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Dash Mount LCD Screen


John Pickard

1998 Prado RV6 petrol, manual

Sydney (john.pickard@bigpond.com)

Disclaimer

I make no claim or make any suggestion that what I have described is legal in any state or territory in Australia or any other jurisdiction. Any person who makes and / or fits one of these devices must determine for themselves if it is legal to do so. I accept no liability for any damage or injury to any persons or property that may arise from fitting and using an external LCD screen such as I have described. Anyone who fits such a device accepts full responsibility and liability for any damage or injury that may occur.

Design criteria

  1. Easily visible by driver and passenger.
  2. Apart from the LCD screen, all materials from what I had available in my workshop.
  3. Easy and quick to fit and remove the LCD screen.
  4. Screen could fold down to avoid attracting unwanted attention.
  5. When folded down, the LCD and its frame can not touch the dash.
  6. Screen does not touch windscreen.
  7. Minimum vibration of screen over corrugations.

Image 1 The screen in place on the dash of my Prado. View looking through driver’s door.

LCD screen

There are numerous external screens designed to view DVDs in vehicles. Most do not have a VGA or equivalent input socket. This makes connecting the notebook to the screen extremely difficult / impossible. After a lot of shopping around, I bought a Xenarc Technologies 700 Y screen with a 7” LCD from CDT Technologies in Melbourne for $698 (www.cdt.com.au/index.asp but when I checked, the URL didn’t seem to work.) It came with a mounting bracket which was pretty flimsy, so I made my own.

12V LCDs that accept VGA input are extremely expensive for their size. So don’t be surprised at the prices being asked!

Image 2 The screen folded down for discrete travelling. Note a) the home-made ring nuts which serve as normal wing nuts as well as anchor for anti-vibration strap; green plastic spacer attached to dash with 25 mm wide double-sided tape; c) power and VGA cables running through slot in base plate. The slot serves to semi-lock the cables and thus avoids any strain on the sockets in the LCD. d) hook in rear used to attach the anti-vibration strap.

Support bracket

Entirely made from materials on hand and in my workshop. When making something like this, I spend a long time looking at the job and thinking alternatives, materials on hand, machining, operation, etc. Thus I have no drawings, no measurements, etc. Surprisingly (for me!) I don’t seem to have made any mistakes with this one. Although I regard it as a prototype, I will probably get around to a “production” version in about a decade or so.

As I made it, the bracket has several components which I describe in pretty much the sequence I made them. There is a logic in the order.

a) Tee nut and “ring-nuts”

The rear of the LCD has a channel that takes tee-nuts. I milled up my own from some brass strip about the same length as the channel. This spreads the load and avoids any tension “hot spot” on the rear of the screen mounting.

Two short lengths of M5 brass stud (i.e. metal thread screws with the heads cut off) were fixed with high strength Loctite into tapped holes. Because I couldn’t find any M5 wing nuts, I made my own “ring nuts” by silver soldering circles of stainless wire onto M5 stainless nuts. These are visible in Image 2. The loops serve to both finger-tighten the nuts and as one anchor for the anti-vibration strap.

b) Mounting arm

A length of stainless strip about 3 mm thick. This has a short length of stainless tube silver soldered into a half-loop bent into the bottom of the arm. In retrospect, I should have just silver soldered the arm tangentially to the tube, or got someone to MIG weld it. It was a bit tricky getting the axis of the tube perpendicular to the mounting arm. The dimensions are constrained by being able to fit the arm / tube into the hinge block PLUS a plastic washer on either side to improve friction when tightening the pivot. (I don’t like metal to metal rubbing even in these light duty situations). I didn’t drill the holes for the tee-nut fasteners till later. This is to ensure that the LCD clears the windscreen when vertical.

Image 3 Base and hinge block with mounting arm in erect position. Note brass tee-nut running up face of the mounting arm. White on the mounting arm is velcro to make tightening a bit easier.

c) Hinge block

A piece of scrap aluminium square tube 30 X 30 X 3.18 mm. I milled the centre slot to just clear the mounting arm. The front of the block is bevelled to provide clearance for the bottom of the LCD when it pivots downwards. The block is fastened to the base with three countersunk metal thread screws. The two at the front are tightened by placing a screwdriver through two holes drilled in the top of the block.

