A key feature in Transmission-drive systems is the Freewheel Chainset: It doesn't push the rider's feet round under power, and avoids injury through feet slipping from the pedals

The crank is unusual as it is threaded onto the chainset using a freewheel. Using the 44T chainring, or a 4-arm or 5-arm spider a chainset is built up with sufficient space to accomodate 2 chains (3/32" Brompton rear and 1/2" 7-speed drive chain)

The standard 3-ring (44T+44T+22T) chainset available from Cyclone may work with larger-wheeled bikes, but a larger chainring (~52T) is usually needed for folders. With electric asssist even a 54T or larger ring may be suitable.

This motor cradle is designed to suit a range of frames and is slotted to allow exact alignment of the cog and chainset. Hidden is the chain exit slot (look at the bottom view of the cradle below). The side is bolted on so that a chain can be installed with a breaker. 3 motor positions are provided - 2 axle slots, and the sides can be exchanged for the 3rd position.

A chain tensioner (not shown) also has 3 positions. 2 frame clamps (with plastic grommet and tube to prevent paint damage and provide grip) hold the cradle to the bicycle frame.

In some cases a torque arm is required from the motor to the frame to prevent rotation of the cradle under peak torque.

To sling the motor behind the seat-tube needs a different approach: here 2 'U' bolts sleeved with clear polythene tube hold the cradle to the rear fork.

The motor is held higher on a small wheel bike: the motor supports are lower for full-zide wheel bikes.

The hub motors used in a presto system have an internal freewheel. so no freewheel is required between the cog and motor. A standard freewheel cannot be used anyway, because it would unscrew!

The cog mounting plate is drilled with 'disc brake' hole centres with 6mm stand-offs to mount a fixie cog. Cogs are available from 15T to 19T to suit a range of gearings. Here I used 'rivet nuts' or 'nutserts' fitted to the adapter plate.

The motor fixings depend on the choice of motor - the nano has 6 x 4mm screws.

Top and bottom views of the motor and cradle fitted to the frame tube.

The tube clamps are sleeved and have grommet strip to prevent damage and improve grip. No torque-reaction arm, to prevent the cradle rotating around the frame tube was found necessary (but I may fit one, anyway!)