Spindle kingpin
- Thread starter Sjg22
- Start date
alvin l nunley
Site Supporter
the kingpin has two angles, kingpin inclination and caster angle.
I should have known
As in the title. The spindle is built with a kingpin inclination.
alvin l nunley
Site Supporter
I'm sorry, I thought you wanted some help. My mistake.
jack burroughs
member
How about the Camber? would it not be a 3rd. angle? The Caster and Camber angles are adjustable but the king pin angle isn't, except by changing spindle. I know there have been karts built that use different angles from left side to right side.
Is the discussion in regards to UAS type open racing or stockers/animal?
I think the power available is relevant to the set-up. With enough power you can turn the rear with the throttle as much as what you can steer the front with the wheel.
paulkish
old fart
There usually is some and the amount is what works or is there.
Ted Hamilton
Helmet Painter / Racer
I think the split is used primarily to control how quickly weight transfer happens, as opposed to sprint asphalt, where it is used for jacking effect (yes, weight transfer is also involved there too)... The "preferred rate" would depend on driver preference / chosen line, track type, available traction, and chassis "waist" behavior. I would also bet that almost any split could be made to work, just that one would have a wider / less sensitive tuning window. I would use a more aggressive initial angle and split for higher power karts with the theory that I want as positive a turn in as I can get, but that's simply my preferred setup...YMMV.
Ted Hamilton
Helmet Painter / Racer
....and also FWIW, the sprint asphalt guys were starting to minimize KPI but use a large scrub radius, theory being that that preserved jacking effect when they really wanted turn-in (large steering inputs) but minimized scrub with small steering inputs. I don't know whether this would transfer to dirt well or not, but I've been curious to try.
Over here the tracks are always so loose compared to the dirtphalt and slicks you guys run on. Because of this I'm never really under powered unless the track is unusually taking rubber and is not watered. I agree with Ted on this. It has a lot to do with the behaviour of the chassis waist or the amount of twist. And the tires spring rate or compressibility of the tire has a lot to do with KPI.
FWIW, I run 10 and 10 in KPI and about 12-13deg on caster for both sides. But these things are also affected by corner weight distribution too. One KPI/caster setup is not going to work the same with 2 different set of scale numbers. I have made a few different spindles/stub-axles. I think I have 2deg 5deg and the usual 10deg. Not running at the moment so haven't tried them. I'll email you some pics of what I have.
I think front tire presentation to the track is what the stockers are most worried about. So I think for a stocker you don't want any excess rolling resistance that might be created from a more aggressive KPI.
If it was for UAS I would be talking to a dirt/asphalt late-model guy and see what there opinions are for KPI and caster.
paulkish
old fart
The king pin points towards where on the ground the chassis works from, to engage the RF tire with the track. Roll centers being worked via the center of gravity, say how the tire is worked when the chassis puts effort to the tire.
Think of a having a screw driver in your hand and sticking it in the ground. The point(where the king pin points) will stick in the ground and then afterwords your hand(the chassis leveraging on the kingpin) can move the screw driver many ways to dig out some dirt. That's about the kingpin only working, it's not about working the tire. The tire is attached via the spindle somewhere up or down on the screwdriver. While the screw driver is digging into the track, forces can at the same time be both pushing the RF tire outward and trying to push or pull it down towards the track.
It's a little tough with karts, but often easy with cars... I've helped fix car front end issues(bigblock modified) by observing the angle the driver tilted his head. Often car drivers will tilt their head indicating pretty close to how the cog is aiming forces. I've never been able to relate it to an issue in the back of the car, but it often shows a front roll center issue, which leads to poor RF tire presentation. yeah, believe that and I'll tell ya another one. ...
edit: In the case of the Bigblock Modified, I did also relate it to the back of the car and suggested a stiffer bar be put on the left rear. But that was mainly to get the driver to run a different entry line, to fix an exit driving issue.
Think of a having a screw driver in your hand and sticking it in the ground. The point(where the king pin points) will stick in the ground and then afterwords your hand(the chassis leveraging on the kingpin) can move the screw driver many ways to dig out some dirt. That's about the kingpin only working, it's not about working the tire. The tire is attached via the spindle somewhere up or down on the screwdriver. While the screw driver is digging into the track, forces can at the same time be both pushing the RF tire outward and trying to push or pull it down towards the track.
It's a little tough with karts, but often easy with cars... I've helped fix car front end issues(bigblock modified) by observing the angle the driver tilted his head. Often car drivers will tilt their head indicating pretty close to how the cog is aiming forces. I've never been able to relate it to an issue in the back of the car, but it often shows a front roll center issue, which leads to poor RF tire presentation. yeah, believe that and I'll tell ya another one. ...
edit: In the case of the Bigblock Modified, I did also relate it to the back of the car and suggested a stiffer bar be put on the left rear. But that was mainly to get the driver to run a different entry line, to fix an exit driving issue.
It depends how you look at it. If you consider a stiffer chassis will mechanically shift more weight with less steering input given the same caster setting, then in order to keep the tire presentation to the track the same you would have to consider altering the KPI. I think it depends how much you need to conserve the front tires. Oval kart racing are short duration races so I'm not much concerned about tire wear unless its over heating the tire. IDK, its almost impossible to over heat a tire where I race so I don't have much experience with temp problems.
Tonypowerkartsupply
Member
I've learned on my karts most of the speed is in the frontend. You really understand and feel it more when indoor racing. You can feel the diff between a 8' and 10' RF spindle. There's so much to take into consideration. Track surface. Corner entry. Banked or flat track. Lets say one type of track on entry you turn wheel and track just drops down at the apex. Now take another track that is flat at corner entry. just think about that. Add in that more rf caster will lift the rf tire in the air when turning left. I can go on and on. Best way to learn is put your kart on the scales. Put camber gauge on and take notes. Turn left with 5 degree caster. Turn left with 10 degrees caster. Now change that spindle from a 10degree to 5 degree. Repeat.
paulkish
old fart
I'll try it again. ...
Both are about both setting and using tire presentation. The RF tire is pushed into the track and the LF tire is pulled against the track. The RF tire because it's pushed into the track will be applied or laid down on the track from the inside of the tire outward. On the other side the LF tire will be applied while being pulled into the track from the inside outward.
You use split because if the LF tire when turned had the same angle of attack to the track as the RF tire and the bank of the track was the same for both, it would be used too much towards the outside of the tire. And if the banking under the LF tire was less then the banking under the RF tire, which it usually is, the LF tire would be used even more towards the outside of the tire.
That will both cause the LF tire contact to be over worked and it will also cause the LF corner to lift up and put even more stress on the outside of the LF tire. Here's another guess thrown in just because I had it to throw. It will also cause you engine to bog down, because without the split you are likely to engage the LR too soon.
So to keep a proper contact patch with the LF tire you put split to it, to angle up on the outside of the LF tire and so you can maintain engine rpm.
Sure someone is going to say, heck we don't even have the LF on the track in the turns, so it's meaningless. Ok then your right and split is meaningless if you don't use the LF tire. ...
I have no clue what I just wrote, just sitting here and felt like writing. ...
but it makes ya think, don't it?