Read This First - Introduction to FF two-wheelers
Introduction to FF two-wheelers
This is different to the technical submissions I've made here about FF's. They deal with specific technical aspects and are based on the development process that started with the Quasar and continues today.
I want to deal here with the response this process has generated from journalists and other people whose background knowledge has come mainly from motorcycles. Some of these people are very knowledgeable about motorcycles, some have engineering backgrounds, others display a level of ignorance rarely found outside journalism.
Almost all these people have made two errors that have got, and continue to get, in the way of understanding FF's.
First, there has been a very widespread assumption that the limitations and problems of the very first FF prototypes, including the 'production' Quasar, are inherent in the FF concept. As many of these problems were identified by the actual innovators, who then went on to continue development for decades, this is both an insult to their abilities and rather absurd. It's worth asking why this happened and I think the answer is fairly obvious.
If, typically, a journalist, assumes that the great weight and length of the Quasar is inherent in the concept, that the limited lock of Difazio's ground-breaking HCS system cannot be extended, that 'all' FF's have odd low-speed handling oddities, then the concept can be ignored, an interesting but irrelevant footnote in the history of the motorised bicycle.
If one the other hand they recognise that FF's weighing 450lbs wet, with wheelbases of less than 60" were on the road by the mid-eighties, that HCS systems with 38 degrees of lock each side were in production by the late eighties and that low-speed handling issues were understood and nailed at the same time - along with demonstrations of outstanding safety performance - then they'd have to start asking questions about the motorised bicycles that injure or kill many people, to this day.
Motorcycle manufacturers wouldn't like this, for obvious reasons. So magazines, who sell them advertising, don't like it either and they'd rather the journalists they employ didn't bang on about it. Obviously easier for 'professional' journalists and editors to accept those early problems as set in stone for all time.
Second, there's a widespread assumption that FF's are some sort of motorcycle 'style', maybe a big scooter, or an over-engineered low-rider. This makes it easy to dismiss these road-going vehicles, banned from racing until the recent E-GP series, on the basis of the technical knowledge derived from motorcycle racing. If Honad Motor Co. raises the CG of it's racer - to minimise polar moments about it's roll axis - then it must surely be absurd for another 'type' of motorcycle to lower it's CG? Even though a little thought will show that lowering the rider, as the FF layout does, achieves exactly the same reduction in polar moments as well as an overall reduction in CG height.
If you have read this far perhaps you will be interested, or annoyed, enough to try the following little thought experiment. But first it will help if you can adjust your mental settings as follows;-
Turn your Mind to 'Open' Set your Imagination to 'On' and your Pre-conceptions to 'Off' You can leave Scepticism on your normal default setting.
OK. We all know what a motor vehicle is. There's a legal EU definition. It's got four wheels and does more than 25 Kph. Now here's a motor vehicle, it's got a hot motor, no roof and only two seats. What do we call it? A sports car. OK. Here's another one. It's basically a big metal box with windows at the front. We call that a van (Or panel truck if you like). It's easy to see similar variations across the type. Here's a car, here an estate car. One of my jobs is maintaining a .. Hearse. All motor vehicles, all different in use, performance and utility. No problems there?
Right. Now lets move to two wheeled vehicles. There's an EU definition there too. These are Powered Two Wheelers (PTW's) and apart from having two wheels they have a minimum power rating - although I forget what it is. PTW's also come in various forms. One type has pedals to assists it's little motor and it's generally called a moped. There are variations on the theme to do with what age people can ride them and so on. Then there's the type with little wheels and some stylish, but generally useless bodywork and, normally, a dubious form of rear suspension. It's a scooter. And here are motorcycles. These are invariably, and visibly, a development of the early motorisation of the Victorian 'safety bicycle' although they come in a variety of sizes and styles. And - Oh, this is a bit rare - we have another type, called an 'FF'. It's very definition sets it apart from other types of PTW. It is more different from a motorcycle, for instance, than a motorcycle is from a scooter, or a moped. It's the riding position that's the big difference.
So what have we got here? A number of different types of PTW. Like motor vehicles they all have different uses, performances and utilities. A van is not a car. A motorcycle is not an FF. There, that's easy enough isn't it?
So now we understand that an FF is a different type of PTW to a motorcycle, scooter or moped, perhaps we can look with a clear mind at the dynamics of this rare, but interesting PTW.
Lets start by considering the definition itself. 'A PTW with a seat base below 20" at ride height and a seat back that fully supports the rider' is about as short as it can get, although I see that attempts to 'de-technicalise' the definition have been assumed by wikipeida for one, to be a dilution of that 20" limit. It's also been criticised for being an arbitrary figure, sometimes by people who have actually built vehicles with an above 20" seat base and have thus 'proved' that FF's don't work.
So I'd like to tell you about the actual event that led to this figure being chosen. It was in 1977, in the car park of the manufacturers of the Quasar, in Bristol. There was a conversation going on between the Quasar innovator Malcolm Newell, his assistant Chris Richardson and myself. (Chris was a chopper/low-rider enthusiast and had built a rather splendid example out of his employers stores). We were attempting to put our finger on the extraordinary performance of the Quasars we'd just taken to that years 'TT week' in the Isle of Man. What we'd observed, from these recent experiences, was that the seat height, and hence CG, had a transforming effect on handling when it got low enough. It didn't happen at 28 inches, the seat height of my own Velocette Venom. That was a fine handling motorcycle, but nothing else. It didn't happen on Chris' chop at 23 inches. But it did happen, unambiguously, on the 15" Quasar seat base.
So we chose 20 inches as the point at which the transforming effect could be expected to become detectable.
What is this transforming effect? Easy. Get a PTW into a fast turn and get some power onto it. Then change direction to an equal turn the other way. Do this as quickly as possible - put some real effort into the steering. But don't close the throttle. At some point below 20" seat height the wheels stop coming off the ground and you no longer crash. The Venom lifts it front wheel first, Chris' chop, the rear. Any decent sports bike should be able to get both wheels off the ground this way.
Once you've got used to turning that fast without crashing you'll discover other useful features. There's a fuller technical description of this in another submission (http://www.bikeweb.com/node/1435). You can go on to read how, in development, this transformation was exploited and extended to produce PTW's that provide a level of performance that cannot be achieved by motorcycles (http://www.bikeweb.com/node/1359).
Finally I'd like to go further with this 20 inches business. It's a while since 1977 and there have been a few more FF designs and a few hundred thousand miles of experience. I now think that to fully exploit the FF advantages you should get that seat base below 18 inches. I recently laid out a racer - for E-GP - with a 12.5 inch seat height, but for general road use, where comfort and utility trump all else, I think 15-17 inches is the ideal window.
I hope you've found this introduction helpful and illuminating. Maybe it'll help you ask questions that are actually about FF's rather than what you think motorcycles would be like if they had a low CG..