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Material choice for large desk slide tray

loydb's picture

Material choice for large desk slide tray (post #170678)

I have recently gotten a nice desk to which I want to  add a large 88-key sliding keyboard  (see http://www.kkaudio.com/images/desks/keyboards/MD-O_FR.jpg for a rough idea).

The gap between drawer units is 60". I've got a pair of Knape & Vogt heavy-duty 24" drawer slides. The keyboard (a Roland RD-700sx http://www.rolandus.com/products/details/666) ) weighs 55 pounds. 

My question is, what do I need to make the tray out of. Is 3/4" maple ply going to be stiff enough? Should I use 3/4" hardwood instead? I though about making an angle-iron tray and cutting a wood insert to fit, but I think that will be overkill. 

Input appreciated, thanks!

Loyd

RalphBarker's picture

The span, the span (post #170678, reply #1 of 9)

A 60" span is pretty wide. You might consider augmenting the front and rear edges of the tray with metal angle or T-bar stock.

loydb's picture

metal (post #170678, reply #2 of 9)

Would the angle bar need to be attached physically to the drawer slides, or would it just need to be attached to the wood to act as a stiffener?

Thanks,

Loyd

RalphBarker's picture

Stiffener only? (post #170678, reply #3 of 9)

I'm thinking stiffener only, assuming the sides of the tray are hefty (e.g. 3/4" ply). But, a lot depends on the total weight of the tray with the metal stiffeners included. With that in mind, you might need something more than 1/2" #4 screws to attach the tray to the drawer slides.  ;-)

loydb's picture

I could use... (post #170678, reply #4 of 9)

a glue gun! :)

My plan at this point is to use 3/4" hardwood for the tray rather than plywood. I'd like to go with Spanish cedar, because of the weight, but am not sure how it will do even with a stiffener. If that doesn't work, it's on to maple or walnut. I was thinking about 1.25" wood screws for mounting to the slides.

Thanks for your input!

Loyd

 

 

RalphBarker's picture

3/4 inch (post #170678, reply #5 of 9)

I assume you mean 3/4" for the side, front and back rails, and perhaps 1/4" ply with under supports for the bottom of the tray?

For something that wide, you might even consider a shallow torsion-box design for the bottom, using 1/8" ply for the skins.

It's always fun coming up with design ideas for other people's projects. Particularly since any failures are not in my shop.  ;-)

RalphBarker's picture

Another option (post #170678, reply #6 of 9)

Another option would be to split the tray into two or three sections. (Hey, if one tray is good, three ought to be way better, right?)

That would greatly simplify the rigidity issues, allowing a more traditional design approach. Plus, the three trays could be labeled, "his", "her's", and "the dog's" (your dog is on Facebook, right?  ;-) )

loydb's picture

hmmm (post #170678, reply #7 of 9)

I'm not sure I'm picturing what you're talking about with plywood supports. The drawer glides are heavy-duty (500 pounds rated) with non-removable drawer slides. I'm planning on a single board spanning the gap (with a piece of angle iron attached to the back underside as a stiffener. The tray will be directly attached to the slides with 1.25" wood screws. 

I'll take some pictures when the slides get here. It has occured to me that I can just mock the whole thing up in the shop and see how it does...

 

RalphBarker's picture

Stiffness, stiffness (post #170678, reply #8 of 9)

Sorta like pizza, pizza. (Significant only if you have Ceasar's Pizza in your area.)

There are two structural elements that you want to keep "stiff" - the tray frame, and the tray bottom. Assuming 1/4" ply for the tray bottom, considering the 60" span, it will want to sag in the middle over time. Adding little support strips (1/4" x 1/2", perhaps) glued to the underside of the tray bottom will add rigidity.

roc's picture

Maybe you can make this help you for your drawer (post #170678, reply #9 of 9)

http://www.finewoodworking.com/SkillsAnd...

Other wise I was picturing using a bowed structure with internal diagonal cables, you know like bicycle shift cables, that you could tension with adjusters to tune the bow so with the keyboard in place the drawer unbows down under the keyboard's weight to where it is flat. (sort of like prestressed concrete beams)

:    )

 . . . . just kidding.  I might do something like that but . . .

nah don't listen to that.  Maybe the Sagulator will help.

roc

Give me six hours to chop down a tree and I will spend the first four sharpening the axe. Abraham Lincoln ( 54° shaves )