Limit cornering on bikes

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Tommy Cookers
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Re: Limit cornering on bikes

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joshuagore wrote:
Fri Mar 13, 2020 1:14 am
....Jim Papadopoulos https://www.nature.com/news/the-bicycle ... cs-1.20281 or you can go back to the work of Tony Faole in Motorcycle Chassis and Handling and Dynamics.
...I have been building riding and tinkering with zero trail or reducing trail suspension, and traditional suspension using bicycles and the larger 'mid fat' tire carcasses available ....
....on a zero trail setup, or negative trail front suspension I CAN ride no handed, but it isn't always easy ....
interesting !
the Nature link shows what might be called balanced steering geometry
ie the 'weight' on the steered wheel not trying to increase (aka 'flop') or decrease the steering angle
this 'balance' happening due to the steering axis exactly bisecting the 'rolling radius' (line from wheel centre to ground)

for each steering axis angle there is only one fork offset aka rake dimension that gives this 'balance'
that's why traditionally each different frame angle had its (correspondingly different) fork rake
using any other fork offset (too often done in this carbon age) gives a bicycle that cannot be ridden 'hands-off'

reducing trail (or increasing it) will lose this 'balance' unless corresponding alterations to offset are made
yes Tony Foale's work was interesting - did it benefit anything ?

yes Moto GP etc knowingly departs from 'balanced' geometry
and off-road does - as soft surfaces make the mechanical drag on the wheel act ahead of the rolling radius ?
and yes motor cycle tyres are much wider than bicycle tyres

J.A.W.
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Re: Limit cornering on bikes

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Tim.Wright wrote:
Tue Mar 10, 2020 9:54 pm
Drivers drive. Engineers engineer.

Hero worshipping aside, there hasn't been any overlap in these two disciplines in motorsport for at least 40 years now.
There has been a certain misapprehension here, since while it is certainly true that the current
ultra-professional approach to top-flite motosports means that the likes of Jack Brabham/Surtees
/McLaren/Peter Williams as designer-engineer racers, are no longer seen, it also means that the
riders/drivers themselves - in order to be championship contenders, must have a fundamental
appreciation of, & thus an ability to discuss - relevant technical concerns, as a winning edge...
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

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Tim.Wright
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Re: Limit cornering on bikes

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Driver feedback needs to be based on the driving actions - not technical aspects of the car. The drivers need to identify weak points where the car is not doing what they ask and the engineers then need to find the technical solution. This is exactly what everyone have been trying to explain over the last two pages.

The better (development) drivers are able to notice patterns in any vehicle behaviour problems and categorise them. I.e. they are able to tell you if a certain driveability problem is only appearing at high or low speed, maybe it's only evident in a certain cornering phase say turn-in and it might also change with tyre degredation. None of this requires any deep technical understanding of the car but requires an impressively fast processing ability of the drivers brain to identify the problems, categorize them and store it while driving the car at the limit.

I have cases where explaining too much technical stuff to a driver just f**ks their feedback afterwards. Mainly because you are adding more useless stuff for them to be thinking about while driving. I've also noticed that the very best development drivers - both motorsport and automotive - are rarely the fastest because they use the portion of their brain to generate useful feedback which the fastest drivers switch off to go faster. It's no secret that the absolute fastest drivers are typically light on when it comes to getting useful feedback for development work.
Not the engineer at Force India

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Andres125sx
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Re: Limit cornering on bikes

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J.A.W. wrote:
Sat Mar 14, 2020 12:08 am
Tim.Wright wrote:
Tue Mar 10, 2020 9:54 pm
Drivers drive. Engineers engineer.

