Physics concerns

[Furious]

Hi there. I have some concerns that came to my mind lately. It's not like "I don't like it so it must be wrong" but some general law of physics that doesn't seem to work now. Hope to discuss it with users with engineering experience.

First of I doubt that clutch simulation works in proper way. By my knowledge from university of technology where I study torque carried by friction clutch ( used in most petrol engine vehicles) is based on the friction parameter, size of the clutch and the normal force working on the clutch. So with the clutch lever I directly decide how much torque I put on the rear wheel and all corresponding elements (gearbox, chain and everything that has mass). The bike engine with it's spinning mass energy on the passive revs (the minimum revs of the engine to keep going. Ones that throttle closed) with torque it generates should be able to get bike going even with really low acceleration ( keeping in mind that bike ecu keeps the fuel level high enough to not let engine stop.) However in GP Bikes even with the revs on about 7000 its not possible to not shut the engine down, no matter how gentle you are with clutch. If you won't add throtle the engine will stop. If you look at this picture for example http://pirateslair.net/RemusS1000RRFullSysDyno1.JPG you will see that on 7000 RPM bike generates about 90 Nm. So If I will use 40 of it by using my clutch the revs should go down to the level when the forces are equal and the bike should keep accelerating with the torque of more or less 40 Nm. But in GP Bikes revs goes down all the time causing engine to stop.

I have no more time now so I'll finish latter with my other concerns.

cheers.

[HornetMaX]

The bike engine with it's spinning mass energy on the passive revs (the minimum revs of the engine to keep going. Ones that throttle closed) with torque it generates should be able to get bike going even with really low acceleration ( keeping in mind that bike ecu keeps the fuel level high enough to not let engine stop.)

I think that's wrong, you can try on any real bike: if you don't give it a bit of gas when you release the clutch from stand, the engine will bog down and die, no matter how carefully you release the throttle.

Also, I don't think the ECU does what you say: it only controls the idle when the throttle is shut and the clutch fully disengaged. You can check this too on a real bike: get in 6th gear and slow down to 10Kmh ... it will shut off. Idle control does not kick in.

However in GP Bikes even with the revs on about 7000 its not possible to not shut the engine down, no matter how gentle you are with clutch. If you won't add throtle the engine will stop.

Not for me: if I hold the throttle still (so that the revs in neutral are at let's say 7000), when I gently release the throttle without changing the throttle the bike moves off.
But you have to be very gentle indeed. I can start with the revs never exceeding 5000.

At least on the 990.

MaX.

[Furious]

The bike engine with it's spinning mass energy on the passive revs (the minimum revs of the engine to keep going. Ones that throttle closed) with torque it generates should be able to get bike going even with really low acceleration ( keeping in mind that bike ecu keeps the fuel level high enough to not let engine stop.)

I think that's wrong, you can try on any real bike: if you don't give it a bit of gas when you release the clutch from stand, the engine will bog down and die, no matter how carefully you release the throttle.

I have managed to do so, so it is possible.

Also, I don't think the ECU does what you say: it only controls the idle when the throttle is shut and the clutch fully disengaged. You can check this too on a real bike: get in 6th gear and slow down to 10Kmh ... it will shut off. Idle control does not kick in.

Maybe I'm wrong about the bikes. But its there for sure in cars. When you are slowing down on a gear, the fuel consumption is 0 untill revs are lower than planed. ECU gives fuel then. You can observe it on the car with real time fuel consumption dial.

However in GP Bikes even with the revs on about 7000 its not possible to not shut the engine down, no matter how gentle you are with clutch. If you won't add throtle the engine will stop.

Not for me: if I hold the throttle still (so that the revs in neutral are at let's say 7000), when I gently release the throttle without changing the throttle the bike moves off.
But you have to be very gentle indeed. I can start with the revs never exceeding 5000.

At least on the 990.

MaX.

