EDIT: check the date of this post….
Melbourne-based Aproké Engineering is set to release a revolutionary new sprocket carrier in the coming months.
Dubbed by the company as a ‘movable leverage hub’, the device allows for increased acceleration without having to add teeth to the axle sprocket.
“When you add a tooth to your rear sprocket you are increasing the leverage by increasing the distance from the centre of the axle to the pitch circle of the sprocket, which is the centre of the chain roller” Aproké Engineering’s Grant Aproké explained to KartSportNews.
“With this leverage hub, you are basically increasing the distance from the axle centre to the pitch circle therefore giving you more acceleration (like adding teeth), but maintaining your gear ratio for top speed as normal.”
Under power, the mechanism built into the hub offsets the sprocket to the axle by pulling the sprocket up and forward to increase the leverage on the working side of the sprocket whilst maintaining the gear ratio, as per the illustration above.
The Aproké Leverage Hub simply replaces the standard sprocket carrier on the axle and uses the same chain and sprockets already in use. The only modification that might be required is for extra clearance on the chain guard when the device is under acceleration.
Importantly, this is not a gearbox or variable ratio, so it is already KA legal.
Unfortunately, Aproké would not supply a photo of the hub mechanism due to patents that are still being processed.
However, two kart shops have tested the device – we believe one in WA and the other in Queensland. Due to non-disclosure agreements, neither would comment on record.
The mechanism does come with a weight penalty and inherent frictional losses in the complex off-setting mechanism. But these losses are more than overcome by increased acceleration.
Aproké claim their own testing (using a KA100 in KA3 spec) has always resulted in going at least three tenths per lap faster, and on one track almost half a second.
To get the weight down and increase durability, production versions will be manufactured from exotic lightweight materials of extreme scratch hardness. As a result, it’s expected the sprocket carrier could retail for close to $900.
But, it’s basically a bolt-on three-tenth advantage, or even more if the circuit has low speed hairpins or steep climbs.