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MFA Gearbox modification

The MFA gearbox was designed for electric flight and works fine when used in tractor mode where the propeller is pulling the shaft forward.

When used on a hovercraft as part of the thrust unit the propeller pushes against the shaft. After a while the front bearing will move back and the propeller boss starts to drag against the frame.

This modification is very simple but enables all the thrust to be taken on the bearing and the bearing cant be pushed back.

I burnt out one motor before I realised what the problem was.

The photographs below show the modification in full much better than I can write about it. The brass ring is cut from a brass tube that is the same dimension as the bearing outer. It's height should be such that it is in contact with the pins once assembled. Dimensions cannot be given as the moulding varies from unit to unit. Ensure that the internal diameter of the tube clears the cir-clip when the clip spins. The two pins are brass rod, drill through the gearbox  body as close to the corner as possible and use a drill slightly undersize so that the pins are held tight when fitted.