Words: Editor ‘Arris Photos: Honda/Colin Fraser
|Canada’s finest (some are finer than others – second from left).|
It’s become an annual event – every January Honda Canada assembly the finest motorcycle journalists in Canada (go with it for now) in some southern US location to ride the latest model releases on the track and road.
This year however, Honda was sparing no expense to get their new 600 flagship bike – the CBR600RR – the attention that they’d like with the Canadian press.
How about two days at the very lovely LV Motor Speedway? One of which was spent at the Freddie Spencer School, the other with one RR per two journalists – for the whole day! The fun and games was then wrapped up with a stint on the road exploring the mountains and canyons in the area, where six CBR600F4is would be added to the mix for comparison purposes.
As you can see, there’s a lot to write about, but for now let’s just focus on the technical aspects of the new RR – a completely new bike over the F4i. The “how’s it ride?” will follow in part two, along with a second view from fellow journalist Steve Bond.
Sorry kid’s but that’s what we’re doing, so you might as well get jiggy with it.
|With X-ray specs, you can see all the CBR600RR’s bits and pieces.|
One thing I’ve really liked about the 17-year Honda CBR600 lineage has been their emphasis towards practicality over sheet-specification and form-over-function. But alas, the painful reality is that this simply doesn’t sell as well. With all the other manufacturers getting more and more aggressive and track-focused with their middleweight sport-bikes, Honda seemingly have no choice but to change with the tide.
With this in mind, Honda have opted to start from the ground up with the 600RR – a completely new motorcycle over the F4i (which is still in the 2003 line-up) – claiming that this is the first time they have built a 600 with the primary emphasis placed directly on the track. Even going so far as to say that the RR was designed first as a race bike and then adapted for road use. So you get the idea where they’re going with this one.
|The gubbins under the skin of the MotoGP RC211V.|
Honda reckon that they’ve learnt a lot form their new race winning RC211V MotoGP bike. One of the biggest lessons being that of mass-centralization.
The centre of mass is at the intersection of the three axis of rotation and so the point around which the motorcycle will tend to rotate.
Basically, you want to do two things with this:
1) Keep it as low to the ground as possible – otherwise the bike will have a ‘top heavy’ feel and a tendency to flop into corners as the high-up mass swings over suddenly from one side to the other. Okay, that’s standard sport-bike design practice.
2) Keep all the mass around it as close to it as possible. This is the mass centralization part.
Alrightee, to explain this principle I’m going to go back to my engineering student days, so please forgive me if it’s not 100% accurate (although I’m sure I’ll be quickly corrected if that’s the case!).
|This rider managed to get his zed down.|
The idea is that if you design a bike with as much of the mass (i.e. the heaviest bits) located as close as possible to the centre of mass of the bike, you’ll get the best possible handling characteristics.
The more the mass is located away from the centre, the greater the inertia (reluctance) will be for an object to start moving in that direction and then stop and start moving back in the opposite direction.
Okay, let’s get your brains picturing this in those nasty school-day terms. Imagine – go on, you can do it – a stationary bike, upright on the ground. Now add the three axis of rotation to that mental picture – one axis coming up from the ground to the air (x), another from front to back (y) and the third from left to right (z) – all going through the bike’s centre of mass (probably somewhere close to where the clutch cover is).
The more the mass is located away from the centre, the harder/more reluctant the bike will be to turn in and out of a corner (rolling around the x & y axis) or even recover from a slide (x axis) – go on, make your mental model do it, just try not to highside it. It would also tend to load up the suspension more during braking and acceleration (z axis).
So you can see, mass centralization is a valid goal when it comes to improving the bike’s handling capabilities.
Oh, if you couldn’t resist and did a mental high-side it, imagine yourself now cartwheeling down the track. Now pull in your arms and legs to your body. Notice how you speed up? Bit like a skater doing one of those spins … only less graceful. What you’re doing is effectively pulling the mass towards your centre and reducing that inertia effect, thus the speeding up.
|Editor ‘arris practices getting his personal centre of mass down low.|
Hey, see the ambulance coming to get you? It’s rolling around its y axis on every corner. High centre of mass! That means it has to go slow to avoid tipping over, while you’re lying flat on your back wondering how the hell you got from reading an article on the new Honda CBR600RR to laying on your back on a self generated mental race track.
One question – can you feel your toes?
But enough theory, what did Honda do to the RR to warrant all this theory?
Okay, firstly, what are the biggest offenders of loadsamass away from the beloved centre? Well, the motor’s bloody big, but that’s already pretty well at the right place to start. Still, stacking the gear shafts on top of each other helps a bit, as well as shortening the engine that in turn allows for a longer swingarm … which in turn adds stability to the bike.
What about fuel? A full tank can an additional 20 Kg of weight, so you don’t really want to slap that high up in-between the bars and rider. What Honda have done is make the gas tank more cylindrical with the top at the back where the filler cap is and the bottom going down almost to the crankcases. This keeps the weight lower and also means that there’s less slop and so less unwanted weight transfer as the fuel moves back and forth during acceleration/braking.
|Mass centralization. Anybody want to be a Honda mechanic?|
But by far the biggest mass is the rider. Apart from not allowing tall, heavy people to ride the bike (that would be me), the next best thing is to move the rider down and forward. Since there’s no mention of the down part I’LL assume that didn’t happen, however, thanks to the new fuel tank there is mention of a forward part to the tune of 70mm.
Another part of mass centralization is keeping the bits that you can’t move closer to the centre, light. Wheels, lights and clocks are all lighter (than the F4i’s anyway).
