Niels007007

Hi!
I'm trying to better understand the inner workings and 'feel' of these 1/8 fast electric Pan cars such as the XRay RX8E, Serpent 977e / 989e. I am sure some experts lurk around these places so maybe I can be enlightened? :-)

1) They have a rigid rear axle and a front one way bearing. Does this mean, as long as any form of acceleration is happening, all 4 tires are just locked to the motor? And then the 'ground speed' of the tires is a function of the tire size differences and the belt/gear ratios? Serpent says the front 'ground speed' by default is a little higher than rears, so the front 'pulls' the car a bit more than it is 'pushed' from the rear? (overdrive I hear it is called)

2) When coasting, is the front axle open between the front left and front right? Or is it a rigid front axle, just disconnected from the rear axle by the one way bearing?

3) When applying lots of power, it seems to be 'easy' to sort of slide / oversteer the car a bit, or too much. But what about gentle acceleration out of a turn? Is that especially understeery because the fully locked drivetrain with 'front pulling' overdrive gearing?

4) When driven competitively, is off throttle oversteer always induced if you steer too much, or is it generally setup in such a way that you can apply steering and there will be understeer? Is it easy to spin off throttle with too much or rude steering?

5) Is off throttle really just coasting, or is there a lot of engine braking slowing the car down? More engine braking also going to make off throttle steering more sensitive I would think.

6) How much are electronics tuned? Torque delivery vs throttle position, engine braking versus RPM, are these things programmed by the pro's in the RC equivalent of an ECU? Or is it just motor amps = throttle position

Curious to learn a bit more about these things!

Niels

Sir 51D3WAYS

^Probably best if you posted or hung out in the nitro-on road forum.

1) Yes. Depending on tyre and pulley sizes, you can set it up such that the front is spinning faster always pulling the rear along, making for a more understeery car on power. More common is the rear spinning faster than the front, so that way you can utilize the massive traction of the rear tyres, get power over steer if necessary if you need more rotation, and the front will still pull you out, so you don't spin out. Note that any differences in axle speeds are very small.

2) Open between left and right. The second option you describe is a one way spool, a very rare option on 1/10 touring cars of the past.

3) If you've ever watched a race with these cars, you'll notice that they are 4 wheel drifting it everywhere. So yes, powersliding out of a turn is somewhat common. You can of course apply power smoothly and avoid oversteer, or through other setup options. It's not really understeery as the front one-way acts like a differential and the inside rear is slightly lifted, so the scrub isn't too bad.

4) It's very easy to spin off power and especially on brakes. You only have rear brakes, so it's like handbrake turning everywhere. If possible, sauce the rears. Get all the braking out of the way in a straight line and enter the corner somewhat faster than you dare, and let the front one way pull you in. You can setup the car to your tastes, mine has been setup to be somewhat understeery on braking and on sweepers under power.

5) This has to be set through the ESC. I don't recommend cheap rubbish. I recommend running without drag brakes. And using the smoothest brake frequency.

6) Most ESCs of this caliber have program cards. I personally setup only the brake and throttle feel, punch and LVC.

Niels007007

Thanks! Yes the 1/8 nitro Pan cars are still a thing, maybe they are the same regarding drive train / one ways ?

Thanks for the comments. Here is a video of what I'm trying to achieve, ignore that it is a 1/8 scale 1970s CanAm car, I have no actual RC car model .. It is my second day with an actual RC controller, but you can see it oversteers into and a bit out of turns. If you go to youtube and add /watch?v=HZZi2d1QGhs

The front tires spin about 1% faster here still, the initial bite is a bit oversteery if I have them equal to the rears. A HUGE amount depends on how the tire generates grip from wheelspin of course. I know for the development of the VRC Pro game, they made some tire test apparatus but it wasn't giving very consistent results. The longitudinal grip of the tire, if it maximizes at 10% or 50% wheelspin, and if the fronts are different than the rears.. All makes a real difference. If I had infinite time and money I would love to try and make a RC tire test rig where we can slip and slide a tire and measure its forces...

Regarding 6, tuning the electronics, you say things can be programmed, what sort of things? I mainly made the throttle less sensitive as, sofar, once I'm 50% throttle, I'm probably going to be at 100% very soon. For smoothness in driving I prefer more control over the first half of the throttle.

Sir 51D3WAYS

The nitro ones are the same drivetrain. The electric ones are adapted from the nitro.

I'll need to know what ESC, motor and radio you are using.

Niels007007

Ah sorry, I wasn't being very clear, I'm making a virtual version of such a car, can't post links yet but add this after youtube.com to see what I'm on about: /watch?v=HZZi2d1QGhs

Hence asking about the drivetrain etc to make sure I model that correctly, and my curiosity about how it 'feels' in certain scenarios. I'm using a FlySky G7p as that works as a USB game controller straight out of the box and I've reduced the throttle sensitivity in the sim.

Sir 51D3WAYS

Saw the vid, it handles very roughly correctly. I wouldn't necessarily change the sensitivity of the controller, but more like adjust the throttle and steering expo etc. Punch levels and drag brake and so on.

The car is supposed to be somewhat oversteery anyway, it's how it's supposed to work. Bear in mind also that this type of car is very heavily influenced by aerodynamics as well.

For reference, I use this ESC:

If you download the manual, you can see the vast array of adjustable items.

I personally don't touch the boost/timing, too complicated and sends temperatures through the roof.

I only really mess with the brake settings and some of the throttle settings. I only ever run 4s and 60% to 80% max. brake force. (can't remember) to avoid rear wheel lockup and spinning out.

I also go for the smoothest drive and brake frequencies.

mrreet2001

iTrader: (9)

Might I recommend putting some time on actual RC cars before building a simulator?

1/8 IC Fan

iTrader: (102)

👆this, and there is a Simulator called VRC. These cars 1:8IC and 1:8EG are far from simple, and far from being able to comprehended, if one is not directly involved!!! They are far from being close to any other RC car, be it 1:12 (which we used to race on asphalt too), 1/10 TC or even the 1:8GT which are just 1:8 buggies with Street tires. They are also the most unforgiving when setup wrong. Get a car and do your due diligence.

OlivierWierda

Guys don't be so condescending please, Niels knows his stuff and is known for making car physics for tons of different cars and even karts that visually appear to be very accurate to the real driving experience.

From my experience with the 1:10th classes, depending on ESC settings and motor timing the throttle response can be very linear and predictable, but running alot of boost and aggressive throttle profile for example can become quite oversteery and reactive.

And I agree that you should probably post this in the onroad nitro section, as many people that drive 1/8th onroad have tried both nitro and electric so they will be able to give better input.

1/8 IC Fan

iTrader: (102)

No one is condescending here.... you can not explain the dynamics of a 1:8IC/E so simply.... you have to go out and drive them.to find out!!! Thats just a fact. The reason Pieter B. was able to make VRC / Serpent Simulator, is because he had experience in 1:8IC. So nothing condescending, just facts!

mrreet2001

iTrader: (9)

That may be, but he is asking all sorts of weird questions that aren't easily answered verbally but would be answered by a day at the track with a real RC car (or two). Hence my recommendation to actually drive some of these cars before building a simulator.