Howard Winter wrote:

> Jim,
> 
> On Mon, 21 Feb 2005 21:12:38 -0600, Jim Korman wrote:
> 
> 
>>Ok I've google'd more rack mount equipment et al, etc...
>>
>>Does anyone know where one might find a specification for rack mount. I know 19" wide and all that but what 
>>
> about the actual specs, i.e. thread sizes, etc.
> 
> Things I've learned the hard way about 19" racks:
> 
> 1. The front panel of a rack mounted item is 19" wide.
> 2. The vertical spacing is quoted in "U" (Rack Units) and 1U is 1.75", but you don't need to know this - just 
> count in U.
> 3. Don't rely on anything else!  Some manufacturers (Compaq especially) do their own thing, and act as if 
> there is no standard involved - as far as they are concerned you use their racks, their servers, and nothing 
> else!  Others make assumptions that you may not expect - you are assuming that there are standards for all 
> aspects of a 19" rack - there aren't.
> 4. The front-to-back spacings are especially variable - a "patch cabinet" will be quite shallow as it's 
> designed for patch panels, hub/switch/routers, modems, whereas a "server cabinet" will be *much* deeper to 
> allow servers to be installed.  The variation from deepest to shallowest can be as much as 2:1.
> 5. Don't assume anything!  Spacing from the front of the rack to the back face of the door may be small - I've 
> seen them where patch cables plugged into patch panels didn't have room to bend before the door got in the 
> way, so the door had to be removed.  Similarly there may be no room to run bundles of cables where you want, 
> and there may be no way for *any* cables to run from in front to behind the front panel, without going between 
> rack-mounted items (losing you 0.5U and looking awful in the process).
> 6. Rack suppliers can be terribly unhelpful when it comes to finding out the nitty-gritty of their designs - I 
> don't know why...
> 7. However much you think you've cracked it, something is likely to bite you at installation time - don't put 
> it on the critical path of any project plan if at all possible.
> 8. Calculating the U spacing is pretty easy to get right, for all other dimensions make sure you have plenty 
> of space to spare.
> 9. Having a shelf-mounted keyboard and a clever fold-out TFT screen looks good in the brochures - in Real Life 
> it's a pain in the bum to use because you have to stand up, and there's nowhere to use a mouse or to put 
> documents.  Much better to have screen/keyboard/mouse on a desk next to the racks, so you can sit down, use 
> pieces of paper to refer to and write on, and so on.  Even if someone only does it once a month, it's a right 
> pain (and for those on the right hand side of the Pond, may contravene EU Working Regulations).
> 10. Don't assume anything!
> 
> Best of luck - I know I needed it every time I got involved in racking...
> 
> Cheers,
> 
> 
> Howard Winter
> St.Albans, England


Thanks to everyone who responded. I finally found the actual spec,
off an EBay auction item, go figure.

Anyway the spec is EIA RS-310C, the document is available from
Global Engineering Documents (all 24 pages) for the sum of $52US
paper or PDF.

  http://global.ihs.com/

and use EIA-310 for the document search.

Jim Korman





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