Motor Coach Industries International Inc. MC-9

Alexander Knoll · Oct 15, 2011

Hello all,
the first public BETA 1.07 is up at my site....

...have fun!

...i'm happy for all comments...

LG
Alex

EDIT: ups...PLEASE read the readme for full credits! ....and yes i have permission....

boomer541 · Oct 17, 2011

Alex,
I fixed the brake balance Qlog error and attach the car.ini file so you can see what I did. Also noted that the rear wheels weren't being powered proprly, you had 2/5 instead of 4/5.

Also try running this beast round Forest park and see what happens when you try to go thru the turn right after the michelin sign.

Alexander Knoll · Oct 17, 2011

Hello Bob,
THX, but it was my intention to use wheel 3/4 via the diff and 2/5 via the power gearing...because if i power them like you, the right way, i know.. i had many times the problem that the bus don't move, only wheel spin at the moment when one of the rearaxles was in the air...at huge bumps or high curbs....
...the other thing...is, i think a fault at the suspension or his mass from ~17t ^^...i have this only with the high body mass...if i reduce it to a "racer frendly" mass from ~6t-8t...there is no problem....but i don't know how to fix this...

Ok....you fixed the brake QLog, but that can't be right!
I had the brake ballance 0.6 (60%) front and 2x0.2=0.4 (40%) at the rear =100% but a QLog...
You use 0.6 (60%) at front and 0.45 (45%) at rear =105%!!! and no QLog....
I can't understand why this works so.........

THX Bob for your comment, i think i change it to this way!

..btw...76 views, 21 downloads...and only 1 comment...respect...

Cosmo° · Oct 17, 2011

Thanks for the bus, I tried it yesterday already but had no time to do some basic research before commenting until now.
The reason why the qlog message disappears with boomer's brake settings is because Racer counts (60+45+45)/3=150/3=50% per axle.

Even if it's a hack, I like the approach with assigning the differential across multiple axles - but obviously, I wish Ruud would just allow us to use several differentials and end this silly restriction. It's just ridiculous to get stuck on a tiny kerb or rock while you're driving a multi-axle offroader for example, or a bus like in this case.

car.ini is a bit wonky at the moment I think - qlog lists a lot of lines it can't read, because there seem to be some unfortunate semicolon placements, which prevent entire sections from being detected properly. Also, there are some outdated or mixed (old/new) definitions like the differential sections, anti_pitch etc. There also a second traction_control listed at the end of the file, so overall it needs a bit of cleaning up

There's no caster_offset defined, so without the artificial friction forces, the steering is completely numb.

The centre of gravity height seems to be on the low side. The bus is a bit over 3m tall, so a first guess would perhaps be ~1.3m instead of 0.965m?
Regarding the total mass, most spec sheets give 27500lb, which is around 12.5tons - I assume that is empty, maybe even dry mass. With 50 people each 75kg, some luggage, fluids and so on... say those add up to 5tons. You then end up at 17.5tons, compared to the current 18.5tons of the model. If the luggage is a bit heavier, I think that evens out too

One of the comments in the .ini says engine.mass is included in body.mass - that's not correct. Every individual mass in car.ini is added together for the total mass (for pedantic readers: smd camera masses excluded ^^). So, body.mass, engine.mass and wheel.[...].mass values all go together. For clarification: You include passengers, payload and fuel in the body.mass.

I only did a rough calculation for the spring and damper settings, it seems the springs are a bit stiffer than I would expect for a bus. Assuming that the current total mass represents a fully loaded vehicle, you get natural frequencies in the range of a little under 1.5Hz. Take out the passengers and that numbers goes up some more. There are a lot of opinions about suggested frequency ranges for different vehicle types, but to give a real world comparison, 1.5Hz is beginning to be quite sporty - Honda NSX, Impreza WRX territory. Personally, I would probably try to get around 1.1Hz for the MC9. The air suspension means that in real life you maintain a constant frequency, regardless of load, but that's not possible in Racer where we only have traditional springs. So I would aim to stay fairly close to that number in empty state and let it drop a bit for the fully loaded condition all naturally by itself (due to the increased mass, a steady spring rate will result in a lower natural frequency).

In the workshop manual I found for the MC9 (http://www.buses101.com/mc9_maint_manual.htm), they list different transmission ratios and options, but that's not a big deal for vehicles where there are so many varieties. They also give alignment specs, so camber, caster, toe and kingpin can be set properly for the front axle (that helps with the force feedback).

You mention the mass of the bus giving issues in Racer - I found that it's normally doing an OK job for most heavy machines (say up to 20tons or so), but above a certain point you might have to increase the force and torque limits in racer.ini. I used to do that for the Tatra 813 development, but it resulted in nasty bugs where normal issues when going over a kerb or driving over small gap in the road mesh would send the wheels shooting into the sky like crazy, because the limits didn't restrict them anymore. So it's actually better to leave the limits at their default settings for now. I mentioned this to Ruud last year or the year before, but yeah, it's not something their commercial customers regularly deal with, so it's not a priority for them to look into these things. One of the things he did change after my suggestions was the increased load range in pacejka player so that heavy vehicle's tyres can be set up there at least - but again, it's a bit of quicky job, where the steps are now too big and the whole thing gets tedious to work with... XD

Alexander Knoll · Oct 17, 2011

hmm...THX Cosmo°, i will see what i can do...
..at first i have to translate it^^ i understand no word :wink:
I know the site with the manual...this and many others have verry different infos about near every thing...so i have to choose some thing in the middle...
This braking thing is some thing i'm not understand...so racer gives no QLog when you use 150% for the brakes?
...i know the cog is to low...(3,127m/100*38=1,18826m)...but the he flips over all time...so i reduced it.....i have to look for it...

