Saturday, 13 July 2013

More Nuts and Bolts

So the last post just got some of the fluffy nut and bolt material out of the way, here comes the good stuff!

The table top panels all get attached to mounting plates that ride in bearing tracks.  The plate itself is made of aluminum but a pair of steel runners are attached as it will wear better over the long term. 

Attaching the Steel Runners
All the Runners in Place and Ready

The plates run in bearings which are attached to the extension arms of the central column.  These extension arms have recesses for v-track bearings.  The bearings are attached with custom designed low profile bolts.  The bolts on the left hold the bearing in place with a center mounting washer.  The bolts on the right use an off-center washer to allow us to adjust the washer horizontally for a tight fit. 

A Smooth Running Plate
Twelve Extension Arms with Bearings
We then focused on the central column of components and built outwards.  The central column gives away how we have designed the vertical movement to occur in our table.  There are a series of three identical tracks around the column in which ride bearings.  As the table is rotated the bearings travel along the track and when they reach the sloped section ride up or down it to raise and lower various components of the table. 

Central Column
The segment of black tube is affixed to the silver ring and this is set into the central column.  The roller bearings are threaded into the silver ring through the slots in the central column and then the large black plate in the right of the photo is attached on top of the black tube.  The black plate is the mounting flange where the central star of the table top is attached. 

Other Parts for the Central Column
The Roller Bearing and Track
Central Column When Low
Central Column When Raised
The central column will be set within an outer column.  This outer column provides the same type of rising and falling motion for the rectangular table top panels.  As there will be some more v-groove bearings used here another set of steel rails are affixed to the outer column.   

Outer Column and Steel Rails
The outer column will be placed inside two sets of arms.  The arms provide the support for each of the wedges and rectagular panels.  When I mentioned earlier that the tolerances were amazing this is the kind of thing I was talking about.  Each of these large pieces was milled from a solid block of aluminum 36" x 36" x 2".  The sleve bushing into which the steel rod is inserted was press fit into a recess in the alluminium.  The press fit was tapped in place with a mallet and the minor amount of compression that occurs in the bushing is what keeps it in place.  An amazing fit. 

Top Set of Arms with Steel Guide Post and Self-Lubrticating Bushing
The second set of arms rides up and down on three steel guide posts that are threaded into the first set of arms. 

Bottom Set of Arms Installed on Posts
The outer column can now be set into place.  There are recesses in both the upper and lower sets of arms for v-groove bearings to guide the rotation of the parts.

Outer Column in Place in the Set of Arms
V-Groove Bearings, Note the Two With Hex Heads to Allow Lateral Adjustment
Installing the V-Groove Bearings
Once the v-groove bearings are in place the roller bearings which provide the lift for the lower set of arms by traveling in the tracks can be installed.  These are inserted from access holes which line up with the tracks on the outer surface of the outer column.  

Installing the Roller Bearings

Central Column with Mounting Flange
The outer column and the inner column can then be attached to the base plate which will eventually be attached to the base of the table.  The base plate has a dozen lobes which stick out along its circumference.  These are the attachment points for the actuator arms which provide the lateral extension of the table top.

Central Column and Base Plate

Central Column, Outer Column, and Arms all Together

Central Column, Outer Column, and Arms all Together
The actuator arms have a pair of bearings inserted where they attache to the lobes on the base plate.  They also have some press fit self lubricating sleeve bearings where they attache to the  mounting plates for the table top panels. 

Actuator Arms and Bearings

Actuator Arms and Sleeve Bearings

We only test fit one of the actuator arms to make sure it would work.  We had to stop work here as there is a part that needs to be rebuilt and it will take approximately two weeks to get the replacement.  As this is the first time assembling the parts there are still some alignment issues to be worked out.  That being said, seeing the parts come together and work as planned was quite satisfying.  

Nuts and Bolts

The heart and soul of this project really is the internal mechanisms that make the table expand from seating 8 to 12 people.  The time and effort put into designing these mechanisms has been huge.  The use of the best veneers and highest quality woods that I could find has largely been because the complexity of the mechanisms sets the bar so high.  The mechanisms were designed by myself and a friend named Devin.  Devin is a mechanical engineer by trade and was able to design every component in 3D to be milled out of solid material.  The milling was done in China and then shipped over for us to assemble.  

As much as we sometimes hear that the manufacturing coming out of China is substandard I think it is important to remember that any manufacturing company will only produce to the level that is demanded of them.  You get what you pay for.  

I had originally hoped to get the parts in time to assemble the table for entry into the SAWS 2013 Fine Works in Wood Exhibition but that deadline sailed by.  Also, back in January I applied for and was awarded a booth at the Calgary Stampede but had to back out of the opportunity as I would not have the table in time.  These were two very big disappointments, but life goes on.  As does work on the table.  After a series of delays getting the parts the last of them finally arrived today, quite a bit later than expected.  

Though late, the parts are fantastic in fit and finish.  The tolerances between drilled out hole centers, diameters of bushings, and everything else is within a fraction of a thousandth of an inch.  In other words within a quarter the thickness of a sheet of paper. 

The Parts Laid Out and Ready for Assembly
A Wide Array of Nuts and Bolts, Some of them Custom Built
In addition to the mechanisms which drive the expansion and contraction of the table, I also had custom allignment slots and tabs milled out of solid brass.  Each on is 3" long, 1/2" thick, and is recessed 3/8" into the panels.  The curvature at the ends of the piece matches the one left by the router bit I used to make the mortises.  It is quite convenient to be able to have custom hardware like this to speed up assembly.  
36 sets of Alignments Tabs and Slots
It turns out the brass screws we ordered had threads which were a couple thousandths of an inch larger in diameter than the usual steel ones so I had to ream out the mounting holes slightly. 

Reaming the Mounting Holes
Each of the alignment tabs and slots had to be hammered into place with a mallet.  Then a center punch was used to mark the center of the screw hole.  Each hole was pre-drilled and fitted with a brass screw. 
Each Component Was Tapped in With a Mallet
One Down, Seventy-One to Go
Lookin Pretty Sharp


After completing the table in such a crazy schedule it was strange to just drive off with it and drop it off for finishing.  Suddenly the shop was empty and there was nothing to do.  I had to go away the following week for work so it was good timing to get it done. 

What an anxious week that was!!!

I couldn't help but think every day about picking up the parts and seeing everything finished and ready for use.  Finally, after a couple small delays I was able to pick up the parts. 

Components for the Base
The Base Fully Assembled
Closeup of the Central Hub
Figure of the Kevazinga
The Wedges
Star-burst Pattern of the Central Rising Star
Ebony Edging to Protect the Veneer and Accent the Perimeter
Mocked up in Small Configuration (approx 5'6" diam)