Image 4 Hinge block and base of mounting arm. Note a) clear lexan strip in front to act as a stop when mounting arm is in horizontal position; b) stainless socket head cap screw pivot running through c) stainless tube silver-soldered to loop bent in bottom of the mounting arm, and screwed into d) tapped hole in stainless plate attached to outer face of hinge block. The hinge block is square aluminium tube machined with a slot to take the mounting arm. Black plastic washers under the head of the SHCS and between the mounting arm and the hinge block make tightening a bit easier.

The holes for the pivot SHCS were drilled as tight clearance holes. I had already decided that tapping the aluminium for the M8 SHCS was not a good proposition, so I added the stainless plate visible on the LH side of the block. This is held with a countersunk metal thread screw at the front (i.e. closest to the windscreen) and a spring dowel near the rear.

d) Pivot pin and tension washers

An M8 stainless socket head cap screw for a couple of reasons. Firstly I have a fetish about stainless in my Prado; secondly I had some in my workshop; and thirdly, I can tighten the pivot using an allen key even if the LCD is upright. Tightening a hex head bolt would be painful as there is minimal room for a spanner.

The shank of the bolt (i.e. the unthreaded section) is a bit longer that the outer width of the hinge block. I machined a lump of nylon rod into washers. One goes outside, under the head of the SHCS and is just thick enough to ensure that the threaded portion of the pivot is barely inside the hinge block when the pivot is tightened. The other two are fitted between the mounting arm and the hinge block inner faces.

Image 5 View of hinge block from LH side showing the lexan stop, and the stainless plate attached to the block with a countersunk metal thread screw at the front and a spring dowel at the back. The end of the pivot M8 SHCS is clearly visible sticking out from the plate.

e) Stop

A short length of lexan strip on which the mounting arm rests in the horizontal position. This stops the LCD hitting the dash.

f) Anti-vibration strap and anchor

A short loop of 3 mm shock cord with a hook attached that stretches between the top “ring-nut” and the hook anchor on the front of the base plate. This is to stop vibration when travelling over corrugations, and despite its simplicity, it works very nicely. Sooner or later I will add a piece of hard foam to the front face of the mounting arm when it touches the hinge block to reduce vibration further.

The shock cord loop hooks onto a hook of stainless wire wound round a bolt sticking above the base plate. This can be seen in Images 2 and 3.

g) Base plate and spacers

A lump of 10 mm thick PVC sheet, screwed onto two 25 mm square rods of unknown green plastic. The green rods act as spacers and were just the right height to allow the LCD to both clear the windscreen when vertical, and the dash when horizontal.)

To avoid putting any tension on the socket where the VGA cable goes into the rear of the LCD, I cut a slot just wide enough to take the VGA cable from the edge of the baseplate to a hole drilled in it. Both the VGA and the power cables are tight fits in the hole, and this holds them both firmly in place. The slot is visible in Images 2 and 3.

Fitting it all together

A fair bit of sucking it and seeing. I made sure that it all worked, and the clearances were fine before attaching the entire edifice to the dashboard. After final fastening of the hinge block, anti-vibration anchor and stop to the base, I screwed the base to the two spacers. I degreased the dashboard with iso-propyl alcohol and attached the spacers with 25 mm wide double-sided tape.

Mounting the LCD is easy: undo the “ring-nuts” to loosen the tee nut, slide the LCD onto the tee nut, and tighten the “ring-nuts”. With the screen still horizontal, attach the power and VGA cables, then stand the screen up and hook on the anti-vibration strap. On most notebooks, you activate the external screen by hitting Fn + F10 several times until both the notebook and the external screens are live.

In use

Like a dream although some maps which appear fine on the notebook screen are a bit small on the 7”LCD. In this case, I just use the magnification button in OziExplorer.

When discretion warrants, I simply unhook the anti-vibration strap and fold the LCD down flat. To protect the LCD from sun when in the field, I cut out a shield from an aluminised sun shade that fits inside the windscreen.

Is it worth it?

For my applications, most definitely yes. I use the notebook with OziExplorer for navigation and I really do have to know where I am , and where my sample sites are. I wish I had done it years ago, but LCDs simply weren’t available then. 

 

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