I was concerned about the Kart rolling when on a slope or when getting in and out so I installed a handbrake. this would also stop the kart from moving forward if the engine revs were high. Worth a thought?

The cable caliper clamps onto the main brake disc.

That's a good idea, might have to add one to my build. Funnily enough I started to make a handbrake lever, but it was just for decoration.

Interesting that this discussion popped up in my feed. The guidelines that we are looking at adopting from Cyclekarts Great Britain specify that a hand brake is fitted. The intent of this is to prevent a runaway Cyclekart.

Seems that runaway Cyclekarts are a common occurrence at meetings, mostly as to start the Cyclekart you have to get out of it and stand next to it to pull the start cord. The issue arises when the throttle is not closed properly, the revs pick up which is enough to engage the centrifugal clutch and so the Cyclekart takes off without the driver under its own steam. This has been identified as a big problem in the US too, where every major meeting has one or more runaway Cyclekarts.

Different proposals have been put forwards in the US. One is that when the Cyclekarts are started they need to be 'tethered' to something solid, like a car tow bar or lamp post. Whilst this sounds good in principle and may work for certain events, in practice it's not a great solution as it does not scale very well and still leaves a residual risk from when the driver untethers the Cyclekart to when they get in it. There is also a potential trip hazard from the tether.

A different solution has been proposed at some events where the driver wears a safety lanyard, similar to the ones worn by Skidoos and jet skis. if the driver becomes separated from the vehicle, the lanyard becomes detached and a safety switch stops the engine. The issue here is that whilst this is fine for things like motorcycles, skidoos or jetskis, as the lanyard port is adjacent to the hand grip, Cyclekarts do not use handlebars, so the hands are constantly moved around the steering wheel, often crossing over with the opposite hand. This is cumbersome and introduces the risk of the lanyard getting tangled, which in turn could lead to the driver losing control of the Cyclekart in normal operation.

The other issue with the lanyard solution is that it is not technically a valid safety control as it is still possible to start the Cyclekart without the tether being attached to the driver. It is completely reliant on the driver remembering to put the lanyard on, which makes it an administrative control at best. Solutions such as these are often seen as an inconvenience, which means that they are statistically much more likely to be defeated or ignored.

In my opinion the fact that both of these solutions introduce a secondary risk means that they simply should not be considered in the first place.

Which leaves fitting a handbrake as the most logical and safest solution. Technically you could argue that it is still possible to start the Cyclekart with the Handbrake off, but that could be remedied with a simple switch. However I think that this is not necessary as integrating it with the electrical system also acts as a barrier to people installing the handbrake in the first place. Handbrakes are common enough that a majority of people are already familiar with them.

With all of this considered, the handbrake clause is likely to stay as it most elegantly addresses what is an identified risk.