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Sideslip angle, wut ?

Started by HornetMaX, August 17, 2014, 07:52:53 PM

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HornetMaX

Quote from: Alby46 on August 17, 2014, 10:48:10 PM
there are some values that can be changed in the garage, that modify what you're saying

Uh ?  :o

Quote from: WALKEN on August 18, 2014, 01:56:30 AM
How about no more Brno?  Ewwwwwwwwww, love Brno!   
Quote from: Alby46 on August 18, 2014, 05:23:18 AM
Quote from: BOBR6 84 on August 18, 2014, 04:02:26 AM
Oh shit you mean they were gonna scrap brno??  :o
yes, karel saved it
Quote from: BOBR6 84 on August 18, 2014, 04:02:26 AM
Oh shit you mean they were gonna scrap brno??  :o
OK, I'm not really well placed to complain about people going off topic but ... anyway, according to objective criteria (like umbrella girl quality) I'd never scrap brno.
WTF, they race in a parking space in the middle of the desert and then plan to scrap brno ?

@Stout: feel free to stay on topic :)

MaX.

Alby46

Quote from: BOBR6 84 on August 18, 2014, 05:43:43 AM
wow! that would suck.. well done abraham!! isnt brno one of the only original tracks from the beginning of motogp? or is that assen.. cant remember
assen, but since 2006 it's not the real assen
Still riding a 50cc, but enjoying it :)

Stout Johnson

Quote from: BOBR6 84 on August 18, 2014, 05:43:43 AM
wow! that would suck.. well done abraham!! isnt brno one of the only original tracks from the beginning of motogp? or is that assen.. cant remember

True! Brno is a classic and it has a huge fan-base. It doesn't generate enough profit, so that puts it on the red-list already :/ More importantly, the track has such a nice layout and always makes for nice races (real life as well as GPB :P) - so it would be a real shame if cancelled.
    -----------   WarStout Kawasaki Team   -----------

Stout Johnson

Quote from: HornetMaX on August 18, 2014, 06:47:27 AM
@Stout: feel free to stay on topic :)
I will for sure :) Here we go:

Quote from: HornetMaX on August 17, 2014, 10:40:56 PM
Hmm, I thought they were more or less mid/end of the turn and hence on the throttle ...
Also because if they were on the brakes and initiating the lean, the front wheel would be pointing towards the exterior ...
No, I am pretty positive, it is on the brake... in the HD slo-mo you can actually see the tyre being almost flat because all the weight is on the front.
In the first Dani Pedrosa replay (with 7 laps left) you can clearly see Dani's right hand braking ;)

On a general note regarding this issue: in your first post you say:
Quote from: HornetMaX on August 17, 2014, 10:40:56 PMyou can clearly see that the front wheel is not "pointing" in the direction it is move towards, aka it is slipping laterally says
I do not feel that the direction of the front wheel in relation to the movement vector of the bike is the problem (although the title here http://forum.piboso.com/index.php?topic=410.0 says otherwise :D When I started the topic it was the way I described it - not in the best way I would say now ;)).

What bothers me with the cornering of GPB, happens only when accelerating (I have no issues with the braking physics in GPB anyhow; imo very realisitic). For a bike, when being turned, it should always only sideslip to the "outside". That means, a bike in a left turn should have a bike side-slip angle towards the right and vice versa. I would like to concentrate on the bike's resultant side-slip. If we discuss each wheel seperately, the discussion will blow up, not leading anywhere as I now feel that there is sometimes something wrong with the overall bike's trajectory - not the front wheel problem as I initially stated in the thread I opened up.

This is how bike's overall sideslip can look like. With...
green  = bike's "heading" vector 
blue    = bike's movement vector
angle between the vectors is the sideslip angle
 


So again, the angle should open to the outside of the bike (to the right in left-hand corners, to the left in right-hand corners). In GPB however, in some instances it can be observed that the sideslip angle will open up to the wrong side, to the "inside" if you will... like imo, it can be seen here from 0:12 on.
http://https://www.dropbox.com/s/lsbqdxhq9imu78m/GPB%20-%20wheel%20alignment%20problem.mp4
    -----------   WarStout Kawasaki Team   -----------

