I have made a standalone raspberry pi player a few months ago which included an amp and speakers. I now wanted to make a media player to have in my front room that I would connect to my AV amp, I would be designing it so I could swap the raspberry pi from one to the other, thus saving on buying a new pi.
I had an idea of having a unit made of bent wood and remember seeing articles about kerf bending which I hadn't used before so I thought it would be a great challenge. I had a spare length of oak so wanted to make it out of that, I was a little concerned though as most things I've seen with kerf bends have been plywood...I guess it was a try it kind of moment and if it doesn't work then its a good lesson learned.
Materials - Woodwork
Oak for the main body - 1000mm x 200mm x 15mm
Walnut for the wedges - approx. a meter length piece
6mm MDF - 300mm x 200mm
Walnut veneer - 300mm x 200mm
Oak for the end - 300mm x 200mm x 15mm
Plywood for internal electronics
Scrap/small bits of wood
Wood glue (Titebond)
PU glue (gorilla glue)
Materials - Components
Raspberry pi 2
External hard drive
Ethernet cable extension
HDMI cable extension
Fused switched mains inlet socket
Table saw with sled if you have one
Step 1: Planning
As this was going to be a journey in to the unknown for me I decided to do a little planning and a couple of basic calculations. The most tricky part of this project was going to be the kerf bends. I think they look quite good but as a finished product they are not so good as the gaps are generally filled with some kind of adhesive. Doing a google image search I saw one photo which used wedges in the gaps which effectively filled the voids with wood and not adhesive, looked great and enhanced the look of the kerf bend Kerf bend
I produced a CAD drawing of what I wanted to achieved - I started off with the width and height of the box I wanted to make and put some sensible looking radii on the corners which looked feasible from the bends I'd seen on the internet. Once I had the outside and inside radii of the corners I made a little spreadsheet to calculate the dimensions of the wedges. I wanted to start and end the curves with the kerf cuts so I would have:
Length of outside curve = n * kerf cuts + (n - 1) * fins
I first calculated what n would be if the width of the fins was equal to the width of the kerf cuts and rounded the answer to a whole number. I then plugged the n back into the equation and rearranged to find the required width of the fins.
Now I knew the width of the fins (these would be the same on the inside and outside of the curve) and the inside length of the curve I worked out the narrow width of each wedge.
Length of inside curve = (n - 1) * fins + n * wedge width
Now I had all the numbers I could finish the CAD drawing - I've been using DraftSight as it is free for personal use and is rather familiar to those that have used AutoDesk CAD.
I have attached both files if you want to have a look....there are a couple of layouts in the CAD drawing where I was using different widths of kerf and wedge.
Step 2: Woodworking Part One - Mark Up and Testing
My original bit of wood I bought was a calibrated french oak QF4 which is defined as "Sound open knots up to 70mm in diameter permitted without any restrictions. Tolerance for two dead or unsound knots, one less than 35mm and the other less than 20mm. Wane permitted up to 10% of the width and 20% of the length. Excluded: rot, holes." and was 210mm wide by 23mm thick, I had a couple of meters left from a bookshelf I had made. As it can be quite knotty the price is nice a cheap at £6.10 /m fortunately I like knots etc so this was a good deal. I bought it from British hardwoods which is quite close by so I can collect rather than have it shipped
I first ripped it to around 195mm as my planer/thicknesser has 200mm blades and then made it a constant thickness of around 15mm. My planer is fairly basic and accuracy is terms of a final thickness isn't too great! Once I had finished that I cut off the end 100mm each side to get rid of the uneven thickness you get at the beginning and end of a board. I then opened my CAD drawing and transferred the main dimensions on to the board.
This is the first time I had ever attempted to make a kerf bend in anything so I thought it wise to make a couple of test cuts on my offcuts I had to try and find a nice depth of cut to use, and to make sure I could get my cuts in the correct place.
I used my crosscut sled as I thought this would give me greater accuracy. Recently I had to replace the shaft and arbour for my fall/rise mechanism on my table saw so I had also re-calibrated my set up and as such my previous slot on my sled was slightly out in relation to the current blade position. I added a straight bit of scrap wood to the reference end of the sled so I knew exactly where the blade was and I could line my kerf cuts up accurately.
