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NEW Black diamond Z4


Chris Blatchley · · Somerville, MA · Joined Sep 2016 · Points: 7
Jonathan Awerbuch wrote: For those following along at home, don't believe a word of this thread. Much (but not all) of the above discussion is wrong.

this advice included, presumably?

Jonathan Awerbuch · · Boulder, Colorado · Joined Nov 2013 · Points: 41

The irony did cross my mind

Mike · · Unknown Hometown · Joined Dec 2013 · Points: 30
Former Climber wrote:

I agree with that, and am curious how Dragonfly’s hold up due to using 6082 aluminum, which is softer than 6061.

I haven't looked into what temper they are using for the aluminum; however, it does matter. T6 is super common. Here's comparative data for 6061 and 6082 both in the T6 condition and in easy to read bar charts for your enjoyment. (Spoiler: 93 HB and 93 HB are quite similar) A good engineer knows that test fixtures and data sheets are only half the story.

So anyone else handled these new Z4's?  

David K · · New Paltz, NY · Joined Jan 2017 · Points: 145
Former Climber wrote: Correct.  The outward force is related to cam angle.  I literally posted values for this a bit ago showing how little difference there is between 13 degrees and 16 degrees.
You claimed that changing the cam angle from 16 to 13 increases the outward force from 1.74 to 2.16. I didn't check your math.

Assuming you're correct, that's a 24.1% increase in outward force. I guess you can subjectively describe this difference as little, but I can tell you that in a lot of sub-fields of engineering, a 24.1% improvement would be worth billions of dollars. Think about how much money you'd save if your car was 24.1% more fuel efficient, for example.

But IT DOESN’T MATTER.
So long as the outward force is sufficient for friction to hold, MORE FORCE ADDS NOTHING.

Surely you can see that more outward force equates to more situations in which the outward force is sufficient for friction to hold? (And that this matters?)

Nate Doyle · · Sierra Foothills · Joined Feb 2016 · Points: 39

Look, I get it, you're all nerds and like arguing about this stuff. That said, ffs (!) can someone just tell me which ones to buy so I can get on with my life and go climbing?

Andrew Krajnik · · Plainfield, IL · Joined Jul 2016 · Points: 1,698
Nate Doyle wrote: Look, I get it, you're all nerds and like arguing about this stuff. That said, ffs (!) can someone just tell me which ones to buy so I can get on with my life and go climbing?

Black Totems

Former Climber · · Unknown Hometown · Joined 24 days ago · Points: 0
David K wrote: You claimed that changing the cam angle from 16 to 13 increases the outward force from 1.74 to 2.16. I didn't check your math.

Assuming you're correct, that's a 24.1% increase in outward force. I guess you can subjectively describe this difference as little, but I can tell you that in a lot of sub-fields of engineering, a 24.1% improvement would be worth billions of dollars. Think about how much money you'd save if your car was 24.1% more fuel efficient, for example.

Surely you can see that more outward force equates to more situations in which the outward force is sufficient for friction to hold? (And that this matters?)

You need to check Tan(cam angle) / 2?

Anyway, picture this:  You try and slide a block of concrete that’s sitting in your driveway, but can’t.  Does it matter if it weighs 2000 pounds instead of 1000 pounds?  Either way, it weighs enough that friction is keeping you from moving it.
Similarly, it doesn’t matter if the holding force is 2.16 times the downward force or 1.74 times the downward force, provided there’s enough friction for it to hold at all.

I suppose you could look at it as a design choice of what level of friction to accommodate for, and Metolius going the conservative route, but so long as Tan(cam angle) > coefficient of friction it will hold.  
al ex · · Unknown Hometown · Joined Oct 2016 · Points: 20
Former Climber wrote:

You need to check Tan(cam angle) / 2?

Anyway, picture this:  You try and slide a block of concrete that’s sitting in your driveway, but can’t.  Does it matter if it weighs 2000 pounds instead of 1000 pounds?  Either way, it weighs enough that friction is keeping you from moving it.
Similarly, it doesn’t matter if the holding force is 2.16 times the downward force or 1.74 times the downward force, provided there’s enough friction for it to hold at all.

