Chassis math formulas

OK I made up !y contact patch's.
Figured my lateral transfer using 1.5 G's.
Calculated my front amount , patch size increased.
Not sure where to go with this from here.
Obviously the left side lost weight and the right gained.
Biggest thing I see is contact patch size using s simple oval for my sq inch.
Smaller than I would have assumed.
Not knowing my cg I used 6, likely not high enough so real numbers
would gain some.
I feel like I am missing something just not sure what.
 
flattop1 said:
OK I made up !y contact patch's.
Figured my lateral transfer using 1.5 G's.
Calculated my front amount , patch size increased.
Not sure where to go with this from here.
Obviously the left side lost weight and the right gained.
Biggest thing I see is contact patch size using s simple oval for my sq inch.
Smaller than I would have assumed.
Not knowing my cg I used 6, likely not high enough so real numbers
would gain some.
I feel like I am missing something just not sure what.
Click to expand...

Biggest thing is to make changes to chassis. I like to use no goats sheets so I know what direction the change should take me. After first time, simply looking at sq in will be sufficient to see what changes. I want to talk about contact patch shapes, but I haven't got that far yet. I always like to use a square or rectangle for contact patch just for illustration purposes. Use the same widths as the tread on tires you run.
The idea is to know what happens to contact patch when changes are made. Some things will become obvious. Some things change not where you believe.
Thanks for hanging in there to get this far.
 
Biggest thing with frt patch shape is going to be camber.
We run high rt cambers so patch size will change as well as shape.
That's where the dynamic would come into play.
 
flattop1 said:
Biggest thing with frt patch shape is going to be camber.
We run high rt cambers so patch size will change as well as shape.
That's where the dynamic would come into play.
Click to expand...

Agreed. Just wanted to be able to see what effects of changes already talked about do before muddying the waters with fine tuning.
 
Look just because you have a theory and got it to work on paper, doesn't mean that it will actually work.
95 Shaw, I mean no disrespect, but do you race , or just stand at the fence and watch. I can't believe that you get on here and ask a question, and then turn around and start giving answer's.
Dude, your thinking way to hard on this. Getting a kart to do what you want it to do can be something so simple, or it could be starting over. In my experience racer's sometimes just over think thing's. That's why many years ago I bought a very good setup guide book, and with 20 plus years of racing karts I'm pretty good at setting one up. I don't always win but sometimes I do.
The most important thing is to have fun doing it, when it stop's being fun then I'll quit.
 
krtrcn said:
Look just because you have a theory and got it to work on paper, doesn't mean that it will actually work.
95 Shaw, I mean no disrespect, but do you race , or just stand at the fence and watch. I can't believe that you get on here and ask a question, and then turn around and start giving answer's.
Dude, your thinking way to hard on this. Getting a kart to do what you want it to do can be something so simple, or it could be starting over. In my experience racer's sometimes just over think thing's. That's why many years ago I bought a very good setup guide book, and with 20 plus years of racing karts I'm pretty good at setting one up. I don't always win but sometimes I do.
The most important thing is to have fun doing it, when it stop's being fun then I'll quit.
Click to expand...

Yes, I race. Been involved since 1982. I field my own IMCA modified and a kart for my daughter.
Lots of people have helped me along the way. I want to give a little back. It's good you have all the answers you need. I've always been frustrated that everyone assumes it is all common knowledge. If there is something someone can use, great. If not, I only wasted my time, because no one is forced to read or use this.
 
95 shaw said:
I have noticed how easy it is to tear things down. I challenge you to build something instead.
Click to expand...
I don't pretend to be a front end guru, but I'm always wondering about it. You talk about scrub radius, but as I understand it, from Wikipedia, the scrub radius point on karts is not even on the tire. And this is a dirt kart right front spindle looking from the back, Sprint karts have the tire even farther out. I'm only trying to understand this better.

You see the point, I understand to be the scrub radius point, doesn't change with a change in camber, not with the way it's changed on karts
 

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It could be just me but it looks like your spindle build Angle changed.
That afects scrub, as does moving the tire out on the axle stub.
A scrub radius can still be changed even though it may not be intersecting on the tire.
 
95 shaw said:
12 to 15 degrees are standard kingpin inclinations. The steering arm design allows the wheel to be inside the kingpin line.
here is an example.
http://karting.4cycle.com/showthrea...s-amp-Chassis-Builders-amp-Fabricators-Thread
Click to expand...
I've heard of the 15 deg setups, but I've heard of 10 deg setups too. That's not the point!
Then you have to think; what about sprint karts??

Sorry about the drawing! But I think, maybe not, you miss the point.

I try, in most cases, to tell people how it works, not just that it does work. I find, maybe you do too, that it's a hard task to find the line between "To complicated and to simple".

When you say "caster turns to camber when you turn" is not only not true, it can be confusing. Yes, the camber of the wheel does increase, (not to be confused with the camber setting) but there is no change of the caster.
 
flattop1 said:
You changed the camber.
Has the king pin to axle Angle changed as well?
As that would affect things.
Biggest thing is the king pin is inside the wheel easily one inch on a modern LTO kart.
Click to expand...
No. The king pin, the axle and the wheel relationship is the same, only the camber has changed, by changing the king pin inclination. This is how it is done with a kart.

