Here is the block after a few other features. I obviously paid very close attention to the drive train and suspension… (sarcasm)
I spent just about the same amount of effort on the wheels.
What I did spend my time on was making sure the vehicle dimensions were close as well as the vehicle mass.
Why do I care about mass and dimensions? Because SOLIDWORKS Motion, that’s why! I want SOLIDWORKS Motion Simulation to prove to me that AWD may help you accelerate, but do nothing for stopping distance.
So I created a “road” component and assembled my car on there. Using the SOLIDWORKS Motion add-in allowed me to run a kinematic study using friction, gravity and motors.
I set up contact sets between the ground and the tires, as well as, between the wheels and body. In the contact definition, Motion allowed me to specify kinetic and static friction coefficients. Since I wanted my study to start with the wheels at full velocity, I could essentially ignore static friction. The friction of cold rubber on ice varies quite a bit, so I just chose a value and made sure it was consistent across both studies (AWD and FWD).
I added motors to all four wheels and gave them a rotational velocity of 200 RPM.
- 28″ tire diameter
- circumference = d * pi
- 5280 feet in a mile
- 60 minutes in an hour.
My simulated car should top out at about 16.7 mph. It doesn’t really matter how fast we go, as long as I run the simulation long enough to gain traction, roll at constant velocity, then slam on the brakes (no ABS), and slide to full stop.
For the FWD study, I suppressed the back two motors, allowing them to freewheel. At 17 seconds, all four wheels “lock up.” You cannot have a motor at zero RPM, and suppressing the motor would allow the wheels to spin freely. To adjust for this, I changed the motor speed to 0.001RPM.
For the AWD study, all four wheels start at 200 RPM. The “lock up” at 17 seconds as well.
I calculated both studies and plotted Velocity in the X-direction. For clarity, I copied the data to Excel and overlaid the plots.
Exactly what I expected! Stopping time was completely unaffected! The AWD car was able to get up to speed faster, but with no ABS, and the same mass, both slammed into the car in front of them. 🙂
Obviously, I made many assumptions here and anyone living in the Snow Belt knows that there is more to snow driving than slamming on the brakes. The point of this study was to use Motion to prove that AWD may not always be a safer bet in a low-friction environment. I got to show you some cools tools in SOLIDWORKS, and create some neat plots.
Thanks for reading and as always, Happy Simulating!