I suppose you could look at it as a design choice of what level of friction to accommodate for, and Metolius going the conservative route, but so long as Tan(cam angle) > coefficient of friction it will hold.  

Harumpfster Boondoggle · · Between yesterday and today. · Joined Apr 2018 · Points: 138
Former Climber wrote:

You need to check Tan(cam angle) / 2?

Anyway, picture this:  You try and slide a block of concrete that’s sitting in your driveway, but can’t.  Does it matter if it weighs 2000 pounds instead of 1000 pounds?  Either way, it weighs enough that friction is keeping you from moving it.
Similarly, it doesn’t matter if the holding force is 2.16 times the downward force or 1.74 times the downward force, provided there’s enough friction for it to hold at all.

I suppose you could look at it as a design choice of what level of friction to accommodate for, and Metolius going the conservative route, but so long as Tan(cam angle) > coefficient of friction it will hold.  

This is all well and good if the placement is ideal. In a less than ideal placement then additional holding power is very significant and good to have.

(inb4 some "pro" posts that all his micro cam placements are ideal)

This is precisely what Metolius has done, sacrifice range for superior holding power in marginal placements. Of course there are many variables to consider and alternative (but very costly) designs (totem).

But fact of the matter is that cams pull out leading to dangerous whips, micro cams particularly. Whether a cam with superior holding power is better than one with more range is a trade the informed buyer should make based on his climbing. Then there is the value argument etc. Arguably, newbies benefit from more range, the experienced on hard cracks benefit from holding power, imo, as they are more likely to be "projecting" cracks and benefit more from lighter designs.
Mike Grainger · · Waterloo, ON Canada · Joined Aug 2008 · Points: 0

It's not just hard climbers projecting thin cracks who benefit from superior designs in small cams.  In areas such as the Algoma region of northern Ontario, the sparse natural protection opportunities are often found in thin, discontinuous, irregular cracks, even on moderate routes.  When you are doing a ground up, no previous inspection adventure FA, the superior holding potential of Metolius offsets or a black totem are precious indeed.  A slightly iffy placement is better than no placement at all, and far superior to truly shitty psychological pro. It can allow you to proceed with caution until something better presents itself rather than being shut down and backing off.  

As in many areas of life, there is an important value proposition to be considered in small cams.

Former Climber · · Unknown Hometown · Joined 24 days ago · Points: 0
Mike wrote:

I haven't looked into what temper they are using for the aluminum; however, it does matter. T6 is super common. Here's comparative data for 6061 and 6082 both in the T6 condition and in easy to read bar charts for your enjoyment. (Spoiler: 93 HB and 93 HB are quite similar) A good engineer knows that test fixtures and data sheets are only half the story.

So anyone else handled these new Z4's?  

Pretty charts, but they don’t agree with Matweb.  Possibly because your site is crowdsourced and anyone can sign in and assign values to things.


FWIW, 6082t6 is 36ksi yield and 6061t6 is 40ksi yield.  Pretty clear which will deform first.
David K · · New Paltz, NY · Joined Jan 2017 · Points: 145
Former Climber wrote: 

You need to check Tan(cam angle) / 2?

You memorized the tangent table? Weird flex, but okay.

Anyway, picture this:  You try and slide a block of concrete that’s sitting in your driveway, but can’t.  Does it matter if it weighs 2000 pounds instead of 1000 pounds?  Either way, it weighs enough that friction is keeping you from moving it.
The problem with your example is that you've assumed, for no reason, that I can't move a 1000 pound block. I have no idea why you believe that.

Similarly, it doesn’t matter if the holding force is 2.16 times the downward force or 1.74 times the downward force, provided there’s enough friction for it to hold at all.
Similarly, you've assumed that 1.74 times the downward force will always create enough frictional force to hold. I have no idea why you believe that.

I suppose you could look at it as a design choice of what level of friction to accommodate for, and Metolius going the conservative route,
Yes, and that would be the only correct way to look at it...

but so long as Tan(cam angle) > coefficient of friction it will hold.  

