Chassis flex

flattop1

Dawg 89
I'm wondering about this myself .
Here is what i see .
three main area's : the rear cross bar , the front hoop and the waist/steeering bar connection on the right side .
with the right frame rail ; if the inside rail runs too the front or the outside rail . IE; narromer would be stiffer.
My feeling is the triangulation at the waist is the most critical location.
another thing i have noticed is the rear frame section's have goten narrower .
 

paulkish

old fart
IMHO and from experience the only new flex which may cause you a problem if flex slowing or delaying weight movement to the RR tire.
The is IMHO to make stagger work or to unload the LR you must put weight to the RR.
Since stagger is ONLY used when turning left weight to the RR is needed to either make it possible for the faster turning RR tire to rotate around the LR when slowing or accelerating.
Don't move enough weight to the RR soon enough or in insufficient quantity in either case will ... make the thing want to go straight and have to be forced to turn by the front tires.

We ran the last Bandit Boss made putting many laps on it both with boxstock hp and UAS hp.
The thing was or should have definitely been flexed out, so to speak.
What I did for multiple reasons was to stiffen up the RR corner/area of the chassis by adding a third motor mount/engine rail to the RR of the chassis.
IMHO that stiffened it up and any delay of weight transfer and especially timing to or from the RF could be handled via other means.
It nets out to if what your riding doesn't push going into the turn .............. yer ok and the rest of what happens is up to your driver.
 

riddler26

Member
Can someone explain what makes the older chassis like a nemesis flex more than the newer karts?what part of the design has changed?
Thanks
 

XXX#40

2A supporter
Can someone explain what makes the older chassis like a nemesis flex more than the newer karts?what part of the design has changed?
Thanks
they flex the same, the only thing that made the nemesis a high cross kart was width between the front kingpins
Several new karts are soft at the waist
 
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Unless you purchase or have the capabilities of putting a chassis on a chassis dyno you will be surprised on how and where the chassis flexes...... bar placement and the thickness of the tubing is key.....
 

flattop1

Dawg 89
I was thinking ? how would you replicate that at home . scales under each wheel and pull down with a measured force .
or lift each corner with a measured force . Probably need scales top and bottom of each wheel .
unfortunatly cut , weld and test is my only option !
 

95 shaw

Premium User
I was thinking ? how would you replicate that at home . scales under each wheel and pull down with a measured force .
or lift each corner with a measured force . Probably need scales top and bottom of each wheel .
unfortunatly cut , weld and test is my only option !
Ideal would be to have the kart as raced, on scales, and pull on the center of gravity to replicate actual flex at various points around the track.

The scales must be able to withstand the side force, which is problematic. Would need a method to measure actual flex at specific locations on the chassis to determine where flex is occurring.

I have seen crude big car rigs that used this method, only using scales under the left side to get some readings.
 

flattop1

Dawg 89
they flex the same, the only thing that made the nemesis a high cross kart was width between the front kingpins
Several new karts are soft at the waist
2001 coyote 22" at the front plates 12" waist 23 rear chassis width.
12 triton 21" front plates 10" waist 21 rear chassis
Beisse cadet. 24" at king pins 12" waist and 24 rear chassis .
Adding 1" -- 1 1/2 " for L blocks all pretty similar . Yet I suppose inch's matter in chassis design .
+ Or - 10% ..
 

"J'-remy

Member
I have talked to several chassis manufacturers about why they do this vs that and how has the kart really changed over the years etc. The narrower rear track was an effort to reduce the rear stagger increasing speed down the strait. What one manufacturer told me was they see a great deal of difference in the kart by changing up the cross bar the front of the seat connects to.the longer they make that bar the more flexible the chassis will be. I was told this can have a dramatic effect to the left rear. A lot of the other stuff they do is for convenience.. how they mount the seat, adding adjust ability to the cassets, the steering column adjustments etc most of the stuff done to karts is just to get you to purchase the latest and 'greatest'. and is a bunch of bunk. i was also told some of the high cross was to keep the front end from being too darty
 

riddler26

Member
Wouldn’t a tighter rear track and less stagger make kart too tight tho?
It’s going to get over on the RR too hard? Or do they have more pre load in the karts these days?
 

alvin l nunley

Premium User
In my understanding of stagger, the only reason a narrower rear track needs less stagger is because the tires are rolling along paths closer to the same length. The farther apart the wheels are, the bigger the difference in the path they are following.

I have software to calculate stagger, outside width is one component of the calculation.

Does anybody know; do all manufacturers make their rear frame width the same?
 

"J'-remy

Member
Maybe that's why it's gone to high cross, to load up the left rear... I can't explain the choices they make. Some things they do are understandable like the front end adjustments that's seems to be something that is good as it has stood the test of time but it has also made that aspect of your chassis up to you and taken any blame of the front end off of them. the chassis do have to keep up with trends such as nerf bars accommodating wide tires and short struts for lay down seats.
a lot of kart manufactures post their set up sheets. phantom has them going back to the banshee dang that kart is old. you can see the trends over the years. the Charger is currently asking for 5/8 stagger. there is no reason you couldn't try that on an old kart to see if it's faster or adding a lot of cross to an older kart. Something has shown an improvement on their stop watch i thinks its still a 32" axle. at the same time some things don't work as you can find a certain 2019 kart with two rails for dirt cheep.
 

riddler26

Member
In my understanding of stagger, the only reason a narrower rear track needs less stagger is because the tires are rolling along paths closer to the same length. The farther apart the wheels are, the bigger the difference in the path they are following.

I have software to calculate stagger, outside width is one component of the calculation.

Does anybody know; do all manufacturers make their rear frame width the same?
A tighter rear track causes the rear to turn more not less?
 
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