RWD setup tips (RWD reguliavimo patarimai)

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RWD setup tips (RWD reguliavimo patarimai)

Post by znd »

Keletas bendrų patarimų, kaip ir ką reguliuoti RWD važiuoklėje.
Informacija yra bendrinė ir tam tikri veiksmai gali neatnešti aprašytų rezultatų jūsų važiuoklei.

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Ši informacija suteiks jums pirminius nustatymo parametrus su kuriais galėsite eksperimentuoti.

F1. Front End Geometry
F2. Front End Rolling Resistance
F3. Front End Grip
F4. Eliminate Bump Steer

R1. Rear Traction?
R1.1 Creating Slip
R1.2 Creating Grip
R2. Rear Weight Transfer

E1. Gyro
E2. Power Delivery
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F1 Front End Geometry

Any of you that have tried RWD have experienced the fight in the front.

That balance of toe in vs Parallel alignment vs Toe Out.

All my setups are designed for a different feel. Unless you try, you can't determine the difference.

So what don't we want? Well we definitely don't want toe-in!!!

Toe in = Forced Understeer = Scrubbing Speed

If you’ve ever seen your car Crabbing… driving sideways with no go forward.
This is the cause. Basically like a downhill skier pointing the skiis inwards to stop.
Don’t use Toe in for RWD.
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Parallel = no oversteer or understeer.

This works very well for straight line speed in the neutral position.

It will also be as fast as possible up to a certain point in your cornering.

But just like Ice skating on the edge, you eventually need a little more control.

The red setup above is slightly limited in angle by components. It's a very fast setup, but right at the limit there's no feedback and it simply lets go in a split second.

The Blue setup is actually the same through most of the steering arc, then right at the end we continue to rotate the lead wheel (closest in view) to get more control and allow on big entries.

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Toe Out = Forced Oversteer = Already Drifting

Now this Toe-Out seems good. Oversteer = drift

Well there are two main views. One says the car has a little more control because the lead wheel and trailing wheel have a little more grip to stop a drift or initiate a transition.
One says that the car is slow because of trailing wheel drag. This can also have a positive effect for increased grip on the track.

It's all preference. This blue machine is tuned for big angle.
RWD cars will really only achieve a constant angle of 40-50 degrees so we should aim for parallel up to this limit then extra control with toe out at full lock, which builds in a safety margin to prevent a spin.
Big Entries at 90 degrees are a specific setting.
We want our lead wheel to push further but the trailing wheel to stop against the sus arm.

These are extreme settings requiring custom components but as these settings are becoming standard, so too are manufacturers providing guaranteed drift setups.
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F2 Front End Rolling Resistance

If you have ever had the front wheel stop rolling either through touching the body or touching the suspension arm or steering link, you will spin. It's just like jamming the front brakes in mid drift.

We need the front wheels rolling with least resistance at all times. increasing mass can do this with wheel ring weights.

Make sure your bearings are maintained and one spin with your finger should last for over a minute or two.
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F3 Front End Grip

It's a huge chunk of misinformation that rear battery setups behind the rear axle are superior. They are a specific setup for high grip surfaces.

Basically the front end of the car is super important to overall speed in all situations. It's important to help forward speed through corners and help steering ability.

If you have the liberty of an open tyre selection on the front, then go for the softer tyre.

As the back wheels push forward against the front of the car you need to minimise front end understeer which wastes energy and have enough grip to steer the car as you wish.

A softer tyre with more grip on the front is a basic solution. but if a control tyre is in place, then use a weight on the knuckle to add front tyre grip.

Softer springs, oils or mono-shock roll systems may contribute to specific goals.
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F4 Remove Bump Steer

The easiest way to remove bump steer is near equal length "double wishbone" suspension and keep the steering link parallel also. the design of the knuckle and the amount of castor / KPI / camber will all work against you. but it's something to strive for.

Why? when the suspension compresses, the front end geometry you worked hard to create will remain basically the same.
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R1 Rear Traction?

OMG!!! This is always a hot topic.

We’ve seen so many ways of modifying the rear of a car to generate forward movement.

The number of rear suspension arms on the market are just the starting point.
Shock Compression vs Weight transfer is one topic. Toe in and out, camber, kick up etc

What I tend to do is build for rear end stability on slippery surfaces or build for slip on grippy surfaces.

These are two complete polar opposites in setup.
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R1.1 Over-coming grip when there is plenty.

Obvious. POWER UP!

Minimise the tyre contact patch. If you have a flat tyre, add camber to run on less of the tyre.
Be careful of compression because the patch will change.