HornetMaX

Quote from: Stout Johnson on August 18, 2014, 09:33:46 AM
Quote from: HornetMaX on August 17, 2014, 10:40:56 PM
Hmm, I thought they were more or less mid/end of the turn and hence on the throttle ...
Also because if they were on the brakes and initiating the lean, the front wheel would be pointing towards the exterior ...
No, I am pretty positive, it is on the brake... in the HD slo-mo you can actually see the tyre being almost flat because all the weight is on the front.
In the first Dani Pedrosa replay (with 7 laps left) you can clearly see Dani's right hand braking ;)
Oh now I (maybe) recall that replay at 7 laps to go: was it the one where you clearly see the front tire being compressed (i.e. the carcass being pushed and pulled like a spring) ?
If yes, then sure, this one was clearly on the brakes. But I thought the two others (4 laps to go) were not on the same spot or at best much deeper in the corner and off the brakes (but I could be wrong).

Quote from: Stout Johnson on August 18, 2014, 09:33:46 AM
On a general note regarding this issue: in your first post you say:
Quote from: HornetMaX on August 17, 2014, 10:40:56 PMyou can clearly see that the front wheel is not "pointing" in the direction it is move towards, aka it is slipping laterally says
I do not feel that the direction of the front wheel in relation to the movement vector of the bike is the problem (although the title here http://forum.piboso.com/index.php?topic=410.0 says otherwise :D When I started the topic it was the way I described it - not in the best way I would say now ;)).
Agreed: in fact I said I didn't think these replays were really related to our previous discussion.

Quote from: Stout Johnson on August 18, 2014, 09:33:46 AM
What bothers me with the cornering of GPB, happens only when accelerating (I have no issues with the braking physics in GPB anyhow; imo very realisitic). For a bike, when being turned, it should always only sideslip to the "outside". That means, a bike in a left turn should have a bike side-slip angle towards the right and vice versa. I would like to concentrate on the bike's resultant side-slip. If we discuss each wheel seperately, the discussion will blow up, not leading anywhere as I now feel that there is sometimes something wrong with the overall bike's trajectory - not the front wheel problem as I initially stated in the thread I opened up.

This is how bike's overall sideslip can look like. With...
green  = bike's "heading" vector 
blue    = bike's movement vector
angle between the vectors is the sideslip angle
 

Hmm, the "bike's heading" is exactly the same as the "rear wheel heading", ignoring chassis and swing arm flexibility, which are irrelevant for the discussion.
Likely you should focus on what happens at the rear wheel, as the "bike movement vector" (guess you refer to something like the velocity vector of the CoG) bring in some additional tricks (e.g. bike yawing).

Quote from: Stout Johnson on August 18, 2014, 09:33:46 AM
So again, the angle should open to the outside of the bike (to the right in left-hand corners, to the left in right-hand corners). In GPB however, in some instances it can be observed that the sideslip angle will open up to the wrong side, to the "inside" if you will... like imo, it can be seen here from 0:12 on.
http://https://www.dropbox.com/s/lsbqdxhq9imu78m/GPB%20-%20wheel%20alignment%20problem.mp4

I'm under the impression that what you're saying is "a bike cannot slide inside the turn" (which I can understand), but I don't think that's happening in your video.
From 0:09 on, what I see is: the rider needs to pick up the bike, so he turns the handlebars towards the interior of the turn (i.e. to the rider's right).
Because of that, the bike's heading progressively points more towards the interior of the turn (before doing the opposite once the bike is almost vertical).

Watching the screen, the fact the bike globally moves to the left of the screen at turn's end is not surprising to me (just the rider having overdone the turn a bit, the bike having been kept a tad too much on the angle, picking it up a bit too late).

MaX.

Stout Johnson

Quote from: HornetMaX on August 18, 2014, 10:24:15 AM
Hmm, the "bike's heading" is exactly the same as the "rear wheel heading", ignoring chassis and swing arm flexibility, which are irrelevant for the discussion.
Likely you should focus on what happens at the rear wheel, as the "bike movement vector" (guess you refer to something like the velocity vector of the CoG) bring in some additional tricks (e.g. bike yawing).
Yeah I know... But I try to make this discussion as understandable as possible, so everybody here hopefully feels free to contribute. It is becoming a discussion between the two of us again ;) I just felt that if I just refered to rear wheel, some might not get what I mean. The direction of the whole bike is easier to grasp I think, but dunno.

maybe this illustrates it better (excuse the lame editing :P):

this is how it is:

Situation 1:


this is how it should be imo:


Situation 2:


this is how it should be imo:


hope this makes it more clear....

