I couldn't find anything on the net (March 20, 2017) showing how to disassemble a Turbinehead Dyson brush. It seems pretty frequent to have the brush no more rotating and the official fix is to buy a new brush, a $100 cost. So here is the real way to completely disassemble the brush. Not sure you may repair it though, if the part is completely broken.

Right click on the images and "display image" to see them larger. I may post a link to the full images later.

1.  Warning

I only describe my case, that may not be yours. Screw drivers are kind of blades, be very cautious not to hurt you!!

In my case, the faulty part was the fan. It's a nylon part, and nylon get fragile with age and broke. It's a shame than the more fragile part is so difficult to remove and probably not available as spare part (I try to ask Dyson, but with little hope).

In fact my dog like logs, as, I guess, most dogs like, and it eat then, breaking them in small parts. For some unknown reason a log part find a way up to the fan, blocked it and it broke. may be it felled there when I tried to clean the brush, because, for sure, it didn’t made it's way through the filter!

2.  The device

Below, three images of the device, up, right and left. It works by air, that is you set the turbine on by opening an air vent below the red filter, it's why you have to pull the part to open. There is no mechanical link between the filter and the fan.

The device at Dyson's site

3.  Looking closer

You will soon to have to unscrew five torx screws, get the good screwdriver.

The active turbine part. Two covers, a small one and the one with the filter and the air intake.

4.  Disassembly, part 1

A simple cover to remove, two locks to turn by hand - obvious.

Result:

5.  Disassembly, part 2

Remove the five torx screws. Notice they are pretty long, don't lose them, take them apart. Remove the transparent upper part.

6.  Disassembly, part three

Optionally remove the brushes. It's enough to pull them and put them apart

7.  Disassembly, part four

The turbine mechanism. There is nothing to do, it's loose now. Keep it and take apart the rest.

The brushes are linked to the axis by knobs that seems to be tighten on the axis, very difficult to remove (and to set back then), so don't try to. Not necessary is you don't have to change the belt. I didn't.

8.  Disassembly, part five

This part was not necessary and you may not have to do it. Do not dismount anything not mandatory. But when I did I didn't know that, so better show the result, just in case.

The axis and the turbine are liked by a toothed belt (like the motorcar camshaft), and the belt carter is in two part assembled by three torx screws, same kind (but shorter) than the ones we already know. You will see the belt better in some photos below.

Two of the screws are easy to find, but the third is naked in the air way. I've seen on Youtube somebody that could remove it with a special made tool, but it's much simpler to remove the grey cover that hide it.

There are two covers. One small, above the screw, and the other, large, next to the red filter.

Warning: from now on, we are going to use brute force to open the boxes, so we will somewhat spoil the pieces. We are also going to use flat screwdrivers to remove the covers, like one can remove tires from a bike wheel.

There is a form on the caps and on the carter so you can only mount the cover at one position, so no worry about that. You will see on the photos that the covers simply hold in place because they shape and a groove. You have to pull hard a screwdriver to get the cap loose from the groove. The small cover is pretty easy to remove. Don't hurt you with the screwdriver!

Now you can remove the third screw. As you may see from the next photos, you can partially disassemble the case to see the belt.

9.  Disassemble, part six

First, examine from there the state of the turbine wheel - that is the white wings you see there. Do it turn with the belt? If you are there, probably not. You may see a crack in it, like the one that is not visible on the next photos, but very visible after disassembly.

If this is the problem, cracks on the turbine, we may try a fix. I did the fix, but the vacuum cleaner in not there, so I can't test it right now and I doubt it will last very long. There should be a spare part (turbine + small axis) and if you can find one, do.

Any way if you have to work on or remove the turbine, you have to remove the large grey cover. This one is very difficult to remove, because it covers a vacuum chamber and there is a moss gasket between the cover and the case. This gasket act like glue, so you have to act very strongly with the flat screwdriver - better have at least two. The covers are in very sturdy plastic that wont brake too easily, but try not to break it because the vacuum chamber will no more accommodate vacuum :-(.

10.  Disassembly, part seven

Now the cap is off, the hard part is done. Now to the turbine. Under the grey cover, you see a black one. Pull it gently out, it's not glued nor fixed in any way.

After removing this part you see the broken turbine. Such helix have to be molded or glued on the axis to hold firmly, when broken it's loose. This part is moved by the wind of the vacuum cleaner and in turn make the brush turn. Brilliant if it was a bit more sturdy.

11.  Disassembly, part eight

Remove the turbine and it's axis (at least two parts). If you are clever enough, you can make your own turbine, 3D printer would be designed for that, but one can also make one with traditional tools and aluminium alloy. I have seen people do so, but it's not (not yet) for me. Finding a computer ventilator with similar fan can be, but very unlikely.

12.  Fixing

I decided to try super glue... both to close the crack and to glue the turbine to the axis. Do not place the turbine on the wrong side, once glued you wont be able to remove it! Large dents are for the belt, small for the wheel. The wheel flat side is outside.

13.  Reassembly

Reassemble in the inverse way, there should be no problem, but wait several hours for the glue to dry before.

Drop a very little quantity of fine oil on the bearings before reassembly.

To refit the turbine dents to the belt, you may have to move the belt (turn the big axis) back and forth. The black cover have a special position, you can't set it in place if not fitted.

Same for the grey caps, they clip in place if well positioned, with a simple tap of the hand.