An Ancient Light Wedge for Back Lighting Slides

Before digital photos arrived, film was used to capture images. There were two basic options for the type of film used including negatives for producing printed photos, and positives for mounting in a frame and projecting with a slide projector. For preparing a slide show to present to a class or audience reviewing the slides it took some creativity. To quickly view and choose the slides you wanted to use, a backlit light table was one option. They weren't portable or that common.  Handheld gadgets you could place a slide on/in to backlight the slide and sometime magnify the captured image to view were also an option. 

When I was in college I kept my slides in plastic notebook sheets designed for that purpose.  To quickly view a page at a time I made this light wedge.  Wedged so it could slip between sheets while still in the notebook.  A single incandescent light tube provided the backlight.

Slid Open

The bulb put off heat though. Although there were vent holes for the heat to escape through I found I couldn't use the wedge for more than 10 minutes or so before turning it off to cool down. Longer than that and the built up heat would warp the frosted plastic cover. 

The frosted plastic cover did a better job of spreading the light than it seems in the first image above shot.

I still have a couple notebooks full of slides I took. Somewhere. They include some black and white photo negatives I mounted in slide frames. I used negatives to project onto 50% gray poster board to then sketch over to make pseudo-realistic posters. I'd color over the dark areas with a white pencil, and color over the light areas with a black pencil.  That was my secret for the posters I would submit with my furniture designs when sent to competitions. I would make an updated version of this light wedge using cooler LED strips, but there are thin LED light panels already available that could be used. This wedge light is destined for a yard sale. 

Switch and Handle

Somewhere I have an ancient slide projector.  If I can find it a trip down memory lane is inevitable. Hopefully my slides are in the same box as the slide projector, buried somewhere in my house or garage.   

4D

An Improved TV Tray Table Design!

There is a dated X frame wood TV tray table design out there, available many places.  I have one, bought from my local Target store. Trying it out I was appalled at how poor the ergonomics of it are.  This disappointment spurred my creative genes to design a simple version that solves every complaint I have with the original. In my iterative sketching process I stumbled upon a geometry that allows the design to be turned inside out to serve in two useful positions.

Slanted Top

My design is patented.

In one position the top is slanted with a stop lip on the front edge. Musician?  A place for your manuscript paper when jotting down a tune. Have a tablet?  A better eyeline to see it when using it. A good place for note or sketch pad, and your pen/pencil can park on the protruding ledge.  

Turn the table inside out (flip the top and pull the leg frame through) and the top ends up horizontal for your lunch tray or laptop or solitaire card game.  

Horizontal Top

You'll appreciate the ergonomics of my design in either position. The bottom stretcher on the original is too low to slip my feet under. My design moves the bottom stretcher up.  It also beefs up the size of the stretchers for a more rigid frame.  The legs on mine are spread out to the edges of the top for more leg space between them. 

Side by Side

The asymmetric X of my design allows swing space for knees, and easier access and egress from being seated at this table. It also allows pulling the table closer to you when seated in a chair. 

Knee Space

My design uses a simple tension cable uniquely routed to lock the geometry in both positions. This option is between the front and back legs. A tension strap could instead be attached to the back edge of the top and the top stretcher. Shown here in another prototype of mine: 

One inch straps

This red oak version can be found here:  Red oak table

My design folds up flat for efficient packaging or storage.  A simple rack to hold 4 or 6 or 8  tables would be easy to make and have a small footprint. 

Two Inches Thick

This table is a simple example of 4th dimension design. It can serve the owner in slanted or horizontal configurations, or be flat for storage or packing at different times. Time being the 4th dimension. 

You can pick up the table to move it by simply reaching under the center of the sides and holding the legs against the top as you pick it up.  Or by picking it up from the center of the top stretcher.  

The wood top could have an added value inlay to appeal to specific audiences. Team logos, family crests, sports icons, company brands/logos, etc.. Something unique on each side perhaps. Customize it for each client for an added fee.  

It can also vary in finished detail. One may have bullnosed front and back edges like the example above.  Another might have the front corners radiused with a squared edge wrapping from side to front to other side.  The back edge still rounded over as shown below.

Red Oak Top Alternative

Rear Corner Detail

The stop ledge can be made from a matching wood or contrasting wood to emphasize it's presence.  It could even be a strip of aluminum or brass or something more exotic.  Bronze or black oxide or chrome or powder coated bolts in just about any color are options to consider. There are also hardware options out there for how to connect the legs and table top. 

This design is patented. For information about licensing the design please contact:

Sarah Nolting
Licensing Associate
Kansas State University Innovation Partners
(785) 532-3910
snolting@ksu.edu
www.k-state.edu/innovation-partners

Comments and questions I encourage and appreciate.  

4D

Using Square Nuts for Connections in Knock-Down Projects

Barrel Nuts vs Square Nuts?

A classic solution to bolt wood parts together is to use a barrel nut (aka cross dowel) to insert threads for bolts to thread into.  Using a drill press you can make a perfect hole for the barrel  nut.  Barrel nuts are relatively pricey compared to standard hex or square nuts.   If you have a CNC though it is possible to embed square nuts for threads rather than barrel nuts.  The pocket for a square nut can be made with a 1/8" spiral upcut router bit.  An optimum shape for such a pocket can be found using these drafting steps:

Making a pocket for a square nut.

From left to right in the image above:

1. Know the dimensions of your nut.  A digital caliper is a handy tool to keep near your CNC.

2. The critical shape to use is the top rectangular view of the nut. 

3. In each corner draw a circle the diameter of the bit you'll be using.  I usually use a 1/8"d spiral upcut bit.

4. Draw in the diagonal lines from corner to opposing corner. 

5. Where the diagonal lines cross the initial circles, center another 1/8" circle. 

6. You can delete the diagonal lines and initial corner circles.

7. Trim away the inner sections of each circle, and the corner of the rectangle where they cross the circle line. 

Make sure all the vectors are joined, and you've got a vector shape you can pocket out  to sink that square nut into.  Although my software (Aspire from Vectric.com) has a dogbone tool it doesn't make corners optimized to leave the most flat surface for the nut.  These steps do. 

I buy square nuts from McMaster Carr.  I prefer using stainless steel nuts as they won't rust if the wood has a high moisture content.

To cover the square nut a simpler rounded rectangle shape pocket above the nut can be filled with a CNC cut plug.  One example of an inserted square nut:

Embedded Square Nut

I've seen many CNC cut slots made to access hex nuts in plywood or other sheet goods. In most there is a little room around the nut for the tips of needle nosed plyers to keep the nut from spinning while tightening or loosening the connection.  Using a square nut and a snug fitting CNC cut pocket the nut won't spin. A side benefit is that you won't have to worry about the orientation of the nut.  Using barrel nuts you do. 

4D