SafeDiscDancing
10 kW
- Joined
- Jan 3, 2022
- Messages
- 514
BalorNG said:Chalo wrote:
"Low center of mass impairs both maneuverability and control, because... "
And he explained why.
BalorNG said:Chalo wrote:
"Low center of mass impairs both maneuverability and control, because... "
And he explained why.
SafeDiscDancing said:BalorNG said:Chalo wrote:
"Low center of mass impairs both maneuverability and control, because... "
And he explained why.
MadRhino said:Low COG makes balance precision
High COG makes balance reaction
I always use the extremes to illustrate this principle: GP racing motorcycles that have the highest COG, and Trial motorcycles that have the lowest COG.
GP bikes need to be balance reactive, meaning little action from the rider is required to initiate a change of trajectory. At low speed or standing still, a GP bike is a PITA because of balance instability. Nobody can keep a GP bike standing still very long before having to land a foot on the ground. Walking a GP bike, one need to hold it with both hands and be careful not to lean it because it does quickly fall off balance.
Trial bikes need to be precise, meaning a wider action amplitude from the rider is required to initiate a change of trajectory. At high speed a trial bike is dangerous because it does lack the reactivity required for quick maneuvering. Anybody with some training can keep a Trial bike standing very long before having to land a foot. Walking a Trial bike, one can hold it negligently with one hand because it does need to lean much more before falling off balance.
Clear enough ?
Try it yourself.
calab said:Argument from authority https://www.dailywire.com/news/watch-ben-shapiro-breaks-down-argument-authority-hank-berrien
If you want to take issue with the argument I would urge you not to use the argument from authority, which is: somebody has a PhD by their name they know what they’re talking about. That’s a dumb argument.
BalorNG said:Are you absolutely sure that supposed high CG of a motoGP bike is a design choice, not an (undesired) consequence of other design contraints?
SafeDiscDancing said:BalorNG said:Are you absolutely sure that supposed high CG of a motoGP bike is a design choice, not an (undesired) consequence of other design contraints?
That's what I've been trying to tell you and it appears the other guy just explained it better.
And the terms get confused here.
When I say "Handling" then I mean "Reactive".
"Stable" is the inverse of "Handling".
A quick handling MotoGP race bike is purposely made to maximize quick directional changes by exploiting a higher center of mass.
BalorNG said:I'll gladly internalise any new model if it seems better than one I currently have - but you are not making it easy with what amounts to condescension trolling.
BalorNG said:MadRhino said:Low COG makes balance precision
High COG makes balance reaction
I always use the extremes to illustrate this principle: GP racing motorcycles that have the highest COG, and Trial motorcycles that have the lowest COG.
GP bikes need to be balance reactive, meaning little action from the rider is required to initiate a change of trajectory. At low speed or standing still, a GP bike is a PITA because of balance instability. Nobody can keep a GP bike standing still very long before having to land a foot on the ground. Walking a GP bike, one need to hold it with both hands and be careful not to lean it because it does quickly fall off balance.
Trial bikes need to be precise, meaning a wider action amplitude from the rider is required to initiate a change of trajectory. At high speed a trial bike is dangerous because it does lack the reactivity required for quick maneuvering. Anybody with some training can keep a Trial bike standing very long before having to land a foot. Walking a Trial bike, one can hold it negligently with one hand because it does need to lean much more before falling off balance.
Clear enough ?
Try it yourself.
Are you absolutely sure that supposed high CG of a motoGP bike is a design choice, not an (undesired) consequence of other design contraints?
ebike4healthandfitness said:I can't believe this topic still goes on and on and on even though we had 10 pages and the people trolling about low center of gravity hurts stability clearly lost.
SafeDiscDancing said:BalorNG said:I'll gladly internalise any new model if it seems better than one I currently have - but you are not making it easy with what amounts to condescension trolling.
Fair enough.
I thought MadRhino made an interesting point about Trials bikes in that they are purposely designed to go the other direction and locate the center of mass very low.
So the recumbent has more in common with a Trials bike than a MotoGP bike.
