Introduction: ParalleloLamp
The ParalleloLamp is based on the original draughtsman's Pentograph machine. It can position the lamp from 50cm above the floor to 1.9m and the lamp is balanced at all times even when fully extended horizontally, it does not need a locking mechanism to keep the lamp stationary as it is balanced by a counter weight. The lamp head is able to be positioned nearly anywhere within a hemisphere.
It's made of 12mm aluminium square tube and 5mm allen head bolts with lock nuts. The counter weight is a 3/8" x 5" bolt and 55 3/8" washers, it screws into the inside of the 12mm tube perfectly without needing to tap a thread. I bought the lamp head at a hardware store and discarded its base. At the elbow is a 3mm x 25mm x 75mm piece of flat aluminium plate and the main centre axis is made of the same material except it also has a 90º bend (more of that later). The small tube sticking up at the main axis point is a handle which you can use in conjunction with the counter weight to position the lamp in space when you are standing behind the ParalleloLamp, it is not critical and can be excluded if you wish - although it's fun to move the lamp head around in space from the back of the lamp by manipulating the two small arms backwards and forwards (or am I just a dork). The aluminium was cut by my supplier and I used a bench drill to drill the holes. Once it was completed I had it anodised black.
Step 1: ParalleloLamp Standard Units and Drilling Procedure Explained
The first image above shows the standard unit lengths I used to make the ParalleloLamp. There are only two length units in the lamp. The units aren't fixed and can be changed to suit your requirements but they must be consistent throughout, any variation will mean the lamp won't work as a multi-parallelogram device! My standard units are: smallest - 55mm (between centres of holes) and longest - 365mm (between centres of holes). The second image shows the ParalleloLamp in an exploded view.
When you start drilling the holes make the first piece you drill your template for the rest that follow, this makes it easy to have standardised lengths. I drilled two holes at each end of the smallest vertical tube first, this tube is 70mm long and the 5mm holes are 55mm between centres and is now my shorter standard unit. You need to use this piece as a template when drilling the two handles, the central L shaped flat and the special tube that comes from the front vertical tube to the elbow. I drilled a hole in the small 3mm flat piece at one end and put the template piece on top of it and put a bolt through the two holes and that fixed the position for the second hole I needed to drill in the second part. I repeated this process on all the parts mentioned above.
There are three sizes of longer tubes. The two shorter tubes which go from the central axis to the elbow and from the elbow to the front which are the standard longer unit lengths. The top tube at the front is a longer unit and a smaller unit combined so there are two holes 365mm apart and then another hole 55mm further on. The two main tubes that run from the elbow to the counterweight are identical and are two longer units in length so there are three holes each 365mm apart in each one.
Drill two holes in the shortest of the long tubes 365mm apart (this is now your standard long unit template), then drill the first hole in the second of the shorter tubes and use the long template tube as I explained above. For the two longest tubes drill the first hole and place the long template tube on top of that and drop a bolt through, you now have an exact position to drill the second hole, move the temple unit down and drop the bolt through the second hole and this will give you the position to drill the third hole.
The L shaped mounting bracket is easy. I used 25mm x 135mm x 3mm plate that had been bent 90º so the horizontal part is 35mm long and the vertical face is 100mm long. I drilled a standard small unit in the middle of the 100mm face and then drilled a larger 6mm hole in the middle of the 35mm face, I used this for the mounting spigot bolt that goes into the lamp stand.
All you have to do now is bolt the whole thing together - have fun doing that (the centre bit is a bit tricky). Keep an image of the assembled ParalleloLamp on the screen and it shouldn't be too much of a problem.