[SML] Motor controls in scenery

[Bill Sapsis]

PLASA’s ANSI standard E1.6-1_2012  Powered Hoist Systems, sec 7.4.3.2 says…..   "There shall be a minimum of two sets of limit switches in any direction of motion.  Normal (end of travel, initial) and ultimate (overtravel) limit switches."

Any time you are using a machine to move things on stage you should have the two sets but especially when you are moving people.  It’s not just for flying performers.  As evidencinced by Bill’ C’s example, moving a platform with people on it also presents serious risks.

Bill S.

bill at sapsis-rigging.com
http://www.sapsis-rigging.com
+1.267.278.4561   mobile
+1.215.228.0888   x206



On Apr 7, 2015, at 7:15 PM, Brian Munroe via Stagecraft <stagecraft at theatrical.net> wrote:

> Was there an encoder/positional feedback device?  The controller should have shut down when it jammed - either some sort of positional tolerance error, encoder fault, or an over current error. In a properly designed system at least. 
> 
> If there was no encoder etc then I would think 2 limit switches in each direction as you described. 
> 
> Brian Munroe 
> 
> Sent from a rather small device with big fingers
> 
>> On Apr 7, 2015, at 4:26 PM, Bill Conner via Stagecraft <stagecraft at theatrical.net> wrote:
>> 
>> For installed motorized equipment, I've rarely not seen at least two
>> limit switches at each end of travel - a normal end of travel and an
>> over travel or ultimate limit.
>> 
>> What do you all do for scenery for a relatively short run production?
>> 
>> This was a one person platform lift - cable and drum pulling a
>> platform up rails.  Single upper limit poorly mounted was not struck,
>> nico and thimble jammed in pulley and the wire rope broke and person
>> on platform plummeted the 6' or so to bottom.  Stitches, no permanent
>> injuries reported.
>> 
>> Thanks!
>> 
>> -- 
>> Bill Conner Fellow of the ASTC
>> 
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