Hero worshipping aside, there hasn't been any overlap in these two disciplines in motorsport for at least 40 years now.
There has been a certain misapprehension here, since while it is certainly true that the current
ultra-professional approach to top-flite motosports means that the likes of Jack Brabham/Surtees
/McLaren/Peter Williams as designer-engineer racers, are no longer seen...
As you say currently everything is ultra-professional so now riders can´t participate in the development process as much as previously, but also take into accound the age of those riders/drivers you´re quoting, and their preparation or experience. For example Brabham worked in a garaje since he was 15 and their racing achivements started more than a decade after, wich huge experience in mechanics. Compare with current riders/drivers who are just teenagers racing for a living even before they were teenagers

Can´t be compared, diferent eras

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Andres125sx
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Re: Limit cornering on bikes

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Tim.Wright wrote:
Sat Mar 14, 2020 11:13 am
Driver feedback needs to be based on the driving actions - not technical aspects of the car. The drivers need to identify weak points where the car is not doing what they ask and the engineers then need to find the technical solution. This is exactly what everyone have been trying to explain over the last two pages.

The better (development) drivers are able to notice patterns in any vehicle behaviour problems and categorise them. I.e. they are able to tell you if a certain driveability problem is only appearing at high or low speed, maybe it's only evident in a certain cornering phase say turn-in and it might also change with tyre degredation. None of this requires any deep technical understanding of the car but requires an impressively fast processing ability of the drivers brain to identify the problems, categorize them and store it while driving the car at the limit.

I have cases where explaining too much technical stuff to a driver just f**ks their feedback afterwards. Mainly because you are adding more useless stuff for them to be thinking about while driving. I've also noticed that the very best development drivers - both motorsport and automotive - are rarely the fastest because they use the portion of their brain to generate useful feedback which the fastest drivers switch off to go faster. It's no secret that the absolute fastest drivers are typically light on when it comes to getting useful feedback for development work.
I´d love to upvote this post =D>

J.A.W.
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Re: Limit cornering on bikes

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Andres125sx wrote:
Sat Mar 14, 2020 4:37 pm
J.A.W. wrote:
Sat Mar 14, 2020 12:08 am
Tim.Wright wrote:
Tue Mar 10, 2020 9:54 pm
Drivers drive. Engineers engineer.

Hero worshipping aside, there hasn't been any overlap in these two disciplines in motorsport for at least 40 years now.
There has been a certain misapprehension here, since while it is certainly true that the current
ultra-professional approach to top-flite motosports means that the likes of Jack Brabham/Surtees
/McLaren/Peter Williams as designer-engineer racers, are no longer seen...
As you say currently everything is ultra-professional so now riders can´t participate in the development process as much as previously, but also take into accound the age of those riders/drivers you´re quoting, and their preparation or experience. For example Brabham worked in a garaje since he was 15 and their racing achivements started more than a decade after, wich huge experience in mechanics. Compare with current riders/drivers who are just teenagers racing for a living even before they were teenagers

Can´t be compared, diferent eras

Different eras can be compared, the likes of Brabham/Mclaren/Surtees et al, also had myriad
other responsibilities within their eponymous teams, whereas fully professional MotoGP riders
with championship-winning ambitions do have the time to focus on the issues which will allow
the best possible opportunities to do so, from rigorous physical fitness routines, to developing
an effective subjective/experiential data-feedback process with their engineers, for which a
fundamental understanding of the relevant systems is required, to enable meaningful analysis...
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

Erunanethiel
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Re: Limit cornering on bikes

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Soo... How do you stand the bike up after limit cornering?

J.A.W.
J.A.W.
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Re: Limit cornering on bikes

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^ Ok!

See below here for deliberate inputs:



& for a reactive/reflexive 'save', see it at 2:48 in, below:

Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

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Tim.Wright
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Re: Limit cornering on bikes

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The rider can move the cg.
Not the engineer at Force India

Slo Poke
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Re: Limit cornering on bikes

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Thanks much, many times over J.A.W.:
Just what my tired old eyes needed to see. No halo, no crumple zones, no seat belts, no drinks bottle why? No Pussies! Just guts.

