Polar Moment of Inertia 2

Polar Moment of Inertia 2

In this video I dive a little deeper into an important physics concept – polar moment of inertia. Not only will this add value to your motorsport knowledge base, but it will show you why vehicle weight distribution is so important.

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Video Transcript

Hey again everyone. Matt Covert here from howtobecomearacedriver.com. And I’m going to backtrack just a little bit here in this video. I already did a video previously about polar moment of inertia but I’ve been thinking about it and there’s something else that I really wanted to touch on. So I’m just going to add a little big to what I said last time and I think that will be valuable.

So let’s hop right in. So in the last polar moment of inertia video I showed you that having weight further away from a fulcrum makes it more difficult for these weights to change direction, OK? In the last video I went and showed you how that applied to a racecar.

Right? And I told you that one of the solutions to this weight changing issue is to simply move weight inboard, further toward the center. And then it becomes much easier to move this weight back and forth.

Well there is another solution and it’s pretty common on racecars as well and I wanted to make sure I hit on that because it’s pretty important. So the other solution to having large weights on the outside is to simply decrease the size of the weights. OK? So there’s less weight on the outside and now it becomes easier to move these back and forth and that has the same kind of effect as moving the heavier weights in toward the middle.

So let’s go ahead and talk about how that applies to a racecar. Let me just draw out a couple of these wheels again like we did last time, like that. There. Alright so now we’re looking at the front end or read end of a vehicle from one of the end sides, whichever way. Alright? So this applies directly to your chassis, OK? And it’s pretty simple. If you get, or acquire, a wheel that weights less than the one you have now, than you’ll have the same effect as moving that inboard weight in, like having the inboard mounted shocks or inboard mounted brakes or something like that.

OK? And it’s so much easier of a solution because requires a huge amount of engineering to move all these parts. But simple, a lighter weight on the outside of the vehicle, or rather a lighter wheel, will get you a better polar moment of inertia. And it’s pretty much as simple as that. And this also starts to cross into another concept, which is rotating mass, well also has an effect on how well an object can change direction while it’s spinning. Or unsprung mass and actually we could go a couple different directions there.

But those are different videos. I’m going to end this one there because all I wanted to do was just make sure I got this lighter wheel concept into your head, it’s pretty important.

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