By Steve Glass

I made a lovely little 45mm fan unit for a CD Rom motor...........here it is.

I had in mind an improved replacement for the KP44 ..........this unit is far more powerful and weighs a lot less.

You will need a motorised sanding-disc with a perpendicular table. A block of wood is drilled with a pillar drill with a 3mm and 8mm holes. The wood-block is clamped to the sander table with a 'G' clamp.
Components of the fan-unit are sanded to shape against the rotating sanding-disc using the drill bits as axles..........see the photos.

1......The shroud is made from 1/64 ply. It is cut 5mm over-length and the ends feathered to make a scarf joint.
 

 2......The shroud ply is wetted and formed on a suitable mandrel (45mm dia). Two lengths of wetted 1/32 hard balsa are wound around with their ends feathered to make a neat job (2 turns)........keep the winds under tension, as you wind, to stop the balsa breaking.

 3......The motor-tube is 1/16th balsa, wetted, and formed on a suitable mandrel with a butt joint.
 

4......The motor-tube ends are made from 1/16 balsa drilled with a 8mm hole and sanded to an exact fit on the disc-sander using the 8mm drill bit as an axle.

5......The blades are formed on a 45mm dia mandrel at a 30 degree angle to the vertical......this gives the blade camber and twist.

6..........The blades are formed by two laminations of 1/64 ply using epoxy adhesive and are set at 30 degrees to the horizontal

7......... Hub parts. 1/4grain balsa discs and 1/64 ply ends. The balsa discs are notched for blade attachment and have 3mm holes.

8........ Sanding the hub to size

9........Hub.  Note how the notches are staggered to give the correct root angle of the blades (45degrees in this case)

10.......Accurately gluing the blades.

11.......Stators are formed on a 36mm mandrel and are laminated from 1/64 ply on inside and 1/16 balsa outside. PVA glue was used. When dry the length of stator material was sanded to aerofoil section.

12......Gluing on the stators. PVA glue.

13......Trimming the stators for an exact fit in the shroud.

14......Stators fitted and glued.

15.......CD Rom motor fitted, front view

16........Motor from rear. Look at the cooling slots.

17........ Rotor blades sanded for exact fit. Then the blades are shaped and sanded to aerofoil section

18.......Rotor fitted (after careful balancing of course)

I use superphatic to glue the rotor to the 3mm carbon shaft to allow disassembly.
Hats off to Peter Shepherd of Westwings who pioneered all of these techniques.

The motor………..

For anyone who is interested?

The 20mm CD Rom motor………..

20mm stator from www.aircraft-world.com.

· 10 turns of twinned 30swg terminated ‘Y’.

· A ventilated 20mm standard can (from www.cdmotorworks.com or www.strongrcmotors.com )

6 magnets 5x4x1

 The bearing holder is 8mm o/d. 6mm o/d. carbon rod. With a 3mm carbon shaft.

The completed plywood fan-unit weighs 19g (K&P unit weighs 32g) and provides over twice the thrust. (5oz. Static installed in my Fury (auw 9oz)) using a 3s 400mAh lipoly.

Latest generation lipolys are needed as the unit takes  9-10A at full throttle.

Free flight scale North American FJ-4 Fury fitted with own design motor speed controller/timer circuit
 

I have another 45mm plywood fan in this for R/C flying……..

Steve Glass