Tamiya got it wrong?

[Juggular]

3 hours ago, TurnipJF said:

An easy way to remember which M-chassis is which: odd numbers are FWD, even numbers are RWD.

Whoa!  Brilliant!  

[Fabia130vRS]

I were browsing RcMart for Zahhak's and came across this

http://www.rcmart.com/532171-free-ship-p-80114.html

FF, MR, RR

[Juggular]

Oh, wow.    

You can actually configure one of 3 ways?  This looks interesting.  

[Kingfisher]

2 hours ago, Juggular said:

Oh, wow.    

You can actually configure one of 3 ways?  This looks interesting.  

I wonder if you can configure 2 of 3 ways, with a motor in the front and one in the back.

[njmlondon]

On 10/15/2018 at 9:02 AM, Juggular said:

Oh, wow.    

You can actually configure one of 3 ways?  This looks interesting.  

MST are really leading the way where Tamiya should have gone. Their CMX and CFX chassis are what the CC02 should be. If these are built to the same quality then they would make perfect M chassis swaps.

[Yalson]

10 hours ago, Kingfisher said:

I wonder if you can configure 2 of 3 ways, with a motor in the front and one in the back.

And then clothe it in a Seat Ibiza Bimotor shell.

https://www.carmrades-blog.com/all-articles/2017/6/10/dual-wield-1986-seat-ibiza-bimotor-group-s-prototype

[jupitertwo]

30 minutes ago, Yalson said:

And then clothe it in a Seat Ibiza Bimotor shell.

https://www.carmrades-blog.com/all-articles/2017/6/10/dual-wield-1986-seat-ibiza-bimotor-group-s-prototype

Thanks for sharing that link, I’d never heard of the Bimotor till now. Awesome stuff!

[Mad Ax]

20 hours ago, njmlondon said:

ST are really leading the way where Tamiya should have gone. Their CMX and CFX chassis are what the CC02 should be. If these are built to the same quality then they would make perfect M chassis swaps.

I can't disagree with this.  I've had MST stuff on my wish-list for ages, but I've got enough scaler projects to last a lifetime so I doubt I'll ever get a CMX unless I come into a pot of cash (or get rid of some of my other scalers).  But the TCR looks like a great little chassis for scale on-road builds.  I don't run my touring cars (just build for the shelf) so I don't really care how it runs - I just love the idea of having the right drivetrain and wheelbase under the body!

[Juggular]

This Alfa Romeo drives like XV01 (in terms of weight distribution), but it's RWD.  

Front motor and RWD will have terrible traction, so I suppose that's almost impossible to drive.  Maybe Tamiya should sell XV01 with Alfa body!  It just looks so awesome! 

 

[Kingfisher]

14 hours ago, Juggular said:

Front motor and RWD will have terrible traction, so I suppose that's almost impossible to drive.

I have a 1:1 MX-5 Miata and disagree. 

[Juggular]

38 minutes ago, Kingfisher said:

I have a 1:1 MX-5 Miata and disagree. 

Sorry, I meant RC.  

[Yalson]

13 hours ago, Juggular said:

Sorry, I meant RC.  

Would it, though? I am genuinely asking as I have never driven a front motor/rear drive chassis in 1:10 scale but I'd imagine the natural squat which all cars display, regardless of configuration, would give it acceptable traction. I would have thought that the handling balance would be better than a front motor/front drive car, at least, and would be ideal for drifting.

[Butler]

The motor is only half the issue in terms of weight. Consider the battery too.

[Falcon#5]

They may be scale models, but physics don't scale the same way.

I've been involved in RC yachts, and for one to sail the same as a 1:1, the keel needs to be as long or longer than the length of the boat.

 

[Mad Ax]

4 hours ago, Yalson said:

Would it, though? I am genuinely asking as I have never driven a front motor/rear drive chassis in 1:10 scale but I'd imagine the natural squat which all cars display, regardless of configuration, would give it acceptable traction. I would have thought that the handling balance would be better than a front motor/front drive car, at least, and would be ideal for drifting.

There are some drift chassis that have the motor up front and drive the rear wheels.  However RWD RC drift is impossible without a gyro.  I think most current RWD drift chassis have a midship motor layout, though.

I had a 1:1 MX-5 too, as well as various other front-engined RWD cars, and the handling was fun but more likely to go pear-shaped than driving a similar car with FWD.  It's the nature of the beast.  I used to do drifting in my MX-5, and it's something you do by the seat of your pants - you feel what the car's doing before you can see it happening.  You don't get that benefit with RC, you have to wait until you can see something happening to the car before you can correct.  By that time it's too late. 

[Juggular]

 

3 hours ago, Yalson said:

Would it, though? I am genuinely asking as I have never driven a front motor/rear drive chassis in 1:10 scale but I'd imagine the natural squat which all cars display, regardless of configuration, would give it acceptable traction. I would have thought that the handling balance would be better than a front motor/front drive car, at least, and would be ideal for drifting.

The traction for 1:1 front motor, RWD is less.  For dry surfaces, it's fine.  

