At Last --- Nearly!
c Tony Foale 1987
About the middle of last year when the SuperBike project machine was announced, TM. in his preamble to the body design competition, likened this project to the concept cars, fielded by most manufacturers at the world's exibitions. The editor bemoaned the lack of similar design exercises in the bike world. The Suzuki Falcorustyco and the early 80's BMW Futuro being the only two that spring readily to mind. One irate reader even took TM. to task over this and questioned his right to draw parallels between the large manufacturers' megabuck show vehicles and our humble efforts.
I tend to agree with that reader, after all how can you compare the two. For a few thousand pounds we, with the help of those readers who entered the competition, have created a machine significantly different from any on the market, but its not just a show machine, its up and running. Just look at the pics. Its not even a one off, more are in the pipe line. Compare this with most concept vehicles, seldom are they runners, often having wooden engines and the like. Like as not they will be crammed full of way out ideas from the fertile imagination of young industrial designers, with scant regard for technical or economic practicalities. Don't get me wrong, I am the last person to try and suppress this type of innovation, but as the man said, how do you compare it with our little dream machine.......
Previous progress reports have been about the body building, and the photos show how little the final shape has deviated from the original styling sketches. This would not have been the case with some of the competition entries had they been selected, and shows the obvious wisdom of the judges' choice! The fuel tank is made of aluminium and is bonded into the body. The construction and use regulations in this country require a metal petrol container. Otherwise I would have just closed in some of the fibreglass body and installed a flexible bag tank, racing car style. It would have been lighter, more expensive and probably safer, but who cares about SAFETY, its the REGULATIONS that count,---- damn it!
The tank was bonded in, rather than being mounted on the chassis for a number of reasons. Including ;-- Ease of mounting, no local mounting loads reducing the chance of cracks in use, stiffens the body shell, and removes alignment problems between the filler cap and the body. That just about covers the bodywork details so let's look at the dirty bits and the reasoning behind their design.
Basically this is a type of hub centre steering similar to that used on my QL. and featured on these pages in the past. In essence, the front wheel is supported on a rotating stub axle which in turn is located by two sealed ball races fitted to what I call an upright. This upright extends upward to above the tyre and curves outward to give clearance around the brake disc and tyre. The location and permitted movement geometry of this upright is controlled by two arms, one in the shape of an 'A' frame above the tyre, and the other is a single sided fabrication mounted just below the wheel centre. This arm curves outward to give clearance for steering lock. Relative movement between these arms and the upright, for steering and suspension articulation, is permitted through the use of aero-space type sperical joints. The castor angle is ajustable via the threaded rod ends that locate the rear of the top 'A' arm, and will initially be set at about 18° , and varied during testing if found necessary. From a side view the locating arms do NOT form a parallelagram as in many other alterative front end designs, rather they are laid out to give reasonable constant anti-dive characteristics, after the principles shown in the July 1985 issue of this journal.
The original intention with this project was to use a design of front end that only used one locating arm, the lower one, and no upright, a la 2CV. Citroen. I have tested a lash up of this system and initial impressions were favourable, but there is a problem in designing a neat and practical steering mechanism, that avoids bump steer. This is not an insurmountable problem, it just requires a bit more thinking time. However, to avoid further delay, for the time being, I decided to go for the double arm design which is now quite well proven on several different machines. The design of the main frame allows for subsequent conversion to the single arm in due course.
The only real difference between the front on this machine and the QL. is in the placement of the suspension unit. On the QL. this is mounted on the top arm just above the upright. This was done because it generally reduces loads and hence can lead to a slightly lighter structure. Whereas on the Q2. the unit is mounted onto the bottom arm. Two reasons dicated this apparent reversal of thought.
1. The original concept of the single arm meant that this would be the only place to locate it, and so will ease any later conversion.
2. It gave greater flexibility to the styling design. Locating the unit in this way, introduces vertical bending tendencies in the arm, which has been beefed up accordingly.
The front brake is the Lockheed developed ISO. ( In Side Out ) rim disc. This is very light and very efficient, and suits this design very well.
This is by a single sided swing arm, and there are four main reasons for this, viz:--
1. Structural efficiency, for a given weight it can be stiffer than most double sided arms. Perhaps in a future issue we can look at actual measured stiffnesses of various configuations.
2. Easy wheel removal, just like a car, undo three wheel nuts and off it comes, without the need to disturb the sprocket, chain or brake.
3. Can use a similar wheel to the front.
4. It looks trick.
Both the front and the rear ends were designed from the outset to use pneumatic suspension, and the French Fournales shocks are first in line to be tested. Air units give a natually progressive rate, the degree of which depends on the piston diameter and the internal volume. Because of this there is no need to use the currently fashionable, complex rising rate linkages. This then leads to the mounting positions as shown. It is simple, light, low in maintainence, and it reduces loads allowing for further lightening.
The wheel mounting hub has been turned from a solid billet of aluminium, for strength reasons, and this hub also carries the sprocket and disc. The sprocket is mounted through rubber bushes to give a cush drive. Sealed ball races are again use to support this hub on a non-rotating stub axle ( actually an E-type Jaguar front axle ), which is fixed in a large aluminium eccentric for chain adjustment. Keen students of alternative design features will note that the swing arm and hub arrangement is considerably different from those used on the Elf Racers and those Hondas with a single sided arm. On these machines the swing arm curves in past the tyre and the end is sandwiched between the sprocket and brake disc. The wheel bearing are fitted into the arm, and the hub is a two piece affair bolted together and connected by splines, as with some cars. This is a fairly complicated and expensive way of doing the job but it has the advantage for racing that sprockets can be changed rapidly. We have used a system more akin to the BMW. mono-lever, but with chain and not shaft drive. This leaves the sprocket less prone to damage and protects those with wandering fingers. It also allowed for the simple suspension unit mounting, previously described.
This has been partially described in the original article on the project, and consists basically of fabricated 'C' shaped box sections under the engine. The front and rear swing arms are connected to this at each end. This was originally intended for Kawasaki engines, and the steering mechanism and the top front 'A' arm were to be mounted off the cylinder head. With the Suzuki engine, however, there are less suitable mounting on the head and so we have a bolted on sub frame to carry these components. .
Well, that's about it really ---- except to own up and say that the bike shown is not the SuperBike project machine, but is for a customer, Paul Griggs. Paul has been staying over in England but is from New Zealand, and unless he gets back there before June they won't let him in again. On route to home he wants to ride around the USA. and perhaps Australia. Because of this Paul jumped the queue and got his first. But, as Paul's was being constructed several duplicate parts were made and so the REAL project bike should see the light of day fairly soon, but don't expect any mention of an actual date.
I think we should leave the last word about this bike to the inscription on Paul's number plate :--- JUST VISITING FROM ANOTHER PLANET.