The Hacky Racer rules require that every racer has a mechanical braking system. Brakes which rub on the tyres or the ground do not qualify, nor do electro-braking and regen.
Here are two ways to create a manual brake.
Convert Automatic Brake to Manual
Many Hacky Racers are based on mobility scooters and these vehicles generally already have two separate brake systems: a manual brake which acts directly on one pair of wheels; and an automatic anti-runaway brake which generally acts on the motor shaft. If the manual brake is in good condition, then it can be re-used unmodified. If not, then the anti-runaway brake can be converted to manual use.
It’s tempting, when converting a mobility scooter motor for use in a racer, to unbolt the seemingly complex automatic brake and bin it. However, with a couple of simple mods, it can be converted into a superb manual brake.
Begin by unbolting the brake from the back of the motor, knock out its magnetic coil (which normally releases the brake) and removing the heavy-duty spring (which normally applies the brake) then reassemble just as before – with those two parts missing – and refit to the motor.
Then, fit/bodge a lever onto the brake or motor body so that the lever presses onto the central spindle of the brake and gives about 2:1 or 3:1 leverage. This will apply the brake when the lever is pulled towards the motor.
This brake is easily strong enough to stall our motor even when it’s at its full 30A torque – which can be handy for getting a quick start off the line because we can max the throttle, let the soft-start build up to full current, and then release the brake at the ‘go’.
Fit Bike-Type Calipers and Brake-Pads to the Driven Sprocket
If your Hacky is chain-driven, you’ll have a large sprocket on the rear axle (or the diff – if any). Provided that you’re happy to remove the chain every time you want to oil it, this sprocket can be used as a brake disk.
Standard rubber brake blocks work fine but the leverage required is considerably higher than a standard bike caliper can provide – around 3:1 or 4:1 is needed. The braking action is dramatically improved if the ‘disk’ is cleaned occasionally with acetone or similar powerful solvent.
Dual-purposing the sprocket is not ideal – lack of proper oiling on the chain becomes a problem after each rain shower – but it’s a cheap, quick way to get a first brake fitted and with the correct leverage it will be powerful enough to lock the rear wheels.