Col Fink from down under did a great series of videos on different topics. Here’s one for slip angle.
I have some comments about the video. It started out promising, with the display of a multipoint wheel, but then it started talking about walking, I see no parallel between walking and driving a high-speed kart. The me give you an example. Coming back from Quincy Illinois, in my new 1975 Dodge Maxie Van, I experienced something I had never experienced before. Coming across the salt flats, there was a very high crosswind. It was blowing right to left. I had to turn the steering wheel to the right in order to maintain a straight line down the freeway. I can just imagine what the angle of the tires look like with me turning right to maintain a straight line down the freeway. It became very obvious when we overtook a 18 wheeler driving in the slow lane. The van worked sideways, severely, and I had to turn the wheel straight ahead to avoid hitting the 18 wheeler. I put Mitchell radials on, I think in 1977 and all lot of that problem went away. I know that because driving south on Interstate 5, you get a severe crosswind there and when you drive past a hill, blocking the wind, the van swerved much less. The slip angle was markedly less with the radials. I believe the same thing happens with a kart when you’re making a turn. Raising the tire pressures is a big help. It’s really noticeable on a high-speed induro track like Sears Point. With low pressures, like some people run, maybe because they’re used to doing it on a Sprint track, it’s really noticeable. Turn 11, a high-speed large radius 180, while observing from the sidelines, you could really see it. Now I could be wrong, that may not be slip angle, but it’s certainly better than seeing somebody walking with a side wind. I’m open for discussion.
If the data does not support the theory, get a new theory! (Al Nunley)
Scientific Truth; Fact displaces Theory!
James,
What happened to this fella? His videos were great and then poof. Was Col a racer in Australia or a coach?
I don’t know him pets but Col’s done a lot. I believe he’s been a successful racer and coach to start off. He’s had his own line of chassis and started kartbook (Australian social network for Karting)
The walking analogy I thought was odd, but it probably helped others that aren’t so mechanically inclined.
I think what col was getting at the idea that slip angle doesn’t actually slip. I think he was saying that the contact patch under side load is twisted and orients differently to rim angle.
I have no clue what to do with that bit of knowledge.
Sounds like you need to create a video Alvin.
Ha ha, not much chance of that, a video, although I think it would be fun.
Tell me something, in the video you posted, if the foot steps were on ice, and the wind was blowing, wouldn’t the feet be moving sideways. In his illustrations, the feet are planted solidly on the ground, of course they’re not sliding. In a kart, in a high-speed tight turn, the karts momentum wants to make the kart go straight, but the wheels are turned, so there’s always a little forward momentum added to the turning of the kart, isn’t that slip angle? Isn’t that why, in a fast, tight turn, there’s always more rubber laid down. No rubber on a straightaways. Tell me where I’m wrong!
Al,
Maybe it’s simply that the friction between the tires and the road simply wears down tire. We don’t see our car tires wear slowly over time but they do. I bet it’s same thing. It’s not that we’re sliding about leaving trails of rubber (well, hopefully!). It’s that it’s soft rubber and when it’s being stretched sideways, it will wear a bit faster and some stays behind.
Explain this to me; when I was going down that freeway with the wind trying to blow my van off the side of the road, and I had to turn the wheel to the right to keep going straight, don’t you think those tires were slipping just a little bit? The tires were not pointed straight, they are pointing to the right, the van is going straight, that’s slept angle in my understanding. Maybe I’m wrong, show me, convince me. I will listen to reason anytime anyplace.
It’s entirely possible and likely probable that they were. I’d imagine it’s like a long turn in a sense (the wind). I think it’s entirely possible that the tires do slide slightly, depending upon the force of the wind and the forward velocity you travel at. There’s probably gusts and/or moments when your speed is creeping up where it slipslides a bit?
Having owned a 72 microbus, it definitely slid in wind with big gusts.
But generally I think rubber accumulation is mainly from wear under stress in corner as opposed to sliding being primarily responsible for peeling off rubber.
What happened if you bled off a bit of speed? Still making noise?
Edit: a thought. Don’t the lateral g-forces rise and fall through the cycle of a turn? As opposed to the constant force applied by a crosswind into a sail, basically. That would have an effect on wear.
It can also have both things going on simultaneously I believe. So your truck probably was counter steering and driving on the slip angle while also sliding a bit laterally as speed/gusts occur.
Finally, I ride in slip angle all the time in sim. It’s that incredibly light highly maneuverable feeling while seemingly on rails (the track rubber usually). It feels like the kart is on its toes.
Subsequent vid from col with more:
