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Topics - Nathan Dunnett

General Discussion / Aero drag
May 29, 2013, 08:00:02 AM
Is it just me or does it seem far too excessive? I didn't realise until I made up engine files for a KT100J based off a real dyno sheet from one of our own engines, and I could barely go over 80 km/h at Lonato. I even made sure it permanently had perfect carburetion and optimum temperatures so that I was getting full power from the engine. Using the same gearing in real life at a track with a shorter straight and a tighter corner leading on to the straight this engine easily does 90-92 km/h without draft or ducking. I had to give the engine way more power than what it realistically has to get almost normal speeds out of it, and then if I tried to duck I would get like an extra 6-7 km/h whereas in real life it's more like 1-2 km/h tops if you're lucky and there is a head wind. Just by ducking I was gaining 1.5 seconds per lap at Lonato which is completely ridiculous for low speeds in good conditions. I haven't been on track with another kart that wasn't blinking and warping all over the place yet but I imagine the draft effect is massive, can anyone confirm this?
I was thinking about how we only have a handful of chassis here and how if the chassis files were to be unencrypted it could get messy with 3rd party mods, so here is my suggestion. Instead of have 'kart' mods, we could have 'class' mods where the class sets the rules and you select the chassis, tyres, engine, etc based on the class rules. I'll use a Tony Kart/Vortex/KZ1 with control dry and wet tyre as an example, something like this with the following parameters could be good:

chassis_id = tkracer
chassis_name = Tony Kart Racer EVK
year = 2013
bodywork = tonykart

front_brakes_hand = 1 // you can fit KF style front brakes to this kart
front_brakes_foot = 1 // you can fit KZ style front brakes to this kart

*brakes details*

axle30 = 0 // you can't use 30mm axles, there are no suitable bearing carriers
axle40 = 1 // you can use 40mm axles
axle50 = 1 // you can use 50mm axles

*chassis details*

engine_id = vortexkz
engine_name = Vortex RVXX
category = kz1

*engine details*

tyre_id = mgfz
tyre_name = MG FZ
category = CIKM

*tyre details*

class_id = kz1
class_name = KZ1

engine_control = 2 // 0 = list of engines, 1 = single engine, 2 = category of engines
engine = kz1

tyre_control = 0 // 0 = list of tyres, 1 = single tyre, 2 = category of tyres
tyre = mgfz, mgwz

chassis_control = 0 // 0 = any suitable chassis, 1 = single chassis, 2 = list of chassis
chassis = // not applicable, open chassis

front brakes = 2 // 0 = none, 1 = hand, 2 = foot

minimum weight = 175 // automatically adds correct amount of ballast, allow the user to position ballast in setups


That's just a very rough example, but this way you can set up the classes, then as engines and chassis are added nothing extra will need to be modified for them to work. It does kinda add loopholes for people to make super engines to use in a class however mismatching should take care of that, or you could just list the engines to use instead of using the category method. At least it's only one file that would need to be changed for extra engines. Thoughts?
General Discussion / Physics Analysis
April 12, 2013, 12:47:28 PM
So, I've done quite a few laps the last couple of weeks getting a good feel for the sim and learning it's quirks, and I think now I am familiar enough to give a rundown of the physical models and post my thoughts.

The tyre model is probably both most important and hardest to get right, making it the most critical component of any automotive sim. IMO the tyre model for KRP is pretty good but it isn't perfect. My primary issue is that there is way too much sidewall deformation before the contact patch breaks into slip, this can be demonstrated by driving a kart to half speed, then locking the brakes and flicking the kart sideways to get to 90 degrees slip angle and wait for the kart to slide to a stop. Once stopped you'll notice the kart slingshot back the other direction when the spring rate of the sidewall exceeds the lateral force. IMO the sidewall stiffness is both too low and too linear. At low lateral force it needs to be a bit stiffer, and at high lateral force it needs to be much, much stiffer. It also feels like the tyres are too load sensitive where they make lots of grip at high loads, but that might just be a by-product of the soft sidewalls.

I'm not sure how complex the chassis flex modelling is, but it feels like the chassis are too stiff in the waist which doesn't allow enough twist in the chassis. This makes the rate of lift too fast which makes it much harder to carry the inside rear wheel unless you increase the mechanical jack a lot (more caster, ackermann, stiff front end, etc.) and use a really soft rear end to get off the corner (40mm soft or 30mm hard axle, loose side pods and rear bar).

I'm not sure how complex the axle modelling is either, but it feels as though they are only corner springs with spring rate being the only difference. If true, this is a critical flaw IMO as axles are very important to the way a kart handles. The axle makes a big difference in the way the rear end of the chassis flexes. Each different axle design IRL is separated by both the cross section and the grade of steel. It is generally not fully understood, but the different axle grades tend to have different damping properties and resonant frequencies which has a big effect the way they behave on track. Generally hard axles are made of high grade steel and soft axles are made of low grade steel, soft and hard axles with the same cross section feel very different even though according to Young's modulus they should have the same stiffness. Adjusting the hub size would also be good.

I have some ideas for the setup page but I'll post them another day in the suggestions forum. :)
Download the latest .zip and extract directly to your KRP directory.

Download Version 0.14

- Updated for beta 9 compatibility
- Slight engine inertia tweak
- Slight torque curve tweak
- Adjusted intake and carberation settings
- Readjusted ballast settings
- Switched graphical model to F100

- Fixed wet tyre issue by adding another slick compound
- Raised rev limiter to 16000 rpm

- Fixed issue causing the engine to seize at the rev limiter

- Fixed issue causing CRG and Birel to be unplayable

To do
- Match torque curve to real dyno reading
- Update graphical model (under progress by LauZzZn)
- Further refine engine inertia setting
- Readjust temperature and radiator parameters to match real life
Setups / Starting Setup / Setup Guide
November 10, 2011, 06:46:38 AM
EDIT: Old info, to be updated.