Working on roll center correction solution

[Vinci]

I ultimately went for a different approach, and raised the inner bushes/joints on the chassis, so I could keep the knuckles stock. The wishbones are based on the original ones, using the original material, only changed the front bushto a ball joint, and used the Tucson balljoint and plate for that. Many other small 'adjustments' were made, also to the mounting points of the steering rack, and the suspension on the rear axle is changed to coilovers from a VW Golf, where I welded in turrets that were drilled out of a Golf shell. Inside the sills the inner sill was extended all the way to the front to stoffen it up a bit more, and the jack points have been beefed up with a piece of 3mm thick material to ensure it to not warp when jacked. A cross member was added to the floor, between the rear beams, in front of the spare wheel well, and the roof has a cross member between the B-pillars to strengthen the roof and provide extra overall stiffness. The car handles just incredible, with much more direct and responsive steering, still having a very responsive suspension, and very little body roll. A friend of mine who owns a bodyshop, and has a Celette chassis bench helped to put everything in straight and optimise the camber, track width and bumpsteer.

[Lucas1717]

Very nice solution, and its good to hear that u feel big improvements.
In future, maybe i can plan something with this side of the wishbones, but right now, the hyundai knuckes give me the ajustments that i wanted for track use, as I progress with this suspension work, maybe its a good upgrade.
Now I just anxious for the result, and having a bunch of data with telemetry on the old setup, Im gonna compare the lateral forces with the new setup.

[Vinci]

On track roll isn't necessarily a bad things it will provide a lot of grip where it is needed, only weight transfer upon fast direction changes can sometimes be slow, but it will depend a lot on the type of track what setup works out faster.

Your setup has a lot of adjustability, which is nice, but just from eyeballing it, I get the impression your hub center and balljoint center are not that much further apart as with the original set up? Can you perhaps post your Vsusp URL to show the data on your measurements?

[Lucas1717]

For now, we are tac welding everything in place, to mesuare stuff.
As it is right now, the roll center is above the ground ~30mm, but im gonna put 15mm spacer in balljoint to reach about +70mm roll center (all estimative)


https://www.vsusp.com/#0.8%26project...ll_center.y%7D

[Vinci]

Ah yeah, I see. Great work, and curious to your progress!

[Lucas1717]

Thanks, i will post my result with onboard videos and some telemetry, I think in about 2-3 months.

[DarrenH]

agree with vinci, bump steer more of an issue with long suspension travel and forest rally cars. stiff spring, low centre of gravity, for circuit or tarmac, it hide allot of issues.

the solution for roll centre in WRC mk2 astra (kadett E) was to use a much taller steering knuckle, which also had wide angle on the engine side for lots of CV join clearance. you guys are along this process yourselves.

p.s nice to see you posting again Vinci hope you are well

[Vinci]

Hi Darren, didn't get email notification of your post somehow... Oh well...

Yes the taller steering knuckle was kind of the first iteration of the idea, but it didn't feel safe to me to ride them with such huge length bolts, and then when you got to the point of progress the size of the whole thing would be very close to the inside of the rim, and also make ground clearance worse. The raising of the inner joints therefore seemed like a better plan to me, also because it only required fabricating on the chassis and control arms, which is all fairly ordinary steel that can at least be welded.

I have had about 1400 kilometers down my belt in the car now and I can not rave enough about the way it handles and grips now. I will look in to camber adjustment still, it has a bit much negative camber as it is now, at around 1.2 degrees, and I was going to monitor tyre wear. At this point for that reason I am still driving fairly cheap tyres. I was thinking of slotting the lower balljoint holes in to the control arms, and then make a plate to fixate the bolts properly.

So yeah that... Yeah, I am good, only had a lot of problems with some family members and their health, and started the project in a commercial garage before that all happened, so been working seven days a week for a few years basically... hence the abstinence....

[Lucas1717]

The large bolt is one big concern on this project, by now, we are developing the bolt especific for this, using high grade steel (4340), and using 60mm spacer on the ball joint. Here in Brazil, we do a lot of "trackdays" in kart tracks, its alot cheaper, and the tracks have good layout for tests with low speeds and high forces on the suspension and the ball joint development.
As i am with one race team that races FWD for living, i have seen a bunch of extreme things in their/others racecars, so i am hoping that this solution is not so extreme and do not make me more problems.

[Vinci]

Well, one way to be sure is calculate dynamic load and set up a representative test bench and do some destructive testing on a test specimen. That will at least give insight and might save you from injury or worse...