Rephasing, What is it?

[wkdenton]

Hello, my name is Bill Denton, long time Yamaha XS650 owner, rider, fixer and listowner of (the now practically defunct) plain text mail list YAM650 on the Micapeak server https://lists.micapeak.com/mailman/listinfo/yam650

I initially became interested in the "Quartered Crank" theory from my love of steam power and steam locomotives in particular, all of which used 90º crank configurations for less vibration via conservation of momentum. Then, in 1995 I read a Cycle World article on the Yamaha TRX850 that further piqued my interest, which led me down a rabbit hole that I'm still in...

Rephase theory is now mainstream tech, known by a new name... the cross-plane crankshaft. If you'd like to know more about primary and secondary imbalance, conservation of momentum about the crankshaft, and why the quartered crankshaft is a pretty good idea that's finally caught on 90 years after Phil Irving (unsuccessfully ) pitched it to the Triumph Brass in the 1930's, I recommend reading the musings that I penned over 20 years ago that's now found at Hughs Handbuilt site at the link shown below. Cheers!

https://www.hughshandbuilt.com/2013/03/28/277-rephased-goodness-vaults-internet/

 

[Mailman]

I initially became interested in the "Quartered Crank" theory from my love of steam power and steam locomotives in particular, all of which used 90º crank configurations for less vibration via conservation of momentum. Then, in 1995 I read a Cycle World article on the Yamaha TRX850 that further piqued my interest, which led me down a rabbit hole that I'm still in...

Well then…..you might just enjoy this timely video from Fortnine , it just came out!

 

[dps650rider]

So which design point has the potential for the least vibration? I have always thought it would be the 270 because it is better at canceling vibration caused by the reciprocating mass.

 

[46th Georgia]

So which design point has the potential for the least vibration? I have always thought it would be the 270 because it is better at canceling vibration caused by the reciprocating mass.

The late Dick Russell, AKA grizzld1, felt that rephasing just moves the vibration to a different place in the powerband and that it didn't increase H.P. Your vibrations may vary. Void in R.I. Cal. and N.Y.

 

[gggGary]

This very thread covers it pretty well if you enter the "way back machine"
A wander around this area has some pretty good stuff.
https://www.xs650.com/threads/rephasing-what-is-it.103/post-401791