I have a chassis question for the chassis gurus on here.

I have to add this. It's indoor season and there isn't anything much cooler then watching a kart fly around the track with all four tires looking like there glued to the track. I'll bet when "real race car racers" see it, all they can say to themselves is "how the heck can they do that". ... :)
 
I know it's late but I'll give it a chance. So far I've tried to explain how I theorize a staggered solid axle works. Rotating the back is something that needs done or else your going to have to turn it with the fronts. Reduce the need to turn it as a whole or reduce the need to put effort into turning the RR because the LR has been unloaded; either way the axle in the back has got to be turned.

I've been trying to come up with some analogy on it and just can't find one. I'm racking my brain trying to relate turning the axle or rotating the back to doing something. What came to mind was digging a hole. I guess I'm good at digging myself into a hole and that's why it came to mind. But if you do dig a hole you need tools to do it. Rotating the axle is something you need to do and you need tools to do it. A hole is simple, all you need is a shovel. To rotate an axle you'll need caster, camber, kpi, weight jacking and a lot of other tools. When you dig a hole you move dirt. When you rotate an axle you move weight. You won't get a hole dug unless you move dirt and you won't get a staggered solid axle to rotate, unless you move weight. When your done with your hole you'll have an intangible hole which you can only show or explain it's existence in relationship to something else. When your axle is rotated you'll also have an intangible thing which you can only show or explain it's existance, in relationship to something else. ... told ya up front I just can't come up with a good analogy. ... :)

Anyhow, you know to dig a hole you have to dig dirt. And now you also know to rotate a staggered solid axle, you have to apply the difference in tire surface speed, in a particular specific way to the track. or not ?
 
kmoody6 said:
Very good point Bryan. Lol

Paul, you have to have a "complex force" to cause the axle to spin.
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Would Newton 3rd law 'simply' put the two systems as the right and left rear tire to get axle rotation? Each end would not only gain or loose on it's own because of joint input and individual input, but because of the connection effect each other... and ?

edit: that led me to think any input from the fronts, needed or not would magnify what's needed from the back. hummm... and while writing this it makes me think it also puts proof to being able to go faster, the more you lessen input from the fronts. maybe ?

edit again: I'll even go so far as to define input or what the fronts do only in terms of turning effort. It means it doesn't matter one bit how much load the fronts carry, so long as the load does not in itself, get the fronts involved with turning.

theory is fun
 
paulkish said:
edit: that led me to think any input from the fronts, needed or not would magnify what's needed from the back. hummm... and while writing this it makes me think it also puts proof to being able to go faster, the more you lessen input from the fronts. maybe ?


theory is fun
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I will agree that driver smoothness through a corner normally correlates with faster lap times, but it's not necessarily because you went a faster speed.
 
I sorry I didn't bother to dig up the reference to the difference of rear tire surface speed, but you always refer to the left being slower than the right. Which is technically true, but we have the LR is preloaded to the point that we are constantly driving off this tire. The face that the RR is going a "slightly" faster speed isn't causing any resistance.

We are taking a about an adjustment that we normally use a 3/8th" range for (7/8"- 1 1/4”) and if I'm uneasy about the stagger we need, I'd rather error on the side of too much. There is so much slip in all the tires, especially the rears, and due to this there is no telling what the true stagger we are running.This slip is tearing of the surface of the tires, if you have absolutely none of this you have no bite.
 
"The face that the RR is going a "slightly" faster speed isn't causing any resistance."

Your statement is absolutely true only if your traveling in a perfect circle, under constant conditions.

With any other conditions, one rear tire or the other rear tire or both rear tires, must slip.



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I should not put what's below in the same reply, but I'm throwing it in anyway for for someplace to put it so I can read it later.

I've never tried to define slip before as it pertains to a solid staggered axle. For my first try I'll say: "Slip between the two rear tires occurs when one tire releases from the track at a different rate then the other or when a tire releases from the track different from the speed it's traveling across the track.".

... there's all kinds of stuff coming to mind putting conditions on the definition. The first thing which comes to mind is if I assign a rate to slipping, I'm going to have to also mix in somehow each tire having a different rate of surface speed and each having a different rate which can be compared to how fast it's traveling across the track.

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ain't this fun
 
Tires always slip, if there is no slip there is spin. Tires grip level improves with a certain amount of slip and of course there is a point where there is too much. Internal prep helps adjust this.

Slip occurs on all tires constantly, not just those on the solid axle.
 
paulkish said:
. For my first try I'll say: "Slip between the two rear tires occurs when one tire releases from the track at a different rate then the other or when a tire releases from the track different from the speed it's traveling across the track.".


ain't this fun
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This is more of a definition of tire hop.

It's been a while since I studied tire slip and slip angles , but I'm wanting to say that optimum was estimated between 7-15 degrees. That the testing equipment is expensive and those that do test guard the specifics.
 
paulkish said:
"The face that the RR is going a "slightly" faster speed isn't causing any resistance."

Your statement is absolutely true only if your traveling in a perfect circle, under constant conditions.

With any other conditions, one rear tire or the other rear tire or both rear tires, must slip.


ain't this fun
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We are going at almost a constant circle. One of my rear tires is going to slip more than the other on a "straight away". I'd rather have it be a tire that will spin faster (therefore not causing resistance), weighted less (because we only make left turns), and with more surface area (to help dissipate heat)
 
Tire hop is when there's "too much" grip, and the contact patch binds instead of slipping, then exceeds the grip threshhold and pogos at a rate determined by the sidewall stiffness and cornering forces involved. Usually proceeds to "bicycling" if the driver's smooth (and track is too), which can be saved by countersteering, or if continued, can result in a traction-induced flip. (see: r/c cars: traction roll).

