Your opinion about a six speed gearbox on the sunburst

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SteveA said:
The gear width difference is the case for the Quaife boxes based on AMC cases. It is one of the reasons I chose to run a 4 speed in the '70s, and yes those Quaife 5 speed boxes were less reliable, particularly those that had a kickstart mechanism and ran the layshaft in the bush like a standard box. Though to be fair, the main issue was shaft flex not gear width.

But if Yves chooses a 6 speed it will be a TTi. This is a completely different proposition. Because, not only do TTi use larger diameter shafts and bigger bearings, but TTi cast and machine the cases and are free to play with the case width and shaft length to accomodate wider gears.

The 6 Speed TTi sacrifices very little in reliability and can handle the power even a highly tuned 750 Commando engine can present to it, and I should think most 850s. But TTi do an 'XHD' 5 Speed, it is stronger and a better choice for 920 plus motors, when in any case it is a more difficult argument to make that you need 6 gears with all of the mid range available.

Mick Hemmings will tell you his current 5 or 6 Quaife builds are far more reliable than the '70s versions, I have no reason to doubt that, and the 6 speed is now widely used in 500cc race bikes.
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Thanks. That answers my actual question, which had nothing to do with ratios.
 
When Rod Quaife and John Surtees got together in the late 1970s to come up with a 5 speed cluster for the Vincent, this same question of relative gear width came up. Some owners felt that the narrower gears of the five speed could never stand up to the power of a mighty Vincent. The big truck gears in a standard Vincent 4 speed were necessary for durability.
Rod Quaife answered that with modern tooth profile design and gear material, the 5 speed cluster was good for 200 bhp.
That put the fears to rest.

Glen
 
SBR use a TTi 6 speed in their methanol burner, which I think supports the 'easily' claim!
 
Fast Eddie said:
Why did you ask him that Al? You buying another bike to put it in?? ;)
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Are you familiar with the concept of 'proof stress' ? Materials in aircraft are stressed to within 95% of their 0.1% proof stress. A Commando is not an aircraft, even when it really flies..
 
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