On Oct 18, 2011, at 9:06 PM, sam sokolik wrote:
> Could you explain your system a little.  When you where explaining it on 
> irc - It seemed to me that you had a bit too small of servos for the 
> application you had.  iirc - you have about 1.5 turns of the servo per 
> inch?  or was it 2.5 turns per inch?  Again - It  was just a feeling.
> 

We think the  motors are a good size for what we designed.  They might be a 
little too big if anything  This might be part of the problem we are having 
tuning it, that the truck is fairly light and motor fairly beefy.  One turn of 
the motor is pi/2 (1.57) inches of movement linearly.  Another thing we think 
might be of issue is that we are using rack and pinion and that it isn't 100% 
linear either.  Servos tend to like a consistent load and we think some areas 
of movement along the rack are easier, some are harder, just due to the 
inaccuracies of the rack and pinion and the design of the 
bearings/rails/assembly we are using.  All of this is speculation at this 
point, just things we have discussed.   We thought we had made progress on 
tuning the Granite drives but when we went to run EMC, the axis will fault 
fairly often even at very low accel and speeds and nearly always faults at one 
specific location (within a couple inches of a specific point).  We have 
scrutinized that place and can see nothing different from another other place, 
but it just faults there quite often and when moving in one specific direction. 
 It is baffling.  We have been over the mechanicals and wiring separately and 
together (two of us having been working on this), and we are quite sure 
everything is mechanically sound and nothing is wired incorrectly or improperly.

These are the motors:  http://www.kelinginc.net/KL34-180-90.pdf

We are really about to give up and put steppers on it. 
-Tom


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