The optimal slip on a contact patch is somewhere around 5-10 degrees on most big car tires. Not sure if it's even been quantifiably measured on karts. Paul's right that the only way not to have slip would be low speeds in a perfect, steady speed, circle.

In my view, you can either get the kart to rotate via a leftward force at the front (inefficient -- you're fighting the rear tires and causing scrub at the rear), via a yaw moment at the Cg caused by unweighting the LR so that the RR "pushes" the kart to the left about the Cg. or via a yaw moment about the center of the rear axle caused by the stagger in that the RR is trying to cover more ground that the LR because it's bound to the same RPM but has a higher surface speed due to larger diameter.

I prefer to balance the yaw moments so that the stagger isn't excessive and causing major scrub down the long side of the elliptical racing line, and the LR isn't so unweighted that it can no longer contribute to resisting lateral force. I prefer a loose setup to tight so that I can always change direction very positively if needed.

There is one additional way of inducing yaw -- breaking the rear tires loose under power so that centripetal force carries the rear outward and the effective path of travel becomes a midpoint between direction you're pointed and direction you used to be going....see: WoO sprint cars. There may be a place for this in UAS-level power karting, but stockers just lose speed this way...
 
1. "In my view, you can either get the kart to rotate via a leftward force at the front (inefficient -- you're fighting the rear tires and causing scrub at the rear)"

I agree inefficient.
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2. " via a yaw moment at the Cg caused by unweighting the LR so that the RR "pushes" the kart to the left about the Cg."

I think it's impossible for the RR to push the kart around the CG with the LR light. I think 2 is the same as 1, with added inefficiency because of also having to drag the LR.
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3. "or via a yaw moment about the center of the rear axle caused by the stagger in that the RR is trying to cover more ground that the LR because it's bound to the same RPM but has a higher surface speed due to larger diameter."

And that will only work on a perfect circle.
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4. "I prefer to balance the yaw moments so that the stagger isn't excessive and causing major scrub down the long side of the elliptical racing line, and the LR isn't so unweighted that it can no longer contribute to resisting lateral force."

And that's generally what's done sprint or road course racing, per accepted theory about how to get around a corner. The elliptical nature of the sprint and road course thought process, also adds to inefficiency.
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5. "There is one additional way of inducing yaw -- breaking the rear tires loose under power so that centripetal force carries the rear outward and the effective path of travel becomes a midpoint between direction you're pointed and direction you used to be going....see: WoO sprint cars."

IMHO, that is not how WoO winged sprint cars work. That's how people in the stands percieve they work and those who race "real race cars" which turn both left and right think they work.
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6. Then there's the way I explain how a staggered solid axle works, when being used in an ideal way. ... :)

I don't think you see it Ted, your making it too hard and complicated. It's not about yaw or rotating anything around anything else. It's about being able to physically slow the left end of the axle down via the LR tire being physically engaged with the track, going into the apex. And allowing the right end of the axle to roll around the LR tire, because the RR tire is physically engaged with the track.

Then maintaining the status quo as needed.

Followed by starting your acceleration off of your already loaded smaller low gear LR tire. And on to exiting from the apex by controlling how you push the bigger RR tire into the track, allowing it to continue staying ahead of the LR tire as needed.

Two other cool things about it are you can maintain the length of the apex as needed and your already ready for the next turn with the LR loaded. It's already pre-loaded because by the end of the straight, your by definition going straight.

There ain't no way any Winged sprint car driver wants to slide anything. All they want is grip to put the power to it and go. The only reason you see any dirt car sliding is lack of grip. Ideally when you put the power to it, corner or straight both rear tire will be driving it with maximum grip in the direction you want to go. IMHO, it ain't about matching up slip angles, it's about hitting matching maximum slip ratios at both rear tires, that make the total axle assembly head in the direction you want to go, at minimal slip angles.

maybe, because it is all just IMHO and ain't necessarily right anyway. ... :) but I think it's pretty darn close, except for I'm winging it and writing as I go and will miss connections along the way.

... and yep, me not being educated, I think I very likely just dug myself into a hole.

edit: Were not far apart on our thinking, I totally agreed with you on the first item. ... :)
 
Watched Midwest Racing Series in Battle Creek last night.

Darn if the fastest stuff except for the Lawn Mowers, were the ones also had their LR planted the hardest. ? Hummmmm ... How the heck could that be with two different size tires on the back and running both varying turns and straights? At least that's what I saw, or forced myself to see. nawwww, didn't force anything, that's what happened !

maybe, because this is all IMHO and ain't necessarily right. ... :)
 
The funniest part of this thread is when you told Ted HE was making it too hard and complicated. I bout spit Dr. Pepper all over my computer!!!

In the above post you mentioned the fastest stuff appeared to have the LR planted. You speak of this as if it's some sort of new revelation. Karts have been untilizing the LR more and more since at least 2004.
 
rebsfan4 said:
In the above post you mentioned the fastest stuff appeared to have the LR planted. You speak of this as if it's some sort of new revelation. Karts have been untilizing the LR more and more since at least 2004.
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Maybe he finally got it!

Nope, never gonna happen.
 
kdm said:
Maybe he finally got it!

Nope, never gonna happen.
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I think he does. He just goes about the looooooooooooooooooooooooooooooooooong way of posting it.

Ask him about stagger on a solid axle. Go ahead....I dare ya. Lol
 
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