I've seen one of those sleek high-end RWD Mercedes in snow.  It was not even heavy snow, maybe like 5mm.  The poor guy was going dangerously slow, while FWD cars were driving just fine.  It might also be the extra-wide tires he had too.  After seeing that, my impression of front-motor-RWD is, "I'm never buying a RWD car unless I live in Texas!"  (also unless it's a second car)  

I want a front-motor, RWD RC car, but realistically, such configuration may not work.  

3 hours ago, Falcon#5 said:

They may be scale models, but physics don't scale the same way.

I've been involved in RC yachts, and for one to sail the same as a 1:1, the keel needs to be as long or longer than the length of the boat.

Very true.  Yalson was talking about how aerodynamics don't scale the same way too!  

This is probably why front-motor-RWD RC cars would have a hard time getting enough traction.  Even rubber eraser on paper might get more traction than rear tires of a front-motor-RWD RC car.  I'm not holding my breath for such configuration...

 

 

[GooneyBird]

Power-to-weight is the key issue here. Our little RC cars have absolutely rediculous PtW-numbers. They're far too powerful for their weight (or not heavy enough for their power.)

Because of that, you need all the weight on or near the driven wheels. For 4WD cars this tends to be a non-issue, as all of the weight tends to fall inbetween the wheelbase regardless. But for 2WD cars this becomes a bigger issue, as you can't stuff everything on the rear/front axle without some serious packaging issues. Look at something like an M03. The motor and servo are up front, and the battery is shifted about as far forward as it'll go. The rear, meanwhile, is nothing but a bare chassis. The rear wheels don't carry a lot of weight, and are mostly there to prevent excessive wear on the rear bumper.

Your MX5 has a near-perfect 50:50 weight distribution, and between 90~140 hp for about 900kg. This is pretty much the golden ticket to a well-handling car. I'm not nearly smart enough to calculate how many hp a simple silver can gives, but considering it can propel an rc car from standstill to top speed in about 2 seconds I'd say that the balance of power to weight tips more to power than weight.

With that said, I now have thought of at least 3 projects involving that MST car....

[Mad Ax]

It occurred to me last night that one of the best-known RWD cars for twitchy, unpredictable handling is the Porsche 911, which has its motor slung out the back, like a RWD buggy or an M06.  I guess because of the pendulum effect, once it breaks free the rear-biased weight will keep it sliding and with no weight over the front it must be very light- and quick-steering.

I suppose 1:10 doesn't have quite the same issue partly because battery location reduces the rear weight bias somewhat and partly because excessive grip (which causes a roll) is more of a problem in 1:10, as opposed to lack of grip causing a slide.  The dynamics don't translate because one is not a direct scale of the other.

[Yalson]

13 hours ago, Mad Ax said:

It occurred to me last night that one of the best-known RWD cars for twitchy, unpredictable handling is the Porsche 911, which has its motor slung out the back, like a RWD buggy or an M06.  I guess because of the pendulum effect, once it breaks free the rear-biased weight will keep it sliding and with no weight over the front it must be very light- and quick-steering.

This is certainly the case for early 911s, which were lighter, had taller, skinnier tyres with less grip and were far less developed dynamically. I have read a number of reviews of early 911s and the general consensus is that they are fast and rewarding to drive, but could be a bit of a handful for the unwary, especially in the wet, for exactly the reasons @Mad Ax suggests. One of the most popular after-market modifications for Porsche 356s and early 911s was a sizeable lump of concrete or iron mounted as low and as far forward in the nose as possible, in order to keep the momentum of the flat-six anvil in the tail in check.

Porsche's whole approach to the 911 since then has concentrated to a greater or lesser degree on trying to dial this inherent twitchiness out of the chassis through whatever methods were available. Porsche's ackowledgement of the 911 chassis' inherent flaws was made most obvious by their plan to phase the car out entirely in the 1970s in favour of the mid-engined 914. We can all see what a roaring success that idea was.

Modern 911s aren't even called 911s anymore and share nothing at all technically with their bare-minimum, air-cooled, featherweight ancestors beyond their engine position and basic layout. They are full of physical and electronic devices to keep that layout in line. But if you have a big lump of metal mounted behind the back wheels of any car, there is only so much you can do to stop it biting you and every so often, if you're not careful, it will.

[Juggular]

15 hours ago, GooneyBird said:

Your MX5 has a near-perfect 50:50 weight distribution, and between 90~140 hp for about 900kg. This is pretty much the golden ticket to a well-handling car.

 

I assumed that front-engine RWD cars would have close to 60:40.  I just thought keeping the weight balance of M03 wouldn't work if it were RWD.  I wonder if this means a front-motor RWD RC would be plausible if the weight is 50:50?  Probably still not enough weight for the driving wheels, because of the power to weight ratio... MX5 having 800hp would be uncontrollable too, I guess.   

 

[GooneyBird]

8 hours ago, Juggular said:

I assumed that front-engine RWD cars would have close to 60:40.  I just thought keeping the weight balance of M03 wouldn't work if it were RWD.  I wonder if this means a front-motor RWD RC would be plausible if the weight is 50:50?  Probably still not enough weight for the driving wheels, because of the power to weight ratio... MX5 having 800hp would be uncontrollable too, I guess.   

 

Most ‘normal’ RWD cars are indeed closer to 60:40, but the cars we tend to think as the reference to how a RWD car should handle are closer to, or bang-on 50:50. (MX5, E30 with a I4, S2000)