Custom Dining Table

Does the center section need to remain completely flat while lifting/lowering, or can it momentarily tilt by the amount of lift? (This would make things simpler.)

Tornado,

Speculating here, but the client may place a centerpiece on this section. Or even perhaps candles. So lifting flat would be preferable.

Except for the center is the 8' diameter table to be solid, split down the middle with the two halves sliding together or the style with left and right leaves folding down? Obviously split down the center would be a significant complication.

Also, just double checking that the table will not have the "butterfly" mechanism for a hidden extension.

What you want is a light duty worm screw jack. it can be either manual or motor powered either ac or dc....

http://www.screw-jack.com/micro-screw-jack.html

https://alliedscientificpro.com/shop/product/asp-wn01va60-motorized-lab-jacks-19606

What stops the top from rotating?

I address that in #16. If the top is larger in diameter than the rotating under-section, then three or more vertical pins could extend downward from the top (outside of the rotating under-section), the pins sliding in oilite bushings or the like. Thus, the top could only move up and down, while the under-section rotates relative to it. All this could be concealed if the vertically moveable top is thick enough or has a sufficiently thick edging to avoid any gap when the top is in the highest raised position.

I would like to add a frosted plexiglass window around the bottom of the rising section and have some lights that chase as the section rises and falls....nothing too flashy

....also it occurs to me that the sliding rods would need to be connected beneath the sliding sleeves, or they would loosen over time...

ps: is it too much to ask that the table plays "Ride of the Valkyries" as the center section rises...?

All good ideas! Maybe if the mechanism were polished exotic wood with brass fittings we would want a gap to appear as the centre section rises so that the diners could see and take pleasure in the craftsmanship of these moving elements.

By adding a flat to the top of the ramp for the rollers to sit on when the center is up you don't need any energy input to keep it raised. You can dispense with the motor and rotate the few degrees required to lift the table with a handle mounted below the top surface extending from the center section out towards the edge. A simple latch on the handle or a detente groove in the flat of the ramp will stop the raised section from dropping accidentally. For extra theatre during the meal, if the handle is positioned towards the host's seat he/she can raise the center during the meal as if by magic.

Just a note regarding aesthetics. If the centre section is 3/4" thick and is lifted 1", this will create a 1/4" gap through which the mechanism will be visible. You might want to increase the thickness of the centre section, or alternatively, make the edge thicker so that no gap will appear. Also, if the tabletop and centre are solid wood don't go for tight tolerances. You want to avoid jamming caused by seasonal wood movement.

I agree, 1" seems inadequate, I would make the edge like 4" high on the center piece and increase lift capacity to 3.5"...then you need a support bracket under the table to mount the lifting mechanism...I would use something like a drill motor so the battery pack could be easily changed and/or charged...I would add a switch that would break the electrical connection at each extreme up or down position for positive position control....

You are likely correct.

I've reached out to the client to inquire how high they would like the center section to lift. Mentioned this in a comment down stream - the client is also contemplating a doughnut section between the lifted center section and outer edge being a rotating Lazy Susan!

Thank you for your suggestions and comments!

Well,

• if the distance is only 1”...
• weight of the pop-out section about 20lbs.
• what is the weight it will carry? (Center piece)

To put something out there, I would think some type of cam offset (Horizontal axis), with possible a linkage for easier access.

where can Toggle it on up and it’s far enough over Center it stays up, and then Toggle it back.

You could just do this by hand by extending the knob...

Not bad for $100....50lb+ limit

https://www.spectrum-scientifics.com/United-Laboratory-Jack-8-x-8-p/6532.htm

This has a 9" x 9" top, I would mount a steel plate on top for a stable platform...

Cheaper option with 100LBS lift $65...

Link...

$60 1100 lbs

Just flip it over....

$120 hydraulic powered 17" x 13" 40lb capacity

Slightly off topic, but on the same line of table lifts.

my first job out of college, I worked at a large commercial furniture manufacturer.

they had a lot of GSA (General Services Administration) contracts. And with the size of contract at time required to have custom equipment for the contract.

one contract required to have a motorized, lift work table, for computer monitors. The table was design, and mechanically tested, The were 10,000 units delivered.

What wasn’t tested, was using the table with a monitor on the table and was turned on.

turns out that The motor on that motorized wasn’t shielded, and the electromagnetic field It produced when running, really raised hell with the monitor.

theynhad to recall each and every motor for replacement.