The mass i got from this:

I know i have to read and learn a bit more about suspensions...to understand this camber, caster, toe and kingpin things.....

...for the next BETA i clean up the ini!

THX

Alex

Cosmo° · Oct 17, 2011

The qlog message about brake bias says that Racer looks for an average of 50% of the total brake factor to be assigned for every axle. In an example with two axles, brake_factor for the front could be 0.6 and for the rear 0.4, because (0.6+0.4)/2=0.5. For this bus with boomer's numbers, you have three axles so you add up the front once and the rear twice -> (0.6+0.45+0.45)/3=0.5.
Another example, on the Tatra I use braking_factor=0.5 on all four axles, thus (0.5+0.5+0.5+0.5)/4=0.5 and qlog is also happy.

Cruden boys probably never played with a vehicle that has anything but exactly two axles, so for them it makes sense to force an average of 50% brake_factor per axle because it will always add up to 100% for the entire vehicle. Their definition is just suddenly not making much sense anymore if you add more axles, because as you noticed, the total brake factor becomes more than 100%.

I guess the logical solution would be if Racer didn't look for this 0.5 average, but rather check if all brake factors add up to 1.0...

The image you posted shows GVWR, which is gross vehicle weight rating. This refers to the maximum this vehicle is legally allowed to weigh for safe driving. So, that is basically supporting what I assumed in my previous post, that the bus model right now is fully loaded up.

I'll drop you a PM so you don't have to use a translator for that other post of mine

1977malibu · Dec 17, 2011

every time i start out with the bus on any map the front of it falls through the map...like the wheels are under the road

Alexander Knoll · Dec 17, 2011

yes this is a known problem...i'm on the way to fix this, but the last month i had not much time for racer, so i please you to give me some days...
A quick and dirty fix is to reduce the body mass in car.ini to ~13000kg and to use this settings in suspension:

Code:

susp_front
{
  y=-0.24
  z=4.42
  restlen=0.54       
  minlen=0.19
  maxlen=0.57
  bumpstop_len=0.10
  bumpstop_k=100000
  k=142075       
  bump_function=2
  bump_rate=13000
  bump_max=3000
  reboundstop_len=0.10
  reboundstop_k=90000
  rebound_function=0
  rebound_rate=9000
  damper_curve=damper/BilsteinDamperLevel_5.crv
  anti_dive=0.2
  anti_lift=0
  anti_pitch=0
  roll_center
  {
    x=0
    y=-0.571    ;~50 cm
    z=0
  }
}
susp_rear
{
  y=-0.24
  restlen=0.54   
  minlen=0.19
  maxlen=0.57
  bumpstop_len=0.10
  bumpstop_k=100000
  k=105362;105361,44*2Axles=210722,88
  bump_function=2
  bump_rate=6500
  bump_max=3000
  reboundstop_len=0.10
  reboundstop_k=90000
  rebound_function=0
  rebound_rate=9000
  damper_curve=damper/BilsteinDamperLevel_6.crv
  anti_rise=0.15
  anti_squat=0.25
  anti_pitch=0
  roll_center
  {
    x=0
    y=-0.514    ;~60 cm
    z=0
  }
}

...but it's not perfect...

1977malibu · Dec 19, 2011

Alexander Knoll said:

yes this is a known problem...i'm on the way to fix this, but the last month i had not much time for racer, so i please you to give me some days...
A quick and dirty fix is to reduce the body mass in car.ini to ~13000kg and to use this settings in suspension:

Code:

susp_front
{
  y=-0.24
  z=4.42
  restlen=0.54     
  minlen=0.19
  maxlen=0.57
  bumpstop_len=0.10
  bumpstop_k=100000
  k=142075     
  bump_function=2
  bump_rate=13000
  bump_max=3000
  reboundstop_len=0.10
  reboundstop_k=90000
  rebound_function=0
  rebound_rate=9000
  damper_curve=damper/BilsteinDamperLevel_5.crv
  anti_dive=0.2
  anti_lift=0
  anti_pitch=0
  roll_center
  {
    x=0
    y=-0.571    ;~50 cm
    z=0
  }
}
susp_rear
{
  y=-0.24
  restlen=0.54 
  minlen=0.19
  maxlen=0.57
  bumpstop_len=0.10
  bumpstop_k=100000
  k=105362;105361,44*2Axles=210722,88
  bump_function=2
  bump_rate=6500
  bump_max=3000
  reboundstop_len=0.10
  reboundstop_k=90000
  rebound_function=0
  rebound_rate=9000
  damper_curve=damper/BilsteinDamperLevel_6.crv
  anti_rise=0.15
  anti_squat=0.25
  anti_pitch=0
  roll_center
  {
    x=0
    y=-0.514    ;~60 cm
    z=0
  }
}

...but it's not perfect...

i did that and the wheels ended up inside the buss XD!!!!! i aint complaing tho take your time

Alexander Knoll · Dec 19, 2011

hmm...i use this atm and it works...maybe you over write one of the "{/}"....

boomer541 · Dec 20, 2011

The car.ini that I posted (as an attachment 7-Zip file) works quite nicely.

Any updates should be posted as attached 7-Zip files, easier to use than copying a bit of code.

just have to watch the bumps.