In MotoGP you have these incredibly high speeds (220+ mph now) and they need to get the bike slowed under insanely hard braking and then in an instant flick the front wheel outward from the intended turn direction to generate maximum counter steering force.
Think of that front tire... it is brutally slowing down... then in probably a second has to take the contact patch and direct it so that the center of mass is essentially dropped off a cliff.
Now if the rider screws up and times his inward steer too late then he might wash out the front with a low side.
But if he times it too early he won't get the lean he needs and that will force his line to go wide and he likely will crash on the exit of the turn.
There is a moment where you are effectively "floating" before you "land" into your full lean.
All this happens at really high speeds and pressures.
Stability just means you are "slow" and will be last in the competition.
Anyway... do you see that?
SafeDiscDancing said:ebike4healthandfitness said:I can't believe this topic still goes on and on and on even though we had 10 pages and the people trolling about low center of gravity hurts stability clearly lost.
MadRhino wrote a very easy to comprehend post that seems to have resolved all the confusion.
And I actually did not know that about Trials bikes so I'm learning new stuff too.
Makes me want to try riding one it might be a totally new experience.
BalorNG said:SafeDiscDancing said:ebike4healthandfitness said:I can't believe this topic still goes on and on and on even though we had 10 pages and the people trolling about low center of gravity hurts stability clearly lost.
MadRhino wrote a very easy to comprehend post that seems to have resolved all the confusion.
And I actually did not know that about Trials bikes so I'm learning new stuff too.
Makes me want to try riding one it might be a totally new experience.
Actually he didn't.
The whole 'walking the bike' premise is nonsensical because MotoGP is simply much, much *heavier* than a trials bike, therefore if you lean it the same way as trials bike it will try and lean harder, even if it had lower CG - which it might or might not have, but walking the bike is simply not an argument.
Are there any actual numbers regarding CG of motogp and trials bikes and why exactly designers chose one over the other?
Again, there is a perfect reason why a motogp bike cannot be extremely low - it must lean 60+ deg to negotiate corners at close to 2g, and if you put the engine and bodywork close to ground you'll scrape it and go down - this is why riders has to lean OFF the bike and scrape their knees instead, something that just does not apply to bikes/bicyles mere mortals ride.
MadRhino said:Low COG makes balance precision
High COG makes balance reaction
GP bikes need to be balance reactive, meaning little action from the rider is required to initiate a change of trajectory. At low speed or standing still, a GP bike is a PITA because of balance instability. Nobody can keep a GP bike standing still very long before having to land a foot on the ground. Walking a GP bike, one need to hold it with both hands and be careful not to lean it because it does quickly fall off balance.
ebike4healthandfitness said:Remember this picture?
Here is the story behind it.
(Read it. The difference in performance has nothing to do with clearance of the bodywork.)
https://www.cycleworld.com/story/bikes/motorcycle-center-of-gravity-motorhead-myths/
Cowardlyduck said:Come on guy's....feel free to contribute to the discussion of the actual thread title "Do you use an fairing or partial fairing on your ebike, emoped or BSM?"
If you want to discuss centre of gravity stuff maybe make a new thread about that.
There is a guy in/around my area in Canberra that rides a recumbent with just the tail fairing. Like this:
I've chatted to him a few times and he reckons the tail fairing has a greater impact than a front facing one. From my limited understanding of aerodynamics I think he's right.
Makes me wonder what kind of tail fairing I could cobble up out of solar panels.
Cheers
BalorNG said:What you elaborate further?
SafeDiscDancing said:but the slow handling (stable) nature of the lower center of mass designs places limits to the ability of them as "sport" vehicles
Chalo said:Low isn't stable. Low is tippy because the roll rate is too fast.
SafeDiscDancing said:Chalo said:Low isn't stable. Low is tippy because the roll rate is too fast.
It depends on speed.
If the low center of mass bike is going 200 mph it's not going to be easy to get it to change direction.
But at slow speed any steering will cause wobbles... "Wheebles Wobble But Don't Fall Down".