I'd use a set of 3 or 4 screws, all connected by a chain and sprockets to a motor, So all screws move up and down together, pushing into sockets on the bottom of the centerpiece. As someone else indicated, a pair of limit switches would be required, or at least highly desirable, to stop the motor at the ends of the motion.

It would be possible to make the screws rotate in fixed nuts, or have rotating nuts on fixed screws. At first thought, I lean toward the latter

This arrangement would lift uniformly level, and could be set and remain stable at any height between max and min.

If you are interested, I could make a drawing...

Be prepared for the next request: continuous slow rotation of the centrepiece. And the decision that 1" is too little.

You're not too far off!

I've reached out to the client to clarify exactly hoe much they would like the center section to raise. It came up that perhaps they might want it to lift several inches, which make some of these scissor lift options intriguing. But what did come up is the notion of a intermediate rotating lazy Susan, between the edge of the table and the center lifting platform. The client thought this should raise up too!

Smashing!

It would be easier to separate the lazy Susan mechanism from the raising mechanisms and deal with them as three individual challenges.

The lazy Susan requires two large wooden annuli separated by a tribo-tape so that the upper annulus can slide freely over the lower annulus. The center lifting portion will constrain it to be concentric (For tribo-tape suppliers check out the Igus™ website)

The raise mechanism of the Susan could utilize Rixter's roller/wedge with my flat tops and detent. The lower annulus has to be prevented from rotation so that rotating the rollers a few degrees will lift the wedges. The shallow slope of the wedges creates a mechanical advantage, multiplied by the length of the operating handle so very little effort would be required to lift 80-100 lbs.

For lifting the center more than a couple of inches wedges are not going to work as the slope would be too severe to make them practical. I suggest a rack and pinion lift with a worm screw incorporated into the gear train. The worm will create a large mechanical advantage to lift 200-300 lbs and will not run backwards so will hold the center up.

As a retired electrical engineer I say very reluctantly that I don't think employing electrics is the correct option for this application.

That will be quite a table! A number of good ideas have been presented here. For the lower lift lazy-susan ring the described ramp system would work, while the higher lift centre disk suggests one of the described vertical screw or scissor lift options. Lee Valley Tools in Canada (a trustworthy company) carries a large lazy-susan bearing. 29 1/2" diameter, so it would fit outside the centre disk. Pricey at $299. Cdn. but has a 990 lb. load capacity (Part #12K6829). Not sure if they ship outside Canada. That's a project I would enjoy - combining high level woodworking with mechanics. I'm currently building a large decorative windmill for a local community garden. Good luck!

http://www.vigorousfurniware.com/product/36-inch-lazy-susan-hardware-swivel-900mm-heavy-duty-turntable-swivel-as-79/

Do they want the lazy susan to turn continuously or on demand?

Maybe both the center and the lazy suzan could be lifted by the same mechanism with a catch at the 3 inch mark of the center pedestal that lifted the lazy susan part with a frame, and the lazy susan would have an addition turning mechanism...

In which case you might consider a geared lazy Susan bearing...

Interesting.

They are assuming a manual lazy Susan. The rotating section is looking to have an inside radius of 14" and an outside radius of 30". This 36" d. LS would work in conjunction with individual bearings located further out.

Seems like potentially that could be a lot of weight, it's not that it couldn't be moved, it's the starting and stopping that might be a problem....might need handles ...

Give it a good spin now !! We don't want plates flying off the edges either...haha

It seems you've been potentially hamstrung between two different styles, formal and non-formal...I think it should just turn slowly continuously with off/on switch, and be motorized....this eliminates competition for position....2 people tugging in opposite directions, could get nasty...FOOD FIGHT!!!

There could be a button recessed into the table at each seating location that stopped the lazy susan for 20 sec, then auto restart...with a bell warning at 15 sec...That way anybody could stop the lazy susan when they wanted something...

Ok that helps. I'll make a few assumptions to spur this along.

Given those dimensions look to build this in 6 or 7 pieces. You will have two nested table assemblies and four quarter leaves that attach to the center tables. Your main table will be the lazy suzanne Section. At 36' diameter you should be able to get through most doors. It will be a stacked assembly with an empty center designed to carry most of the weight of the table.

You build the lazy Suzanne (LS) as the main support structure and stand alone. Leave the center open so you can 'drop in' the elevator piece. (EP). This is a separate piece designed to fit in the space in the LS. This can be made to rotate also this way. As long as you stick with local manual mechanisms you wont have to worry about utilities. if they want power drive, that gets a bit more interesting but there is plenty of room in the center section. The four quarter leaves would be best served with at least one leg for support.