The kerf of my blade is 2.5mm so I went for a 2.5mm fin to make things easier. I therefore marked a line every 5mm on the top of the wood which I would line up with the end of the cut in the scrap wood, cut and move along to the next mark. I tried a few different blade heights out and started to bend the test pieces and established that having 0.7mm of material left gave me a little room for error and a pretty straight forward bend that doesn't snap the wood.
Step 3: Woodworking Part Two - Kerf Cutting
A quick word about safety - use ear protection and a dust mask otherwise you'll regret it in the future!
Having established the height of the blade I added some pencil marks at 5mm increments on the top of the wood which I used to line up with the cut from the blade on the crosscut sled. On my sled I have some clamps installed so I used these to keep the wood steady as it was being cut. I also only did one pass at a time.....so pushed the sled forward to make the cut, switched off the table saw and then pulled the sled back to the starting position with the blade not running. This did take a little while longer but I think the quality of the cuts will be a better. The first two sets of cuts were easy to do and they went very well but when I got to the next set of cuts the wood was overhanging the table sled and started to bend due to the cuts. I just then added a piece of plywood adjacent to the sled to support the overhanging wood.
I next made the wedges that would fill the cuts. This was mainly done by trial and error....in the end I started cutting some walnut with the blade set at 6 degrees moved the fence towards the blade 2mm and finished the cut. This made some fairly consistent looking wedges. I then cross cut the wedges in to 20mm lengths.....all in all I must have had over 100 small wedges. I opted to use short wedges in the ends as I thought it would be easier to bend and no one really sees the inside anyway so the middle part isn't as important. I then glued one side of the wedges and stuck them to one side of the fins, so during the final glue up I had less bits to contend with.
Once I had them installed I had a go at bending the wood, which was far too difficult for my liking and I think it would had snapped or split far too easily. So I decided to add a couple more kerf cuts to each corner which definitely helped.
I next needed to cut a groove/dado to the front of the box so I nailed a straight edge to the wood and started to cut the groove with the router. Before I did this I was a bit dubious about the router snapping the fins, as it happened this did start to happen so I stopped as soon as I noticed and decided to come back to this later. I then cut some rebates/rabbets further in to the straight but of the box to act as stops for the back cover and supports for the base the electronics were going to sit on. I then cut a couple of rebates to the ends of the wood where the two ends would finally meet. To make the rebate for the front of the box I decided to use a biscuit type router cutter which I'd need to use when the box was in its closed state.
So I bend the box in to its final shape which is where I started to get a bit nervous knowing that everything I had done up till now could be ruined. One set of kerf cuts left a larger amount of material to the top which made one corner very difficult to bend (I think my thicknesser was just a fraction off) so I put a damp tea towel over that corner and weighed it down for a few minuets. I then bent the box in to the final shape listening for cracks and snaps.....I did hear some small ones near the end but carried on and clamped the top join and the sides to keep the shape. I could then use my router to cut the rebate in to the front edge. Luckily this worked and there was no more damage inflicted on the fins.
Step 4: Woodworking Part Three - Gluing Up and Finishing
I then made the front panel which I made from 6mm MDF with a piece of walnut veneer glued to the front. I also made a couple of small lengths of wood to act as stops for the back panel and support for the electronics base and glued the front one in to place.
The next stage was to glue all the box - I decided to use normal wood glue for the wedges and PU glue for the rest of the slots as this glue would expand and hopefully fill all the gaps and add extra strength.This was another one of those moments were it could all go wrong....once you start gluing up you just got to go for it no matter what happens. After all the glue was in I started to bend the box and could hear louder cracks than I'd heard previously but carried on anyway, once it was all clamped together I inspected the corners and there was quite a large split and some other areas where small amounts of the oak had come off exposing the ends of the walnut wedges. As it was all drying I added some glue to the underside of the split and held it in place with some blue tape and a small clamp.
After a few hours I started to release to clamps and could see that join at the bottom hadn't held enough and was coming apart so I quickly put the clamps back on!! The only way I could see fixing this was to hold the joint together with bolts, so I drilled three holes and added some bots to the box before releasing the clamps.
As it happened, with this fix the box managed to hold up. Looking at the inside of the box next time I'd use more PU glue as not all of the gaps had been filled.
I then proceeded to make the rear panel which would need some holes added for the switch, HDMI cable and the Ethernet cable. I marked out the holes and drilled the majority of the waste out with a drill and squared the sides up with some chisels.
