At the tail end of last year, I decided it was time to put some of my accumulated woodworking skills to the test. I set out to build an Oak Cabinet.
Not just an Oak Cabinet, an Oak 19-Inch Rack! So, why a 19-inch rack? And what is one anyway? I’d better do some explaining…
We have an end-room in our house, that used to be the living room before the previous owners added an extension (see the blog on The Kitchen). It’s a beautiful room, with a parquet floor, large window to the front and patio doors to the rear. It has a wood-burning stove that justifies all the Wood Stores I’ve built over the years. Oh, and the first project I wrote about in this blog was the story of a set of Tumbledown Box Shelves I built for this room. We call it our Music Room as it plays host to a piano, squeezeboxes, bodhrans, guitars…
and, of course, the Chap’s Drums.
He has an Electronic Drum Kit that needs an amplifier. He’s studying for Grade 5 at the moment, so he’s doing all right. I figured that now he’s at secondary school, he’s not long off playing in a band, so I took the plunge and replaced the noisy and temperamental 2nd hand amp we had with a small Mixing Desk and a pair of powered speakers. The mixing desk allows lots of instruments, microphones, etc to be plugged in and their sound balanced properly. It also opens the door to having effects units, synthesisers and other things plugged in. Oh, and it connects to a computer so that what’s being played can be recorded, and other music (such as the backing tracks he plays along to) can be mixed back into the sound. Most important of all (for us at least) he can plug in some headphones, so we don’t need to hear every note he plays.
Anyway, my guess is that The Chap will accumulate a selection of musical gizmos over time that will need a home. The mixing desk already needs a proper base, as does the laptop that controls it all – this old TV Stand we’ve been using up until now is not really right for the job.
This is where the 19-inch rack comes in. Many years ago, electronic equipment manufacturers started to standardise on the boxes that kit gets fitted into. They devised an equipment housing that has a standard width and a choice of standard heights. They defined that equipment front panels should have ears that protrude by a standard amount at each side, and these should have holes at a standard spacing to allow the equipment to be secured in place. A 19-Inch Rack is basically a pair of rails running up each side of an open box, with screw holes at regular intervals. Equipment is then screwed into these rails to hold it firmly and to line up the front panels nice and neatly. If I make a 19-inch rack for our music room, then there will be a proper space for new musical bits and pieces to be accommodated.
My thought was to build a frame out of strips of oak, that would be the right dimensions to hold a 19-inch rack. I would then give it a tabletop for the mixing desk to sit on, and would make a stand for the laptop or tablet. The basic structure of this frame would be something like this:
So, with these sketches in mind, I was off to Oxford Wood Recycling to buy some strips of oak. And that reminds me of the other part of the challenge I set myself: I would make this cabinet using rough cut wood, and would do all the wood preparation work myself. If I needed a particular sized piece, I would be the one to cut, plane, chisel, glue and sand it. Here’s what I came back from OWR with:
Step one was to tidy up each piece and start to make them similar dimensions. So out came the hand plane. The first thing to do -always- with a plane, is sharpen the blade and set the cut so that it takes off an even slice that is as thin as possible. I get through quite a lot of scrap wood doing this, but it’s worth it. Incidentally, I found that the wood shavings are excellent for starting the fire in the wood stove, so nothing gets wasted here.
The first pass with the hand plane is just to make the wood smooth and flat-sided. Polish and finesse can be added later.
So now I have some smooth strips to work with
Next, I revisited my sketches to work out which piece would be used where and how.
I had three basic sizes of wood; 4x2cm strips, 9x2cm planks, and 4x3cm strips. I decided to use the first of these to form uprights for the cabinet, and the second and third to form cross pieces. By putting the 4x2cm and 9x2cm sections together using biscuit joints I could make two rectangles, one for each side. I could then join these rectangles together using the third strips. Actually, with a bit of juggling of dimensions I might have enough wood in the 9x2cm planks to join the rectangles at the bottom too. This would give a consistent and even base to the unit, and would help with its rigidity. Then, I would need to use only a single 4x3cm strip for the two top pieces, saving the other strip for another project.
Measurements would be critical in ensuring I conformed to the correct 19-inch Rack Dimensions. I needed to firm up the design and get all the lengths right. Back in PowerPoint I drew up scale views of the frame so I could visualise the pieces I would be sawing up.
I marked the most important dimensions in red. These defined the space required by the rack. First, the 48.5cm horizontal measurement. This is a fraction over 19 inches, and reveals where the rack name comes from. This key dimension means the two pieces that stretch across the top (both cut from my ‘Piece H’) and the two pieces across the bottom (cut from ‘Piece A’ and ‘Piece B’) had to be precise lengths.
This is where some maths came into play. My pieces A and B were both about 121cm long. If I cut 48.5cm from each, then I would be left with two 72cm long strips. If I cut each of these in half, I would get four 36cm sections. That would be ideal for setting the depth of the cabinet. N.B. the 19-inch rack specifications don’t give a standard for depth. 30-40cm depth seems to be quite common for electronic kit, and with these strips at 36cm plus the 4cm wide upright pieces I should end up with a deep enough cabinet.
The second dimension in red is a vertical measurement of 62.5cm. This came initially from an estimation of overall cabinet height. I decided a cabinet about 80cm tall would look ok. Subtract a bit for the tabletop and for the top and bottom of the frame and I would be looking at about 65cm of internal rack space. As mentioned, rack heights are measured in Units, each being 44.5mm high (so a 2U high piece of equipment would need a space 89mm high, 3U would need 133.5mm and so on.) 65cm divided into 44.5mm units gives space for about 14U (which is 62.5cm.) So, then I knew how long my rails should be, and hence how big to make the cabinet. From this I also knew what I would need to order to create my 19-inch rack.
An online search for 14U Tapped Rack Rail led me to a company called Penn Elcom who were able to supply me with the requisite rails, as well as a collection of other useful bits and pieces such as 2U Rack Shelves…
A Rack Mounted Power Supply Unit…
And a jar full of Rack Screws (which are of course a particular American screw thread, not compatible with metric systems.)
A quick assembly of rack pieces gives a view of how big the interior of the cabinet will be.
With this temporary assembly, I can check another key dimension. It is important to ensure the right distance between the screw holes that secure the equipment into the rack. I need to have approximately 465mm between the centre-points of the screw holes in the rack rails, which equates to about 18mm between the side of the cabinet and the screw holes. There is a little lee-way here as rack-mounted equipment usually has slotted holes in their front panels, but I need to be sure that a correctly sized rack unit will fit flush to my cabinet and still be able to be screwed in. I can see from this view that if the rails are secured into walls that are 19 inches apart then their holes will be in the right places.
Anyway, I now had my measurements for the cross pieces and the uprights in the frame. The four uprights would be 75.5cm long and I had four lengths of 119cm to use. Four spare 43cm pieces of oak would be a good contribution to the Laptop Stand, which I would begin to work on after this.
So, following much sawing and planing, I have the pieces ready for the basic cabinet.
I shall begin to put it all together in the next post.