This needs to be built extremely heavy as the size of the piece will lend itself to overloading.

That's the off top of the head design.

This project suggests to me the merits of torsion box construction - a hollow core construction comprised of a wood grid skinned over top and bottom with plywood. The resultant assembly is strong; dimensionally stable through the seasons; lighter weight than solid wood; can be easily built to any desired thickness. In this project, pie-shaped torsion box leaf sections could, for ease of disassembly and transport, be bolted together via bolt pockets on the underside. If built of sufficient thickness, no strengthening perimeter apron would be required, resulting in a simple, clean appearance.

If solid wood is the preferred appearance of the finished piece, a layer of sawn veneer (1/8 - 3/16" thick) could be applied top and bottom to the torsion box sections - glued using clamping cauls or vacuum bag - the perimeter then edged with solid wood to allow milling to the desired profile.

This hollow core construction would also, unlike solid wood, accommodate various elements related to the discussed mechanics - such as wiring if a electro-mechanical system is used; push or twist rods if a manual system is used.

There is information on-line about torsion box construction. My introduction to it was an article written by Ian Kirby years ago in Fine Woodworking magazine.

Agree. This thing will be a beast if made from solid woods.

I agree with your torsion box suggestion. I've offered the client both the pedestal option and legs. I am waiting for her response. We'll be using a "combed grain" rift white oak veneer on plywood. Fortunately, access to the area is wide open with French doors at the entrance and an open great room inside. Your suggestion for pie-shaped sections for the TB fits with my plan to have the veneer oriented in a reverse diamond pattern. Thanks again for your time and attention, everyone!

My experience has been that people are often more impressed by simple wood and metal handcrafted mechanical solutions than complex electro-mechanical assemblies.

If a 1" lift is truly enough, the internal ramp solution proposed by Rixter could be manually operated via a discreet knob and gear system, as follows:

Assuming the table has four legs and an apron between the legs, a small round knob of matching wood could be fitted in the centre of each apron. A 1/4" or 5/16" shaft running in oilite bushings could extend from each knob to the centre of the table, where the inner end of each shaft would be fitted with a small bevel gear which would engage a larger bevel gear fitted to a shaft extending vertically downwards from the centre of a rotatable disk. Integral to the disk would be the curved ramps shown in Rixter's illustration. Turning any knob would cause the disk to rotate relative to the centre circular platform resting upon it - the circular platform prevented from rotating via vertical pins slidable in oilite bushings. The circular platform would be fitted with rollers on its underside to ride on the ramps (as per the mechanics of Rixter's illustration). Therefore the rotational movement of the ramped disk relative to the stationary circular platform would effect the required up and down movement of the platform (to the delight of the diners). If necessary, a horizontal flat at the top of each ramp would ensure the raised position of the platform is maintained under load.

I tend to agree that "...people are often more impressed by simple wood and metal handcrafted mechanical solutions ...". The OP must be an experienced woodworker, so instead of bevel gears, I'd suggest using dowel pins inserted into a very small disk for the driving "gear", and a much larger disk with many more dowel pins for the rotating disk of your and Rixter's concepts.

The curved ramps could easily have several ramp-flat sections, so there could be several different stable heights of the centerpiece. a very slight dip in the flats could make it more stable.

I'd follow the KISS principle, and have only a single driving knob or crank/shaft/drive "gear".

On the other hand, I agree with GM1964 that 1" of lift is nowhere near enough for that large a table, and my previous concept of screws would be stable at any height, so I'm going to follow up with a drawing...

Very nice drawing...how are the sprockets tied to the base?

Thanks. The three screw sprockets simply rest on the bottom plate, with something like a Teflon washer to help them turn freely. The drive sprocket would be fixed to the gearmotor shaft, and of course the gearmotor would be fixed to the bottom plate.

The weight of the centerpiece pushing down on the screws would hold the sprockets down, but it would be a simple thing to add a Z-bracket at each sprocket to prevent lifting of the centerpiece.

http://www.screw-jack.com/small-lightweight-screw-jack-actuator.html

I'm assuming if the nut/sprockets each had a thrust washer or thrust bearing under they would rotate in place due to the weight of the vertically adjustable top section. The depicted solution would provide the OP with a greater range of vertical adjustment than the stated scant 1".

