Collars on the Bar: The Details

[Mark Rippetoe]

Collars on the Bar | Mark Rippetoe

[Matt James]

Is there a brand you recommend? I've seen various versions of the quick release plastic ones, but the ones they had at the local Y tend to wear out and get sloppy.

[Mark Rippetoe]

They all have a lifespan, but they're all cheap.

[AndrewLewis]

I've never heard of ductile iron plates. Have you seen them before?

[Mark Rippetoe]

I wouldn't know ductile iron from gray iron by sight, but I've heard of them. I think York used it for a while.

[AndrewLewis]

That's pretty neat.

You can't tell by sight if it's unbroken. You tell by sound. Hit it with something hard and ductile iron will ring with a bright sound. Gray iron will produce a dull thud.

[Steve Cox]

Rogue is selling a line of ductile plates. Beautiful to look at but too expensive for me.

[TalEphrat]

In the article, you state that the surface area affect friction, which is very intuitive. But it doesen't, friction is affected by the material of the two objects, and the normal force.

[AndrewLewis]

Rogue is selling a line of ductile plates.

This is so weird. What problem does this solve?

In the article, you state that the surface area affect friction, which is very intuitive. But it doesen't, friction is affected by the material of the two objects, and the normal force.

This is true of translation, but when rotation caused by moment comes into play, it matters because location of friction changes the moment.

In the squat, for example, a plate that slides directly along the axis of the bar is only affected by the coefficient of friction and force imposed. Plates that "slide off" because they are moving back and forth orthogonal to the cross-section of the bar will move less if the plate is tighter to the bar because it's not just sitting on the top. Most of the bar on the sides are in contact with the plate.

However, my experience has been that ridged barbell sleeves slide less easily than smooth ones - which makes sense to me because interactions with smoother surfaces generally have lower coefficients of friction.

[Mark Rippetoe]

This is so weird. What problem does this solve?

The problem of not selling ductile plates.