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Author Topic: Supporting rack mount equipment Frank Cox Film God Posts: 2234 From: Melville Saskatchewan Canada Registered: Apr 2011 posted 03-01-2019 01:02 AM                        One of my amps died and I just replaced it. My sound rack has no rails so the only thing holding the equipment in place is the bolts through the wings on the front panel. As it happens, the amp I replaced was the bottom one in the rack so I actually managed to find a box that was exactly (to the fraction of an inch) the right size to sit between the amp and the bottom of the rack to support the amp while I removed the bolts, changed the amp and put the bolts back. The amps aren't hugely heavy but they aren't nothing either. They're QSC DCA2422's and the spec sheet says they weigh 21 pounds. So my question is, how are you supposed to support these things when you remove the bolts so they don't fall down or drop onto the next component below them in the rack? Pulling everything out of the rack from the bottom up to the faulty component seems pretty inefficient and I'm not sure I could find a box to fit each iteration if I had to change the amp at the top, for example. I don't think I could hold it from the back with one hand and undo the bolts at the front with the other; I don't think I could support the weight that way and I don't think I could reach that far. Is this stuff just supposed to be a two-man job and that's all there is to it, or am I missing some clever trick?  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 03-01-2019 01:50 AM                     First off, if all of your amps are DCA's there is no need to mount them with empty rack spaces between them...I have always stacked them from the bottom up, so only the bottom amp would require support if needed. They have flow thru fan cooling and no vents on top or bottom. If you have one rack space between amps, the trick I always used was 35mm film cores or trailers. It was close enough to the required height that the amp would not fall far enough to be an issue. For other spacings, I would stack cores or trailers. As for getting one out in the stack, I would remove the four screws then push the amp out partway from behind, then use the rack ears as handles to take it out the rest of the way. Easy peasy. The same principles apply with other equipment, and for processors and the like, I tend to remove all but one screw (usually leaving the bottom left corner), loosening that last screw until just a few threads were holding it. I then put my right arm under the equipment, to support it, then took out the last screw with my left hand. Then, pull the equipment out with both hands. As a tech doing service calls solo, these were the only ways I found to work for me with minimum fuss.  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 03-01-2019 05:47 AM                     I've never really seen an equipment-rack with rails, those rails are usually provided by the manufacturer of the equipment itself. Most audio-equipment however, is supposed to be mounted in a 2-post fashion, without rails. Those 2U QSC DCA units are made to be stacked, as long as the airflow at the front and the back is sufficiently guaranteed. So, when you stack them with no space in between, it's usually pretty easy to get one out and back in there. The only thing that annoys me is that the mounting holes in the rack ears are in the most outward position, this sometimes clashes a bit with cage-nuts and bolts of equipment that's directly adjacent, in many cases, other DCA units. For really heavy equipment, that doesn't come with rails, I often install a 19" rack shelf first. That way, I can slide it onto the shelf and then mount it to the rack posts. Depending on how much it will sag on the backside, I might decide to leave the shelf in there.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 03-01-2019 05:55 AM                     Frank, at some point I had to do the exact thing, and solved it with a few foam bumpers I cut from a lamp packaging. I just place them below the amp to be moved out, you can cut them to size so they just sneak in between and nothing's falling down. If you cut them small enough, you can leave them sitting there, or store them somewhere after you have taken them out when the new amp went in. I'm sure you'll be able to find thick foam in some boxes you stored somewhere, or, go to a white goods store and request some of their packaging. Usually they'll be glad to get rid of some. - Carsten  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-01-2019 06:33 AM                     Wow...you find it hard to pull a DCA amp by yourself? Those are lightweight amps. Try it with an MX1500 (or MX2000 or MX3000). As others have said, there is zero reason to separate the amps but if you choose to, remove the blank below it. Remove the two top screws FIRST. Then remove one of the bottom screws while supporting the amp so it does just lower on its own (it will want to pivot via the remaining screw). As you unscrew the last screw, the amp will start to lean back and again, support the front as the screw comes out. Once the last screw is out, ease it down on the front. Slide it out. Reverse for reinsertion. Depending on the length of your rack screws and your finger mussels, you may need to device some assistance. For instance, put the blank back in first so it helps support the front. If your screws are long enough and you can push hard enough with your screw gun/drill (or even your hand if you are just using manual screwdrivers) you can get it to raise up just with the screws. Otherwise, most anything will prop the rear up from what is below it. It need not be precise. You just need the face of the amp close enough for the screw to catch. Once your bottom screws are almost all of the way in, remove your rear prop or risk it getting pinched into place. Now, if you did have a heavy amp like the MX series, then yes, I like using rear hangers as it not only supports the amp better but makes installation easier since you can slide the amp in, lift up on the rear and put the screws in on the rear hanger to support the amp. Loading/unloading amps as a repair is not a 2-person job but if the other person is there, then by all means use them to make it an easier job.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 03-01-2019 07:58 AM                        We use rear rails and vertical lacing bars in all of our racks. These things make cable management and equipment mounting so much easier. We will often use shelves upside down or horizontal lacing bars on the rear rails to support equipment that doesn't have rear mounting rails.