When I looked out for solutions on how to carry along my modular synthesizer I noticed three options:
1. spend a lot of money for one of the (seldom) commercial solutions
2. put the stuff into a massive 19" rack which wouldn't fit onto my desk
3. build something for my own
I decided for the last option, got a used paramedic suitcase from ebay plus some accessories from the building center and spent a noon with taking apart my existing rack and assembling this piece of modular freedom.
Step 1: Getting the parts
I already owned a small modular setup so i took apart my racks to get the 19" SB-rails, the power supply and busboards.
I planned a system of three 19" rows (3x3U) so the parts-list turned out as the following:
1x Transformer 220V to 15V
1x Power Supply for stabilized +12V and -12V voltages
6x 19" aluminium rails
6x 19" threaded strips
Wood stripe for the frame ( 80cm+ for a 3x3U, 6cm in depth)
4x square brackets to mount the frame in the suitcase
Bolts & nuts
So, let's hunt for the right suitcase
Step 2: Find the right suitcase
Finding the right case is 90% of the work. My object of desire should be light but durable so I went for a field-proofed paradmedic suitcase from the german forces. Size depends of your setup but if you plan to build in a 9U of Modules you should consider those values (internal size):
Width: you'll need 48,26 cm inside your frame + the width of the frame itself + some extra space for the power unit
Height: 3U (which is the height of a standard Eurorack module) equals 13,33 cm, allow for an extra and you'll end up with 41cm
Depths: Now, that depends on your modules. Mine are up to 6cm so 11cm of depth seemed enough for me. Also consider a certain depth (2cm) for the cover if you plan to align the front panels of the modules with the top edge of the suitcase, so that there is enough room for the knobs.
Apart from the size you should also think of the materials as well as the construction type. The combination of a thin aluminium shell around a wooden interior sounded good to me and turned out as easy to work with.
Step 3: Build the frame
First, cut the wood in two pieces of the same size (40 cm) and drill the holes to attach the rails.
Screw the rails and use a blind front panel to check the distance between the rails. The Frontpanel must slide easily from left to right inside the rails. Repeat the steps with each row.
Step 4: Attach the frame
Now that the frame is finished you might want to marry it with the suitcase.
Attach a bracket on each lower corner of the frame pointing to the inside. Place it loosely into the case and choose the right position (mine was at the right side), then mark all holes of the brackets touching the inside of the suitcase. Drill through the marks and place bolts from the outside. Fix the rack with nuts from the inside and check the result.
Step 5: Install the electronics
Once the frame is fitted into the case it's time to provide it with some power.
To save space for the transformer I used only two busses for the three rows. I used offcuts from the frame as sockets for the boards and simply attached them by using double-faced Scotch tape. The transformer was screwed on another wood socket and this was again taped with the Scotch. The lower bus board got an extra 5V supply via a DIY-interface that I fixed with two screws on the frame.
I didn't want a dedicated cut for the power cable - in normal use you wouldn't need power while the case is closed, so why do the extra work.
Connect the +12V/-12V and ground between transformer and bus boards and connect the power supply to the transformer. Once you've done this, switch it on to test the connections. In my case all four LEDs on the lower board and the lower three LEDs on the upper board should light on, and that's what they did.
Step 6: Finalize
Now, that's the fun part. Populate the frame with modules and enjoy your new mobile freedom :)