Steering kingpin location-Why?

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rkcarguy

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Coming from an R/C car background(raced regionally-had a few sponsers, etc etc), I'm looking at these race kart chassis's wondering wth is going on with the steering kingpin locations.
Why are they so much inboard of the centerline of the front wheel which makes it swing a radius when steering?
Is this to allow adjustments in track width? Keep things cheap and light?
I realize with the small 5" and 6" wheels it's not going to be possible to get it inside the wheel to C/L, but why way the heck out there?
 
Doc Sprocket

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You've got me- there are fellas here that have forgotten much more about race karts than I'll ever dream of knowing. That said- from where I stand, you would want to get the kingpin as close to the center of the contact patch as possible, and then dial out the rest of the scrub radius with an appropriate KPI angle.

...In a perfect world, anyway.
 
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rkcarguy

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Ahh that makes sense. Most of these are upgradable to shifter kart specs which include adding front brakes.
I'm looking at fabricating my own frame for a clone kart and want to question some of the construction methods of the popular race frames.
Thinking a bolt in front wishbone setup would allow it to be changed out and customized to get the pivot point out there further in non-front brake apps.
 
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Looking at some other brands, some are not as bad as the margay and I don't think with the 5" wheels that they could be inside the wheel as there couldn't be much height(and inherent strength) of the spindle assembly.
I don't think it will hurt to get it out there as close as I can though.
 
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i know that on my neighbors red kart before it was taken apart, that the steering location was set because of how far the seat set back, where the steering wheel was, if it was flipped on the outside you couldnt reach it, im 5'3 and i could barley reach the pedals from the seat
 
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It has to do with the live axle. With the wheels that far out from the kingpin and the camber/caster those karts have, it pushes the front inner wheel down and font outer wheel up when turning, allowing the rear inner wheel to leave the ground. They are one wheel drive in the turns.
 
Doc Sprocket

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NiceToy said:
It has to do with the live axle. With the wheels that far out from the kingpin and the camber/caster those karts have, it pushes the front inner wheel down and font outer wheel up when turning, allowing the rear inner wheel to leave the ground. They are one wheel drive in the turns.
Click to expand...

Must be an asphalt/race thing. My scrub radius isn't anywhere near that bizarre, and yet my kart handles like a cat on a carpet on pavement (for the non-race monster on turfs that it is).
I have KPI, caster and camber angles to load the frontend correctly in turns.
 
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I would say it has o do with strength and light weight.

the frames are shaped to be very space conscious and in race conditions frames have to be built strong. and having the frame extend out to the wheel width would require more bracing as the wheel must still turn and clear the frame.

im almost positive the added weight and added design would make marginal improvements if any. you may corner faster. but having a heavier kart may slow you slightly where it nullifies the benefits.

but...besides brakes etc. tuning the kart for specific tracks may utilize that room also. with different size and offset wheels
 
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rkcarguy

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I think I realize what they are doing. Nicetoy got it, it induces cross-weight transfer to the outside front and takes some off of the inside rear tire. Not optimal by any means, but when you have no differential it's a necessary evil.
What I'm looking to do, is a fairly standard racing kart frame with some changes to the front end.
If you look at the setup on the front of a Trinity EV-10(R/C car), they use a pair of tierods to adjust the upper pivot point of the spindle to control both camber and castor. It's this setup I'd like to add to what would be a pretty normal racing kart chassis otherwise.
I would use a lighter tubing for the front end to offer a little more flex, then use the tierods and adjustable "flex bars" between the inner termination points of the tierods as adjustment. Infinitely adjustable camber and castor, and a flexible but more predictable front end would be the result. Done right, weight gain would be negligable.
 
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racerc2000

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basically like this? but with a thinner tubing? the flex may work but..... damage will be much easier to get and much harder to fix.





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