So the RR has had a lot of design work put into it to achieve all this, but is it night and day compared to all other motorcycles as a result? At Las Vegas, we had the benefit of a load of F4is with which to compare. The result? Subtle.
Hmmhhh, is that searing pain the pain of the Honda needle going through the cranium of the Editor ‘arris voodoo doll? Well before they get a second pin and aim it lower, let me qualify that statement.
I’m not the best track guy in the world. Far from it. And being 6’ 4” I don’t have the best posture on the track either. What I’m trying to say is just because I wasn’t personally blown away by this element of the RR when compared to the F4i – although it did handle beautifully – doesn’t mean it was all for naught. It just means that it’s a subtle difference rather than revolutionary. For the average Joe at least.
This is one probably left to the likes of Steve Bond to analyse, who will be doing so in part II. Handy that.
|Lower linkage compresses the shock.|
You may have heard that the RR6 features the same unit pro-link as the RC211V and wondered what possible benefits could be gained by mounting the top of the rear shock to the swingarm rather than the main frame. Of course, you might also have better things to do and not even thought or even heard about it. But if you’ve gotten this far, let’s assume you’re curious, or simply don’t have a life (hey, at least I get paid for doing this).
Okay, in order for the whole thing to work, the lower end of the shock is attached to the motorcycle’s frame by a bell-crank and a couple of linkages. Thus, as the swingarm swings up, the distance between the top mount and the bottom is progressively reduced by the action of the linkages, compressing the shock. Which is good, as otherwise it wouldn’t work at all, which would be bad.
The advantage of moving the upper mount to the swingarm itself means that the big forces transferred there with every bump are now kept within the heavily braced swingarm, instead of being transferred to the main frame.
|How the new unit Pro-link actually works.|
This has the following claimed advantages:
1) If the rear gets all bent out of shape, it will no longer transfer that chaos to the frame and so upset the front and the steering (Freddie Spencer seemed quite confident on this one anyway).
2) There is now no need for a big mother cross member to take that loading in the main frame, allowing for the space required for the new fuel tank, allowing the rider to move forward, etc, etc, etc.
Free of the need to support the rear shock loads, the RR6 frame has been redesigned to focus on that mass centralization thing and, thanks to to a new casting process, focus the frame proportions to where it’s needed most – the steering head and swingarm shock mount.
Back to physics 101. For a structure to resist bending – which is what’s happening every time you try and wrestle a bike around or hit a bump – it should have maximum depth against the direction of the bend.
|It’s made up of nine different bits of castings welded together.|
Grab a ruler.
Go on, I’m serious here.
Okay bend it. Look at the way it’s bent. Odds are it’s around the thin part, not the tall wide part – otherwise you’re probably holding a broken ruler right now. That’s the thick-bit-will-resist-bending theory. In order to prevent your frame from flexing like a creme brulee – only without the hard sugary top bit for strength – you want the frame to receive those maximum forces at the deepest parts.
By casting a frame you can make it as deep as you like, where you like. Nothing really new in that, except a cast frame tends to be too heavy.
What enables Honda to use a completely cast frame is a new frame casting process (Yamaha use a similar one on their R6 too) which allows for much greater precision in design and thinner walls to boot.
Combined with the new rear shock/swingarm design, Honda claim that the tendency for wheel spin when exiting corners is greatly reduced – allowing the rider to start accelerating earlier.
|Note the new exhaust port angles enabling for a tighter header set-up – allowing motor to be closer to the front wheel.|
Okay, time to get to the beef of any bike – the motor.
Sharing only bore and stroke dimensions with the F4i, the RR motor is new from the ground up. We’ve already mentioned the stacked gear shafts for reduced length, but by repositioning the alternator and starter gear they’ve also narrowed off the motor for an extra 3 degrees of lean.
Internally, the rev limit has been upped by 1,500 rpm to a howling 15,000 rpm. This has been achieved by using lighter internals (less inertia), slipper pistons (less friction) and a sump that drops all the way down to the lower fairing (less oil drag on the shafts).
This means that overall gearing can be lowered enabling for more of that higher-rpm power to be accessed at lower bike speeds. This also has the effect of making you feel that you’re always over-revving the bike – especially on the road – but more on that in part II.
Peak claimed power of 115 hp comes in at 13,000 rpm, after which it flattens out to the 15,000 mark, dropping off before the rev cut-out at 15,500.
However, all this engine speed causes problems for conventional inlet port located injectors. You see, fuel takes a set amount of time to change from liquid to vapour – which it needs to do in order to burn. Try putting one of those sparky bar-b-que lighters into a bucket of gas and see if you can get it to ignite. Now pour the gas all over the floor and do the same thing just above it. Notice that you’re now standing in an inferno? You just ignited the vapours. Well done, now get to hospital.
|Second set of injectors on top of air box.|
Or maybe just take my word for it.
At 15,000 rpm the fuel has to leave the injector and fill the combustion chamber ready for burn within 4 milliseconds. That’s simply not enough time. To compensate for this, the RR6 incorporates a second set of injectors in the airbox, above the inlet holes, about four inches further away from the first set.
Whenever 5,500 rpm hits with a wide open throttle, the second set join in the fun, ensuring that a goodly chunk of the fuel is in burn-friendly vapour state by the time the spark plug sparks.
It’s like the V-Tec of the fuel injection world, only seamless.
SO HOW’S IT RIDE?
Good question and one that we’LL be happy to answer next week in part II.
Go on, get jiggy.