Hx-Kool Ferrofluid: installation guide for the Falco eDrive
A few millilitres of Hx-Kool turns the motor's air gap from an insulator into a heat path. Your Falco eDrive runs cooler on long climbs, heavy loads and hot days. Installation takes about 15 minutes and needs only a drill and a steady hand.
How it works
Inside a direct-drive hub motor, the copper windings sit on the stationary stator. The heat they make has to cross a thin air gap to reach the magnets and the rotating shell, which is what sheds heat to the outside air. Air is a poor conductor of heat, so the gap acts like a blanket. Hx-Kool is a magnetic liquid: once injected, the motor's own magnets pull it into the air gap and hold it there. It bridges the gap with a fluid several times more conductive than air, so heat flows to the shell instead of building up in the windings.
The motor's magnets hold Hx-Kool in the gap. It stays there whether the wheel is turning or parked.
Before you start
In the box
- Hx-Kool ferrofluid, 5 mL pre-filled syringe
- Applicator tip
You will need
- Drill with a 1.5 mm bit (1/16 in is close enough)
- Steel rule or calipers, fine marker, centre punch
- Masking tape (depth flag) and a dab of grease
- Aluminium foil tape or electrical tape to seal the hole
- Nitrile gloves, safety glasses, paper towels
- Isopropyl alcohol for clean-up
Compatibility
For Falco eDrive direct-drive hub motors, including the HX 750 W motor in the f7.9 system and earlier Falco eDrives. Do not use in geared hub motors or mid-drives: their gears and clutches are not designed for it.
Under warranty?
Drilling the motor cover is a permanent change. If your motor is still under warranty and you have any doubt, call us at 877-278-6323 before you drill.
Where to drill
Any point on the 89 mm circle works. Choose a spot clear of screws, labels and the cable exit.
Step by step
-
Power down and prepare
Switch off the system and remove the battery. Leave the wheel on the trike or bike if you can: it holds the motor steady. Wipe the motor cover clean and lay a drop cloth underneath.
-
Mark the hole
Measure 89 mm from the centre of the axle and mark the cover. Give it a light tap with a centre punch so the bit does not wander.
-
Drill the 1.5 mm hole
Rotate the wheel so the mark is at the bottom (6 o'clock). Wrap a flag of masking tape on the bit a few millimetres from the tip, smear a little grease on it, and drill slowly with light pressure. Stop the moment the bit breaks through: you are drilling the cover, nothing behind it.
-
Clear the swarf
Wipe away any chips from the outside of the cover and lightly deburr the hole with a larger bit turned by hand. Keep the hole facing down while you do this.
-
Inject Hx-Kool
Rotate the wheel so the hole is at the top (12 o'clock). Fit the applicator tip, insert it into the hole and inject slowly.
- Inject about 1 to 2 mL, then turn the wheel slowly by hand two or three revolutions so the magnets draw the fluid around the gap.
- Bring the hole back to 12 o'clock and repeat until the full 5 mL is in.
- If fluid wells up at the hole, stop, spin the wheel a few more turns and wait a minute before continuing.
-
Seal the hole
Clean the area around the hole with isopropyl alcohol and let it dry. Cover the hole with a square of aluminium foil tape or electrical tape, pressed down firmly. For riding in heavy rain, a small dab of neutral-cure silicone over the tape adds a long-term weather seal.
-
Check and ride
Spin the wheel by hand: it should turn freely, with at most a slight extra drag. Refit the battery, take a short ride at low assist, then ride as normal. You should notice the motor staying cooler on long climbs and under heavy loads.
Do
- Use the full 5 mL for one motor
- Drill with the hole down, fill with the hole up
- Seal the hole before riding
- Clean spills straight away with isopropyl alcohol
Don't
- Exceed 8 mL in total: more fluid means more drag
- Drill deeper than the cover
- Pressure-wash the motor cover
- Use in geared hub motors or mid-drives
Questions
Will Hx-Kool leak out?
No. The motor's magnets hold the fluid in the air gap, whether the wheel is spinning or standing still. The tape over the fill hole keeps water and dirt out.
Does it slow the motor down?
At 5 mL, the added drag is negligible. Drag rises if you overfill, which is why we say never more than 8 mL.
Does it need topping up?
Not as routine. If the motor is ever opened for service, the fluid should be cleaned out and a fresh syringe applied after reassembly.
I spilled some. How do I clean it?
Wipe it up with paper towels, then clean the surface with isopropyl alcohol. On fabric or porous surfaces it can stain, so work over a drop cloth.
How should I store an unused syringe?
Keep it capped, upright, at room temperature and out of direct sunlight.
Need a hand?
We are happy to talk you through it, or to fit Hx-Kool when your eDrive is in for service. Call 877-278-6323 or send us a message.
Buy Hx-KoolContact usLearning Center