Book informationIn my quest to find information on the problems of cooling a V-twin engine mounted with its crankshaft transverse (at 90°) to the frame, as it is in Harley-Davidson motorcycles, I found the book Streetbikes: Everything You Need To Know by Bill Stermer. On page 29 of the book, I thought I found just what I needed in this line: "Even on the ubiquitous longitudinal air-cooled V-twin, the rear cylinder tends to run hotter...". All I would need further is a statement on what they mean by "longitudinal" because, with vehicles in general, "longitudinal" usually means that the crankshaft of the engine is parallel to the centre line of the frame of the vehicle. The use of "longitudinal V-Twin" in the manner Stermer has used it in that line clearly means that the cylinders are in line with the frame and the crankshaft is transverse. It makes no sense otherwise; if the crankshaft of a V-twin is parallel to the centre line of the frame then there is technically no "rear cylinder" as such.
|Title:||Streetbikes: Everything you need to know|
|Location:||St. Paul, Minnesota, U.S.A.|
However, on page 155 of the book, I read this statement: "In a transverse arrangement, the crankshaft is arranged across, or at a 90-degree angle, to (sic) the direction of the frame. On a longitudinal engine, the cranckshaft runs parallel to the frame. The crankshaft of a V engine may run longitudinally (as with a Moto Guzzi), or transversely as with most cruisers." This is the conventional definition and is the opposite of what Stermer means by "longitudinal V-twin" as used on page 29.
So I went through to see how often Stermer's use of "longitudinal V-twin" contradicted his definition of "longitudinal". The results are as follows:
The term "longitudinal V-twin" is mentioned four times.
First mention, on page 25: "The greater the V-angle, the longer the wheelbase may have to be to accommodate it, which is why some manufacturers tilt their longitudinal V-twin engines forward for better cooling and a shorter wheelbase. Arranging the cylinders transversely, into the airstream, enhances cooling."
Second mention, on page 26: "A longitudinally mounted (crankshaft runs front to back) V-twin is a natural. It keeps the bike narrow, which aids in moving through the air and in cornering clearance, and the crankshaft and transmission gears rotate on the same plate as the wheels, so it's easy to hook up a drive chain or belt. However, there can be cooling problems with the rear cylinder."
Third mention, on page 28: "Turn that V-twin from lengthwise (longitudinal, like a Harley-Davidson or Ducati) to transverse (across the frame), and you have the Moto Guzzi line with its 90-degree air-cooled V-twins."
The fourth mention, on page 29, has already been commented on in the first paragraph of this review.
Every single use of the term "longitudinal" as applied to V-twins is used opposite to how the book defines the term "longitudinal", even the use on page 26 that includes the book's definition of the term in parentheses, which turns the entire paragraph into complete nonsense. The usage on page 28 completely redefines the term "longitudinal" in the opposite manner from the definition on pages 26 and 155.
How can Stermer be telling us everything we need to know about streetbikes when he can't keep his terminology straight?