Step 5: Finishing the Inside, Raspberry Pi and Electronics
Now I had my complete box I turned my attention to the internals. I decided that I would mount all the insides on to a piece of plywood that I fixed in to the back panel, so I could get access to everything by pulling the back panel out. I glued a couple of guide rails to the base of the box and to the underside of the plywood base so everything would stay in line when removing or fitting the rear panel.
Now I knew exactly how much room I had internally to fit all the bits I needed. I experimented with a few layouts and found one I was happy. I could now cut the extension lead to a nice small size, add the spade connectors to the wires so I could fit them in to the switch. I then used this plug for my USB plug.....I'm not an expert in electronics and I'm sure there would be a better way of doing this, maybe by wiring the USB plug directly but I wouldn't feel comfortable with doing this so went for the bulkier but safer (for my skills) option.
I added four tiny screws so I could mount my Raspberry pi on them and keep it in place when all the wires where in place. As you can see from the photos it was a bit of a squeeze but very manageable.
Now I had all my hardware sorted I just needed to set the software up on the pi. I have used XBMC before in PC's and on old laptops and there is a pi version called OSMC. Its a great bit of software and very easy to install. You can choose to download the whole image and burn it yourself to a micro SD card or download the installer to Windows, Mac or Linux which is easier for beginners and also lets you set up wifi keys and such so you don't have to mess around with the config file later on.
Once it has been installed on your SD card boot your raspberry pi up which will initially take a while the first time as the OS is performing tasks it only needs to do once.
I then downloaded the Kodi remote form the Android play store which worked straight away. The only thing left is to now point the music/movie folders to the correct place on your hard drive. I navigated to music/files/external hard drive/music and then long pressed enter to get some options and selected scan item to library. Do the same for movies and you're all ready. I can also use it as a headless music player as it goes through my AV amplifier anyway so don't need the TV for sound.
Step 6: Finish
Lastly I just needed to add a finish to the outside. I sanded the box with 100, 180, 240, 320 and 400 grit making sure not to work too much on the corners as I didn't want to remove much of the oak.....you just need to get the corners as round and smooth as you can.
Once it was all sanded I put on 4 coats of danish oil rubbing down with wire wool in between then added a final coat of wax leaving it for half an hour before buffing it to a nice shine.
All in all I am happy with my player and I have learned a lot about kerf bending. There are a few things I'd do differently - I think I need to experiment with different size kerf cuts and the amount of material left after the cuts, in conjunction with maybe damp cloths and an iron to make the wood more pliable/bendy. Maybe a different wood species would be better?? Any feedback or questions are welcome and if anyone has any kerf bending experience some tips would be gratefully received.
Step 7: Edit: Additional Software Info
After a few days of having this I wanted to be able to stream radio (specifically bbc radio 6 music) so I thought I'd add an extra step here detailing how to go about this.
After looking around the internet for a while it seemed like the best way to have radio was to install a 'tune-in radio'
plugin. I found and used this plugin here Tune-in radio. After downloading the zip file I needed to transfer the file to the SD card in the pi.
There are a couple of ways to do this
1) Take the SD card from the pi and put it in to your laptop or desktop and manually copy the files on to the SD card. One of the problems with this is that the best partition to put this in to isn't seen by the Windows operating system, if you have a linux OS this is much simpler as both partitions are visible and you can copy appropriately.
2) Use a file transfer program and copy the file via your router in to the pi while it's still running. This is a good solution as you don't have to turn your pi off and you can copy any number of thing across once it is set up. Here I'll go through this method as once you have spent a little time setting it up you can use it over and over again easily.
The program I use for transferring files is FileZilla which is available for multiple OS's.
Once downloaded you can connect to you raspberry pi with the pi's IP address, user name and password. When I first tried this FileZilla couldn't connect so I looked in the OSMC forums and found out I needed to enable the FTP (File Transfer Protocol) app from the app store.
To do this go in to My OSMC/App store and select FTP Server. While this is busy you can find out your IP address in My OSMC/Network (you can also change the IP address to be static by assigning the last set of digits to a number not normally used by the router, normally a high number).
Now yo can go in to FileZilla and input the IP address, username and password at the top and connect that way. By default the username and password are both 'osmc'. Once connected you will see your PC directory on the left and the home folder of the pi on the right. I copied the plug-in to the home/osmc folder.
Now on OSMC go to Settings/Add-ons - install from zip file......locate the tune-in zip file in the home folder and install it. Tune in radio will now be in Music/Music add-ons. You can now add radio stations to your hearts content.