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Old 02-28-2017, 03:07 PM   #46
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I started thinking about all of this when I saw Tamiya's F103GT Nissan Launch car:


I started reading about the full size car and found out it is FRONT wheel drive. So, the Tamiya model is a low-tech (F103GT) RWD model of a high tech FWD car, and I just thought that was kinda odd.

(I suppose I could buy the Tamiya TA06 chassis and disconnect the REAR drivetrain, and plop the Nissan Launch body on it. Then I'd have a scale FWD car).

I applaud Tamiya for their variety of RC cars like their FWD and RWD selection of M chassis cars, the F103GT platform, etc.

I know for organized racing, we need a limited number of classes, so a rwd independent suspension car will likely never be the norm but it's interesting to think about. Thanks for the replies all.
Look what they did with the MAN truck racer, its 4wd in model form from Tamiya.
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Old 02-28-2017, 03:26 PM   #47
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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.
I've seen M04 banned from mini racing because it has an unfair advantage over the other M chassis cars. It has a gearing advantage. That's why you don't see as many people compare the M04 to the M05 as much.
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Old 02-28-2017, 08:26 PM   #48
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Well, somebody had a Tamiya TA-06 for sale here on rctech for a very good price, so I just bought it so I can prove to many of you how right you may be.

It should be fairly easy to switch it between 4WD and RWD. I suppose I could just remove the rear dogbones to make it FWD, unless there is a quicker way.

I'm happy. I will soon have something to tinker around with.
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Old 02-28-2017, 08:34 PM   #49
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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.
Surface I'll be trying F1 on this summer is far from perfect. But I've seen that they can run on it.
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Old 02-28-2017, 10:11 PM   #50
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My standard of "clean and flat pavement" is probably pretty low. I'm talking no holes and no large pebbles. F1 doesn't have the clearance for any of that.
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Old 02-28-2017, 11:26 PM   #51
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I've seen M04 banned from mini racing because it has an unfair advantage over the other M chassis cars. It has a gearing advantage. That's why you don't see as many people compare the M04 to the M05 as much.
Yes, it has gearing advatage. But also, it drives like sh* - at least straight from the box.. M06 is far better and easier to drive


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Originally Posted by Nerobro
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.
Maybe drum brakes would work? They are pretty simple and 1/10 doesnt need to absorb much energy, so it doesn need disc brakes
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Old 02-28-2017, 11:42 PM   #52
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Maybe drum brakes would work? They are pretty simple and 1/10 doesnt need to absorb much energy, so it doesn need disc brakes
The problems come with lockup, lack of feel, and getting side to side brake bias the same.

I think I did just come up with a solution. Before we talk about that.

So.. if you link the front wheels together, you can use a single brake, and then you don't have a brake bias issue.

a disk might work, with a cable drive. But again, side to side bias matters.

A way to avoid lockup, is to use a viscous coupling. So.. you could use a fluid braking setup. Or you could use an aluminum brake disk and apply a magnet to it. If that magnet is an electromagnet... you now have brakes you can control with a conventional ESC.
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Old 03-01-2017, 01:21 AM   #53
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You can use disk brakes from RC motorcycles.
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Old 03-01-2017, 01:29 AM   #54
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left right balance would still be an issue. And the trouble with friction pad based braking is that they make more grip the slower they turn. Lockup, would be permanant until you release the brakes. Magnetic braking "can't lockup".

But is all of this heavier than just going 4wd...
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Old 03-01-2017, 02:28 AM   #55
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Magnetic braking can't lock up, but its braking strength also diminishes quickly as the disc slows down.
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Old 03-01-2017, 02:38 AM   #56
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left right balance would still be an issue. And the trouble with friction pad based braking is that they make more grip the slower they turn. Lockup, would be permanant until you release the brakes. Magnetic braking "can't lockup".

But is all of this heavier than just going 4wd...
This gets to the root of the issue. Engineering is always a compromise, and as it turns out, the most effective compromise for touring cars is to run 4WD, because it provides plenty of traction and four-wheel braking with the lowest possible weight. Physics doesn't scale (at least not linearly, which is what most people think of when they try to scale-down the physics of real cars to RC cars), so design compromises that work on full-size cars don't work on scale models that have ten times the power-to-weight ratio. All real cars, even supercars, are slow heavy pigs compared to RC touring cars, and that's why the vast majority of them can get away with two-wheel drive. Even pickup trucks, which are notoriously lightweight in the rear, can put most of their power to the ground using only the rear tires. An RC car similarly configured would be impossible to drive, even with a gyro to help.

