Motorcycle steering
Motorcycle steering
(OP)
I'm sure this has been discussed before
It is all down to the effective combined forces of gravity, and centrifugal force caused by turning, and it's position relative to the tyre contact points.
Try 2 experiments....on a straight, empty road. Try to steer by weight shift only..it doesn't work.
Now, with your hands off the bars, apply a little forward PRESSURE on one side, then allow thebars to push your finger back. As long as you continue to apply pressure, the turn continues to increase. What you are actually doing, is keeping the CofG to one side of the contact line...keeping the bike slightly off equilibrium. When you release the pressure, the turn remains, or gradually reduces.
The initial pressure moves the front wheel slightly, thereby moving the contact line out from under the GofG. The fork rake, then turns the steering into the turn, attempting to get the force vector to act through the contact line.
It is all down to the effective combined forces of gravity, and centrifugal force caused by turning, and it's position relative to the tyre contact points.
Try 2 experiments....on a straight, empty road. Try to steer by weight shift only..it doesn't work.
Now, with your hands off the bars, apply a little forward PRESSURE on one side, then allow thebars to push your finger back. As long as you continue to apply pressure, the turn continues to increase. What you are actually doing, is keeping the CofG to one side of the contact line...keeping the bike slightly off equilibrium. When you release the pressure, the turn remains, or gradually reduces.
The initial pressure moves the front wheel slightly, thereby moving the contact line out from under the GofG. The fork rake, then turns the steering into the turn, attempting to get the force vector to act through the contact line.
RE: Motorcycle steering
Sorry, skenn...I must respectfully dissagree. I read your post and decided to try the weight shift as I felt your conclusions incorrect. As I determined on my 1948 Norton, I can very effectly steer the little beastie by shiftin my weight from side to side as long as speed is maintained with my hand off the throttle. I tried the finger push deal, but it only takes a VERY slight touch to make the Norton really take off...too spooky to continue on the canyon road I was on.
Rod
RE: Motorcycle steering
RE: Motorcycle steering
In fact if you think about it countersteering is effectively weight steering, it displaces the cg laterally.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Motorcycle steering
Rod
RE: Motorcycle steering
And your theory works on standard to sport-rake motos. Start heavily changing that tube angle (think choppers) and the experiment goes down the tubes.
RE: Motorcycle steering
I had an ES-2. Good handling machine, but not much go.
Pushing on the handle bars to upset the center of gravity is the best way to initiate a turn. Counter steering is then required to continue the turn.
RE: Motorcycle steering
RE: Motorcycle steering
It would seem taht well balanced bikes would be largely imune to weight-shift alone. No offence intended to vintage machines. I CAN get my Duc to turn, but only with a series of nudges...just leaning out has almost no effect, as the CofG actually remains that same...over the contact line. You lean one way, the bike leans the other. Your weight shift causes an equal and opposite shift in the bike's.
RE: Motorcycle steering
My 48 is much modified, as I stated it belonged to a world champ in WA (Oz) and has a very much modded 500cc with an extra close ratio racing gearbox, International tanks, Brooklands exhaust, Int. forks and brakes, 19" and 21" wheels, etc. Still the "look" is pretty stock to the uniniated, non Norton fan.
skenn.
I live in an area of southwest Riverside Cnty. near the Ortega Hwy. I see a very large number of bikes on a daily basis and am somewhat surprised that there are so FEW choppers being ridden in the area. Perhaps only one in a hundred or so...and even then, they are not of the hugely extended fork variety. ??? Perhaps I watch too much telly?
Rod
RE: Motorcycle steering
I think Choppers are for long straight roads !.
S.
RE: Motorcycle steering
RE: Motorcycle steering
I'm just a month away from 67 and I just don't have the desire to drag my knee in the corners any longer. I rather prefer to just cruise around on a nice vintage bike. I have so much invested in vintage racing (cars) that there just is not enough of me to go around or get back into bikes full time. I'm guessing that I've paid my dues. I still love to stop and talk/look at the gals on the custom bikes, though.
