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Old 11-12-2012, 06:31 AM   #196
Tiggs
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Quote:
Originally Posted by Craneguy View Post
Likewise, I was just referring to how I manipulate the location of the combined load's CG to enable unusual loads to be moved by rail.

We are merely trying do dispel the ridiculous premise that when a rider stands up, the CG goes down. The canoe analogy is entirely appropriate to illustrate the concept.
I think that has already been established. Please let's move on!
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Old 11-12-2012, 11:31 AM   #197
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What if you were standing in a canoe in a test tube where the meniscus is more pronounced , surely that would effect your stability?
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Old 11-12-2012, 11:44 AM   #198
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Troy, are you telling us that your rider input was responible for suzuki's reducing rate linkages? What were you smoking?

Ps Zebs got a point, when aquaplaning with the front wheel locked you want a nice w ide bashplate so your feet don't get washed off the pegs...been there, done that, not going to have any more kids
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Old 11-12-2012, 02:44 PM   #199
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Just cause you went to uni for a few years you think you know it all don't you...

Instead of going to some fancy school you should be made to work on a real job site for a few years, then you might see how much shit you engineers speak and how little you actually know.

Why do you have to go to uni for four years just to learn how to drive a train anyway?

Seriously though, I had always been fascinated by the way some uneducated laborers, plant operators, truck drivers, etc on a job site will tend to sit around trying to point out holes in things the engineers have designed or suggested claiming they know more, and that the engineers are just copying from a book and don't know what they are talking about.

I should have known there was a name for it.

By the way, I am an uneducated plant operator that has just accepted a laboring job with the Scenic Rim council, but I am one of the ones who realise that that just because I don't understand something, it doesn't mean it doesn't make it wrong, just means I'm not smart enough to understand it fully.
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Old 11-12-2012, 03:11 PM   #200
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Originally Posted by eepeqez View Post
I made no claim at all about the relevance of my story about the canoe to the handling qualities of a motorcycle. In that respect, I am like the bat and its sonar; I have no need to analyse the physics of the system to control the path my motorcycle follows.

I simply set out to address one issue, the perverse idea that by standing up on a lower support, the centre of gravity of a system including a human being is somehow lowered. I believe I have adequately described an analogous situation which illustrates the folly of this nonsense.

Do you believe that by standing in a canoe you lower it's centre of gravity?

And don't give us any irrelevant guff about surface tension. Seriously! Don't try to tell us that adding a few drops of soap to the water will alter the stability of a canoe.

Just tell us, does standing up in a canoe lower it's centre of gravity?

You might want to read this before telling the engineers here that all our training and professional expertise is nonsense.

I think we are on to somthing here!
This thread could go in a new direction. By standing up in my canoe ( sorry I mean bike ) I am not really affecting the COG by much. But I have now become a FOOLcrum and I am pivoting my canoe ?
Give me a lever and a point to use it and I can move the thread.
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Old 11-12-2012, 03:28 PM   #201
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Quote:
Originally Posted by eepeqez View Post
I made no claim at all about the relevance of my story about the canoe to the handling qualities of a motorcycle. In that respect, I am like the bat and its sonar; I have no need to analyse the physics of the system to control the path my motorcycle follows.

I simply set out to address one issue, the perverse idea that by standing up on a lower support, the centre of gravity of a system including a human being is somehow lowered. I believe I have adequately described an analogous situation which illustrates the folly of this nonsense.

Do you believe that by standing in a canoe you lower it's centre of gravity?

And don't give us any irrelevant guff about surface tension. Seriously! Don't try to tell us that adding a few drops of soap to the water will alter the stability of a canoe.

Just tell us, does standing up in a canoe lower it's centre of gravity?

You might want to read this before telling the engineers here that all our training and professional expertise is nonsense.

