Clay, Application to Refinement

 

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Modeling Table

The table to accommodate the scale model should be sturdy enough to carry the weight associated with using clay as the modeling medium. The 1/5 scale Corvette will weigh between 80lbs to140lbs depending on the clay thickness used. The plywood and foam armature will add an extra 8lbs to 10lbs.

 

The modeling table should be large enough for free movement of  the angle brackets on either side or end of the model and the table ideally needs to be mobile to allow for positioning when taking photographs.

 

With all these considerations in mind lets continue with the construction.

 

 

For the base of the table I decided to use a two shelf cart with a load capacity of 500lb. The top measures 24"x 36" with the trays 3 1/2" deep. The cart has two fixed and two swivel 5" wheels. This type of cart is available through suppliers such as McMaster-Carr, Rutland Tool or Grizzly? Industrial.

 

The load capacity of this particular service cart will be more than sufficient for this project and will also allow for equipment and templates to be stored on the bottom shelf.

For the top of the cart a platform needs to be constructed to carry the model. The main materials for this stage are 3/4" plywood and 2"x 4" lumber.

 

Material List

 

                       A Lumber 55"x 2"x 4" 2 off

                       B Plywood 52"x 30"x 3/4"

                       C Plywood 40"x 18"x 3/4"

                       Drywall Screws 1 5/8" 12 off

 

As you can see from the exploded view of the table top, I have two cross members to support the main platform. This consists of two pieces, 55"x 2"x 4". 

 

To ensure that the pieces were flat and parallel I skimmed the edges by passing through a table saw. A better solution would be to use a jointer and a thickness planer to achieve the parallel stock.

 

Once parallel, lay the first piece across the diagonal of the 52"x 30"x 3/4" plywood top. Position so that the ends of the 2"x 4" are equally spaced from the corners of the plywood. Mark around the 2"x 4" with a pencil and remove. Repeat the procedure for the other diagonal and you will have the position for securing the cross member to the table top.

 

This mark-out also provides the angles for marking out the edge cross-lap joint (see illustration). The edge cross-lap joint requires removal of equal amounts of material from both pieces so that they notch over each other and become flush.

 

Once the joint has been marked out, use a hand saw to cut to the mid point of the lumber and remove the excess material with a wood chisel. Repeat for the second rail. Fit both rails together and check for flushness.

 

Using the position of the cross members that were  previously marked onto the plywood top, set up the drill with a 3/16" drill bit and drill six holes along each diagonal for securing the cross members into place. Countersink the holes, then clamp the cross members into position, ready for securing.

 

Once clamped, use a 1/8" drill bit to drill pilot holes into the cross members for the 1 5/8" dry wall screws that will secure the top into place.

 

At this stage the modeling table should look similar to the photograph on the right. You may have noticed that I have rounded the corners off on the 2"x 4". This is to prevent any accidents when placing templates under the cart.

 

At this stage it is a good time to check the top for flatness with a 48" straight edge.

 

The straight edge can be purchased from most art supply stores or tool suppliers.

 

Use the straight edge to check across the diagonals, across the width and along the length. If you find any hollows more than 0.020" or 0.5mm (approximately a double thickness of a magazine cover) shim between the top and the cross members. 

 

For shims you can use blue tempered steel in various thicknesses or folded paper. The main object is to achieve as flat a top as possible.

 

I found that the top still had a curl to the board across the width even after shimming the diagonal cross members.

 

To overcome this problem I braced the board with 1"x 1" square metal tube across the ends of the table, in between the cross members. I then marked the position of the tube on the underside of the top then drilled two 3/8" holes in the plywood, 2" in from the ends of where the tube would lie. The holes where then countersunk.

 

The square stock was placed into position and the holes scribed on through the plywood top. With the hole positions marked, the square tube was drilled and tapped for 1"x 3/8-24 countersunk machine screws (tapping drill = letter Q or 8.5mm). Once bolted into position with a couple of shims to help, the top was flat to within 0.020" or 0.5mm in all directions.

 

The center plinth 40"x 18"x 3/4" can now be placed on top of the main table. This will carry the model and also act as the rails for the angle brackets to run against. Measure in 6" from the edge, on all sides of the main table top and fix the plinth into place with drywall screws. Once fixed the modeling table should look the same as the photograph above.

 

 

 

With the modeling top now flat I then notched out the 2"x 4" in the areas that connected to the cart. This allowed the top to sit over the edges by approximately 1/2". Using a couple of wood wedges and a spirit level, to level the top to the cart. I then bonded the top into position using Bondo ( Automotive body filler). This provides a permanent fix and maintains the flatness of the top.

 

The photographs above show the top fixed down and the 1"x 1" steel square tube across the width. The final job is to apply a sealant to prevent any moisture absorption.

 

The modeling table is now ready for the project!!!!

Copyright © 2004 - 16 Steven Austin

 

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