Cabinet back question

[Trace Wilson]

Hi all,

I've recently undertaken building an entertainment center for my house. The design is a typical two tower setup, with a bridge across the top. Each tower is composed of two pieces, a base cabinet with doors that is about 33 1/2" wide and 30" high, and a top cabinet for stereo components and front speakers.

The top cabinet is about 32" wide and 48" tall. About 12" from the top is a horizontal shelf dadoed into the sides. In the bottom area, there is a verticle panel, dadoed into the cabinet bottom and the horizontal shelf, about 10" from the "inside" (the side that faces the TV) edge (I'll try and draw below...best viewed with a NON-proportional font:

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The two towers are mirror images of each other.

Right now, I don't have any backs on the top cabinets, and I'm noticing a little racking in the cabinet, about 1/2 - 3/4 in. with moderate pressure applied to the top-side of the cabinet. Ideally I'd love it be rock solid, but I'd also like to leave the back off the bottom section to allow for airflow for the stereo components.

My plan is to glue/nail a 1/4" back, roughly 32"x15", that covers the space above the horizontal shelf (roughly the upper 1/3 of the cabinet). Anyone have any thoughts on how much that would help with the racking.

Origionally I had planned to glue 3/4" x 3/4" strips to the back edge of each verticle surface, put threaded inserts into them, and that way I could put on a removeable back. Also, the 3/4" strips in the back gave me an automatic space to let wires travel between shelves. However, if I can make the cabinet rock solid and leave the lower backs off, that would be even better.

Thanks in advance for the help...

Trace Wilson

[David]

a 1/3 back will help tremendously. It should reduce your racking from a horrendous 3/4" to next to nothing.

Dave

[gw]

Make a back for the lower section with a rectangular hole in it leaving 2-3 inches of material around the perimeter. The solid piece should give plenty of torsional stability, and you can attach it to all vertical and horizontal elements with screws. Your racking problem will only get worse with weight on the shelves.

[Larry Blanchard]

I'm also in the process of building such a tower for an entertainment system. What I'm doing is to inlay shelf standards so I can move the shelves as equipment changed. Each shelf has a C-shaped cutout about an inch deep across 3/4ths of the back edge. The top of the tower has a grill across the back edge. Hot air rises through the cutouts and the grill and cooler air is drawn in from the front to equalize the pressure. The back will be solid.

Obviously my method doesn't work if the tower has solid doors. Mine has no doors and a door with a grill in it will also work.

[DamnYankee]

I'm currently building an EC too and have also been trying to decide how to "do" the back of the case. The main box is 25" deep, 56" wide and about 56" high. (I can't the remember height exactly but that's within a couple of inches) There will also be media storage on both sides 20" deep, 8" wide and 48" high. Inside the main box I built a 46 wide by 13 high base unit that the TV will sit on and will house 4 drawers for more media, remotes, wires, or whatever. At the top of the main box is a hanging unit 46 wide and 9 high with 4 4x22 cavities for media players.

For the back, I think I'll put a piece of 1/2 inch ply by 13 high at the bottom. This will be where the base/drawer unit is. Besides that, I think I may put in another piece that will be about 6 inches high just below where the hanging unit is. By doing it this way, I'll have all the backs of the equipment exposed for hookup and hopefully still have enough support to keep it from racking. After reading the posts here, I'm pretty sure I'm on the right track and you should be as well.

I'm not sure how I'm going to move this thing.... It's all 3/4 inch plywood and solid oak. I think I may have to get everything finished and then assemble it in the living room. In fact, I'm sure that's what I'll have to do!

Good luck with your project!

Bryan

[ljaques]

On 1 Feb 2006 11:03:52 -0800, with neither quill nor qualm, "Trace Wilson" quickly quoth:

That will take care of it. I built some rolling rock racks for my neighbor, essentially open-faced boxes with removable shelving. To reduce racking on the front (back was enclosed), I inserted 3" triangles of oak, 1 glued in each of the top corners. He has up to

500 pounds of rock boxes on each one and they're solid as ever now. Four 5" swivel casters make them easy to roll around his garage. He made me use his spare wood-faced MDF plywood for the darned things in order to cut costs. That was the first (and hopefully last) time I'd ever worked with it. ;)

Nearly complete.

The partial back should add considerable stability to the box, Trace.

Alternatively, a pair of 6" strips (top and bottom on the back) would also take care of it. Most of the flex is in the connection between the vertical and the horizontal planes. Brace the corners and you get solid in a hurry.

[Swingman]

Fastening your proposed back to the sides, top, and back of the shelf, should solve the problem.

[Trace Wilson]

Bryan,

FWIW, I found some approx. 3 in. double wheel plate mounted casters at Rockler that are rated for 250 lbs. each. On mine, each tower base has a small (4"-5" wide) piece of trim around the front 3 sides. The bottom of the cabinet is dadoed in about 4" from the bottom of the sides. With the casters mounted, there is 1/8"-1/4" clearance from the floor. The hope is that the casters will make turning the units MUCH easier when needed, but the small clearance will be mostly concealed by the carpet.

Good luck...the unit sounds sweet!!!

Trace

[Trace Wilson]

Thanks to all for the replies!!! Just finished cutting the shelves last night. All that's left is to put the trim on the front of the shelves, build the doors, stain & finish!! Wait, what's that...oh, a light at the end of the tunnel!!! ;-)

Thanks again...

Trace