Spike Strength on BD Ice Tools

[Lambone]

quote:

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Originally posted by Ibex:

Lambone, worked with a bud of mine name Tim, also a prisoner...er student at Iowa State Univ.

Shawn

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Tim sucks....

[Ibex]

Freeclimb,

I agree with you up to this point:

quote:

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Originally posted by freeclimb9:

The folks at BD use "lbf" as a unit of mass, and there's 2.2 of em per kilogram. So, Tommy Chandler at BD said the head on cobras often holds with 5,000lbf on it (i.e. 2272 kg, or 22kN --that's kN-kiloNewton, or 1000 Newtons),).

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The "f" in lbf means 'force' not mass. You can't use mass to break something. You use FORCE to break something. lbf has units of displacementxmass per sec ^2 (ft-lb) and when spoken is commonly said as "suchandsuch pound-feet of force" to ensure that people know it is a force not a mass.

You cant go (english force) to (metric mass) to (metric force) the quantities are just not the same. You can only go (english force) to (metric force). Either way, as long as we all stay on Earth, its no big conceptual leap to think of mass vs. force being applied to (or hung off of) something

One really good point you brought up is the different coefficients of thermal expansion of CF and steel. I suspect that the steel would restrain the CF from shinking-expanding so much, but doing so would only add addtional stresses to the joint. I am not sure how the BD engineers got around that.

Another interesting point you bring up is the end to end pull test, vs pick loading test. Loading the pick (force applied via a lever arm) is going to stress the tool much differently than a ordinary pull test. I am curious if that is also a part of the CE testing. The BD guy only mentioned the pull test, but intuition would think that CE would require a pick load test.

Is any of the data from Craig Luebben's testing on the web?

Good points my friend.

Shawn

[ 12-08-2001: Message edited by: Ibex ]

[ 12-08-2001: Message edited by: Ibex ]

[Ibex]

[ 12-09-2001: Message edited by: Ibex ]

[Lambone]

quit talking to yourself shawn...

[freeclimb9]

the testing by Craig Luebben was put in a book that he wrote, "How to Ice Climb" (I got a free signed copy at a tradeshow).

I reiterate that BD uses the abbreviation "lbf" as a mass. If you don't believe me, check out their website and look at their specs for strengths of equipment (www.bdel.com). And you can convert from SI units to English ones and from force to mass (we know that force=mass*acceleration, and the acceleration due to gravity is 9.8m/s**2, or 32ft/s**2). That conversion is how equipment manufacturers quote strengths in either force units such as Newtons, or in mass units such as kilograms or pounds.