Track Tac

Spindle Angle

alvin l nunley said:
You and I have totally opposite views of how the front end geometry works!
Click to expand...
Just because you view it differently does not mean that is how it works.
Draw the system in 3D and show where it is wrong.
Be sure to show movement in camber, and at center of contact patch, as that is the only thing holding kart to track.
Drawings out of context do little to show the whole picture.

I'm here to learn also.
 
Last edited:
I have had several older sprint karts with 0 KPI. One thing I have always found was the front end bite was so high the kart would wear you out. Never liked them even though they worked fine. Never tried it on an oval kart.
 
racer said:
I have had several older sprint karts with 0 KPI. One thing I have always found was the front end bite was so high the kart would wear you out. Never liked them even though they worked fine. Never tried it on an oval kart.
Click to expand...
"It's got to be easy to steer." I raced my Mayko Shark for several years and never ever noticed it was hard to steer. Nobody who bought my frames ever told me that they were "hard to steer". Still, your opinion counts as much of mine. I'm just saying, if the kart doesn't push, and doesn't get loose, but it's hard to steer, I can live with that. It's just not something I ever noticed.
 
95 shaw said:
Here is a drawing Al posted a few years ago, when we were discussing this same thing. Other than incorrectly noting the center of the contact patch for the purpose of describing scrub radius, it is a good depiction of our setup on the right front.

I think if you check, you will find very little weight jacking on turn in, in the range we actually use, because of the KPI/caster shown.
The curve Al showed earlier for 12/12 setup will help explain why.
View attachment 6868
Click to expand...
Very nice drawing. Wish ypu had a book of everything about chassis set up.
 
FlatheadsForever87 said:
Very nice drawing. Wish ypu had a book of everything about chassis set up.
Click to expand...
Been involved in racing since the early 80's.
Been looking for that book almost as long.
The truth is, the way different people think about things lead to a lot of conflicting information, especially when considering the racecar as a whole.
I've found looking at a small specific area, and following it to the contact patch, helps me get a better view.
There are reasons things are done a certain way. Sometimes we need to reverse engineer the process to truly see.

Frankly, discussions such as this, which forces me to really assess my views. I feel to truly justify your position, you should be able to process it all the way to the track

Then you need to see if the adjustments normally acquainted to this section also justify your views. If it doesn't make sense, need to work on your theory.

The drawings in this thread are all courtesy of Alvin Nunley.
Pretty sure I did not use them in the context he intended, but the evidence is there, regardless.

Thanks Al.
 
paulkish said:
With a round plate front end I don't know but I think you can't rotate it without effecting multiple adjustments at the same time unless the plates are straight up and down.
And even if there not fully round plates unless there straight up and down doesn't the same apply?
But seems to me most all are slanted top inward... yes on any of this?
In a static picture sure camber gain and scrub may be ok, butt??? then doesn't the bank of the track effect both camber gain and scrub?
And then might you want the vertical alignment of the plates adjustable so you can keep things working as you need depending on banking?

... yeah proly all wrong thinking on it ... ?

... sorta like i'm thinking it's about what works because with most plate front ends you can't adjust caster without changing kpi ???????

yep i'm just seeing it wrong ?????

Doesn't banking effect what you need for camber gain from kpi and caster along with spindle angle?
Click to expand...

Yes
 
95 shaw said:
Been involved in racing since the early 80's.
Been looking for that book almost as long.
The truth is, the way different people think about things lead to a lot of conflicting information, especially when considering the racecar as a whole.
I've found looking at a small specific area, and following it to the contact patch, helps me get a better view.
There are reasons things are done a certain way. Sometimes we need to reverse engineer the process to truly see.

Frankly, discussions such as this, which forces me to really assess my views. I feel to truly justify your position, you should be able to process it all the way to the track

Then you need to see if the adjustments normally acquainted to this section also justify your views. If it doesn't make sense, need to work on your theory.

The drawings in this thread are all courtesy of Alvin Nunley.
Pretty sure I did not use them in the context he intended, but the evidence is there, regardless.

Thanks Al.
Click to expand...
That is what intrigues me. Chassis/engine theory and watching setups come in and fall off and everything in between. You will not see me more happy than when I am doing my thing and have a driver that is consistent to the point of tenths. Ahhh it dont get better than that. My younger self thought I was gonna be a great driver but in reality I'm ok. Once I admitted to my self that my teammate was the better driver by far and we as a whole could get a lot more accomplished if I was the pit guy and working behind the scenes and he drive it. Instead of us both running around trying to accomplish it all on our own, things went alot more smooth and we both had the time to fine tune our abilities and in turn start to enjoy the sport like we should.
 
Does this help anybody?
The figure on the right is my rendition of a previous post showing scrub radius. The picture on the left is that same picture turned 90°. Notice that the center of the scrub radius is not even under the tire when you have 12° caster added.

Personally, I believe the term "scrub radius" has no relevance when applied to kart design. How could it when the theoretical center of the scrub radius is not under the tire. Contrary opinions are welcome.
spndal camber 3.jpg
 
From Wikipedia, the free encyclopedia



Jump to navigationJump to search

Zero scrub radius (top) positive scrub radius (center) negative scrub radius (bottom)
The scrub radius is the distance in front view between the king pin axis and the center of the contact patch of the wheel, where both would theoretically touch the road. It could be positive, negative or
 
You're right, but then it wasn't meant to be. It's a representation of a line, that passes through the kingpin and where it intersects the road. Where it intersects the road is the point. It's not under the tire.
 
flattop1 said:
Again scrub radius is a front view measurment .
Sideview is not representative of scrub radius .
Click to expand...
So how would you draw it up to best explain your way of seeing it? About the time i start to absorb it it gets contradicted and makes me think its not a correct way to memorize it
 
FlatheadsForever87 said:
So how would you draw it up to best explain your way of seeing it? About the time i start to absorb it it gets contradicted and makes me think its not a correct way to memorize it
Click to expand...

Caster can only be seen in side view.
Kingpin inclination, spindle build angle, camber can only be seen in front view.
The component shown in Al's drawing is actually caster trail.
This component is what makes your bicycle go straight when you remove your hands.

Most of us has taken the front fender off our bikes and tried to turn front fork around.
It's a lot harder to ride and control like this.
Spend some time working with your chassis, either on scales, or just measuring frame heights as you steer the kart.
Make sure the commonly made adjustments make sense with the theory you chose.
Make up your own mind.
 
Last edited:
You must log in or register to reply here.
Back
Top