42 minutes ago, steven newman said:

Beginning to wonder...IF I should start a Build along thread for this little box....just another Box Project?  

For the official TPW record, my vote is Yay.

As with nearly all of my projects, a test of any mechanical properties is worth my time while I wait for final hardware to arrive. This is a side section showing the area between top and shelf below it.  Paracord wraps around the wheel.  Two cords per side eventually. Video shows with just one cord attached how the action works.  Pull the lower shelf toward you and the top slide back.  Pull the top toward you and the shelf slide back.  Both, 14" wide, stop them they are 7" out.  

 

Lessons learned include that 4mm paracord is very difficult to push through a 4mm hole.  The second opposing cord is needed to keep the first one in tension no matter whether you push or pull on the top or the shelf. 

Test here simply has walnut strips sliding on a dovetailed strip.  Actual 2-direction soft closing ball bearing slides will be used on the final table. Those must be on a slow boat ride from some foreign country.

4D 

As for the box build series by Steven, I vote for "Either works for me!" 

4D

Opposing cord finally attached. Works quite well.  A bit better than I expected.   No video as the first took my slow web connection an hour to upload.

Photo though.  BTW I reduce the resolution of the photos I post on the web by 50% before uploading them. 1/4 the data makes a big difference. 

 

Ultimate goal is to embed the wheel and paracord into the sides.  Still visible, but taking up no surface space on shelf or top. That may have to wait for a second prototype.  Still have details like how to trap the cord once in place to figure out. Current idea is an ugly knot in it so it won't pull back through the hole.  Not so bad for under the shelf.  Real bad for atop the table top. 

How about a keyhole slot in the bottom of the table? Would there be enough tension to trap a knot?

32 minutes ago, HARO50 said:

How about a keyhole slot in the bottom of the table? Would there be enough tension to trap a knot?

I like your thinking.  Knot in the end.  Push up in the wide part, slide over. That would take care of a blind connection that doesn't pierce the table top.  The melted end to keep the cord from unravelling makes a knot hard to undo.  Found that out already. 

Pulling the cord taught and pinning it after wrapping around the wheel and into a hole in the top of the shelf is more of a challenge.  Only approach side to intersect the hole is under where the slides will be mounted. Thought maybe a thin finish nail intersecting and piercing the cord in a snug hole would trap it there.  I could easily drill a small hole through the slide to push the nail through. Pre-drill a hole for the nail so there is no chance it'll split the edge of the wood. If the nail head doesn't interfere with the action of the slide then it would be easy-ish to remove if the cord needed replacing,  All things I can test before committing to the final parts.

 

Thanks,

4D

Edited December 27, 20241 yr by 4DThinker

2 hours ago, 4DThinker said:

I like your thinking.  Knot in the end.  Push up in the wide part, slide over. That would take care of a blind connection that doesn't pierce the table top.  The melted end to keep the cord from unravelling makes a knot hard to undo.  Found that out already. 

Pulling the cord taught and pinning it after wrapping around the wheel and into a hole in the top of the shelf is more of a challenge.  Only approach side to intersect the hole is under where the slides will be mounted. Thought maybe a thin finish nail intersecting and piercing the cord in a snug hole would trap it there.  I could easily drill a small hole through the slide to push the nail through. Pre-drill a hole for the nail so there is no chance it'll split the edge of the wood. If the nail head doesn't interfere with the action of the slide then it would be easy-ish to remove if the cord needed replacing,  All things I can test before committing to the final parts.

 

Thanks,

4D

In early radio tuners they used a spring to keep tension on the wraps. 

9 hours ago, lew said:

In early radio tuners they used a spring to keep tension on the wraps. 

Another great thinker.  Thanks.  Pull the cord through the lower shelf, slip a compression spring over it, then a washer, then tie a knot in the cord with the spring compressed a bit.   Not a discrete method, but clever.  The cord though doesn't slip easily when it turns 90 degrees to pass through a 4mm hole.  Keeping the tension isn't needed, just setting it securely once is my design hope. Preferably with nothing poking out under the shelf.  I might leave it long enough to tug on the cord as I set it, then cut the cord flush to the bottom of the shelf. 

There is no abrasive or tugging action on the cord when the shelf/top slide over the wheel.  The cord lays down until they pass by the wheel.  The cord doesn't slide on the wheel either, it just lays in the coves I cut as the shelf/top slide past the wheel. 

T-slot idea has bumped into the need for a special T-slot cutter that I don't have.  Both the small and larger versions have a 1/4" center, which is 6.35mm for the 4mm cord. A bit too sloppy I'm afraid.   Searching for a more unique bit that may work. 

