Why does passive pro have a smooth surface?

It occured to me that all brands of nuts and hexes have smooth surfaces whereas cams have textured surfaces (e.g. dmm dragons, mastercams etc). Why?

At first I thought because they'd quickly wear off nuts, but since they are passive, wouldn't they last longer? And they dont really wear off on cams which move, right?

Is it just not necessary? Or would there be any value added? Would it make em harder to clean?

I read the article here and saw a few old examples of stuff with textured surfaces like these:

camlocks

wedges

I bootied a Camp Pro Nut a while back.

I've placed it a few times.

This review matches my experience: ukclimbing.com/gear/review.…

Smooth = more surface area = more better?

Since you're relying on constriction rather than friction, right?

I think with a cam you're trying to maximize friction, and with a nut you're trying to maximize surface area. Friction keeps a nut in the placement until it's loaded, but it's the inclined planes on it that generate the force to save your butt. I think that even a frictionless nut placement would be bomber as long as there was only downward force.

Most rocks are non-smooth.

If it ain't broke, don't fix it.

SwabianAmi wrote:It occured to me that all brands of nuts and hexes have smooth surfaces whereas cams have textured surfaces (e.g. dmm dragons, mastercams etc). Why? At first I thought because they'd quickly wear off nuts, but since they are passive, wouldn't they last longer? And they dont really wear off on cams which move, right? Is it just not necessary? Or would there be any value added? Would it make em harder to clean? I read the article here and saw a few old examples of stuff with textured surfaces like these:

Cams rely on rotation of the cam lobes to hold, therefore, you want textured surfaces that the crystals in the rock will grab to start the cam lobes rotation instead of just sliding out.

Nuts rely on the nut sliding deeper into the constriction for them to hold, therefore, you want a smooth surface to allow them to slide and to keep the crystals in the rock from grabbing them and making the placement less secure.

What he said ^

kennoyce wrote: Cams rely on rotation of the cam lobes to hold, therefore, you want textured surfaces that the crystals in the rock will grab to start the cam lobes rotation instead of just sliding out. Nuts rely on the nut sliding deeper into the constriction for them to hold, therefore, you want a smooth surface to allow them to slide and to keep the crystals in the rock from grabbing them and making the placement less secure.

Understand that, although the smallest cam sizes often have smooth surfaces (C3's, teh 00,000 mastercams etc).

so I wonder, is there any value in adding texture to a nut/hex, or does it basically make no difference givent hat you're jamming it in a constriction that it can't move out of anyway?

So they're easier to clean after they've been wedged in

SwabianAmi wrote:is there any value in adding texture to a nut/hex

I would guess textured nuts are more expensive.

If you wanted to try out textured nuts yourself you could look into a set of CAMP Pro Nuts, Gear Express has the whole set on sale right now 42% off. The few reviews I've read basically say the texturing doesn't seem to make any noticeable difference from a standard smooth nut.

SwabianAmi wrote:... cams have textured surfaces .... they dont really wear off on cams which move, right?

That texture does wear off cams. Nuts wear as well. But all else being equal, a textured surface will wear more quickly. So texture is used judicially ... when friction has a primary role in holding power as in cams.

You could likely argue that textured pro is a good idea in smooth, sandstone type of rock.

Textured would be tough to remove. I have a couple old ones from the 90s that I carry to leave behind on raps.

Cams pinch down so removal is less of a problem.

rockandice.com/lates-news/d…

"When Ray Jardine rolled out the first commercial camming unit, the Friend, in the mid 1970s, he tried to be practical by making smooth-faced cams. But the first climbers to see the units scoffed and said they'd never hold. Only after Jardine added teeth to the cams did climbers begin to trust them."

Seth Jones wrote:Because friction doesn't have anything to do with passive gear holding a fall. Plus, I imagine textured nuts would get welded like a mofo after being loaded.

i don't necessarily agree with some of the posts above that state that friction doesn't affect how a stopper works. less friction in a wedge will create a larger outward force - which isn't always a good thing. particularly when placing gear in flakes.

i think one of the main reasons that passive gear is generally smooth is that noobs tend to jerk the gear into place. if you did this with a knurled/textured surface, it would be even harder to get out than if it had a smooth surface.

slim wrote:
less friction in a wedge will create a larger outward force

Seth Jones wrote: how so?

A nut is, basically, an inclined plane -- like a splitting wedge or axe for splitting firewood. It converts a downward force into an outward force.

As you pull downwards on it, say in a fall, that force has to be countered. If none of it is countered by friction, all of it will be turned into outward force. But, if some of it is countered by friction, that which is "lost" to friction will not be converted to outward force. So, less friction means more outward force.

In most rock, even cams really should be smooth. When cams first came out and people didn't yet trust how the outward outward force was produced, texture was added to make them seem more trustworthy - and it's become a habit of the industry. red, yellow, and blue X4s work - no texture. Aliens work - no texture (though they also have softer metal). Chatted with some folks at metolius about this. Notice how the new Mastercams have less aggressive texture than before. Apparently they're phasing the whole texture thing out to improve surface area. DMM, not so much - they're going for the opposite logic. Interesting stuff.

Zachary Winters wrote:In most rock, even cams really should be smooth. When cams first came out and people didn't yet trust how the outward outward force was produced, texture was added to make them seem more trustworthy - and it's become a habit of the industry. red, yellow, and blue X4s work - no texture. Aliens work - no texture (though they also have softer metal). Chatted with some folks at metolius about this. Notice how the new Mastercams have less aggressive texture than before. Apparently they're phasing the whole texture thing out to improve surface area. DMM, not so much - they're going for the opposite logic. Interesting stuff.

I am not a fan of the change in texture made to mastercams. Seems like the sharktooth texture is the worst available texture for climbing on smooth, hard rock (e.g. quartzite, recently fractured limestone, vitrified sandstone), although it might be a better design for climbing on kitty litter...

I think the DMM Dragon 2 lobes are the best all-around design going right now, although I don't have the data to prove it. Despite the addition of the "triple grip" texture, the surface area is actually larger because the cam lobes are wider.

I'd be interested in an engineering/physics perspective on what if any difference texture vs smooth makes on cams and nuts/hexes and especially if there's anyway to objectively test and measure it.