Thanks for the link re Dunning-Kruger effect. At the bottom of that page there are some other interesting links, including this one http://en.wikipedia.org/wiki/Curse_of_knowledge

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Old 11-12-2012, 06:48 PM   #202
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Aye, Eepeqez, you touched on a good point there. There's been more than one or two Dunning-Kruger-like opinions expressed in this thread.
Which is particularly strange, since the underlying concepts are very straightforward. Nothing Rocket Science about it. For CoG, a year-9 high school textbook covers it all . . . and most of the rest just requires common sense thinking (and avoiding fuzzy or misleading terms).

Admittedly, at the extremes of the Grand Prix racetrack, it is very much a case of Rocket Science [where to advance the science, requires the combination of a lot of theorising & experimenting].
But that's a helluva long way from the basic stuff we've been discussing here . . . which is whether [and why] the rider should sit down or stand up, or lean his body out to one side or the other.

Though I will say you are being a bit harsh if you're pointing the finger at Troy. Troy provides some excellent humour here . . . and if his post [#194] appears [in places] to be disagreeing with you . . . then I suspect it is because he is ironically winding you up. Cos it is impossible he could seriously hold such unscientific ideas (and because he loves using a lot of Smoke & Mirrors to confuse us . . . even so much so, as to risk confusing himself ! ).

So relax. It's all good fun, generally.
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Old 11-12-2012, 07:27 PM   #203
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Quote:
Originally Posted by Midnullarbor View Post
.
then I suspect it is because he is ironically winding you up.
Troy winding anyone up?? Geddoudahere!

:)
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Old 11-12-2012, 07:37 PM   #204
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Seated versus standing position for maximization of performance...

We really need to conduct this research in a scientific manner...
http://www.ncbi.nlm.nih.gov/pubmed/18569564
And not one mention of CoG in the extract... obviously amateurs!

At least that article has some numbers, percentages, measurements... what do we have? nothing!

well almost, apart from this bit from eepeqez: Which looks pretty impressive, even if i tends towards to n, but we'll leave the rest as an exercise to the reader!
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Old 11-12-2012, 09:25 PM   #205
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No no no, Itsgunnahurt . . . please delete your reference to those pedal cycles, forgawdsake.

Somehow I can't see a usefully close comparison between a 100 Kg motorcyclist on a yet-heavier motorcycle . . . and a 100 Kg bicyclist on a 7 Kg bicycle.
Or at least until I see a competition bicyclist power-sliding around a curve, with his [left] steel shoe-piece spitting out sparks from the gravel !

And geddoudahere about Troy winding anyone up.
Nah. Never happens.
Though I am curious about where Troy got his name from . . . cos I have heard that, in some languages like French and Italian, the letters double "LL" are sometimes pronounced like the letter "Y".
Or is it the other way round ?
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Old 11-13-2012, 12:41 AM   #206
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Ok, I'm a tradie now studying to be an engineer and in my professional opinion, if your bike is lying on its side and you are lying on the ground near your bike, then you have managed to get the centre of gravity of both you and your bike as low as it can possibly go without starting to dig holes in the ground.

I think in laymans terms it means you've fallen off your bike...
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Old 11-13-2012, 12:51 AM   #207
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Let me just start by apologising for sending what was an interesting thread south with my opinion/ thoughts on the subject. After having read the first few pages and scanning the rest of the posts, I hadn’t seen what I considered a reasonable explanation. There may have been one but I could not then and cannot now be bothered reading every post.
Now I am not sure why Eepeqez was so angered by my thoughts, I clearly said at the end that it was my opinion, I never said it was a fact. Perhaps I should have worded it differently by saying something like “Put simply to my way of thinking”, or apologising in advance if I was wrong or something similar, I am not sure (I guess that’s something else I don’t know).
As they say, Opinions are like as$3holes, everyone has one and some of them stink. It would seem that my thoughts on the matter are wrong, not the first time I have been so and I dare say not the last.
Had my learned friend responded in a civilised way (as I would expect most reasonable people would have done) stating that my thoughts were wrong and possibly explaining where I went wrong I would be happy to be corrected.
The problem for me was the condescending way in which he went about it and the petulant way he went about boasting of his examination success and name calling that caused me to respond, thus further raising his ire. The condescending tone indicated a seemingly learned man but the petulant childishness of the disparaging remarks would indicate a childlike nature so I am thinking child genius or perhaps idiot savant,,, or perhaps he was just having a bad day.
At any rate, I apologise for causing offence in the first instances but not so much in this instance though.
So again I apologise for bringing this thread into disrepute and shall visit it no further, have fun whether you stand or sit and stay safe good people.