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 03-01-2019 11:02 AM                     These amps don't need rear support, although it is possible with an accessory if you have a rear rail positioned correctly. We do this when a stuffed rack has to be shipped, although preferably just the rack wiring is completed and the amps shipped separately. Much lighter rack to get up the inevitable stairs as well. Doremi chassis servers can hang on the front bolts but it's marginal, threaded hole racks tend to strip the rail threads eventually. Racks with snap-in nuts are better for that since the nuts are stronger and can be replaced (but those nuts are a PITA). There is a slide kit for Doremi if you have a rack with rear rails. A (crazy long and heavy) Dolby DSS200 definitely must be supported at the rear or be on slides (included with the servers). The trick assembling racks is to mount the bottom amp first, then use a spacer (like cardboard) between each amp or pry each up a bit when tightening the screws. This leaves enough clearance to slide any amp out, none are clamped in place. Using 1U panels between amps is fine if you have the space, you still have to leave some clearance between components. If you have saved a few old 35 cores they are close enough to 1U height to use as spacers while you screw in an amp or whatever. When assembling new racks I like to lay them down on their backs and drop the amps etc in, much easier and it's simple to space them out so none are held in tight by those above.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-01-2019 01:11 PM                     For the record, I HATE HATE HATE caged nuts. Using decent screws and racks, I've never had a tapped hole strip out. Cage nuts, aside from the absolute pain they cause (physical) also have the equipment sag a bit since they also act like a cheap-ass spacer to the equipment (the clip part comes between the equipment ear and the rail). As for loading racks...the best way? On their backs (typically with a piece of wood to allow lifting them vertical when done under the rack near its top). And YES always center the equipment vertically on the screw holes so equipment can be slid in/out without being jammed by the thing above it.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 03-01-2019 03:20 PM                       There must be a trick to inserting cage nuts. The ones with the Christie bases seem the worst. I waste more time installing these than any other single task in the process.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 03-01-2019 03:29 PM                        Caged nuts and square hole racks are EVIL! I think they are much more popular in the IT world. We (BLS) use Middle Atlantic racks pretty elusively and almost always the WRK series with the removable side panels unless theres a reason not to. One great thing for Atmos installs is to use the optional wire raceway for the wrk series. Yes, Middle Atlantic is pricey but they look nice and i've never had an issue with one of their racks. Now their Mid Atlantic branded electronics on the other hand... For projector pedestals I really like the MIT pedestal. One thing I like to do sometimes especially if I am putting a christie power supply in there is to order another door and provide access to both sides if you dont need the rack space.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-01-2019 04:12 PM                     +1 on Middle Atlantic racks. We use mostly ERK series for sound. Only the WRK if we need the extra channels. The only reason we would use removable side panels is if we were ganging so of the WRKs, quite a few have been the WRK-SA style.  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 03-01-2019 04:39 PM                     quote: Caged nuts and square hole racks are EVIL! Well, yes, it's not always rosy, but you learn to live with it. We also prefer to standardize. Try to mount any IT equipment with their standard rail-sets into a rack with round holes for example. quote: Sam D. Chavez There must be a trick to inserting cage nuts. The ones with the Christie bases seem the worst. I waste more time installing these than any other single task in the process. You need one of these. It avoids getting your fingers stuck between nut and cage or experiments involving screwdrivers and pliers. We order cage nuts by the bag of 100 or so from Rittal, which we also order most racks from. It's a German manufacturer and they're kind enough to put one of those little metal tools into each bag of cage nuts.  |  IP: Logged Adam Martin I'm not even gonna point out the irony. Posts: 3686 From: Dallas, TX Registered: Nov 2000 posted 03-01-2019 08:28 PM                     For cage nuts, I use a cage nut insertion tool.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 03-02-2019 08:35 AM                     +1 for Middle Atlantic racks, and their custom power bars are great. The legacy racks we work on that get stripped threads are not MA, their threaded rails are formed from thinner sheet metal. MA rails are thick and stout. Christie pedestals have always been evil. The removable sides are good, yes, but the snap nuts are horrible... and why 1/4" threads rather than the almost universal (for audio racks) 10-32? Plus no way to support the rear of a deep server or slide rails. The Barco standard pedestal is pretty good other than its screw on side panels, I think maybe MIT makes them for the Americas? Not a fan of the Barco flat pack pedestal.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-02-2019 08:56 AM                     Here's the thing about the "servers" as the reason for using a caged-nut type rack rail system. At first I liked them for when we did Dolby DSS servers...Dolby supplied the slides that just clicked into the holes. But then it dawns on you...so that saved you 3U worth of mounting and the rest of the equipment you'd be fighting to Effin caged nuts and again, they don't hold equipment well without sagging. Dolby supplied you with the adapters to use traditional 10-32 rackrails so what was the big benefit there? So screw the cage-nut system for most of what we do in cinema. If I were put in a server farm like some IT people do, then yes, I'd see the advantage. But if you are mostly putting in traditional equipment with maybe one piece that needs the hole-type rail, then screw that. Adapt the one piece to the 10-32 system. There are just too few benefits to the caged nut system (which are really just the adapters for things that don't use the holes directly). The negative column is just overwhelmingly long. Dave, funny you mention the Christie pedestal...that didn't consult anything for its dimensions. It is too long for most servers of the day and too high for standard lens heights used in the prior art (film). The current pedestal is a bit better in the height department. What one of our techs did with the Christie pedestal is take the supplied rack rails used for forming two horizontal racks and band saw them apart. Then using suitable standoffs (I believe he made them himself out of square stock and drilled a hole down its length) made standoffs for them to provide an inner set of rails so normal server lengths (DSS200) could be used. But who wants all of this in "kit" form...which is part of what a caged nut system is.  |  IP: Logged

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