Racing and physics, weight does matter

A couple weeks ago I wrote Does Weight Matter? about trying to find the best weight for a car. Well, it’s safe to say that total weight will effect your car, I just didn’t come to any conclusion for the ideal weight. I also stated that a balanced car is key. Turns out that is completely, utterly wrong – thanks science.

Taking the fun out of it

Great Scot!

Up to and after writing that article I continued to work on cars in an effort to get them balanced and focused more on total weight and less on the distribution of weight. Well, turns out our old friend physics has shown me the way. And yes, I’m sure if you are a physics-minded person you already had this figured out, but for the rest of us…probably not.

The one gripe I have against hard science is it sometimes takes the fun out of trial-and-error. Coming up with your own theories and then testing them is half the fun. You think a car will be fast, you race, and you find out. But as I tried different weights on different cars with much of a pattern, I finally said, “there has got to be a trick.” I am science-minded enough to know that physics makes a difference, I just didn’t know where or how much.

I did some research on our pinewood derby cousins. I remember doing the pinewood derby when I was a kid and that probably lent directly to why I love racing Hot Wheels today. Instead of working with wood, I’m now working with metal…and at a much smaller scale.

Physics, she is a harsh mistress

If you undestand this, you're smater than me

I found several sites discussing the physics of pinewood derby racing. The consensus is that most of the weight of a pinewood derby car should sit in the bottom-rear (back corner) of the car. Based on what I could figure out from the reading and glazing over of formulas, when going down a hill, you want the weight to fall as far as possible when released from the starting gate. This is because gravity+weight is what will give the car its speed, basically, especially when it comes to the home stretch. Keep in mind this (may) only apply to derby-style tracks, like the official Redline Derby track. It may not apply to downhill tracks.

My only hang up with weight was the scale. Pinewood derby cars are up to 7-inches long and somewhere around 7-ounces. Hot Wheels are barely 3-inches and less than 2-ounces. I wasn’t sure if that weight distribution mattered at such a small scale. Well, with help from a physics friend, I’ve learned that it does apply at the 1:64 scale…science scales well until you get to the super micro level. (Boy I wish I would have paid attention in physics class)

Balance is overrated

A faster race car?

So when I said a balanced car is key – I was wrong. Sorry. That data was based on my own tests and trials. Cars that were balanced seemed to perform better than those that weren’t. But I was only checking for balance. I never tested for alternate weight distribution, either to the front or the back. Shame on me.

I haven’t done a lot of testing with the weighted rear theory, but physics isn’t wrong. It will work and it will make a difference if you put weight in the back end of your car. How much weight becomes the variable that needs testing.

Of course, weight isn’t the only factor and I don’t believe it is the most important factor either. Wheelbase, axle stability, and car width will effect performance far more than weight…I don’t need science to tell me that. But knowing what should happen when handling weight is a big advantage.