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Andres125sx
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Re: Limit cornering on bikes

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Erunanethiel wrote:
Sun Mar 15, 2020 4:43 am
Soo... How do you stand the bike up after limit cornering?
Andres125sx wrote:
Mon Mar 02, 2020 7:45 am
I think the problem with the OP is he´s taking a rider-bike on a corner as a natural balance, and it is, but he´s missing rider can apply new forces wich will break the balance at will, just a gesture to lean the bike a bit more or less is breaking the balance
Even if you´re sliding on the very limit, you can always straighten the bike (leaning your body a bit more) to stop the slide wich will automatically stand up the bike. Or make you crash, depending on your accuracy and smoothness :mrgreen:

J.A.W.
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Re: Limit cornering on bikes

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Andres125sx wrote:
Sun Mar 15, 2020 3:32 pm
Erunanethiel wrote:
Sun Mar 15, 2020 4:43 am
Soo... How do you stand the bike up after limit cornering?
Andres125sx wrote:
Mon Mar 02, 2020 7:45 am
I think the problem with the OP is he´s taking a rider-bike on a corner as a natural balance, and it is, but he´s missing rider can apply new forces wich will break the balance at will, just a gesture to lean the bike a bit more or less is breaking the balance
Even if you´re sliding on the very limit, you can always straighten the bike (leaning your body a bit more) to stop the slide wich will automatically stand up the bike. Or make you crash, depending on your accuracy and smoothness :mrgreen:
Actually, if you check the slow-mo slide/recovery shown in the 2nd vid, as I'd linked above, you'll see
the rider using 'counter-steering' ('opposite lock' in car terms) to straighten up, even though he
has not completed cornering, & thus must cope with both the 'whiplash' bucking/snaking response
from his protesting machine & try manfully, not to contact the wall on the outside of the corner.

Two bike-particular factors assist him in succeeding with such fraught, chaotic evolutions,
one being the low 'engine braking' inertia of the 2T machine, when he cuts the throttle to stop
the powerslide, plus the high ratio of the rider-to-bike weight %, which enables him to get
over the steering axis in order to damp its gyrations, & wrest the bike back under control...
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

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Andres125sx
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Re: Limit cornering on bikes

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J.A.W. wrote:
Mon Mar 16, 2020 5:24 am
Two bike-particular factors assist him in succeeding with such fraught, chaotic evolutions,
one being the low 'engine braking' inertia of the 2T machine, when he cuts the throttle to stop
the powerslide
, plus the high ratio of the rider-to-bike weight %, which enables him to get
over the steering axis in order to damp its gyrations, & wrest the bike back under control...
sorry JAW but if you cut the throttle to stop a powerslide you´ve crashed even before your throttle gets completely closed #-o

And controlling a power slide is very different to what we were talking about, if you´re oversteering (powerslide) obviously you need to countersteer, but that´s a completely different scenario

J.A.W.
J.A.W.
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Re: Limit cornering on bikes

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If you check the 'save' vid, in slo-mo Andres, you can clearly see just where
the rider backs off the throttle, then winds it back on, to straighten up,
(as a needful inertia-control input function).

There are many complicated inter-related dynamics involved in cornering a
one-track vehicle, & any scenario may develop unexpectedly - yet must be
managed accordingly - via skilled responses involving proper inputs,
applied in a timely fashion, if a crash is to be avoided, no?
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

McMrocks
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Re: Limit cornering on bikes

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Edit: "Countact patch" well spelled

Image

When cornering you should have four forces acting on the bike: Gravitational force and Centrifugal force. Both act at the centre of gravity (Cg). And the forces acting on the tire (vertical and horizontal).

The gravitational force (Fy) wants to pull the bike down. While the centrifugal force (Fx) wants to straighten the bike up.

When cornering steady, the torques of those forces (rotating around the contact patch of the tire) are equal.

You have two options to stop the cornering(without changing the loads on the tyre):
Increase ly to increase the lever of the centrifugal force(Fx) --> i.e. move your upper body upwards
Decrease ly to decrease the lever of the gravitational force (Fy) ---> reduce your hanging off