpal branded knee servos. When they get some kind of axial load (pushing on the servo horn for example) they move counter clockwise to their extreme position - the hexapod raises his leg. One is so sensitive that this happens during normal movement of the hexapod. 

The replacement servo works fine on both ports and the servos show the same symptoms on other ports of the servo controller, hence I suspect the potentiometer losing contest when the axis is being pushed. I hacked together an axial „bearing“ by putting an M5 washer between servo and servo horn which prevents any axial forces on the axis.

Is there a way to fix the servos? I’m also a bit worried about the hip servos as the hexapod crashes down during some dance moves and the servo axis have to take the impact. Does anyone have any ideas about this?

Have a nice Sunday,

Dan

[Steve Pendergrast]

Hi Dan,

This is a defect, we will have to send you two new servos.  When we first started working with tower pro around february of this year we identified this issue in about 2% of the servos they sent us. It's an issue with the circuit board, pressure toward the axis causes something to flex and throw off the angle.  They changed their QA at that time and we thought the issue was largely resolved.  We always test 10% of the servos with every new batch we receive looking for this exact issue (and a few others).  We didn't detect any from the batch right before you got your kit but that doesn't mean a few servos didn't have the problem and just didn't happen to be in the ones we tested.  I'll raise this issue again with tower pro to see if they can get a more definitive solution.

But for now I'll send you two more servos monday.

-Steve P.

[Daniel Nolting]

Hi Steve,

I very much appreciate it.

Dan