[simpits-tech] Bike Sims; a physics lesson (was: Re: Air & Space Smithsonian....)

[Sean Galbraith]

At 02:39 AM 5/22/03 -0500, you wrote:
>Matt Bailey wrote:
> >
> > Err, I didn't even know the steering was fixed! So how does the bar
> > control
> > lean?
>
>Not exactly sure how countersteering works, but you put pressure on the
>inside bar or pull the outside bar and it leans. Pull right, lean left.

<Sean puts riding instructors hat on now...>

Counter-steering is one of the most important, but least understood skills 
in a riders arsenal.

To understand what happens you need to know a little about gyroscopic 
precesion <sp?>.   Try spinning a bicycle wheel while holding on to the 
axle... then try rotating the axle as if pushing on the handle bars i.e. 
rotating about the steering head.  If you try this you will find that a 
force is exerted at 90 degrees to the force you applied, in other words the 
wheel when turned left to right will try to fall over as well.  Same thing 
happens when you push on the handle bar.
Cruise along at 30mph, take any weight off the bars, then gently (GENTLY!) 
push on one bar and see what happens...  A push on the right bar will make 
the bike lean to the right, quite quickly.  On my GSXR-400 track bike using 
counter-steering I could weave in and out between the white dotted lines in 
the middle of the road at 70mph without any real hassles... (except from 
the feds...doh)
Now this whole theory turns to custard when the speed of the bike gets low 
enough for the forces exerted by the front wheel become to small to have an 
impact on the handling... then the bike will steer like a car, and tend to 
fall over a bit :)
Most people when asked about counter steering will say they don't use it 
probably actually do.. they just don't know it :)  As for using body weight 
to steer a bike, yes you can, it's just not real effective, but useful in 
some situations like exiting a slow corner with the front wheel in the air, 
while counter steering will still work to a certain degree, moving body 
weight, and standing on the relevant peg will be much more effective (don't 
ask me how I know this... <g>)

Now to re-create this in a sim environment:
-  Good luck :)
- I agree with Matt's theory on G forces, I don't think you will want the 
"bike" to lean that much... otherwise with no balancing force you will tend 
to fall off the thing :) A bit like the whole motion cueing vs actual 
motion discussion for full motion sims....
- I saw a  write up a few of years ago of a sim built by (I think) Honda 
for testing rider ergonomics.  They used a projected view, which had the 
lean angle in software, and a much smaller motion of the "bike".  The 
coolest part was that they had the road on an angle on either side of the 
bike so that the riders could get their knees down :)
- Biggest problem I can see is creating the physical relationship between 
counter steering and lean angle.....

Now bear in mind that not a lot is actually known and proven in regard to 
motorcycle physics.. Honda are world leaders in vehicle physics research, 
and know something like 95% of the physics involved in why cars handle like 
they do, but know less that 50% of the physics of bikes.... scary stuff.

I am a 10 year veteran of one on NZ's best (at least we like to think so) 
riding schools, and have specialized in road and racetrack work, and I'm 
still learning!  I have been lucky enough to have learned from some great 
riders including Aaron Slight (he's from my hometown) and I am still 
absolutely amazed at how much we don't know......

Oh, and when you get it finished I'll bring the beers, my leathers and Arai ;-)

Sean