I had a thought yesterday, that many of the handling problems with RWD touring cars could be reduced by locking the front wheels together with a spool that isn't connected to anything, just to provide a bit of bias towards understeer. But if you're going to have a spool and driveshafts in the front axle, then the only weight you'd save is the weight of the center driveshaft, or possibly the front drive belt depending on which chassis you start with. That few grams of weight savings is completely negated by the loss of performance due to poorer traction, acceleration, and braking by not running 4WD.

Building a RWD touring car is certainly a worthy experiment if you're the sort of person who learns a lot from experience. Just be aware that the outcome of the experiment is already known for all configurations that remotely resemble normal touring cars. If you could design a touring car with the same huge downforce that an F1 car has, you *might* get something that's driveable, but good luck fitting F1 wings to a touring car body without hacking the body to the point that it might as well be a F1 car.

- - -

Now, having said all that, I built a touring car last year that has FWD with part-time 4WD to assist with acceleration. It achieves this by underdriving the rear axle slightly, and using a one-way pulley to let the rear axle freewheel under normal circumstances. So it accelerates like a 4WD car, and steers and brakes like a FWD car. It's an interesting driving experience, and not nearly as frustrating as my RWD touring car was.

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Old 03-01-2017, 03:45 AM   #57
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If you could design a touring car with the same huge downforce that an F1 car has, you *might* get something that's driveable, but good luck fitting F1 wings to a touring car body without hacking the body to the point that it might as well be a F1 car.
Sedan bodies already have more downforce than 1/10 F1s - have you noticed that huge wing in the rear?

You are still talking about RWD as it was doing nothing but donuts - interesting, I have different experiences with RWD - only time I experienced something you're describing, was on wooden floor

You just need different driving style from AWD or FWD - throttle has larger part in handling than in other two, making car more sensitive.

Ofcourse RWD is going to have trouble putting power of 500W+ motor to ground, but if we are talking about 17,5 or 21,5T classes, there is no problems with driveability even for solid axle cars.

With independend suspension, RWD could be very close to AWD. With more efficient drive, they could even beat them in some conditions (carpet races). But for sure, it'd be fun to have one class for both FWD and RWD cars with full independent suspension, to compare how they perform. Problem is that no manufacturer tried to make even hobby-class RWD with full independent suspension.
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Old 03-01-2017, 04:57 AM   #58
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You have to modulate throttle inputs, brakes, and steering. Sometimes you have more power than you can put down. It puts the emphasis on the driving and the setup. It avoids the touring car battery and motor wars too.
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This is right along with my line of thinking. Thanks.
Most of us old farts think like this, too.

the issue is, most people who want to do RC don't. What's the first upgrade 99% of the RC'ers dump money in? Yup, you guessed it, more power
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Old 03-01-2017, 05:00 AM   #59
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Originally Posted by Papi View Post
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.

Correct - RWD M03 parts-bin car I honestly could NOT drive the thing more than a few turns without spinning it, no matter how smooth my throttle finger was back then. Real cracker of a body, though
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Old 03-01-2017, 05:29 AM   #60
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Shouldn't there be a RWD touring car chassis? Wouldn't that be cool for USVTA? Power slide around the corners in your '71 Cuda?

If I wanted to build one - other than not being able to race it in any recognized class - would it work? Could I just buy a touring car and take out the front wheel drive train?

Thoughts?
The 2WD 1/10 nitro class in the 90s was possibly the most fun I have ever had in RC car racing. The cars were fast, nice to drive and easy to maintain. We used sedan, GT1 and GroupC/Can Am bodies on them in various series. But, the cars were wide (not very scale) and had large foam rear tyres. The rear tyres were normally quite a lot softer than the fronts as well.

So if you get a cheap touring car to experiment with, try a set of foam 1/10 nitro tyres. 40 shore up front and 32 rears would be a good start.
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