Rod
RE: Motorcycle steering
I had wanted a Pantah since they were in production, and finally decided to buy one from England....when I brought it back to ireland, I found that there was on residing 4 miles from me that was open to offers !.
S.
RE: Motorcycle steering
I had a 78 Ducati GTS which I thought handled pretty good,
until I spent the summer riding my Norton out of a canyon in Colorado. When I went back to riding the Ducati I actually pulled over trying to figure out why it wouldn't turn..Flywheel effect was all it was.
I started noticing that all my bikes had a different flywheel effect from the Guzzi to the Norton and in between.
I know the newer Ducati's have less flywheel than my old GTS
but I can only attest to my 900 Monster..
Cheers
I don't know anything but the people that do.
RE: Motorcycle steering
You effectively tilt the bike, and apart from cog, you have different tire profiles front and rear so all this helps you turn.
I race, and apart from the knee dragging that happens 'cos yer do' shifting your weight is a hufgh part of the turn. Several tracks that I race on see me shifting my weight before the turn to make the turn sweeter. To enable me to do this & still travel forward in a straight line I have to tilt the bike and countersteer. belive me it's common place
Dansoarr
RE: Motorcycle steering
RE: Motorcycle steering
RE: Motorcycle steering
He clearly explains the physics of countersteering to initiate the turn.
Hanging off the bike like all good racers is explained simply as allowing a tighter radius turn with less bank angle (and more ground clearance and less lateral tyre load) on your bike.
I could go on all day quoting from Tony's work but have a look at the free articles on his website (www.tonyfoale.com) and read the one titled "Balancing Act" which sums it up....or order his book.
RE: Motorcycle steering
RE: Motorcycle steering
You live in OZ? Well you probably don't see that many choppers because of the reggo rules you have over there...
Friend of mine builds them in Sydney and from what he's told me, getting them through the engineers inspection is a bit of a mightmare.
RE: Motorcycle steering
Rod
RE: Motorcycle steering
Quote Skenn( OK, so I was wrong...weight shift can make it turn .. depending on the (geometry)?)Quote.
Depending on speed.
Quote Skenn(Hanging off can't affect lateral load. That is purely mass and angular velocity. It only affects how far up the side of the tyre the load acts.)
Yes that would be right, if the steering axis was vertical, but it is laid back at an angle of 22 to 30 degrees from the vertical. As the bars are turned, two things happen, first the frame of the bike will move to the same side that the wheel was turned to. Second the weight bearing axle will drop closer to the ground, forcing the wheel to turn.
This is what allows Greg to ride his bike 'no hands', by moving his weight to one side, causes the frame to lean and the axle height to drop, turning the wheel in the same direction. You can do this by just holding the seat and leaning the frame side to side.
This happens when stationary, or at the low speed that Greg can pedal. As the speed rises and the wheel develops Gyroscopic force, the wheel starts to resist turning, so leaning the bike has less effect. In fact the wheel now resists turning. Turning the handle bars now will cause the Gyroscopic force to lean the frame in the opposite direction. So to turn the bike to the right, we now have to push the bars to the left, to get the bike to lean to the right, then allow the steering axis to bring the wheel back to track the corner.
Thundair
Compares a 78 GTS Ducati to a Norton. This is opposite ends of the steering axis angle. The Duck has a 30* head angle, that increases the Gyroscopic effect and the high speed stability, while decreasing its fast steering ability. The Norton has a 26* head angle, that allows it to turn fast, but is a bit twitchey at high speed.
Rod.
I had two Ducks, a 76 750 SS and a 72 450 single. The 750 with a 30* head angle is rock steady at high speed, but changing lanes is by appointment only. The 'Silver Shotgun'with a 24* head angle, could turn fast enough to drag your elbows, but anthing over 160kph was dicey.
Harvey.
RE: Motorcycle steering
There are a lot of things that make them different IE tire size, trail, head angle, length and weight... but my focus was on flywheel effect..That was made clear to me when I shortened the swing arm and change the head angle on my 78 Darma. It was quicker through the tight stuff but still had a lot of flywheel effect
Cheers
I don't know anything but the people that do.