Ducati's Apollo prototype...
Ducati's Apollo prototype from 45 years ago shares an intriguing detail in common with Honda's new VFR1200F.
One of the many interesting aspects of Honda's new VFR1200F is the engine layout, which has the rear cylinders inboard of the front pair. In a conventional V-four configuration, the front cylinder bank is staggered to one side of the rear, with the cylinders in each bank equally spaced. The left pair of cylinders share one crankpin while the right pair share another, with the front connecting rods both to the same side of the rear rods. This makes the amount of stagger between the banks the width of one connecting rod. On the VFR1200, the rear cylinders' connecting rods are both mounted inboard of the front cylinders' rods. The benefit is that the rear cylinders end up closer together than they would otherwise be, making the bike narrower between the rider's legs. The front bank ends up being wider, of course, but this is a worthwhile tradeoff.
When I first read this in the press material, it sounded oddly familiar but I couldn't figure out why. It dawned on me that I must have seen it somewhere before, and sure enough some digging revealed I had. In 1963, Ducati manufactured a prototype V-four intended for the American market: the Apollo. While Ducati had before that time made nothing larger than 350cc, the Apollo was intended to compete with Harley-Davidson and displaced a whopping 1260cc. This machine also has the rear cylinders inboard of the front, likewise making it narrower. I had seen the engine in the Ducati museum a few years ago, and subconsciously filed that little detail away.
Why is this such a big deal now when it was done years ago? The Apollo used individual, air-cooled cylinders and heads with overhead valves, making practically any spacing or layout possible. But in the intervening years, things like water cooling and overhead camshafts have led to single-piece cylinder blocks and heads for each bank. With equal spacing for the front and rear banks, parts like the cylinder heads, camshafts and valve covers can be identical. Make that spacing different with today's technology, however, and all those parts are different, increasing the cost of design and production. With a modestly sized V-four engine, the width of the rear cylinder bank isn't much of an issue. But grow it to more than a liter and one connecting rod's width can make a substantial difference. Honda must figure the additional cost and trouble to be worth the benefits the narrower cylinder bank offers.
I've always found it interesting to see how manufacturers each come up with different ways to put the motorcycle puzzle together. In my previous job I did a lot of work in electronics packaging design, so I'm familiar with the process and the juggling act that's required to fit a bunch of pieces into a tiny space. Oftentimes it's the little details-like the VFR's cylinder spacing-that give a clue to the path of overall development. Subtle things like engine placement and the location of ancillary components can reveal what the manufacturer values for handling. Engine specs can point to an emphasis on a certain type of power. And compromises made in the design show what's important to the company in a particular area-sacrificing weight for power in an exhaust system, for example. As sportbikes evolve and these priorities change over time, it's not unusual to see a design feature discarded at some point only to be utilized again at a later date-as soon as one model iteration later, or as long as a few decades.
Sometimes-as in the VFR1200's case-an update and the reasons behind it are apparent and discussed in the press material. But the changes always highlight the positive and omit the negative (for example, single valve springs are used one year for light weight and less friction; the next, dual valve springs are used for better high-rpm control). Other times, a change isn't mentioned nor all that obvious-but there must have been some reason for it. Asking questions about these not-so-obvious details at a new bike introduction can result in an amusing reaction from the engineers. Usually they are glad that someone is curious about the new bike and more than happy to discuss the changes. But occasionally they are not; the engineer that can answer that question is not present, or the translator suddenly has difficulty. This is usually an indication that development has reversed direction in some manner, and the company is reluctant to admit that something that was touted as beneficial a few years ago is now regarded as a drawback-or vice versa.
Whatever the reasons for updates with any new model, each manufacturer has its own ideas as to how a motorcycle should be packaged, and the details are often a window into the designer's mind. In my case it's part professional curiosity that piques my interest, but that window is also what gives each bike a little bit of its own personality.