Wire-to-turnbuckle size

[Brion Toss]

Hello,
The available pin sizes are there to accommodate different wire constructions. The pins should always be at least a third stronger than the wire (as should turnbuckles, tangs, chainplates), and 3/8" is right for 1/4" 7x19 and 7x7. But it is barely stronger than1/4" 1x19, which is why the 1/2" pin is the correct size.
What too often happens is that builders will simply decide to save money, putting swages (and turnbuckles, tangs, chainplates) meant for 7x19 onto 1x19, with predictable consequences for safety factors. Similarly, they might choose aircraft eyes and forks instead of the spendier marine ends. Make sure of your wire size -- perhaps you don't really need 1/4", for instrance -- and then choose components to suit.
Fair leads,
Brion Toss

[Bw1]

Thanks. That clears it up.

What's the reasoning behind making the pins 30+% stronger than the wire?

-Bryan

[Brion Toss]

Originally Posted by Bw1

Thanks. That clears it up.

What's the reasoning behind making the pins 30+% stronger than the wire?

-Bryan

Hi again,
A couple of things. One is that we expect pins (and chainplates and tangs) to last longer than wire, so we make them stronger than the wire. And because these structures are more vulnerable to fatigue, and often harder to inspect, we make them stronger still. Which brings up one of the great mysteries of my life: Skene's chainplate specs are supposed to result in 4/3 the wire strength, but if you run the numbers they are quite a bit higher than that. Does antyone know why?
Fair leads,
Brion Toss

[P38]

Hi Bryon,

Just a guess, but holes in a part increase the stress in the area around the holes by 300% to 400%. Perhaps Skeene was allowing extra to give some fatigue protection?

Regards, Paul