A six speed, Shimano geared, dual freewheel differential has been developed for a mid-drive electrically assisted tricycle.
This unit is intended to replace the existing one wheel drive axle on the rear of a trike to give better traction whilst retaining good turning characteristics.
This being important due to the increased power given by the electric assist mid-drive motor.
The original trike had drive to one rear wheel and the other freewheeled on its axle.
The incorporation of the dual freewheel differential fitted with the Shimano six speed hub enabled both axles to provide drive to the rear wheels whilst retaining the ability for a tight turning radius.
The Shimano six (or seven) speed gear cluster fits in the same position as that of the trike’s original axle and uses the same derailleur gear shift mechanism.
Due to having a differential the trike now required to be fitted with a brake on each rear wheel/axle rather than the single band brake of the original.
The dual freewheel differential unit uses 15mm diameter keyed axles on both sides.
ER4 Electric Reverse for Chain Drive Differentials
We have now added a new electric reverse to our product range.
Our ER4 Electric Reverse Unit drives a 95 tooth ring gear mounted to the right of the differential’s sprocket and with the geared electric motor mounted to the differential’s mounting cradle.
Unlike our previous systems, the ER4 has a solenoid actuated gear engagement rather than requiring pull cables or rods.
The ER4 reverse can be fitted to most of our chain drive units with the exception of units with inboard disc brakes.
The ring gears can be drilled to suit other differential units such as the Quaife QDF7ZR unit.
For units with inboard disc brakes we can supply a different electric reverse which is fitted remotely to the differential.
A reverse system is required on vehicles undergoing IVA testing in the United Kingdom as well as being a requirement for circuit racing, not to mention that a reverse is quite handy for manoeuvring in tight spaces.
The Dual Freewheel Drive is intended for use in very low powered and human powered vehicles where a conventional differential unit would be too heavy or costly.
These units can be used on velomobiles, quadricyles, trikes, cyclekarts, karts and small electrically powered or electrically assisted vehicles.
A variety of sprocket sizes or belt drive pulleys can be fitted.
The dual freewheel uses a two freewheel units mounted in a light aluminium housing.
The freewheels are threaded onto keyed bosses which transmit the power to the axles.
The standard unit is designed for 25mm OD axles with 6mm drive keys.
Other axle diameters can be accommodated using different sized bosses (max. axle dia. 25.4mm, 1″ )
The mass of the Dual Freewheel Drive unit is less than 1.5 Kg (without axles and sprocket).
The drive from the chain or belt is transmitted to the housing of the dual freewheel unit via the sprocket or pulley.
In the forward direction, drive is transmitted to both axles via the freewheels.
As power is equally transmitted to the axles, this provides excellent traction on slippery or loose surfaces (a bit like a limited slip or locking differential).
The freewheels will still allow either axle to rotate at different speeds during turns.
On overrun, the freewheels rotate allowing the drive chain and housing to slow down or stop whist the vehicle continues to roll forwards.
The drive chain cannot be used to drive the vehicle in reverse.
Installation & Maintenance:
The unit is designed for axles supported in self aligning bearings.
The axles should be supported with bearings at the dual freewheel drive as well as at the wheel hubs.
The axles lock to the bosses of the freewheels using grub screws and the power is transmitted via the keys in the bosses/axles.
The axles should also be restrained via collars at the support bearings.
Axles can be supplied with full length key slots to facilitate the attachment of disc rotor hubs.
(a disc rotor is required on each of the axles).
The unit is fully serviceable by the customer and uses readily available freewheels.
Westgarage Engineering’s Bulkhead mount with eccentric adjustment
Chain Drive differential Mounting
There are several ways to mount your chain drive differential.
1 – Bolting to your chassis via the side mounting bearing carriers.
Not a very satisfactory method.
2 – Fitting using a basic bulkhead mount
Difficult to fit shims to tension chain.
3 – Fitting to a sliding plate mounting carrier.
Easier chain adjustments, needs longitudinal chassis rails to mount side plates.
4 – Fitting to a pivot type mounting carrier.
Easier chain adjustments, pivots from a bulkhead,
5 – Fitting using a bulkhead mount fitted with eccentric bearing housings
Fits to a bulkhead, very easy chain adjustments.
A drop-in module for the rear of a MEV Rocket.
The Aluminium frame combines a mount for an AC35X2 (twin motors on a common shaft),
reduction jack-shaft assembly on eccentric adjusters,
Quaife QDF7ZR ATB chain drive unit fitted to Westgarage Engineering eccentric adjusting bulkhead mounts and a 3rd eccentric mount for the extended driveshaft on the right hand side.