Extending table - Design in progress!

[RobertMP]

There seem to be lots of other things that have to be done before I can get to make anything for my comp entry so no WIP thread from me for a while. I need to get the basic idea for the mechanism sorted before I can progress with the rest of the design. thought a design in progress thread would at least get me moving.

The pictures below are just to show the principle I was thinking of. Exactly how I make it work I haven't settled on yet and I welcome any comments

I've spent some time wandering round furniture shops and even visited the grand design exhibition looking at how extending tables work. The one common factor I found is that most solutions (if you want a large amount of extension) are pretty ugly.

So I started thinking about finding my own way of doing it. What I've come up with I have not seen anywhere but doubt it is original

Anyway the idea...

Ignore the aesthetics/proportions for now as that will change. The closed position -

The table top is secured only in the middle to the frame/legs. pulling out the middle 'spacer' underneath raises the top by say 10mm. method of achieving rise and fall to be decided

The extensions now slide out on some kind of drawer runner.

Pushing the 'spacer' back in lowers the top down between the extensions

What I don't like about designs I have seen is the gaping holes left when the table is extended or ugly hinges on folding designs... and this avoids that. If I can make it work is another matter!

Anyway thoughts?

 

[OPJ]

Looks quite similar to a draw-leaf table, which was discussed in another of my own threads. :wink: Except, your method of raising the main top sounds different; sliding out the spacer and all...

If you're not familiar with how a traditional draw-leaf table works then...

Each leaf rides on a pair of runners, parallel in their length but tapered at the end below the leaf. They're not set parallel to the surface of the top and run in notches cut in to each end rail. As the leaf is drawn out, the top (which isn't fixed securely, only for location) tilts slightly to allow the leaf to pass by. Ernest Joyce's book has some good information on this.

I agree with your concerns about the gaps being left below with the leaves extended.... If you allow for more overhang all round the top though, this may help to disguise them. I can't think of another solution that wouldn't interfere with the main top.

I like the fact that you're trying to come up with a way to lower the top again and hide those gaps although, I'm not sure how that would work.

Perhaps we should take a leaf from Alan Peters here and "make a feature" out of it...? I look forward to seeing what you come up with.

 

[RobertMP]

I've got this other daft idea that if I can guide the travel of the top so it does not tilt during raising or lowering then it could be left with things on it whilst being extended.

I have seen tables where the leaf comes out on some kind of joggled guide. it comes out 2" too far then pushes back into alignment. Not seen any where the top moves (or tilts).

I did try the local sub library but it was a waste of time. I'll have to get myself down to the main library and have a look for books. I do have confidence I can make my idea work but I'm also lazy enough to look for a proven method if it gives me what I need.

Just found your thread and looked through it. Don't think I can get the rails and legs recessed enough to hide the cut out enough. If I was using dark wood it might be less of a problem. The other things that occur to me is the leaf must scrape on the top as it comes out and the amount of size increase is not as much as I am aiming for.

 

[OPJ]

Your right about the edge of the centre rubbing against the top surface of the leaves. Adding a very slightly bevel or just loosing the lower arises should help to prevent and long-lasting damage. Rails would probably need to be at least 89mm to hide the runners. All dependant on table size, of course.

Don't take the proportions in my drawing too literally! I've only drawn the leaves 250mm wide because it suits the dimensions my client requires. There is apparently a formula for calculating the correct proportions, although I've not come across it in any text... My tutor said it was something like "three-sevenths" of the total width. :?

 

[RobertMP]

Well I've done some more work on this and it still seems like it could be possible Plenty of supporting woodwork to be added underneath but leaving it off for now help make the idea clearer.

So here is the sequence for extending... Pull middle 'handle' out (either side) and table top lifts.... slide out wings on 400mm 45 x 12.7 drawer runners.... push handle in to lower top between wings.

the lift comes from wedges riding up a roller when the handle is pulled. One important missing part from the views is some kind of linear guide to steer the table top in a true vertical motion only. I have someideas on that just not drawn them in yet.

View of one handle assembly with the top and other handle hidden. It attaches to the table top with a single 250mm drawer slide of the same type as the wings. The table top with 'handle' assemblies attached will lift off of the vertical slides that are not drawn yet.

Might use something like this from sugatsune for the vertical guides which will be in the spaces left near the handle shaft.

So... extended

And an underneath view (runners not drawn extended). All the internal gubbings can be hidden by an under table cover panel near the bottom of the rails.

Table is 900mm square. I still have not considered the leg aesthetics so they may change a little. I may also decide to adjust the rail and other sizes to lose the trims currently hiding the ends of the drawer runners when the table is closed as they look a bit ugly.

So over complicated or simples? Comments and ridicule welcomed

 

[RobertMP]

Moved it on some more. Think I'm ready to buy some wood and try it out.

So this is the table top assembly with its lifting slides and vertical guide rails on wood blocks.

Top and table combined and seen from underneath with top raised ready to extend wings

Normal view. Fake breadboard ends. Dimensions adjusted to make runner protrusions neat and legs reduced to 60mm square section

Guess if it all turns into a disaster I could just lose all the complicated stuff and make a basic table using the frame and top