The Dyson Turbinehead rotary beater brush attachment. Doesn't have tons of torque, but it gets the job done and cleans my rug. I noticed some unusual symptoms the last time I tried to use it: terrible noise when the turbine valve was open to use the brush, and little to no torque at the brush. In the spirit of curiosity and making-the-world-betterness that inspired James Dyson to create his vacuum in the first place, I attempted to investigate what the problem was, and see if I could fix it.
What follows is the teardown procedure for most of the Turbinehead attachment, and my attempted DIY fix for the cracked turbine that I found inside. Although I wish the turbine hadn't failed, the process gave a satisfying look at some good industrial design and product engineering.
I have no idea if this particular problem happens to anyone else, but I hope it is interesting to someone, or provides access for other issues. Others have published youtube videos of this process.
Step 1: Remove Brush Cover Plate
At this point you're still in routine maintenance territory, and Dyson has a guide for this and the next step.
Twist the locking tabs as shown on the sticker, and slide the locking slide toward the back. Hinge the cover plate toward the front and remove it.
Step 2: Remove Brushes
Slide the brushes off to the sides. This is a good time to clean them. When reinstalling, make sure to note all three arrows are pointing the same way.
Step 3: Brushes Removed
Brush drive bushings (blue arrow) are pressed on. I don't recommend removing them.
Step 4: Remove Top Cover
Remove 5 Torx screws. I didn't have the right bit, but a 2.5mm allen key works, if you're super careful.
Step 5: Remove Turbine Assembly
Lift the black turbine assembly away from the wheels.
Step 6: Remove Side Covers
This is the most difficult step. Removing the inlet cover will give you access to the turbine itself, while removing the outlet cover provides access to a screw needed to inspect the drive belt. They are removable, but it takes some patience. It is very much like working a bicycle tire onto a rim. Take two flat head screwdrivers, and begin prying the cover off, starting at the locating tab. In the second picture, you can see the groove that the covers seat into. Keep pulling the cover away from the centerline of the vacuum, while teasing it out of the groove. Work your way around the circumference, and it will come loose.
Step 7: Open Belt Housing
Remove 3 more torx screws (red arrows) to inspect the drive belt and timing gears. Also the exhaust side of the turbine is visible at this point (blue arrow).
Step 8: Remove Turbine
Carefully pry the turbine inlet casting out of the housing. I don't have a picture of this process, but it is located at the red arrow in the first picture, and you can see what it looks like once removed in the third picture. Pry it loose with a flat head screw driver or small pocketknife. Work gently around the circumfrence, prying in several locations. You want it to come out gradually and more or less on its own axis, not tilting too much.
At this point you should be able to determine if the issue is a cracked turbine, like mine, dust needing to cleaned out, or bearing problems. My turbine had cracked, and lost its grip on the knurled drive shaft. It then moved out of position and began rubbing on the housing. You can see white plastic and roughness transferred to the housing in the second picture. If I had some fine sandpaper handy, I would have smoothed this out for better airflow.
Step 9: Problems
The plastic turbine has cracks radiating from the central bore, and rough bits of plastic on the blades where they've been rubbing the housing. I removed the burrs by gently scraping with a knife. I epoxied the shaft into the turbine, and filled the central well with epoxy for good measure (or overkill). Make sure not to get glue on the bearing journals at either end of the shaft, or on the machined grooves for the timing belt.
Step 10: Reassemble
There are four bearings, two for the turbine shaft, and two for the brush shaft. I choose to lubricate them with a couple drops of bicycle oil. Something with silicone or teflon for dust-shedding properties would be ideal. Sewing machine or spindle oil would also be fine. Do not lubricate the drive belt or pulleys. The turbine bearings operate in ambient room air, and the brush bearings are enclosed, but surrounded by dirty carpet air.