You've actually got this exactly wrong: the cam holds when Cf > tan(a), not the other way around (for those who are skeptical that the forces cancel out, the proof is here). But even assuming that's what you meant, this is just an equivalent claim to your previous claims about the forces: you're still assuming that the coefficient of friction will always be greater than tan(16), and I still have no idea why you believe that. To show you the problem with your reasoning, let's quote someone who actually knows what they're talking about:

rgold wrote:
According to David Custer in web.mit.edu/custer/www/rock… , the coefficient of friction of aluminum against granite has been measured at 0.38.   These students got 0.41 hypertextbook.com/facts/200… , and The Valley Giant folks say 0.5 valleygiant.com/cam_math.html.  If Mapeze is around, as a designer he probably has some values, especially for Euro limestone, where cams are known to be less reliable.   Obviously, the particular combination of aluminum against granite is not of great interest to researchers, so it isn’t easy to find values.   But beyond that, the simple coefficient of friction concepts found in Amonton’s law are in fact the roughest of empirical estimates and are not any kind of natural law—people write PhD dissertations on friction; it is in fact an extremely complex and far from well-understood concept.  The concept is most applicable to contact between highly polished surfaces, in which the friction forces are primarily influenced by molecular interactions.  Once the surfaces are physically irregular, all hell breaks loose because of the variety of ways the bumps and recesses can interact to produce resistance. I think that the almost universal practice of notching cam lobes is intended to leverage potential roughness interactions.  I think the message from research on the subject is that until you get up to loads of geological magnitude, the roughness of the surfaces matters far more than the materials, and so speaking as if there is a coefficient of friction between, say, granite and aluminum is far from illuminating.  When surface roughness and deformability matters, so does contact area, in which case one of the fundamental precepts of Amonton’s law is out the window. (Everyone knows more shoe rubber on the rock produces more adhesion, even though Amonton’s law would say not.)  Another important issue is the well-known disparity between static and sliding friction.  Since cams often move when a fall happens, the applicable coefficient of friction may well be the lower sliding value  rather than even a locally-measured static value.  Then there is the fact, totally unrelated to friction, that a well-placed cam fails not because frictional forces are insufficient to hold it in, but because of shear yield stresses on the aluminum lobe material. In such cases there will be evident gouging of the cam and it may be possible to find aluminum deposited on the crack walls. (I've seen the aluminum left behind in testing jigs but not in real rock.)   Given that Amonton’s law may be a poor description of what happens between a cam lobe and crack wall, I think it is something of a miracle that cams designed in accordance with that law work anywhere near as well as they do.
Gosh, between 0.38, 0.41, and 0.5, those are some very different coefficients of friction! But given tan(13) = 0.23 and tan(16) = 0.29, we've got a good amount of margin for error for either angle, if we're only going off the coefficient of friction. The problem is, we can't just go off the coefficient of friction of aluminum and granite. Just to bullet point out rgold's post:

  1. Granite isn't the only rock--limestone, for example, has much lower coefficients of friction.
  2. Surface roughness, deformability, and contact area aren't considered in the cam equations, but there's good imperical evidence that they may outweigh the coefficients of friction entirely (see the first link in the quote).
  3. The coefficients of friction here are coefficients of static friction. Since cams often start off moving, the coefficient of dynamic friction (which is much lower) may apply.
  4. The cam equations don't consider material failure such as aluminum detaching from the cam, or, on the other side, pulverization of rock.
With these things considered, it starts to look like making a more conservative choice with your cam angle is a good idea.
Tyler Bjorkman · · Taiwan/Spokane · Joined Oct 2016 · Points: 0
Nick Drake wrote: Weights listed: blog.weighmyrack.com/2020-b… blog.weighmyrack.com/2020-b…;

Cool!  Looks like the new Z4 .2 has a narrower head than the X4 .2 but is like half a lobe wider than the green C3.  

Matt Castelli · · Unknown Hometown · Joined Feb 2017 · Points: 240

Thanks David K - that was the type of useful info I was hoping would come out of this (now hijacked) thread!  

Now back to predicting how many months of production delays z4s will have ...