4D

Edited December 27, 20241 yr by 4DThinker

Put the spring in a recess "inside" of the wheel. 

7 minutes ago, lew said:

Put the spring in a recess "inside" of the wheel. 

The wheel doesn't need to wind up. It needs to spin freely as the shelf/top slide back and forth past it.   The slides I ordered are soft closing which should help the top center perfectly over the shelf when in the middle.  Tension in the cord is just to balance the push/pull potential so a push of the top or a pull on the top is easy with no slop in the cord when changing directions.  Any slop in the cord might let them slip off the grooves in the wheel that they lay in. This paracord doesn't have any perceivable stretch to worry about.   There is no need for any spring in the mechanism.  It might be useful to make the cord easily serviceable/replaceable should it get dirty or frayed.  Something I'll park in my "need to figure out" file to use in future projects.

Currently waiting on hardware to be installed..

When I next get to the shop..

Stay tuned..

On 12/26/2024 at 11:08 AM, steven newman said:

Beginning to wonder...IF I should start a Build along thread for this little box....just another Box Project?  

Right now...bench vise is at work..

The bottom part of this box is sitting over on the tablesaw..

I might get the clamps off, later, today?

Whatcha waitin' on?

Do eet!

On 12/26/2024 at 6:50 PM, HARO50 said:

How about a keyhole slot in the bottom of the table? Would there be enough tension to trap a knot?

I found a keyhole bit with a 3/16" center so ordered it and it came in yesterday.  I did a test cut with it to see how well it would work with a knot in the paracord end. I rounded over the approach end to ease the paracord entry. 

3/8" diameter T-slot bit was just the right size. 

Good fit.  Seems to work fine. The knot is snug in the hole and had to be pushed back to the undercut area with a small screwdriver. The chamfer you see was part of the t-bit profile cutter.  I didn't notice or expect it but it isn't a problem.

4D

 

Glad to hear that, 4D! Every once in a while I still get a good idea.

You might want to put a little glue (probably CA) on the knot to insure it doesn't come untied.

7 minutes ago, Fred W. Hargis Jr said:

You might want to put a little glue (probably CA) on the knot to insure it doesn't come untied.

The end of paracord has to be melted after being cut or it will fray back quickly.  The swell of the melted end makes untying the knot very challenging, and impossible if there is tension on the cord.  The end won't slip through the knot.  Your advice is good though and something I'll park in my "good ideas" drawer. 

 

Got the slides for this project yesterday and they aren't usable.  They looked to be made for a special application which conflicts with my intended use so I've sent them back to Amazon.  My sample made with a stick of maple scrap slides for the walnut strips works extremely well so I may just do another test with the cherry I'm using for the project and maybe HDPE for it to slide on.  Save myself the $20 those slides cost as I already have some HDPE I can use. 

4DThinker; Couldn't sleep last night, so I just lay in bed thinking about anything and everything. Kept coming back to your sliding top/shelf idea. Have you considered anything along THIS line?

Edited December 31, 20241 yr by HARO50

15 minutes ago, HARO50 said:

4DThinker; Couldn't sleep last night, so I just lay in bed thinking about anything and everything. Kept coming back to your sliding top/shelf idea. Have you considered anything along THIS line?

 

Yes.  In fact as I iterated about the idea and sketched out a few ideas using a gear/sprocket and toothed rails was one of those ideas.  That and a telescoping link pinned in the middle, and a few other alternatives.  I crossed out the sprocket/rails as knowing a pen or pencil or game piece or whatever might accidently get pushed over the toothed rail and lead to something crunching as the table and shelf started to slide. If the same thing laid across the paracord the wheel would simply stop as it bumped into it. In fact any mechanism I use may succumb to interference with shelf items that get in the way. Not a problem for the top, but since the mechanism is above the shelf and below the top it imposes into the gap between them where problems lay in wait.  Ideally, and I'm working on it, the mechanism would live inside the side panels. A connection to the center of the shelf/top edges rather than on their face and near their ends would project out into a slot in the sides. The slot would extend 7" in both directions. Inside the side panels a cable/cord would loop around wheels near each end rather than a single wheel in the middle. Pushing the top back would pull the shelf toward you. Push the shelf back would pull the top toward you.  All just tugging on the center pin of shelf/top.  This would be mostly hidden, but also more complex to make. 

I somewhat enjoy seeing the wheel spin as the cord is picked up by it when the shelf/top slides. I might carve some yet unknown detail in the face of the wheels to draw attention to them as they spin.  Being exposed also means it is easily serviced/fixed if the cord breaks or the wheel splits, etc.. 

4D

Sitting on the bench, waiting on the last of 2 coats to cure..

I think I can call this one done?