Saturday 23 April 2011

In the Land of the Machines

So it was time to do the first stage of the screen: the copper tubes that will hold the sections of the screen. Copper has a very handy property: It's soft initially, but the more you bend it the more rigid it gets, making it ideal for my application. Since it is next to impossible to get a screen of toroidal shape it will be put together by individual sections, each of which will be attached to the skeleton. This picture shows the screen skeleton made out of copper tubes in the 3d model:

Once again I had a field (half) day at a workshop, this time however it was the physics workshop as opposed to the (very small) neuroscience workshop where I did the black frame. The machinery there instills fear and awe. You wonder what kind of people can tame those machines that appear to be only a step away from growing arms and legs and start crushing everything in their way. There are rumors that on every full moon the technicians sacrifice a virgin's eldest child to appease the machines.

Anyway, after a short chat with the lead engineer we've decided to bend the copper tubes around an appropriate shape. To get that shape we drew a 23cm radius circle on a board and drilled screws halfway in around the perimeter (if you don't know what I mean, look at the pictures below). This allowed me to bend the copper tube around the circle and end up with semi circles of the right size. We placed the screws slightly inside the the 23cm circle because the copper wouldn't stay exactly in the shape I bent it but rather spring back a little bit, so if the circle was exactly 23cm we had ended up with a larger radius.

Above you see the method to bend the tubes around the ring of the screws. Bending full circles allows me to get 2 at a time. My fingertips were hurting after 4 out of 20 semi-circles. The bottom picture shows how I fixed the start of the tube so I don't have to hold it permanently.

21 semi circles. Why 21 when you only need 18? So I have 3 for testing purposes. Why an odd number when you always get 2 at a time? Because I'm a retard and cut one too short.

 In order to mount the tubes to the rings (see previous post here) I had to flatten the ends and drill a 3.5mm hole into them. This would allow me to fix the tubes to the ring with M3 screws. Because copper is quite a soft material the holes had to be cleaned up a bit. This was done with a drillbit of bigger size which was turned manually to take of the excess copper left by the drill:

Bottom picture: the result of 5 hours work

Back in the lab I've mounted to top and bottom ring and mounted three tubes to see whether they fit. And they did. Below are a few pictures of the tubes on the rig, for a short while I was tempted to mount all 18 to make it look really nice for the pictures, but putting then first 3 on made me realise that putting all of them on and taking them off again will give me carpal tunnel syndrom.

The tubes fit well and look as I imagined (read: modelled) it.

The next step is to cut the screen sections into shape and mount them on the tubes. In the first instance I will use tape to connect the sections, depending on how visible they are if the projector is on I might have to find a less visible solution. And for those who made it to the very bottom of this post, here is a detailed model of how the mirror will be mounted from the ceiling. It will be hard to oversee the similarity to the Harvey et. al. (2009) setup and I want to give it the according credit at this point. A happy easter everyone!


Harvey, C. D., Collman, F., Dombeck, D. A., & Tank, D. W. (2009). Intracellular dynamics of hippocampal place cells during virtual navigation. Nature, 461(7266), 941-946. Nature Publishing Group. Retrieved from

Friday 8 April 2011

Bit by Bit

Today another part arrived which I've designed myself. The engineering workshop has cut and drilled it to my description and not only does it look like in the 3D model, it fits in perfectly. It's a very satisfying feeling planning something for so long and then seeing how it all fits together so nicely.

What I'm talking about are the rings which will hold the skeleton for the screen. The skeleton itself will consist of copper tubes bent into shape and screwed to these rings. Between those tubes I will span the screen itself, although I haven yet to decide how exactly I will do that. In the model this is what it looks like:

So far only the bottom one has been mounted to see whether the dimensions are ok, the one for the ceiling will be mounted as soon as the rest of the screen is ready. Here are some more pictures:

Wednesday 6 April 2011

(Manual) Labour Day - update

As promised, here are a few pictures of the frame mounted to the table. The bars across which will hold the ceiling plate have not been mounted yet simply because I will have to do some drilling to bolt the plate to the bars which I very much prefer not to do around animals.

The frame covers the outermost row of holes on the airtable.

Hooks screwed to the table hold the frame in place. 2 at each corner make sure the frame stays where it should 

Here a total. Quite a resemblance with the 3d model, isn't it?

Right now I'm working on a few things in parallel, so I can't tell you what will be posted next. On top of my priority list is getting some coffee.

Tuesday 5 April 2011

(Manual) Labour Day

Now that the treadmill is up and running I have started building everything that goes around the treadmill. Concurrently my second focus is familiarising myself with the Quake 2 game engine which I will use to create the virtual reality for my mice. If somebody knows a better piece of sofware for that, don't hesitate to leave a comment!

So, it was time for the frame which will hold the overhead mirror (angular amplification mirror and plane mirror) and support the screen. Here is a picture from my 3D model so you get a better idea what I mean (we are talking about the black frame):

After a quick discussion with the workshop wizard I have decided to use Dexion SpeedFrame(t). Essentially what you have to do to put a speedframe together is cut the bars to the right length and connect them with joints. I have designed it so that it covers the outermost row of holes on the airtable, on my 900x750mm table that makes a footprint of 800x650. The height of the cube was determined by how high the screen is, although the current solution allows to adjust height of screen support and mirror to make it less dependent on the absolute height of the cube.

Now you can see why 3D modelling is very handy. Without being able to put all this together virtually it would be very difficult to get the dimension right and know how things are arranged before it is actually built (at which stage it is very difficult to change dimensions or design). Again, I'm more than happy to share my 3D model for strictly non-commercial purposes.

It took me about 5 hours to make this cube, here the usual photo-documentation of my fun labour day.

 Top: the holder to cut the bars was provided by the workshop and was very handy to get a clean, straight cut. One must not forget though that we are cutting iron here, so it is not without effort and some experience comes in handy.
Middle: 4 bars cut, out of 14. Ugh.
Bottom: bars, also perfect for bar-charts

Filing all around to take off sharp edges (top). The finished result is below. 
The next step inolves a hammer and a lot of noise.

There are 2 steps to connecting a speedframe: 1) insert plastic ends into bars which give the joints extra grip. 2) hammer in joints. DO NOT do this around animals. This creates a lot of noise. And not just any noise, it's the kind of noise that shakes the very structure of a building. Anyway, while feeling a little bit sorry for everybody else in the building I hammered together the cube.

The cube is moutned to the airtable via small hooks that are screwed down. The standard hooks are too small to put an M6 screw through it, so I whipped out the drill. Now the cube is ready, here is one final picture of the cube. Looks pretty much like the the model, eh?

Tomorrow this cube will be transferred to the animal house and put onto the airtable, stay tuned for a quick update tomorrow.