Quit being an ass. The Sticht Plate was also a single slot device and was the standard belay device for years. And a hell of a lot more than two guys used the chain links.

If you're going to comment on climbing history, at least get it right.

homey i dont know what crawled up your hex and died but what do you expect when you nitpick like a high school math teacher?

I'll show my work and not just the answers from here on out, I promise!!11

This is a minor blip in the radar of climbing history. I know my climbing history, real history. White spider shit and stories from way back when before you were a curmudgeon. Don't try to pigeonhole me in with other young guys who don't know what they are talking about.

I'm gonna have another beer, enjoy your internet nazi'sm. I'm sure its appreciated.

Belay device for single or double ropes. With 2 allen keys it is possible to change the diameter, so it can be used with thinner ropes (always from 7.5 to 11mm)

Stop hijacking my thread, and get back to the topic at hand?

Mad Lock - Mad Rock


There was a reason Petzl discontinued this design. Though some may appreciate the versatility of a belay device that can magically turn into a knife, I think I'll stay away. And what's with this removable pin crap? I say hell no to the frankenreverso.

But all these devices show one problem we are facing today: The range of ropes used is too wide!
There are still places/ situations where 10.5 or even 11mm is a good choice, whereas on the other hand we are using sub 8mm doubles (or sub 9mm singles). so its either stick to one rope type, or carry multiple devices. (or try to reinvent the wheel, err ... belay device)

qwert

Wild Country VC Pro. Worst ever modern belay device. I bought while waiting for the reverso 3 to be available (and I'm a gear whore). I thought it would work well since it looked like the BD ATC XP and it was cheaper. I returned it to the store the next day.

[image]http://www.wildcountry.co.uk/imgs/3791i2783.jpg[/image]

This Faders device is amoung the worst around. On fatter ropes at least belay is horrible.



Stich plates are better. Or better yet for those on a budget go the ALDI device!
http://www.aldi.com.au/...offers/2827_9045.htm

Maldaly may have some comments on this, but as I recall it was Craig Luebben who first came up with the idea of putting flanges on a rappel device to dissipate heat. I had discussions with him as he developed the idea, which ultimately became the Pyramid.

At that time, there had a been some rappelling accidents reported ANAM where the rappel device had heated up (in the sun, heavy loads, etc.) causing a decrease in the friction of the rope in the device and the climber losing control of the descent.

Qualitatively, the flanges do increase heat dissipation. The question, Is this quantitatively significant? And that's not so easy to answer.

Cheers,
Rob.calm

It would be worthwhile to build a belay device (for testing purposes) with the same mass as the pyramid, but with a minimized exterior surface area, and compare the cooling times of the two after identical rappelling/lowering simulations.

Why? I could see building one of the same core size (minus the cooling fins) to see what difference was incurred.

Because the point is to test the overall effectiveness of the cooling fins, not just the theoretical effectiveness of the cooling fins. We want to know if the increased rate of cooling due to the added surface area of the fins is sufficiently large to offset the resistance to cooling caused by the additional mass. The only way to control for that is to create a belay device of identical mass but that minimizes the surface area. Otherwise, you'll introduce unequal heating rates as well, and your eventual data will be worthless. Basically, a pyramid without the added mass of the fins will heat faster, so we'd have a higher max temperature for the exact same rappel.

...

I can do the calculations for a fast 50m rappel:
80kg * 9.8 * 50m = 39200
39200 / 50g / .9(J/gK) = 871K

thats a fast rappel

You cleary have little understanding of the physics involved here. Increased mass will always result in a lower peak temperature achieved. Increased surface area will always increase the rate of cooling and thus lower peak temperature.

80kg * 9.8m/s/s * 50m = 39200J

Lemme make sure I understand your argument here:

By increasing the mass, we decrease the maximum temperature achieved.

WHICH IS PRECISELY WHAT I SAID IF YOU'D BOTHERED TO READ IT.

I said that we can't simply compare a pyramid with fins to a pyramid without fins since a pyramid that simply lacks fins will have lower mass.

And again, the issue is not of overall heat in the system, it is heat that remains in the device.

And ANYBODY who says that a rappel device shouldn't heat up that much has NEVER done a 60m rappel on dual 10.5mm ropes, much less a fast rappel.

Should I write out the energy in/energy out equations so you can see why a fast rappel would heat up the device faster than a slow rappel? Or can you work that out yourself?

9.8m/s^2 is free fall, not a "fast rappel."

Well, for one, 30s for 165 feet is pretty bleedin' fast. I'd burn out a pair of gloves doing that.

Still, it'd take a lot of time to have a major impact if the only time that the device was cooling was when it was on the rope.

And furthermore, the question is not "does the device dissipate the heat put into the system?" but rather, "does it effectively dissipate the heat input into the device?"

Your second calculation is meaningless because you ignore the most useful part of your first post, that the rope is the primary sink in the system.

I actually wouldn't be that surprised if 300J was the difference between melting a sheath and not melting a sheath since there's a much larger amount of rope mass to deal with the rest.