Quote:
Originally Posted by Robot360
Jeff, thanks for the response and details. For your setup, could you ever get in a situation where your lift snagged, maximizing the spring stroke (that is, to its limiter), and then if you continued driving the lift, cable slack would end up in the system?
Also, how many layers of cable wraps are typically on your full drive pulley, and with what diameter cable? Even a few layers of 1/4" cable could result in several inches of cable slack.
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When the carriage was obstructed there would be a small amount of slack develop on the up side but not enough to de-track the cable or cause problems. I'm talking about a small amount of spring range, just enough to take up small variations in the rigging. If stretched tight and driven too hard we would stall or break something.
We size the diameter and width of the winch drum to require only one layer of cable wrap. With the proper alignment the cable can be made to wind uniformly in one layer. The spring tension helps with this. Note on the photo of 254 the drum is wide enough to easily allow one layer. This keeps the rigging length constant with only small variations, such as for parellelism. We have used 1/16 to 1/8" wire cable. It is surprisingly strong, more supple than larger cable, and adequate if the apparatus is properly counterbalanced. Few FRC mechanisms really need 1/4 cable IMHO. That's dang strong.