Need some physics help

[Richard Neel]

I'm almost ready to begin my next project which will be a small, drop-front desk similar to this:

http://www.jlfurniture.com/Gallery1/Drop_Front_Desk/drop_front_desk.html

I really like this design which I feel is unique as most drop-fronts you see have slanted tops.

I have a concern about the construction of the dropped desk top. In the picture it appears the only support of the top (when open) is the ledge of the lower frame. This doesn't look adequate to me as only a few inches of the top are supported.

Does anyone have ideas on improving this design? Could the drawer be used somehow as is the case with some slanted drop-fronts?

[CPeter James]

Maybe a piano hinge would help?

CPeter

[Jim Goldrick]

Assuming that the hinge is stable and not breakable, then I believe your only concern would be the sheer strength ( and perhaps the elasticity for bending ) of the drop front. Perhaps a table of the physical properties of different woods would help you decide what to use. Something stiff and strong.

Check here:

http://www.woodweb.com/knowledge_base/Wood_Handbook.html

Chapter 4.

HTH

[Bob Aliano]

Actually the hinge screws are in shear, the shelf is a cantilevered beam and represents an overturning moment. That design looks fine as long as you don't lean heavily on the edge of the shelf, it won't break but the cabinet might tip. In normal use I wouldn't expect any problems.

[Kristian Wild]

True, it doesn't look super-strong, but for the intended light duty it's probably fine. Do you think you'd actually be sitting down at this and writing on it often, or would it be more of a show piece?

To make it stronger you might shrink the depth of the top cabinet or increase the depth of the lower portion so that there is more support under the table surface when lowered. you would also be reducing the leverage on the hinge point by doing this.

You could also incorporate a slide-out support under the centre of the table which would look like little more than a little rectangle with a pull or knob on it when not in use.

food for thought...

Kris

[Barry O'Mahony]

Make sure you use good hinges. Either extruded brass ones, or a piano hinge like CPeter suggested.

With that, it should be OK for occasional use. For every pound of downforce exerted on the edge of the desk, there will be ~3 pounds of force on the hinges, so take it easy.

[Randy Meijer]

It does "LOOK" a little delicate; but my guess is that it will be OK if you don't, like someone else warned against, sit on it. Go back to the link that you provided and look at the "OTHER DESIGN." It is a slant top and has some brass brackets to support the writing surface. They are attached to the back 3-4 inches of the "shelf" and provide support in the same general area as the shelf on your proposed design. I doubt that the guys on that site would offer the design if it was not reasonably sturdy??

[Rick Thom]

Richard, I have an antique desk similar to what you are considering. The drop front is in fact secured by only 2 hinges but in addition it has a lid support that keeps the pressure off the hinges and doesn't allow the lid to rest on the horizontal member. It creates a solid, stable writing surface.
Lots of places sell these in a variety of types but I've included the link to LV because they have several, and this might help you visualize it.

Friction lid support
http://www.leevalley.com/hardware/Search.aspx?c=1&action=n

[Jay Knoll]

Richard

Thanks for posting that website! What great design inspiration.

Actually the hinge should be fine, as I look at the cabinet it seems that the top of the desk acts as the major support and the hinges are "screws" that hold down the writing surface to the top of the desk.

So you're going to have the writing surface supported by the full width/depth of the portion of the desk that it folds down on.

Jay

[Mark Singer]

If you use good hardware, I think it will be fine. Make every screw count with a proper pilot hole and a tight fit....nice design!

[Cliff Rohrabacher]

Looking at the design on the URL it appears more decorative than practrical.

The design is guaranteed to destroy the finish on the outer face of the writing tablet as well as the top of the lower half: If it is actually used that is. I doubt it's actually intended to be terribly functional.

At either event I'd change the design shrink the drawer install a couple traditional pull out supports and insert two sets of bearing pads of some oily hard wear resistant wood - just little buttons on the pull outs and on the outer face of the tablet little inset fluch buttons corresponding. Could use other to accent to fact of them or just have the two.

That way you could hold the finished surfaces away from each other a tad while shortening the moment arm bearing any applied weight.

[Richard Neel]

After reading everyone's feedback, it seems to me the biggest problem with the design is related to the way the top rests against the lower frame and will most surely spoil the finish over time. I think with proper care and the right hinges, the strength factor is not as important an issue as is the finish question.

This desk will sit in my entry way and hold incoming/outgoing mail, notepads and such, and all my pocket junk (keys, wallet, cell phone etc). It will definately not be a highly-used writing surface but will be opened and closed often.

Perhaps a solution would be to create small gap between the top (when open) and the lower frame and rely on hardware to hold the top horizontal like Rick and Randy suggested. This would require changing the design to include a stile under the door (desk top). That just might work! Suggestions?