RWD, 4 Wheel Independent Susp. Onroad Cards - Why Not?, Why?, How?

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  • Quote: It is a great idea, but the cars would be very hard to drive....
    Like driving a race car instead of a video game? Count me in.
  • Quote: I think the reason RWD hasn't stuck around on-road is simple. 4wd is easier to drive. Maybe, just maybe, it's a braking thing. But I think the tendency to push, and greater all up weight all contribute to a car that's easier to drive.

    [...]

    Grip falls off with weight. Weight means slower responses to things like slides (this is not a bad thing for small cars..).
    Seems you are contradicting yourself a bit. Is weight helping or not, then?

    Without weight you have no control over the car. Weight gives you grip and that means you can put power to the ground and use brakes.

    I don't see how "grip falls with weight".

    Sure, it does slow you down a bit if you din't have enough power to accelerate, and it does mean that a slide will be more difficult to control, but in 1/5 scale, they seem to have overcome those problems. I am not sure you could do it in 1/10 scale with much lower weight and much smaller tyres. You would have to increase the tire contact patch proportionally to get back the grip you lost because of the reduced weight and that is simpy not an option.
  • Quote: I think its a great idea though. If we can make F1 cars handle (with 2WD, rubber tires, and a solid axle in a pan car) there's no reason that a fully independent touring car can't be made to handle with 2WD.
    The reason F1 cars can run RWD is because they have TONS of downforce and no body-roll to speak of, they run on the cleanest flattest pavement available, and they hold almost all of their speed in corners so there isn't actually that much hard acceleration and braking that might cause the rear wheels to break traction.
  • Quote: It's my personal opinion that the DS was the best all around parking lot/subdivision street car of all time. It was simple and fun and has enough suspension that it can run where pan cars can't. I like that it doesn't have the complexity of a touring car but you could still use realistic bodies with it. On a smooth asphalt or carpet track, it wouldn't stand a chance against any other car classes but a bunch of them together was a riot.
    You should try a Tamiya XV-01 sometime. Yes, it's complex, but it's very rewarding to drive on rough pavement.
  • I built such a RWD-Touring Car two years ago. The idea was to save the weight of the AWD and use it for a low center of gravity. I combined a TC6 rear with an Xray X10 front and connected them with a custom aluminium chassis. I used it for a couple club races (21,5, blinky) but suffered all the problems mentioned above.
    After having retired the car from racing I equipped it with an AVC-Receiver which made driving much easier.
  • Hehehehe! That is the ticket. Or using heli gyros (which would give away your cheating though). I always thought of running this experiment with my heli gyros, but have been to lazy to pull it off. Besides my gyro is the size of a normal ESC. Difficult to hide.

    I guess these days any drone receiver would be fine.
  • Simply speaking: RC'ers want stuff that is easy to drive. If you give them something hard to drive, it won't sell. Hence manufacturers won't make it

    Now, going through it one by one:

    PanCars (be they 1:10 or 1:12) : What they loose in front grip from absence of front transmission, they gain with Tyres (sauced foam), and Aero. these aren't "entry-level" classes either. 12th is THE historical class, the "original" one, even before offroad. 10th came two decades later as 12th was deemed too small and converted 10th buggies paved the way for a bigger scale (see below)

    "modern" DTM: easy to drive (to some extent). Hammer-fisted "drivers" can still squeeze the trigger (to some extent) while not doing donuts every other corner. that's 4wd magic for the masses, and also why most offroaders also wanted to drive 4wd rather than 2wd, until everyone started making hi-grip tracks DTM would actually probably work with non-independent suspension, but the class has historically evolved from converted buggies... hence the 4-wheel suspension as standard.

    F1 has come and gone, it already died once in the 90's... you get 2wd pan cars, without the aero (yikes). What makes the class work nowadays is the mild motors. They are hard to drive, mind you, but they seem to be here to stay. Which is great cuz they look like the real thing and provide some RC appeal to the non-RC masses (as opposed to the blob-shaped touring cars...)

    FWD touring: Once you bear with the complexity of independent suspension, non direct-drive cars, why not go the full monty and get rid of wheelspin? Plus, there's the inherent bias that a "proper" race car can't be FWD... it's like stick vs. auto FWD never really took off globally (there are some pockets of popularity, mostly in Asia) and most RC'ers when given the choice will go 4wd instead. Which is a shame, because a decidedly driven FWD can show a trick or two to most 4wd sedans... Ask Masami and his YRF2-SP

    And lastly, Rwd touring: All I can say is, have you ever driven one? I had an M-chassis boxster a couple of decades ago... saying it was a handful to drive is an understatement, even with a Mabuchi 540! By nature, given the "rudimentary" RC tire technology, the fact that you have to control the car "by eye" as opposed to feeling the acceleration as you would from a 1:1 car, and the fact that electric motors are developing most of their torque from low rpm (think about it... most hybrids/electric 1:1 cars are either FWD or AWD) you have a recipe for driving disaster here, switching from painful understeer to snap oversteer all the time...

    But I agree it'd be one heck of an RC driving school
  • Quote: I don't see how "grip falls with weight".
    Nerobro may have been referring to the coefficient of friction of the contact patch, which does decrease with increasing weight. Given the same size contact patch, higher weight results in lower maximum lateral acceleration, and of course slower straight-line acceleration and braking.

    But higher weight definitely makes the car easier to drive! (With the recent decrease in our minimum weight in VTA, the car is much livelier and responsive.)
  • Don't know where you got the idea that F1 is failing. It maybe a niche class but it's interest levels have remained constant for the last couple of years *shrug* maybe not in your part of town ��
  • Quote: Nerobro may have been referring to the coefficient of friction of the contact patch, which does decrease with increasing weight. Given the same size contact patch, higher weight results in lower maximum lateral acceleration, and of course slower straight-line acceleration and braking.

