one spring cable instead of two ?

[Jake Danilchik]

I am about to make my first spring plugs so I am trying to determine if I can use 1/16 " cable because my spring OD is smaler than suggested  ( .750 ) so I am worried about clearance issues for the tandem 3/32" cable.  I am also considering the use of only one cable instead of the tandem design that Cody's plans call for.    Both for clearance issues.   I realize that the tandem cable design is to keep the springs from torqueing and twisting but I am curious how important that is.  Any opinions are appreciated.

Are there any strong opinions against using one spring cable instead of two.    Also, is   1/16 "  cable too small.   I believe that 1/16 " cable is rated higher than needed ?   Cody's plans  suggest (  3/32" ).

Does the cable get frayed over time ( as implied here : )

http://www.steadyrig.com/Silver%20Spring%20Arm.htm

Has anyone ever had a cable failure ?

cheers,

Jake

[Wade Francom]

We used 1/16" cable on our rigs. It seems to be doing just fine. The strength rating on 1?16 cable is way above what the arm can put out, especially when you have 2 cables.

I believe the purpose of 2 cables in 3-fold. First, there will be a super amount of twist/torque on the single cable. This is what would cause fraying and failure. Two cables prevent twisting.  Secondly, with 2 cables, if one fails, you won't have a catastrophic collapse like you would with a single cable. The arm may give a little when the cable fails, but it won't drop your load like a single-cable failure would. Third, even with a groove in the pulley, cables like to wander off the mark. With two cables, each cable forces the other to stay aligned in the groove. So far I've never had cables missalign during operation. With a single, a missalignment means stopping down, dismounting the rig, loosening the cable assembly so you can re-seat it, and re-tuning your arm. Pain in the keister if you ask me. Do it right, don't take shortcuts, and do it with two cables.

[Cedric Akins]

Well after looking at the evidence from the Silver Springs Arm from [url][http://www.steadyrig.com/Silver%20Spring%20Arm.htm/url]

Spring twist and cable skew problems resolved with new spring end design.
The old style of spring end was designed with the anchor point at the rear of the unit which led to spring end twist and cable skew. This contributed to cables fraying as they did not always travel squarely in the pulleys.

You have answered your own question.

[Joe Sanders]

We used 1/16" cable on our rigs. It seems to be doing just fine. The strength rating on 1?16 cable is way above what the arm can put out, especially when you have 2 cables.

I believe the purpose of 2 cables in 3-fold. First, there will be a super amount of twist/torque on the single cable. This is what would cause fraying and failure. Two cables prevent twisting.  Secondly, with 2 cables, if one fails, you won't have a catastrophic collapse like you would with a single cable. The arm may give a little when the cable fails, but it won't drop your load like a single-cable failure would. Third, even with a groove in the pulley, cables like to wander off the mark. With two cables, each cable forces the other to stay aligned in the groove. So far I've never had cables missalign during operation. With a single, a missalignment means stopping down, dismounting the rig, loosening the cable assembly so you can re-seat it, and re-tuning your arm. Pain in the keister if you ask me. Do it right, don't take shortcuts, and do it with two cables.

This may not have anything to do with what they were thinking, but 2 cables also have less cross sectional thickness.  So the difference in the radius from one side of the cable to the other is less, resulting in less internal sheer movement within the cable as it moves around a pulley, thus producing less cable bend friction.

[Jake Danilchik]

Thanks for the thoughts.   All rational points.   Love this forum !!!

I'll use 1/16th and the tandem cable as designed. Wade's point regarding cable wandering and "downtime" is enough to warrant not trying to oversimplify and it will force me to use the more elegant ball swage ends that are depicted below.

My brother suggested that small boat building / outfitting companies might be the best place to have the ball swages crimped.      Did you purchase the tools to crimp the *more* specialized ball swage or is it best to "outsource" the crimping work ?

We used 1/16" cable on our rigs. It seems to be doing just fine. The strength rating on 1?16 cable is way above what the arm can put out, especially when you have 2 cables.

I believe the purpose of 2 cables in 3-fold. First, there will be a super amount of twist/torque on the single cable. This is what would cause fraying and failure. Two cables prevent twisting.  Secondly, with 2 cables, if one fails, you won't have a catastrophic collapse like you would with a single cable. The arm may give a little when the cable fails, but it won't drop your load like a single-cable failure would. Third, even with a groove in the pulley, cables like to wander off the mark. With two cables, each cable forces the other to stay aligned in the groove. So far I've never had cables missalign during operation. With a single, a missalignment means stopping down, dismounting the rig, loosening the cable assembly so you can re-seat it, and re-tuning your arm. Pain in the keister if you ask me. Do it right, don't take shortcuts, and do it with two cables.

[Cedric Akins]

Well if you are going to use the single cable method I think it would be a good idea to use the spring collars as well. Springs tend to "unwrap" on one side as they extend. Unwrap may not be the correct term, but as you extend an extension spring one side uncoils before the other, which puts more tension on the other side.

Spring twist and cable skew problems resolved with new spring end design.
The old style of spring end was designed with the anchor point at the rear of the unit which led to spring end twist and cable skew. This contributed to cables fraying as they did not always travel squarely in the pulleys.

Original style with anchor point at the rear causing spring ends to twist and skew .

Silver SpringÔ spring ends stay parallel and hold the cables straight.

[Wade Francom]

I had that "unwrapping problem, too. They just love to pull off the threads when under heavy load.

I made some simple spring collars out of some 3/4" PEX crimp rings and some set screws. I think I have pics of them in my rig thread.