Reproducing the Velador Experiment

The following is a preliminary parts list, and may be revised over the course of assembly.  Any equivalent that will serve the same function and still fit the support beam is acceptable. 

Table 8 - Parts List

Suggestions for Assembly 

1”x6” yellow pine is relatively flexible, but is susceptible to warping.  Care should be taken during selection to find flat, straight pieces that stack well.  Unfinished lumber is typically cheaper, but is only sanded after sawing, not planed.  Finished lumber (planed and sanded after sawing) is desirable but not required.  (Use of slightly heavier white pine may be acceptable if suitable yellow pine is unavailable.)  Mill cuts typically have a tolerance of 3.2mm (1/8 inch), and board lengths will vary by up to 6.5mm (1/4 inch) – the width of two mill cuts.  This is adequate to allow boards to be used right from the lumber yard without further cutting or finishing, but can be improved if the boards are re-worked before assembly.

Attempting to match board lengths while simultaneously checking for adequate flatness and straightness is not practical.  It is simpler to arrange to cut the boards to the correct length.  (Note: Most lumber yards will cut small lots of lumber for customers, but will not guarantee better precision than mill cuts.  If you want better precision than ±6.5 mm, you must cut the lumber yourself.)  A tolerance of ±1mm is easily attainable with a circular saw and carpenter’s square.  A rasp is necessary to trim cuts to precisions better than ±1mm, but this can be done after assembly if the support beam internals are protected by a cover.

The end for which it is most necessary to obtain a flush fit for the ends of all component boards is at the camera.  During assembly, the board ends at this side of the support beam should be kept even.

To prevent splitting, yellow pine should be drilled if fasteners will completely penetrate the board.  A wood screw every 0.3m should be adequate for assembly, and holes should be pre-drilled accordingly along a single line 1cm (3/8 inch) from the edge of each board.  Washers will be necessary to distribute loads for the mounts, but not for the other screws. 

Bolted eye hooks with a minor diameter of at least 5mm (3/16 inch) should be used for any single point cable mount.  Bolted eye hooks with a minor diameter of at least 2.5 mm (1/10 inch) should be used for any cable mount, regardless of whether it is part of a multiple point support.  Thicker bolting is allowable, and preferred.  (Keep a record of the size bolt used, as you will need a matching drill bit to install them in the wood)  Use nuts for each bolt, with two washers for each single mounts.

The only required internal structure is the screen, any additional insulation, nuts for fasteners, and mounts for the camera and laser.  Heating elements (for calibration) and wiring should also be allowed. These should be assembled and installed before final assembly.

Drill holes for the support beam mounts should be measured and bored first.  First, stack and align the boards to determine the ends which will align most evenly.  Then, carefully stack the boards loosely to find the configuration with the smallest sway and/or gaps between boards during final assembly.  Label this end on each board, and label the outside surface so that the boards can be returned to this configuration for final assembly.  Decide on a top, bottom, right side and left side board at this time, and label them.  Separate the boards, and measure each to position the cable mounts. 

Cable mounts for the top board will be positioned at 0.1 m from each end of the support beam top, over the central axis of the beam (not the central axis of the top board), and at the same position on the suspension beam. Drill all the way through, using a bit sufficient for the bolted eye hook of a single point cable mount.  Fit two bolted eyehooks using a nut and washer on either side of the board, with the hook on the outside surface.  The top of the support beam should be installed last, and should not be glued.  The top of the support beam should remain removable for maintenance.

Mark a line 1cm (3/8”) from the edge down one edge of each outside face of the support beam boards.  Use this line as a guide to secure the boards together using a 1-1/4” wood screw every 30cm (1ft), in configuration #1 discussed in the section on optimal support beam sections. 

The mounts for the camera and laser can be made from two 17.2 cm (6.75 inch) pieces of 1”x6” board.  Cut the boards.  Measure and mark the 17.2 cm boards for bore holes which will line up with the bore holes in the blocks installed in the support beam end.  Using a 6mm bit (1/4”), drill three bore holes at each so that a #6 machine screw can be passed through the 17.2 cm board and into each bracket.  If necessary, the bores in the 17.2 cm board can be widened by re-drilling to improve alignment, but not wider than the width of the large washers.  Pre-drilling with a smaller bit will allow better accuracy in placing the mounting screws, but is not necessary.

Mark the position of the support beam center axis on the board’s intended inside surface.  Place the camera on the board’s inside surface so that camera aperture is over the marked center position, then trace the outline of the camera.  Remove the camera and place a flat metal bracket/strap across the drawn outline in the position they will need to clamp the camera to the board without obstructing the camera’s aperture, buttons, or electrical connections.  Mark the positions of the end screw holes, and drill a 3mm bore hole through each to the other side. 

Install the camera batteries and affix the camera to the inside surface of the mounting board using two machine screws run through two metal brackets starting from the outside surface.  Use small washers on each end of the machine screws, and place wing nuts on the screws.  The wing nuts should be positioned on the brackets, rather than the outside surface. 

For a camera large enough for a screwed camera mount connection, a large block incorporating a screw of sufficient size to fit the camera can be affixed to the mounting board in a position sufficient to hold the camera with its lens at the beam center, rather than holding the camera in place with brackets.  This is not an option for the selected camera, and brackets are available that will secure most cameras.

Secure each spindle screw to its bracket (extending outward, with the head inside the corner bracket) with a hex nut and washer.  Tighten this assembly with a wrench and screwdriver so that the spindle screw will not turn.  Slide a spring over this, with the nut or large washer serving as a spring washer on the bracket.  Slide a washer over the free end, capping the spring, and insert the screw end through the backboard of the mounting cell.  Secure it with a washer and wing nut on the other side of the backboard, and tighten by hand until the spring is compressed solid but can still turn.  Be careful not to over tighten the spring – it’s easier to assemble if set solid, but not if you accidentally crush the spring.

This is a preliminary schematic of the apparatus.  It will be revised over the course of assembly.