    But higher weight definitely makes the car easier to drive! (With the recent decrease in our minimum weight in VTA, the car is much livelier and responsive.)

    Yeah, I see your point.

    But talking about contact patch and other things like that is worrying what you're going to do with all those millions after you win the lottery. A moot point when you don't have enough weight to make use even of the contact patch you have.

    The large scale cars I linked to have enough weight to take advantage of their tires, which is not the case for smaller cars. Those cars have about the same power to weight ratio as our cars (or less), but much more grip to use the power (and as someone commented hydraulic brakes to slow down), plus a weight distribution that helps the front grip.

    I have given this example to suggest a solution to our OP. Solve these problems for the scale you want, and you've got your wish.

    The 1/12 cars found a solution to these problems by using outlandish aerodynamics and foam tyres. The weight problem is solved by generating massive downforce in this case.
  • Quote: The reason F1 cars can run RWD is because they have TONS of downforce and no body-roll to speak of, they run on the cleanest flattest pavement available, and they hold almost all of their speed in corners so there isn't actually that much hard acceleration and braking that might cause the rear wheels to break traction.
    Have you raced a 1/10th scale F1 car?

    Contrary to popular belief, a 1/10th scale F1 car doesn't create anywhere near as much downforce as a 1/10th scale sedan. Aero doesn't always scale down.

    In our neck of the woods (Wisconsin) we have raced them outdoors on parking lots (not smooth pavement, it freezes HARD and thaws here every year, so there's no such thing as smooth pavement anywhere) and our local carpet track is on the second floor of a 100 year old building, so as you would expect there is some character/variation/bumps on the track. Both situations emphasize setup dramatically.

    Our local racing organizations have come up with some amazing track layouts too, almost always incorporating a hairpin turn that requires heavy braking zones followed with long straights. If you can't brake hard and put the power down coming out of the corner, you lose.
  • Quote: It's my personal opinion that the DS was the best all around parking lot/subdivision street car of all time. It was simple and fun and has enough suspension that it can run where pan cars can't. I like that it doesn't have the complexity of a touring car but you could still use realistic bodies with it. On a smooth asphalt or carpet track, it wouldn't stand a chance against any other car classes but a bunch of them together was a riot.

    I regret not buying one back in the day. I also regret not buying the conversion kit to convert my RC10T into a DS. They were such cool cars. They weren't complex but offered a ton of adjustability. The Mustang, Camaro, and Mercedes bodies were beautiful and the BBS-looking wheels were awesome too. Sure a 4WD touring car would smoke them all day every day but who cares?

    If Team Associated released them again I'd buy 3 LOL
  • Quote: Seems you are contradicting yourself a bit. Is weight helping or not, then?

    Without weight you have no control over the car. Weight gives you grip and that means you can put power to the ground and use brakes.

    I don't see how "grip falls with weight".

    Sure, it does slow you down a bit if you din't have enough power to accelerate, and it does mean that a slide will be more difficult to control, but in 1/5 scale, they seem to have overcome those problems. I am not sure you could do it in 1/10 scale with much lower weight and much smaller tyres. You would have to increase the tire contact patch proportionally to get back the grip you lost because of the reduced weight and that is simpy not an option.
    I assure you, I'm not.

    Less grip, doesn't mean harder to drive. Spools give less grip, yet those make AWD touring card easier to drive.

    Grip is a ratio. "Coefficient of friction". What is important to know, is that with rubber, if you double the weight on a tire, you don't get double the traction. You get something like 180% more traction. So, if your car weighs twice as much, you get something like 10% less cornering traction.

    So, heavier, means slower cornering.

    Heavier also means the car reacts slower. In the case of a 4wd car, the polar moment of inertia is huge. Higher overall weight. Weight spread to the ends, sides, and corners, all make for a very big polar moment of inertia. Thsi makes the car react slower to rotation, pitch, and roll. Slower reactions makes the car easier to drive.

    If you need an example, think of how many people can sustain a mid corner slide with coutnersteer on a 1/10 touring car, versus the people who can even catch a mid corner slide on a 1/12 pan car.

    Pan cars have very centralized mass. When they spin, they spin ~yesterday~. (this is true even with the 1/10 pan cars)

    Quote: Nerobro may have been referring to the coefficient of friction of the contact patch, which does decrease with increasing weight. Given the same size contact patch, higher weight results in lower maximum lateral acceleration, and of course slower straight-line acceleration and braking.

    But higher weight definitely makes the car easier to drive! (With the recent decrease in our minimum weight in VTA, the car is much livelier and responsive.)
    Yup. That's exactly what i'm talking about.

    I'd love to see brakes on a RWD car. But I can't think of a reasonable braking system that would work with 1/10 scale cars.
  • This has been brought up. But the point should be repeated, and clarified. R/C cars are massively overpowered. This is a big reason why 4wd is popular, as well.

    If efficiency, were really the thing, 2wd would be the rule. 380 powered touring cars would be ruled by 2wd and loose gear diffs.

    Anybody interested in current limited r/c car racing? :-)
  • Quote: And lastly, Rwd touring: All I can say is, have you ever driven one? I had an M-chassis boxster a couple of decades ago... saying it was a handful to drive is an understatement, even with a Mabuchi 540!
    That boxster was M-04, right? That's not best example of RWD chassis... Look few threads lower to M-06 thread - people compare M-05 and M-06 there and they are very close in performance. M-06 can be even faster, but as its more challenging to drive, its laptimes are not as consistent as M-05, that's true.