Right on both issues. The length of the screws could be any reasonable value, with a clip ring near the bottom of at least one of them to prevent going too high. I was assuming a vertical travel of around 4 inches, so the skirt would always hide the mechanism. The skirt would also limit sideways motion of the centerpiece, so the screws don't need to be very heavy.

If the skirt was made 10" deep, it would be perfectly possible for the centerpiece to rise 10".

If the table is to be of the centre pedestal type (unlikely given its 8' diameter, but let's suppose) then your illustrated mechanism could be contained within the pedestal and have a lift capacity of almost 30" (typical height of a DR table). The skirt could be of polished wood to match the table so it would form a very impressive column as it rose to its highest position. The top would be a good place for the owner's priceless Ming vase (now being used as an umbrella stand) which could be filled with dirt to contain a large cascading indoor plant.

"If the table is to be of the centre pedestal type (unlikely given its 8' diameter, but let's suppose) then your illustrated mechanism could be contained within the pedestal and have a lift capacity of almost 30" (typical height of a DR table)." True! I like the idea, and hadn't thought of it.

We need that sarcasm symbol on your last line...

I'm thinkin' we could put a 3D holographic projector that could raise up out of the table....

LOL,

We are shooting for a single massive pedestal base, with some sort of apron. Our challenge is to keep the apron to a minimum (3" max). With a 30" high table, too deep of an apron begins to encroach on the legroom of the taller guests. However, given the large diameter, we'll have room toward the center of the table.

My thought was that 4 knobs spaced equidistant around the table in the centre of the aprons would be a visually balanced composition, and convenient (and fun) for the diners. Of course, it's viable only if appropriate sized off-the-shelf bevel gears could be sourced for the central gear cluster. Also, given the diameter of the vertically adjustable centre section, I'm thinking that a greater than 1" adjustment range would be possible using the described ramp system (up to 2 1/2" maybe?).

With a large ball bearing and a maze you could make a game of it...

You'd better be tall and have long arms; this is to be an 8 foot diameter table!

I fit neither of those descriptions, so I can't play, unless I climb up on the table.

No you use the knobs to tilt the center piece, you know if you went that route...You've got 4 knobs, one on each corner...you could have a goal pit on either side...you have to work together to get from one side to the other, one of those executive team building exercises...and shots for the winners

With a decent center guide, couldn’t you install an array of push to open cabinet latches, increase the quantity to suit the load, long stroke models are available. No need to plug it in, no humming noise as the equipment ages. Push it once to rise, push it again to make it flush. Or as Phoenix911 mentions, a simple rotary cam operated by a small 180 degree lever, or a ramp sliding radially under the table.

You don’t suppose your client want to use the center section as a Lazy Susan, that could make life difficult?

It's doable...

First concern. Moving it in and out. This effects construction more than anything else.

Is this a solid single piece built in place or is it going to need to be disassembled and moved? if moved what are the clearances? Elevator? Doorways? Stairs?

Once that has been determined then we can look at different techniques to accomplish your task.

The addition of a lazy suzanne section surrounding the lift section (is the lift section to rotate also?) will complicate matters.

Really good point! An 8' diameter table won't fit through any ordinary door in one piece, even with the pedestal removed. As you point out, If it has to fit any common elevator, the top would have to be in four (or more) sections.

Firmly joining the sections is no trivial matter. If the radials supporting the main top are sufficiently massive, they could hide angle irons used to join the sections.

Apprenticed with the Freeport Organ company for several years. If you want interesting things made from wood in places and ways you wouldn't expect look no farther than a pipe organ.

Aquarium air pump and a whoopie cushion.

One must not discount the possibility of overload....

I know it sounds bad but iit wouldn't stink too much.

I have a very simple solution. Under the table, make a solid bracket in the shape of an X. Attached to the bracket will be four small shock absorbers (like the ones used on a car hood or hatchback). You can adjust the height by setting the distance the X is from the top of the table - once set, it's fixed, so you'll need to get the height desired from her. Further out from the four shock absorbers will be four of those click-click locks. You know, the ones that you push to unlock (spring pushes it out) and then to lock you push back in. Those are to lock the table in place. To open the table, just push down evenly. You can even put guides to keep the top in place (a cylinder with a post in the middle).

The hood/hatch shocks come in many different lengths, so you can choose the one that works the best for your application.

I hope this helps.

You could do it easily with a small toggle scissor mechanism and you could potentially put the center on a lazy susan. You should be able to do this without any power at all. The operator for the lift could be a simple push rod that extends to the edge of the table under the edge.