Time Will Tell
Posted: Wed Jun 02, 2010 10:19 am
Greetings:
These clutches act a lot like a drum brake, operating in "reverse". Instead of the drum spinning and the shoes applying stopping forces, it is the shoes that spin, and they apply accelerative rotating force to the drum upon contact.
Drum brakes and these clutches both have a sort of "self-lockiing" feature, or not, depending on the location of the fixed pivot point. If the shoe on a brake or a clutch pivots from the end Away from the direction of rotation, then the spinning drum tries to drive the shoe further outward upon contact, thus exponentially increasing the friction and the clutch "locks on" in engagement. Drum brake systems featuring a Double Leading Shoe - Two cams - were developed to take advantage of this phenomenon, though not found on our scooters. Single leading shoe - single brake cam - brakes found on our scooters have only one shoe that uses this extra force, while the other does not. The "leading shoe" often wears faster than the passive one.
Back to these clutches: If the clutch shoe pivots from the other end - closest to the direction of rotation - it just drags passively and uses centrifugal force alone to maintain contact. This obviously can lead to more slippage. I suspect the respective clutch designs of the single-reduction Spree and SB models are different from the Variated, double-reduction models whose clutches spin in the opposite direction. If the shoes are symmetric in the radial plane, it might be possible to flip them over and install them in the opposite direction to regain that self-locking feature. If not, I agree that the greater slippage might lead to a very hot drum and rapid "clutch fade". As was said, time will tell, but a geared-up kitted Spree could sure use a bigger, better clutch to deal with the extra power and tall launch ratio. This is a great idea if it works.
These clutches act a lot like a drum brake, operating in "reverse". Instead of the drum spinning and the shoes applying stopping forces, it is the shoes that spin, and they apply accelerative rotating force to the drum upon contact.
Drum brakes and these clutches both have a sort of "self-lockiing" feature, or not, depending on the location of the fixed pivot point. If the shoe on a brake or a clutch pivots from the end Away from the direction of rotation, then the spinning drum tries to drive the shoe further outward upon contact, thus exponentially increasing the friction and the clutch "locks on" in engagement. Drum brake systems featuring a Double Leading Shoe - Two cams - were developed to take advantage of this phenomenon, though not found on our scooters. Single leading shoe - single brake cam - brakes found on our scooters have only one shoe that uses this extra force, while the other does not. The "leading shoe" often wears faster than the passive one.
Back to these clutches: If the clutch shoe pivots from the other end - closest to the direction of rotation - it just drags passively and uses centrifugal force alone to maintain contact. This obviously can lead to more slippage. I suspect the respective clutch designs of the single-reduction Spree and SB models are different from the Variated, double-reduction models whose clutches spin in the opposite direction. If the shoes are symmetric in the radial plane, it might be possible to flip them over and install them in the opposite direction to regain that self-locking feature. If not, I agree that the greater slippage might lead to a very hot drum and rapid "clutch fade". As was said, time will tell, but a geared-up kitted Spree could sure use a bigger, better clutch to deal with the extra power and tall launch ratio. This is a great idea if it works.