[EIDXA] Physics question

[Jason Joens]

That's what I use for fall arrest, actually, but I usually get my stuff from
GME Supply I use a pair of those shock lanyards on my harness for tie-in.  I
do not use static line for fall arrest.  And with the information others
have brought to the table today, I'm glad I don't!

Wow, Glenn.  Thanks for the lesson!  That's some really good information to
have!  Glad to hear that the new antennas have taken the storm.  I hope they
are working well.  It was great to come visit, and climbing with Paul was
unforgettable!

Jason

-----Original Message-----
From: Culbert, Allan B [mailto:allan-culbert at uiowa.edu] 
Sent: Friday, June 21, 2013 1:23 PM
To: Jason Joens
Subject: RE: [EIDXA] Physics question

Jason,

All the OSHA approved stuff has a shock absorbing system designed into them.
They are available here in Iowa City at White Cap Construction Supply - 2003
S. Gilbert (south of Hiway 6). You can get lanyards with the shock absorbing
material. If I recall my OSHA training it stops the body w/in 6 feet, so the
idea is to keep the tie off point as high as you can.

73

Al, K0AL


-----Original Message-----
From: eidxa-bounces at mailman.qth.net [mailto:eidxa-bounces at mailman.qth.net]
On Behalf Of Jason Joens
Sent: Friday, June 21, 2013 12:43 PM
To: EIDXA Reflector
Subject: Re: [EIDXA] Physics question

Ok, my normal static line is rated at 10k.  I know I need to get some more
dynamic line.  I only have a couple short pieces that I use.  I only use my
static line for positioning and rappelling. My crab hooks are my tie-ins.  I
didn't know about that calculator, Joe.  Thanks for the knowledge. I kinda
tend to like to keep my safety margin higher than that though.  I will have
to think this over some.

Jason

-----Original Message-----
From: Joe Hungate - K8OM [mailto:radiojoe_k8om at msn.com]
Sent: Friday, June 21, 2013 12:19 PM
To: Jason Joens; EIDXA Reflector
Subject: Re: [EIDXA] Physics question

Hi Jason,

I think the answer is going to be about 4600 pounds.

I used the "Rock Climbers Force Calculator" 
(http://www.myoan.net/climbart/climbforcecal.html) to get the force on the
rope for a mass of 200 pounds free falling 3 feet and a static rope with
negligible stretch . The solution is in Kilo-Newtons so to convert
Kilo-Newtons to pounds I used the calculator at
http://www.convertunits.com/from/kilonewtons/to/pounds.

That could sure shake some teeth fillings loose!

A 100% safety margin (9200 pounds) probably would be advisable. Grainger
sells some 5/8" nylon rope that has a tensile strength of 9350 pounds
(http://www.grainger.com/Grainger/Rope-1VEL8?Pid=search). Not sure how you
would connect the rope to the climbing hooks to withstand that kind of
force.

I hope this helps but use the info at your own risk...... I sure hope you
never have to test it. Anyone else come up with a different solution?

73,

Joe - K8OM

-----Original Message-----
From: Jason Joens
Sent: Friday, June 21, 2013 11:28 AM
To: EIDXA Reflector
Subject: [EIDXA] Physics question

Grr!  My phone seems to like to send blank emails. Sorry about that!



Ok.  I weigh about 200 pounds.  So if I'm hanging on the end of a rope, I'm
putting about 200 pounds of force on that rope.  But what happens if I fall
3 feet, and the rope stops my fall?  How much force did I just put on that
rope?  Assuming a static rope with negligible stretch.



Jason

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