p.s. One last thought on the matter and let me again apologise if I am wrong but,,,,,,,,,,,,,,,,,
Could it be in part due to when cornering seated and the bike leans, your weight is further away from the point of grip i.e. wheels to ground then when you are standing. Yes we are told to weight the outside peg but when standing you are able to apply more of your weight to it.
Just a thought so please don’t shoot me.
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Old 11-13-2012, 03:49 AM   #208
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The problem with folks like eepeqez is that they have a little learning but not a lot of understanding.
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Old 11-13-2012, 04:14 AM   #209
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Quote:
Originally Posted by Beemerboff View Post
The problem with folks like eepeqez is that they have a little learning but not a lot of understanding.
I'll freely admit that I'm not a skilled off road rider. I have no opinions on the benefits of standing up to ride - it doesn't seem to do anything for me, but then I ride what is essentially a farm bike.

But I certainly do understand about centre of mass (misleadingly called centre of gravity by some) and that it is a property of masses, not of forces. It is entirely about masses and their locations, not about the forces that support them.

If you cannot grasp this, I would suggest it is you who has a little learning and very little understanding.
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Old 11-13-2012, 04:47 AM   #210
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Jeffro, I reckon you have put your finger on a very important point in this whole topic.

Yes, we are often told to "weight the outside peg" during dirt cornering.
As far as I can see (and apart from the minor readjustment of hands forces on the handlebars) the extra weight on the outside peg [and less on the inner one] is there BECAUSE the rider has moved his body more to that side of the bike ~ and the consequence of that movement is that the bike is pushed "down" slightly closer to the horizontal i.e. the bike is "over-leaned in" while the body is "under-leaned out".
(Which is the opposite of what a bitumen road racer does during hard cornering.)

Obviously, regardless of the amount of Body English used, the combined body/bike CoG lies along the same angle line down to the line between the two ground-contact zones of the two wheels [sorry, not expressed well !] . . . provided that the cornering speed is the same.
And the same "combined" angle applies to the "opposite technique" used on bitumen.

As I mentioned in some other posts, it seems to be that the "overleaning" of the dirt bike is what brings the better cornering.
In other words, the better cornering is produced by the Body English which results in an "overleaned" bike . . . regardless of whether the more-weighted foot is on the peg; or on the crankcase; or wherever [or even on the seat !!].
No, I don't actually recommend those other support points . . . the peg will do just fine, thanks . . . but you can see that it is the Body English which is the dog here and the peg-weighting which is the tail following after.

So, does it really matter whether we call it "weighting the X or Y peg" or "swinging some Body English" or "moving your Centre-of-Gravity to the X or Y side" ??
Well, we have just seen how the whole topic of CoG can fall into a black hole of misunderstandings.
And that happens so easily too with the "weighting" label ~ just look at a more recent "dirty" thread which has started up under The Perfect Line sub-forum : the guys are already in controversy about WHICH peg to weight [inner; outer; or one then the other; etcetera].

My thoughts are : "Forget about concentrating on this or that peg ~ just move your body to the side and the peg-weighting will follow naturally."
The peg-weighting is not the CAUSE but the consequence of the Body English change of position that you want to achieve.

Hope that makes sense.
And please correct me if that seems wrong !

Now, as to WHY overleaning the bike is better for dirt cornering . . . is a Whole 'Nuther Question .
And it's got nothing to do with wheels "putting more weight on the ground" or other such nonsense.

And I hope we can get away from personalities and egos, and just consider the riding topic itself.
"What is said, is more important than Who speaks," . . . as someone or other famous once said.
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