I have never seen a king pin entirely inside a wheel. Show me a oicture.
 
alvin l nunley said:
I've heard of the 15 deg setups, but I've heard of 10 deg setups too. That's not the point!
Then you have to think; what about sprint karts??

Sorry about the drawing! But I think, maybe not, you miss the point.

I try, in most cases, to tell people how it works, not just that it does work. I find, maybe you do too, that it's a hard task to find the line between "To complicated and to simple".

When you say "caster turns to camber when you turn" is not only not true, it can be confusing. Yes, the camber of the wheel does increase, (not to be confused with the camber setting) but there is no change of the caster.
Click to expand...

My caster turns to camber was a simplification instead of saying with a near zero scrub radius, the major effect of caster is not weight jacking, but the increase in caster. Yes, it still moves the tire vertically when the wheel is steered, but a very small amount.

I find we typically need to be looking at the same picture, or we will argue all day. You are correct in your argument using the picture as it is drawn. However, as was pointed out, that is not the way it is used in modern lto karts.
The strategy employed dictates how the scrub radius is used.
changing kingpin inclination and moving the wheel on the axle in relation to the kingpin changes the scrub radius.
 
95 shaw said:
Lateral weight transfer can be calculated anywhere in a corner.

[(Total weight × center of gravity height) ÷ track width] × g force = amount of weight transferred laterally.

Same formula works for front/rear transfer.
Click to expand...

Your formula is only valid with lefty righty cars turning both left and right, assuming grip is infinite.

LTO' with a staggered solid axle will only have the possibility for enough grip to suit your formula while traveling in a perfect circle or while transitioning through enough grip to suit your formula.

Grip has to be available before weight transfer can occur and with LTO's the amount of available grip is constantly changing. Another thing which makes your formula invalid for both LTO's and lefty righty's is it assumes all lateral g's are created from weight which has been moved to the outside tires. Especially in LTO's with a staggered solid axle a portion of weight which is increased by g forces is located or held at the inside tires.

I have a question for you.

Lets assume it's possible in a left turn to weight the chassis in a way you have the outside tires slipping and it's being held in only by the weight on the left side of the chassis and the left side tires. In that case is there any weight transfer because g's increase? I can in my minds thinking accept the possibility I presented and then adjust thoughts on how tires work to a given amount of weight moved to the right side tires.

IMHO in circle track racing your weight transfer calculations will relate to performance most closely between turn in and the start of acceleration. Everyplace else looking at g's and relating it to performance will be miss leading because of how the use of individual tires is transitioning.

... wow that's a lot of bull and I'd better say it was all IMHO and sure ain't necessairly right anyway. ... :)
 
95 shaw said:
My caster turns to camber was a simplification instead of saying with a near zero scrub radius, the major effect of caster is not weight jacking, but the increase in caster. Yes, it still moves the tire vertically when the wheel is steered, but a very small amount.
Click to expand...
"Simplification", I think not.

Now here is an instance where I think you might be confused when comparing an automobile to a kart. The major affect of castor, in a kart frame, is weight jacking. In a Sprint kart, caster takes the weight off the inside rear tire so that the kart can turn. It doesn't take much, referencing your comment about it being very little. With a live axle, in a Sprint kart, if you don't break the traction on the inside rear tire, the kart will, at the very least, push.

With an LTO kart, although I have never driven one on dirt, because of the rear axle stagger, it fascinates me that they run so much! caster. If the purpose of castor is to break the traction on the inside rear tire, why would you want to do that with an offset kart that has stagger?
 
paulkish said:
Your formula is only valid with lefty righty cars turning both left and right, assuming grip is infinite.

LTO' with a staggered solid axle will only have the possibility for enough grip to suit your formula while traveling in a perfect circle or while transitioning through enough grip to suit your formula.

Grip has to be available before weight transfer can occur and with LTO's the amount of available grip is constantly changing. Another thing which makes your formula invalid for both LTO's and lefty righty's is it assumes all lateral g's are created from weight which has been moved to the outside tires. Especially in LTO's with a staggered solid axle a portion of weight which is increased by g forces is located or held at the inside tires.

I have a question for you.

Lets assume it's possible in a left turn to weight the chassis in a way you have the outside tires slipping and it's being held in only by the weight on the left side of the chassis and the left side tires. In that case is there any weight transfer because g's increase? I can in my minds thinking accept the possibility I presented and then adjust thoughts on how tires work to a given amount of weight moved to the right side tires.

IMHO in circle track racing your weight transfer calculations will relate to performance most closely between turn in and the start of acceleration. Everyplace else looking at g's and relating it to performance will be miss leading because of how the use of individual tires is transitioning.

... wow that's a lot of bull and I'd better say it was all IMHO and sure ain't necessairly right anyway. ... :)
Click to expand...

The whole premise is to realize that weight is transfering, and that weight transfer has to be accounted for when tuning and viewing what the changes do. Its just a method for looking at things. in no way is it accurate all the way around the corner as the g forces change all the way through the turn. The point was to be looking at what changes do to the contact patch to see what happens when a change is made. Its simply a tool. If you had read the whole thread, I stated that at the end to allow you to make assumptions of you own.
If it doesn't work for you, not a problem. just a way to look at things.
 
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