PS: ignore the front wheel in my edited pictures... I didnt have much time.

    -----------   WarStout Kawasaki Team   -----------

BOBR6 84

First picture describes everything iv been disliking in gpbikes since day 1. Happens everywhere! Even at low speed.. Which is probably the answer to why its so unstable on hairpins etc

HornetMaX

I don't know in other cases, but in the video above I'm starting to think you're being confused by the camera perspective.

I try ultra hard to find something wrong in the above video but I really don't see it (at least in the video above and in the other one Stout showed me a long ago). Again, maybe I'm just blind but ...

@BOBR6: low speed instability in hairpins comes from something else, namely that a 2 wheel bike at low speed is ... well, unstable :)
(so the virtual rider has more difficulties in doing what we'd like him to do).

MaX.

Forty6

I totally agree with Stout and Bob. You can see it more in 3rd person view while turning it's like the bike goes slightly the opposite way so you can see more of the side of the bike than you should. Almost like its 'crabbing' like the rear spindle is out of line causing it to not follow the front.

BOBR6 84

My theory is.. (lol)

Because the bike goes through, around some corners at an angle (front wheel not tracking properly) on the corner exit the front end is dragging itself across the track surface to get back into line with the direction you are going! As the tyre drags across the track surface it causes the bars to shake which sometimes leads to a crash.. Sometimes it comes back into line and away you go! Almost like the virtual rider hasnt got a clue what to do other than hold on lol

On some tracks its so flippin obvious that something isnt right.. Brands hatch NC is the extreme example but it happens everywhere..

Stout Johnson

Quote from: HornetMaX on August 18, 2014, 08:26:56 PM
I don't know in other cases, but in the video above I'm starting to think you're being confused by the camera perspective.

I try ultra hard to find something wrong in the above video but I really don't see it (at least in the video above and in the other one Stout showed me a long ago). Again, maybe I'm just blind but ...
Well, I try ultra-hard to explain it the best way I can. Not sure what else I can do.

Quote from: Forty6 on August 18, 2014, 08:55:18 PM
I totally agree with Stout and Bob. You can see it more in 3rd person view while turning it's like the bike goes slightly the opposite way so you can see more of the side of the bike than you should. Almost like its 'crabbing' like the rear spindle is out of line causing it to not follow the front.
Agreed Forty6. I never ride in 3rd person anymore, but I just did and it was really obvious. I did some laps on Victoria and for me it was particularly noticeable in Lucky Heights.

Thank you forty6 and Bob for joining the discussion! I have been fighting a pretty lonely fight here  :D
    -----------   WarStout Kawasaki Team   -----------

HornetMaX

OK then, make one or two videos of extreme cases.

Or, even better, make the videos and save the replay.

Or, even better than better, make the video, save the replay and also save the telemetry with the telemetry plugin/app (I should be able to take a look at that in 3 weeks though).

It would even be good if any of you (Stout, BOBR6 and forty6) made his own videos/replays/telemetry, as I'm not even sure you're all talking about the same thing.

Stout knows that, for the others: I've shown the videos (the above one and another one Stout made) to a fairly competent friend who has shown it to a very qualified rider (WSBK level) and they found nothing strange (the pro rider even explained some surprising behavior that can happen on fast corner exits on the throttle).

I guess that if we all want to make this clear, you'll have to document it and open a topic in the hope Piboso himself has a look.

MaX.

BOBR6 84

its not an extreme case by any means but its there... brands hatch NC is where you will find an extreme case..

https://www.youtube.com/v/ZzHRT4I9wh8

HornetMaX

Hmm, these are banked corners ...

Just to be sure, where do you see the issue ? In which od the 3 turns (1st left, right, 2nd left) ?

MaX.

Forty6

Hi max, for me Stout has done a great job of doing that already mate. In the video and the stills it shows the nose of the bike pointing to the outside of the track but it's coming towards you. And your right about Lukey Heights at Victoria Stout. As you come over the crest of the left and into the tight right hand hairpin it's all over the place.