[SML] Automating Single-purchase

[Bill Conner]

>>> Hello All-
>>>
>>> What would be the challenges, as you see them, in moving a single purchase
>>> lineset off of a motor and a drum/mule/wench?
>>>
>>> It seems like such a simple idea.  Just replace the hemp with a longer
>>> piece and take 3 or 4 wraps around the drum to move the line.
>>>
>>> Add steel, gear motor, and control.
>>>
>>> There must be pitfalls


I think you have some good responses but I see nothing about limit
switches (I guess hard struck might work if really using a mule
winch), e-stops, or basic redundancy in the controls. It's like drill
op winches - too easy for one simple human operator error to result in
catastrophe.  Plus, if a mule winch with capstan as your post
suggests, which requires an operator, why not just let them operate
the counterweight manually?  So many questions about what you are
asking about that it's hard to see all the pitfalls.  People under it
when moving?  Always balanced or possibility (hang up) or plan for out
of balance?   Safety switch on bottom of piece?   Where is your
operator?  Just don't know.  I strongly prefer a continuous loop, not
just a tugger, but if its slow and balance does not change, perhaps a
tugger winch - either as a tag line on the batten or on the arbor -
with proper normal end of travle and over travel limits, e-stops, etc.
is an acceptable risk.


-- 
Bill Conner Fellow of the ASTC