Harumpfster Boondoggle · · Between yesterday and today. · Joined Apr 2018 · Points: 138
David K wrote:
With these things considered, it starts to look like making a more conservative choice with your cam angle is a good idea.

Well, who the fuck knew? Metolius and the orginal Friends (of course).

Look, there is more than one way to skin a cat and BD cams and Totems are the living proof with very different designs with plus features and minus ones.... In variegated cracks (ie Gunks) range **may** be more useful to some if nothing more giving confidence to a leader that they will get a good placement.

In splitters (most Yose test piece cracks or at The Creek) its mostly immaterial. You just need a lot of cams, that hold, and the lighter the better. If you need 6 cams that fit an 1-1/4" crack you just need 6 and the lighter the better and the range of the individual cams means nothing.

This is also why Metolius makes a series of cams with wider lobes to reduce pulverization of the rock (for sandstone mostly). When you've seen the skid marks from cams getting ripped out of cracks at The Creek you will know this is a thing.

Needless to say this has fuck all to do with coefficient of friction and everything to do with force on a small surface area crushing the rock.

Regardless, this entire hijacking was started by some lauding the "range" of the new BD cams. The point is you have traded something (ultimate holding power) for that range and it may not be the best choice in small cams.
Former Climber · · Unknown Hometown · Joined 24 days ago · Points: 0

FYI:

https://patentimages.storage.googleapis.com/7a/15/89/e33cfc1595e4fc/US20060231708A1.pdf
Mike · · Unknown Hometown · Joined Dec 2013 · Points: 30
Former Climber wrote:

Pretty charts, but they don’t agree with Matweb.  Possibly because your site is crowdsourced and anyone can sign in and assign values to things.


FWIW, 6082t6 is 36ksi yield and 6061t6 is 40ksi yield.  Pretty clear which will deform first.

Come on first off you said softer before now you're making a moving Target, for what it's worth matweb lists the hardness of both as 95 HB.  Matweb is sourced from a bunch of random vendors I've found flawed data on there multiple times. I use it frequently but sometimes the comparison tool in the site I used is nice. 4 ksi is something over long term statistics but material variability will likely be more than 4 ksi. So no it's not clear which will deform first. Yeah it's more likely to be the 6082 but not necessarily always. Pretty much any website out there lists a spec for minimum allowable ys typical values. Honestly I just decided to post because of your shoddy science and know it all attitude. 

Former Climber · · Unknown Hometown · Joined 24 days ago · Points: 0

My goodness!  An Engineer who thinks he knows everything!  That *never* happens!

In any event, if you have an explanation for how a cam will slip when Tan(cam angle) > coefficient of friction I’d love to hear it.  That’s simply how they work, hence the attitude.

Note the above chart listing friction for various rock types and the fact that 16 degree cams have been in use for 3 decades.  

Rob T · · Unknown Hometown · Joined Jun 2006 · Points: 10

^^you don’t say.  I’m kind of surprised the conservative crew here hasn’t started a petition to harass totem into changing to a 10 degree cam angle. They and metolius are playing with our lives as they needlessly increase range at the expense of holding power!

David K · · New Paltz, NY · Joined Jan 2017 · Points: 145
Former Climber wrote: My goodness!  An Engineer who thinks he knows everything!  That *never* happens!

In any event, if you have an explanation for how a cam will slip when Tan(cam angle) > coefficient of friction I’d love to hear it.  That’s simply how they work, hence the attitude.
How about this: if what you're saying were true, then none of the cam angles you're claiming would work.

1. tan(13) = 0.23, tan(16) = 0.29
2. The vast majority of coefficients of friction are greater than 0.29.
3. Therefore tan(cam angle) < coefficient of friction in most cases.
4. So congratulations, you've mathematically shown that cams don't work.
5. Since we know that cams DO work, your math must be wrong.

If you'd like the actual proof that cams work when Cf > tan(a), NOT when tan(a) > Cf, see here, which I already linked.

Just to continue to demonstrate the problems with your claims: your claimed cam angles aren't even correct.
Guideline #1: Don't be a jerk.

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