X-cell Fan alignment/collet selection

The cooling fan assembly is one of the most critical parts of assembling any
X-cell helicopter. The twin collet system should guarantee perfect alignment; Unfortunately in the real world it doesn't.

I do certain things to help get things as true as possible. First, the cooling fan should be balanced-this includes the Aluminium CNC machined version. I always insert the clutch dampners before balancing as they can affect the balance. Please remember that the fan clutch rotates at 14-18,000 RPM! Any imbalance or misalignment will cause a vibration. The collets and fan are machined to tight tolerances, the motor you choose will affect the way you tackle the fan installation.

OS 50 motors for the Fury 50 series shouldn't cause any real problems using
the collects supplied in the kit.

The OS 61 or OS91 however are not quite as easy.

The top collet supplied for as OS has an 8mm hole. This is designed to fit over the plain area of crank between the thread and step up in diameter to 9.5mm. This section is not machined or ground and can be greater that 8mm diameter.

The alignment of the fan does not rely on this section as the collet is counter bored 9.5mm to align on the ground section. If the collet is a tight fit it will affect the alignment.

If your collet will not slip over the crank easily, it is acceptable to file out the hole to give clearance. In some X-cell kits two 9.5mm i/d collet are supplied allowing a second large collet to be substituted as used in a YS motor installation.

Coat the collet with washing up liquid to reduce any chance of them picking
up during tightening. A piece of dowel or hard nylon is the best thing to use in the carb/crank shaft opening to stop the engine turning over during tightening. It is always of benefit to check the fan alignment with a DTi. Do this on the
outer most edge of the fan hub.