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  Topic Review (Newest First)
Oct 12th, 2010 11:45 am
kbmwrs Well thanks guys. It was explained very well and I accept that standing on the pegs doesn't lower the CG.
As for one individual who considered my question a statement of fact why the hostility?
Oct 9th, 2010 12:20 am
Meese
Quote:
Originally Posted by G-DAVE
Quote "Yes, it rises because you've moved the weight up higher. Just as you do when you stand up " Unquote

Not correct ---The moment you lift the "weight" 1 mm off the ships deck it's immediately transferred to the top of the Derrick
Which simply proves my point. The moment you raise the weight even 1mm, you no longer have a single rigid body but now have decoupled the total weight of ship and cargo (or bike and rider) into two separate masses that can move independently.

We're seeing the same effect here, just describing it differently.

Remember, gravity is one type of force acting on a body, but there can be other types, too. And a weight or a bike sitting on the ground is acted upon by gravity in the direction of gravity, towards the center of the earth.

A free-swinging weight on a boom is also acted upon by gravity straight down, and thus the single support cable will settle pointing straight down, whether it's a two-ton heavy thing or a simple contractor's plumb bob.

But add a second support cable, and the straight-down gravitational force is now split evenly between both cables, and acting in the direction of both of the cables simultaneously. So there are now two independent forces at work which add up to a straight-down gravity force, but are not each identical to it.

Again, it's different interpretations of the same observed phenomena here. I'm just saying that gravity (or CG) alone doesn't tell the whole story.
Oct 8th, 2010 9:35 pm
GillyWI
Quote:
Originally Posted by shook sez
Interestingly enough, I went to noon Mass today over at St. Mary's.

All I got from God His Very Ownself on the discussion was the following,
and I quote..." Tell my boys Happy Friday."

Thanks Big Guy!

Gilly
Oct 8th, 2010 1:20 pm
shook sez
Quote:
Originally Posted by JCW
if you think of it as the center of mass instead of center of gravity it might make more sense.

.
Interestingly enough, I went to noon Mass today over at St. Mary's.

All I got from God His Very Ownself on the discussion was the following,
and I quote..." Tell my boys Happy Friday."
Oct 8th, 2010 11:46 am
G-DAVE Quote "Yes, it rises because you've moved the weight up higher. Just as you do when you stand up " Unquote

Not correct ---The moment you lift the "weight" 1 mm off the ships deck it's immediately transferred to the top of the Derrick
Dave
Oct 8th, 2010 9:32 am
Jbartlett
Quote:
Originally Posted by Meese
And that only works because it allows the bike to move around underneath you. But the total CG is still higher than if you were sitting.

Again, you and the bike are not one, single rigid body here.

Sorry, still incorrect, even if it "feels" right.
I'm with Ken here, but I base my opinion only on practical experience, rather than any scholarly approach. I rode a motorcycle (H-D FLHTP) in the course of my job as a police officer for several years. I've been to 80 hours of basic Motor School, 120 hours of Motor Instructor School, through the H-D/Northwestern University program and many hours of refresher training. I also took the Lee Parks Total Control Level 1 class this Spring. I can tell you without hesitation that neither I, nor any other Motor Officer I have ever seen, would consider standing up to maneuver through a slow speed course. I know lots of police riders that are way better than me and have never seen them do it either.

That doesn't mean that police riders are the end all in terms of skill, but we do have the slow speed stuff down pretty good. I'm sure there are differences if you ride in the dirt, but I have taken my H-D in some places that common sense would tell you not to go and never had to stand up to increase my control. Granted, standing up on the floorboards of an H-D FLH would require some maneuvering, but it can be done.

Just my opinion, but based on lots of time spent on my side on the ground and picking up my motor. It's all about balance and stability. I think if you were standing up it would be too easy to get off balance.
Oct 8th, 2010 9:15 am
XMagnaRider +1 for everything Meese posted. I started reading this thread and was thinking of a reply, but Meese beat me to it.

Meese is 100% right. I will back that statement up with years of teaching experience in the physics department of a large university.


Quote:
Originally Posted by Meese
True enough, as my GT handles much better with my ass parked on it than it would with yours parked there.
Alright, Meese is 99% right.
Oct 8th, 2010 8:43 am
Meese
Quote:
Originally Posted by GillyWI
Once again proving that the GT would handle a hell of a lot better if my ass wasn't parked on the seat..........
True enough, as my GT handles much better with my ass parked on it than it would with yours parked there.
Oct 8th, 2010 8:38 am
Meese
Quote:
Originally Posted by G-DAVE
In marine terms - if you have a weight on the deck of a ship and you sling it onto a derrick (crane),the moment you pick the weight up it is acting as though it is at the top of the derrick. Therefore the CofG of the vessel rises
Yes, it rises because you've moved the weight up higher. Just as you do when you stand up.

And again, when the weight is sitting on the deck, it and the ship are tied together as a solid unit. But once you lift it, the weight is free to swing about on its cables, and so the forces act differently than if it was simply lifted to the top of a rigid tower and stuck there.

Standing up moves the combined CG higher, period.

But it also allows you to bend your legs and apply your body mass to the pegs, or to just one peg if you wish.

There is a difference between pure center of gravity of a combined solid mass and the individual forces applied by loosely coupled bodies.

For example, if I stay seated on the bike, and a car hits me from the side, the bike will move sideways. That doesn't change the center of mass of me and the bike, but it does add a sideways force acting on my bike.

Standing up simply means that you, as a flexible body, can apply your force (weight) to a different part of the bike. But the combined body of you and the bike will still have a higher CG.

You simply cannot lower the center of gravity of an object or set of coupled objects by raising it.

Trust me guys, this is correct, regardless of what it may "feel" like to you.
Oct 8th, 2010 8:15 am
JCW if you think of it as the center of mass instead of center of gravity it might make more sense.

the mass of your body sits higher moving the the center of mass higher. regardless of where you are standing.
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