Steel cable startup 1

[bluesman0007]

I am winching a 37,000 lb. load along several sets of rollers on a level plane. The winch is a simple on/off in/out motor no ramping etc. I would like to add something like a spring or shock cord to allow for the startup and possibly a little safety at the hard stop end of the pull. Does anyone have any experience doing this? A better idea?

Thanks in advance.

 

[ccw]

Hi bluesman0007,
Typically what happens when you do that is a "stick-slip" motion, where the load accelerates out of control until the stretched shock cord or spring relaxes, then the load stops, then the shock cord or spring stretches again, then the load moves again, etc. Theoretically one would like to have an infinitely rigid (in tension) cable to avoid this erratic motion. Often, inserting a spring or shock cord will make matters worse.

The wire rope is a spring in itself. For instance, a 1/2 inch cable, 6 X 19 IWRC Carbon construction, has an approximate spring rate of 0.0001 inches stretch per 100 loaded inches of cable per pound load. Fortunately as you near the stop the loaded inches of cable reduces so the spring rate gets stiffer.

Try to run the rig with as low a line speed as practical. In addition you can run a tag line around a viscous damped capstan to steady the motion. Dashpot bumpers at the end of the pull are also helpful.

Rig a multipart line block and tackle as this will give a equivalently higher stiffness and at the same time a lower load speed.

 

[CMfgE1]

Im just posting to say WOW to CCW!!!!
Thats one of the best answers Ive read In a post!!!!
Very informative and right to the point.

Now if I onl knew what you were talking about!! LOL



Good Luck!

Quote: "Its not what you know, its who you know" - anybody trying to find a decent job
Everyhtings a learning experience-Everything

 

[bluesman0007]

ccw,

Thanks, you gave me almost more than I needed to think about right now. I have seen the "stick-slip" motion in other applications I just needed to hear it I guess. I think I have the option of using a variable speed control which may give me the soft start and stop that I would like to have. I agree with CMfgE1, now if I only knew how to give you a star.....

Dennis

 

[ccw]

Hi bluesman0007,
like the emperor said in "Amadeus", "too many notes". Sorry about that.

 

[bluesman0007]

Just a follow-up to what we did and how it worked. We used the winch but modified the switch from a maintained to a momentary action. We decided to try running with just the cable attached to the load directly. This was all it took to make the load scoot across the rollers to the registration point on the press and back to the table. Thanks CCW, it was amazing to see this work first time out of the box. I've even got it to where I can release the button and have it coast to the end. Shocks on the end would make it even better but customer is very happy with final outcome.