Saturday, July 7, 2018

2018 RC Trends



Over the past 18 months there are some distinct trends that appeared and they relate to competition speed, traction and scale replication of weight transfer.

With now standard RWD rc concepts of correct steering ackerman and precise throttle usage the two main factors for drift , lets look at the newer concepts.. 






Target : RC Competition Traction

In the hunt for competition speed. RC makers have been targeting traction in a big way. RWD top runners do not run front motor cars... this is not optimal in terms of going "RC" fast. With freedom in layout these days common, for comp... most have adopted the MR formation.

While gaining traction is nothing new with custom applications. The mainstream now gets a selection of parts that makes it easier for people to gain traction from torque.

Lets say, these things will not on their own make a slow car fast, but these are competition focus items where if you had a good setup with all the small things working together, you may gain that extra 1% advantage. they also are the basis of newer chassis on the market.

This traction focus is evident in the Yokomo YD-2, the SX and the Overdose GALM with extra parts and relate to what small companies like kamikaze have also been up to over the last period.



The main point is torque transfer trough the Gearbox design

The Gearbox design uses the rotation of motor and gears and transfers the torque through the position/layout of the gears and how the circular arc of that connection is transferred to downward pressure at the rear of the vehicle.  Starting with the YD2, the options are now available.







The overdose galm is similar but adds to this by allowing the motor physical movement to also be transferred through the driveline through a floating mount.

This requires rigidity in the chassis to support the transition of energy through the gearset itself, but the concept is the same. the extremely powerful and violent motor on/off  can contribute to the behavior of the chassis.

The hybrid RE-R also recommends leaving in some front gearbox parts to aid torque transfer during braking. A similar concept that may add that 0.5% you need.

While traction "can" be also supported by weight shift, it has a dual function, so I'll discuss that below.



Scale Weight Shift and rear roll centre adjustment.

Its well known that an older  Porsche 911 has good traction with the motor at the back but steering feel and balance would kill you in a big slide, where the momentum transfer at the rear was hard to control... usually resulting in the death of the rich.

This is an example of weight shift.

The two heaviest components are the Motor and the battery contributing together to about 1/3 of the RC chassis weight.

High Motor Mounts are now fairly normal and mid/rear/high battery positions are available....

Rear battery can gain traction while the pendulum during change of direction is hard to overcome. Just like the Porsche example.

High motor or high battery with either component just in front of the rear axle seems to be effective for RC. Transferring weight to the rear wheels for more traction and good balance during on/off throttle and left right movement.

Now, as race cars favour low CG or centre of gravity as the tyres have adequate grip... drift cars have arguably low grip (because the tryes are spinning or sliding)  and maximizing that grip means moving the weight to the front or back of the car that needs it most through throttle or braking.

Simulating this is now a real trend in RC. D-Like RE-R is the definition of chasing this weight shift mentality.



Remember if you aren't braking... you are not using the benefit of weight shift.

You really see this in FormulaD and D1 now as the high ride height and rear squat is visually evident.
the front will dive onto the front of the car under braking. 

The importance of the shock setting these days is evident in all forms of motorsport and RC is no different.

From Baja to Rally and other forms, the stroke of shocks have increased amazingly recently. Race cars ride bumps brilliantly. Understanding of bound and rebound is still a key component, but on top of that, you can add or remove weight balance through the chassis layout as a track's grip level dictates.

You can really get realistic chassis movement. But there's still more.




A few years ago at the peak of 4WD, the RC scene split with some in favor of flexible chassis over suspension tuning. People who could eventually predict the amount of flex could get an advantage if they tuned their shocks to work together or after the flex of the chassis was complete.

very difficult but achievable.

This trend is re-appearing in conjunction with a twisting chassis, however the traction of above components is not lessened as the rigid torque transfer remains in a straight line.

Remember, if you aren't straight, you won't be fast to that first initiation point.

This is related to how the upper deck may connect to the front. Enter the kamikaze DMR Mikasu Works conversion. The ball ends connecting the upper deck will be rigid in a linear direction but will allow twist when cornering adding to chassis movement.

If you don't know about Mikasu-san, he is a wealth of RC knowledge  and someone I follow with great interest.



RC oahu's Trigger chassis also has innovative ways of shifting weight through lateral flexibility and a T-bar axle mount.


Rear tower and Arm configuration.

While Yokomo shows you this picture with new parts. The positions they show by mounting the upper arm dead center and the shock dead center will change nothing over the standard config. It's those extreme positions that offer changes to chassis behavior.

With a language barrier, it's hard to get advice on what do all those holes do. There are 1156 combinations on this rear tower bar... too many? you decide.

It's only people like Bagi-san and Mikasu-san that offer people outside japan a video insight into the tuning scene. With my limited Japanese, I'm lucky that I can pass on some of this info, but it takes a dedicated job to do this, not a part time blog.

We are lucky to pass on 1/100th of the knowledge these guys have.


So this image from Mikasu-san shows you an alternative.

Inboard vertical shocks and almost >< formation upper and lower arms opposed to the Yokomo shot and = parallel arms.

This central >< roll formation can be increased by central weights for insane changes in cornering behavior.  High mount motor and a flexible chassis, you start to see the differences in how RC chassis can function.


On my chassis that I use for experimentation, it's good to try these layouts and feel the differences.

go for the extremeties and see what happens then apply that to your normal setup in small increments.


Wheels are additional items targeting traction with thin flexible plastic.

While older HPI wheels were a secret traction advantage along with mounting techniques for even more.... new wheels are available to all and marketed as such.

Such as Overdose R-Spec, Topline Nmodel V3, Yokomo 6 Spoke drift wheel.

While the words may say high traction... there is theory attached.

The secret here is the thin flexible plastic. As the torque transfers through suspension to the tyre, slight compression of the wheel causes the tyre to gain a very slight increase in contact patch. I'm talking slight. as we know 0.5+0.1 = 0.6% advantage.... that maybe all you need.

The other benefit of the thin design allows more steering angle as the wheel inner lip won't bind as much as there is more clearance. Steering feel may "slightly" increase during turning also. again sum of all methodology. This is how teams win.


I'll just make a sub note on wider front track as it too is a newer trend. Wider front track will give greater stability, it will also result in sharper steering feel. the thinner lower arms tend to give more clearance for lock also.

But EVERYTHING is about balance. in F1 the sum of all small parts makes a big gain. they talk about less than 0.01s over a lap makes .1 over ten laps and 1s over a 100 laps. thats a long way at 300kph for a single component find 2 parts for that gain and you will be unbeatable.


RC is a small community. personally, i'd rather help people get their machines to a similar level than keep knowledge. I'd rather have those awesome tough battles, than the easy win. Reward driving and engineering, as it takes both. So help you local drivers and engineers.

Stock vs Modified, Scale vs Competition... There are gains that lead to different chassis behavior in both directions. Chose a direction and go for it.

I hope you now have more to think about.

Russ.

2 comments:

  1. Awesome article, you teach me so much things, and I also loose some parts due to the traduction, but you are realy implicated that's nice! Thank you for everything. You give me, in france the last and best way to set-up my rwd (actually: r31 grk global)
    And yup sadly RC club disappear.

    ReplyDelete
  2. Great writings you have done! Thank you very much for your effort towards the RC drift community.

    ReplyDelete

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