[c-nsp] 7201 rack mounting

[Ted Mittelstaedt]

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net]On Behalf Of Peter Rathlev
> Sent: Wednesday, April 23, 2008 10:19 AM
> To: Dean Smith
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] 7201 rack mounting
> 
> 
> Not really on topic, but we just finished mounting three 6509-V-E
> chassis; I know they come with some stub "shelves", but otherwise they
> just hang in seven 4 mm long screws in each side. (It doesn't matter how
> many rack mouting nuts you use, the panel you fasten to the rack is
> fastened to the chassis with those seven screws.)
> 
> The chassis itself weighs in at just below 50 kg. Add a supervisor and
> some heavy line cards and you're approaching my weight, and I'm not
> exactly lean. Fourteen tiny screws... I wouldn't rest in a hammock
> mounted in that way. :-)
> 

Shear strength of mild steel is roughly 25 tons square inch.  These
small screws probably could each hold close to a ton each in shear
force.  When you have this in a rack, the force on the screws is 
virtually 100% shearing force, which is far different than the
force exerted on the threads of a steel hook inserted into a tree.

The problem is in the end mounting because the leverage exerted by
the far end of the device is considerable - far in excess of 50 kg.
Center mounting and there is no leverage exerted.

Earthquake resistence really calls for center mounting in any kind of
2-post rack.  This is why everyone is going to 4 post cabinets.  The
problem is Cisco doesen't really put good mounts on their gear for a
4 post cabinet.

Ted