Zero toe setting on the the rear will promote instability. (Silver chassis).

Much like the parallel setting in the front. It's the fastest/least resistant when rolling forward, but when you are at 45 degrees, being on the edge is risky.

Most cars are designed for anti-squat.
In RC chassis the rear suspension arm is FLAT. There is no anti squat.
place a 3mm spacer under the RearFront RF sus mount will increase anti-sqaut.
The rear suspension arm will be angled up at the front almost like walking on the heel of your foot only with your toes in the air. It's unstable. (prevent squat / create skid)
Note: Braking ability is also effected.

Increase bound sus rates. An increase in rear bound will typically reduce grip.
But remember if you have tuned your car to squat, then reducing squat may transfer weight differently actually have other effects. It's all a compromise.
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Increase rear chassis rake . A higher rear hide height in the rear will add to all the above.
Go for a solid spool. A spool will spin both wheels past the grip point quickly, this lower wheel speed will break traction more easily.
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R1.2 Creating Grip when there is next to none.

Obvious. POWER down!
But typically we will always have enough power to overcome traction.

Increasing rear toe in will promote stability like the skiis pointing inward.
Rear toe-in is also useful for additional rear braking at high angle.
RC cars already transition unrealistically fast. So it will slow your transition speed also on a low grip surface.

Cars on super low grip surfaces need help. Slowing things down has a great impact on control.
This additional toe angle braking effect can slow the rear and create more stable braking.
A little like holding the handbrake slightly while on throttle.

Increasing the contact patch will keep grip. This setup above is designed for that with a curved tyre, I can still use about 1/2 of the tyre through the suspension arc. A zero camber setup with equal length sus arms will typically run on about 1/5th of the tyre. I'm using increased camber under suspension compression to add bite.
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With more toe-in, one wheel will have up to 3.5 degrees more forward facing ability when the car is at angle. The inside wheel will be at 40 degrees and the outside wheel will be at 43.5 degrees. the inside wheel has more traction in the direction of the corner.

If big big constant angle is your requirement. When you combine this with a differential , the wheel with more grip will still have more forward drive.
Adding rear Anti-Squat (Add Spacers under the RR sus mount)
The wheels will be trying to dig into the track and generate grip.
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R2 Weight Transfer

We all know that as rear suspension compresses and the front of the chassis lifts, the rear of the chassis typically becomes a lower ride height under under shock compression.

Keeping a lower rear ride height will typically help promote grip by keeping the weight focused towards the rear. The chassis will not rock to the front.

Raising will be the opposite. Shock Pre-load adjustment does this, but also does other stuff and I am trying to keep it pretty simple... if that's possible with talk of geometry and weight..

Weight transfer with a mid battery will transfer less weight over the rear wheels and the transfer happens horizontally.

The Weight Shift high battery / High motor philosophy invites vertical weight transfer. Or more push onto the rear. Actually the higher the better, but typically we are bound by body restrictions.

Weight behind the rear axle is simply going to reduce front end grip and generate understeer. On a super grippy surface, you may get more hang time but you loose the steering ability to stay on line.

On super-flat high speed tracks like Yatabe Arena are less dependent on this because corner radius is much larger and front grip isn't so important.

That's why new Yokomo chassis like the YD-2 have a super low center of gravity and are designed for promoting drift through slip and slide from lateral weight transfer, rather than grip.


E1. Gyro

Gryo gain settings should be made as high as possible, however if you encounter a wave effect in your steering, reduce the gain to avoid this. The more front grip you can generate, the less gain you will need.

E2. Power Delivery

Bringing on the power in RWD is a big part of the game.
Jam the throttle, do you go forward or do you sit there spinning the wheels ion full burnout mode.

If you have less grip, you really have to bring the throttle in easy.
Get the car moving, 1st, second, then initiate.

If your car has 1000hp and only limited grip, there are compromises. Like a wet road philosophy.
If you car has 1000hp and full rubber slicks, you simply go forward.

We balance our cars on throttle to get as much grip or as much slip as we need. But unlike 4WD where mashing the throttle will get you out of trouble. RWD bill simply overcome rear grip and spin.
So finding the grip point on your finger takes practice, nearly always I have to adjust throttle end points for grip matching.

If you can't overcome rear grip. ie Full throttle all the time. Back off and punch the thottle in short bursts to break traction in an unsettled manner. As wheel speed meets road speed the ability to overcome grip is reduced. like hitting top speed in 5th gear.

In RC, gear your car to always have a little more power than you need in reserve to break traction and keep angle.

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