S&S X-Wedge
The January 2007 issue of my Cycle World has an article an the S&S X-Wedge motorcycle motor, a big V-twin that walks away from its Harley roots.
The main thing it walks away from is the hoary hemispherical head Harley has used for ages.
The article says the hemi-head made sense when compression-ratio was around 6 or 7 to 1.
But as gasoline was improved, and CRs could climb, eventually the hemi-head had to be filled with a raised piston-dome.
The increased piston-surface that came with a dome makes the piston hold a lot of heat.
Hemi-heads are still in vogue; more-or-less. The head on the LHMB is a hemi, but the valve-angle is so small it’s almost flat (a wedge). The fact it breaths as well as it does at high revs is because of open valve-area. And that comes with four valves per cylinder.
S&S’s X-Wedge is huge; 139+ cubes — which would make a 557-cube V8. As such it can generate a humungous amount of torque: a Big-Bang motor.
Another thing it abhors is the vaunted Harley tradition of 45° V-twins. The bore-angle is 56.25°; it allowed a bigger bore than a Harley will allow — at 45° bigger bores can conflict.
56.25° also reduced the vibration; a 45° V-twin vibrates like a single. No balance-shaft on the X-Wedge.
The X-Wedge has three cams; all operated by an inside Gilmer-belt. Two cams operate the exhausts; the single center-cam operates both intakes. Valves are operated by automotive-type stamped-steel rockers and pushrods. The cams are down next to the crank.
No long, contorted, springy steel-tube rockers like in the Harley. Better valve-control.
The X-Wedge looks a lot like a Harley Big-Twin. It’s still air-cooled, and was designed for the Big Dog chassis and its ilk.
It eschewed a roller-bearing crank, for plain bearings. My 1980 Ducati had a roller-crank — I don’t think the new Ducks do. (I don’t know what the Harley TCs are.)
What I’d like to know is if the X-Wedge eschewed the knife-and-fork crank. (Looks like they did.)
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| S&S X-Wedge. |
The article says the hemi-head made sense when compression-ratio was around 6 or 7 to 1.
But as gasoline was improved, and CRs could climb, eventually the hemi-head had to be filled with a raised piston-dome.
The increased piston-surface that came with a dome makes the piston hold a lot of heat.
Hemi-heads are still in vogue; more-or-less. The head on the LHMB is a hemi, but the valve-angle is so small it’s almost flat (a wedge). The fact it breaths as well as it does at high revs is because of open valve-area. And that comes with four valves per cylinder.
S&S’s X-Wedge is huge; 139+ cubes — which would make a 557-cube V8. As such it can generate a humungous amount of torque: a Big-Bang motor.
Another thing it abhors is the vaunted Harley tradition of 45° V-twins. The bore-angle is 56.25°; it allowed a bigger bore than a Harley will allow — at 45° bigger bores can conflict.
56.25° also reduced the vibration; a 45° V-twin vibrates like a single. No balance-shaft on the X-Wedge.
The X-Wedge has three cams; all operated by an inside Gilmer-belt. Two cams operate the exhausts; the single center-cam operates both intakes. Valves are operated by automotive-type stamped-steel rockers and pushrods. The cams are down next to the crank.
No long, contorted, springy steel-tube rockers like in the Harley. Better valve-control.
The X-Wedge looks a lot like a Harley Big-Twin. It’s still air-cooled, and was designed for the Big Dog chassis and its ilk.
It eschewed a roller-bearing crank, for plain bearings. My 1980 Ducati had a roller-crank — I don’t think the new Ducks do. (I don’t know what the Harley TCs are.)
What I’d like to know is if the X-Wedge eschewed the knife-and-fork crank. (Looks like they did.)
The LHMB is my motorbike.
posted by BobbaLew at 5:19 PM
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