But still, revs should go down AND STOP at certain level. Now its going all the way to 0 if you are not giving it more throttle all the time while accelerating. How much throttle you use to start rolling with a bike? just a little in real life. in GP Bikes you have to use about 80% of it just to not shut your engine down. Maybe I'm wrong, but can someone tell me something like "racing bikes have it like that because..." or something. I just see some problem.

[HornetMaX]

But still, revs should go down AND STOP at certain level. Now its going all the way to 0 if you are not giving it more throttle all the time while accelerating.

Well it all depends on how gentle is your release of the clutch. The still bike has a lot of inertia.

How much throttle you use to start rolling with a bike? just a little in real life. in GP Bikes you have to use about 80% of it just to not shut your engine down.

I have to agree that with beta6 I initially found it more difficult to start compared to previous betas, but I'm not sure it wasn't just due to the break I took from GPB between beta5 and beta6

MaX.

[Furious]

My other problem is related to this video
https://www.youtube.com/watch?v=Ymd4Y83W8tw&feature=youtu.be

I have already seen that you claim that that's ok, but I'm not that sure about that.
What itches me the most is the moment when the bike is finishing the trick. When the bike spins on yaw axis, when the front wheel touches the ground and magically it stops. When the bike spins with the speed like on the video and the force comes from the contact of the tire/track where is the spinning kinetic energy of the bike? When the force is not in line with (basicly speaking) center of gravity, there is no way to act like this. I feel like the spin inetria (kg*m^2) parameter is wrong in some way. Or the positioning of the forces.

The other thing. At some point in the video bike is going backwards on the rear wheel. How is that possible? I asume that no one have used a clutch at that moment so it was tottaly wrong.

Wheel should either slip on the tarmac as the direction changed dramaticly as so the friction forces or it somehow menaged to get a grip it should make a tottal mess with the engine. What was it doing? Engine spining in other direction? I would love to se replay file and analyze it.

Ps. Simulated physics is never perfect. It can't be. But you can be close Piboso

[BOBR6 84]

In GPB sometimes when I loose the rear on the brakes, ( rear wheel slides out too much then grips) im expecting the virtual rider to be launched off the bike.
Instead, the rider stays seated and the bike does a crazy spinning flip! Its only when the bike comes to land the rider falls off..

So.. If the rider was thrown off the bike when the initial flick happens.. Would that stop the crazy flips??
Most things seem to point back at the virtual rider as lots of people have already mentioned.

[HornetMaX]

My other problem is related to this video
https://www.youtube.com/watch?v=Ymd4Y83W8tw&feature=youtu.be

I have already seen that you claim that that's ok, but I'm not that sure about that.

Actually in my comment I was referring to the MXB crazy spin one, not this one.

What itches me the most is the moment when the bike is finishing the trick. When the bike spins on yaw axis, when the front wheel touches the ground and magically it stops. When the bike spins with the speed like on the video and the force comes from the contact of the tire/track where is the spinning kinetic energy of the bike? When the force is not in line with (basicly speaking) center of gravity, there is no way to act like this. I feel like the spin inetria (kg*m^2) parameter is wrong in some way. Or the positioning of the forces.

The other thing. At some point in the video bike is going backwards on the rear wheel. How is that possible? I asume that no one have used a clutch at that moment so it was tottaly wrong.

Wheel should either slip on the tarmac as the direction changed dramaticly as so the friction forces or it somehow menaged to get a grip it should make a tottal mess with the engine. What was it doing? Engine spining in other direction? I would love to se replay file and analyze it.

Not to say the the whole thing is realistic, but in the video above you see the smoke when the rear wheel lands moving in the wrong direction, hence it's slipping.

MaX.

[EdouardB]

A lot of things are possible on a motorcycle if you train enough...
https://www.youtube.com/v/MqyW8NlNwuA&list=UUR9WFt5mZmzvUS7uHQeUdCg

[yoshimura]

the front is never lost, not in this simulation.Positioning of the rider makes all the difference.

https://www.youtube.com/watch?v=-Ld1IxqToJA