Q: Hi guys and thanks for a superb site, we go onto it everyday, so keep it going.
I’d just like to ask a question. I read about ‘straight cut’ gears and/or ‘helical cut’ gears and was wondering if you could clarify the difference, and the advantages, if any?
It was just something that popped up in our local pub conversations – looking forward to the answer.
A: Both are usualy used in the primary drive from the crankshaft to the clutch/gearbox. Quite simply the helical gear system is to make the mechanical engine noise, not so noisy, and that’s about it. However if you put a lot of extra power though a helical drive (turbo charging for example), it can ‘deflect’ the gears between the crank and clutch, as they can push/ride apart, causing irreparable damage.
Straight cut gears do make more mechanical noise but offer a stronger direct connection between the crank, clutch and gearbox – drag racers especially choose this due to the shock loading off the line. If fact all modern super bikes have primary straight cut gears now because of the high horsepower output.
If you look into a car gearbox they’re usually helical cut – again to keep the mechanical noise to minimum.
