- This topic has 28 replies, 10 voices, and was last updated 12 years, 8 months ago by Jeff in Kentucky.
“Weighting the pegs” does NOT lower your center of gravity!
July 21, 2010 at 1:40 am #27641
…you just terminated the most fascinating thread on this site
I know better than to argue with a lady and bow to your superior degreeJuly 21, 2010 at 1:58 am #27643
…that the simplification that physics always wants to do (treating the rider and bike as a single unit) falls apart to come close to describing the actual interaction of bike and rider.July 21, 2010 at 2:03 am #27645
Let’s take a free body diagram of the bike. Now let’s apply the riders weight as a point mass at the point of contact. Where is that point mass applied?
The seat vs the pegs.
Tell me that the location of that point mass doesn’t affect the center of gravity of the bike.July 21, 2010 at 2:16 am #27646
I suspect they are challenging semantics here and not practiceJuly 21, 2010 at 5:19 am #27654madjak30Participant
One is talking static CoG…the others are talking effective CoG…
You take an object and find the balance point, and that is inline with the CoG…but take that object out of a vacuum and wind will ruin the balance by introducing an external force…moving the effective CoG…if the CoG can’t move, transfering your weight would have no effect on the bike…
Anyway, it’s been a long time since I took a serious Physics course/lab…sooo….I could be wrong…(probably am…)…wasn’t a physics major, just electronics…but that was 20yrs ago…I think most of it has leaked out my ear in my sleep…lol
Later.July 21, 2010 at 5:23 am #27655eonParticipant
What’s my prize?
But the argument continues
If you were to take a 75kg lump of lead off the seat and then put it on the pegs, I agree you would lower the bikes COG. But you are not a point mass. You are somewhere around 5 to 6 feet tall. When you stand you raise your cog.
Where you apply your weight (which is a force) has a profound impact on how the bike behaves. But cog has nothing to do with forces. It is the mean mass (or mass center) of an object. Two separate concepts.
But now I am waiting for Owlie to explain for us how countersteering works.
July 21, 2010 at 11:38 am #27657
Eon, taint no argument here, we’re just trying to solve all of the worlds problems according to priority Your diagram is missing his motorcycle ! … and his knees aren’t bent at all … contributes way too much unsprung weight !:i
edit: in my case it’s a spring loaded 64 kg. hunk of meat without a seat, standing on the pegs
If we can agree that weighting the pegs works ( and I sure hope it does or I have been standing up way too much ) The pressure is on for the Physicists to explain, why ? Is there a Physics 301 ?
I ride a 4 stroke so I know it’s not all smoke and mirrors, I just ride the damn thing.July 21, 2010 at 11:44 am #27658MunchParticipant
Trials….you were looking for your tag line…… your last sentence is priceless… and if you don’t use it consider it stolen.July 21, 2010 at 2:10 pm #27660
“But you are not a point mass.”
And while that is correct, when you contact the bike with that mass at a single point (we’ll neglect the handlebars for now, because you’re not supposed to be weighting them in the first place), it’s affect on the bike is a point mass.July 21, 2010 at 11:49 pm #27678Jeff in KentuckyParticipant
This bike lowers the center of gravity while seated:
The Subaru boxer engine has the lowest center of gravity for a budget car.August 1, 2010 at 12:35 am #27864owlieParticipant
Suffice it to say that any explanation that makes use of the term “centrifugal force” is incorrect.
And I love how as soon as I killed the CoG argument, they came up with new and exciting terms to try to show how their arguments are correct…August 1, 2010 at 9:24 pm #27872MunchParticipant
Ok…. intermission…. some humor but philosophical interjection….
Do you KNOW what you know…. or do you KNOW what is TAUGHT to you?August 1, 2010 at 10:26 pm #27873Jeff in KentuckyParticipant
Feet on the seat does raise the overall center of gravity for the bike and rider, and even more for this bike and rider:August 1, 2010 at 10:43 pm #27871AParticipant
How about putting your feet on the seat?
Does that raise the CoG of rider & moto?
While traveling at 30 mph, imagine which is more stable:
Sitting atop of a 12 ft. ladder or
standing 2 steps down from top of 12 ft. ladder..
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