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Old 12-27-2015, 02:03 PM   #601
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Originally Posted by BJS414 View Post
A spool is a lot lighter normally and makes a noticeable difference
In the case of FWD, less weight in the front is actually a bad thing. If you want to save a couple grams of weight on a FWD car, use a softcase LiPo.
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Old 12-27-2015, 02:10 PM   #602
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Hello, this is my small contribution. I just created me a prototype based on the architecture of Yokomo YR-F2 SP. The pieces come from a Sakura D3 and chassis joints come from an ASSO 12R5. Other carbons parts and aluminum pilasters are made with milling machine.
I also own a YR-F2 SP brand new in box.
Awesome work

I often contemplated doing something similar but not owning an original would've meant a lot of doing it by "feel". In the end I went a different way and its worked pretty well thus far
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Old 12-27-2015, 02:21 PM   #603
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Originally Posted by fyrstormer View Post
In the case of FWD, less weight in the front is actually a bad thing.
Less weight is NEVER a bad thing in a car which is so heavily biased towards the front. Given there is often 160+grams of motor hanging out there, the difference between a spool and a diff in weight terms is negligible as far as that weight having an affect on handling, but the difference in drive characteristics makes a HUGE difference.

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If you want to save a couple grams of weight on a FWD car, use a softcase LiPo.
Softcase lipos are pretty much illegal at every club, under every sanctioning body RC has. Would be be better off suggesting using a low profile lipo which has a hard case at least.
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Old 12-28-2015, 04:37 AM   #604
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In the case of FWD, less weight in the front is actually a bad thing. If you want to save a couple grams of weight on a FWD car, use a softcase LiPo.
My experince with fwd is that the motor hanging over the front should be moved as much as possible rearward. FWD is not only about traction, it is also about how the car handles corner entry, midcorner and through fast chicanes.

In full scale fwd racing most notably with supertouring tacing cars the engine was moved as much as possible to the rear, touching the bulkhead/firewall to improve the handling. Cars with heavy V6 engines or longitudal mounted engines were normally struggling in this race format.
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Old 12-28-2015, 04:48 AM   #605
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Physics doesn't scale. It doesn't matter how 1:1 race cars are engineered, because 1:1 race cars have hundreds, if not thousands, of pounds of frame and drivetrain parts outside the engine bay, and that will always represent the vast majority of the vehicle's weight, whereas a 1:10 FWD touring car will be about evenly split between the weight of the motor/front gearbox vs. the entire rest of the chassis, assuming it uses a carbon-fiber double-deck chassis. Moving the motor is fine-tuning for a 1:1 race car, but it has an ENORMOUS effect on a 1:10 touring car.

My experience with FWD is that having the motor anywhere except in front of the front axle is disastrous because it's impossible to get any traction to accelerate with. (even with the motor overhanging the front axle it's still hard to get traction, hence the reason for the part-time-4WD car I built.) Of course acceleration isn't the only important thing in racing, but it is *an* important thing, even for FWD. In regards to steering, I have noticed zero loss of steering responsiveness or precision from having more weight on the front axle. (within reason, of course -- I'm sure you could stick a pound of lead on the front and ruin the steering, but that wouldn't mean you have a valid point, it would just mean you're an idiot who will go to absurd extremes to win an argument.) Having the rear wheels freewheeling at all times means there no push to compensate for, so steering responsiveness is always laser-accurate compared to 4WD (to say nothing of comparing to RWD), even with the motor in front and a "heavy" gear-diff in the gearbox.
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Old 12-28-2015, 04:56 AM   #606
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I just introduce another prototype that I made there already 4 years.

I left a rear transmission "Vintage" Kyosho TF3, I have pasted rolling trains TF5 Stallion, all the way "TT traction 80s."

the behavior is very healthy and even too much. I can not seem to "leave" the rear axle, the chassis is reactive in the slow parts but pretty understeer in the long corners and pronounced support. The adhesion was very precarious during testing because the track was extremely dusty which did not allow me to pass power to the ground.

I leave that up to the photos speak for themselves:







































































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Old 12-28-2015, 08:10 AM   #607
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Nice!
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Old 12-28-2015, 03:06 PM   #608
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Originally Posted by fyrstormer View Post
Physics doesn't scale.
Of course Physics scale ... they have whole series' of classes they teach in physics at school about scaling laws and how to apply them. They may not always be simple as 1+1 but they do scale!

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It doesn't matter how 1:1 race cars are engineered, because 1:1 race cars have hundreds, if not thousands, of pounds of frame and drivetrain parts outside the engine bay, and that will always represent the vast majority of the vehicle's weight, whereas a 1:10 FWD touring car will be about evenly split between the weight of the motor/front gearbox vs. the entire rest of the chassis, assuming it uses a carbon-fiber double-deck chassis. Moving the motor is fine-tuning for a 1:1 race car, but it has an ENORMOUS effect on a 1:10 touring car.
Simple response - bollocks. Complicated response - The motor in the average 1:10 car represents about 12% of the total mass of car RTR. I've not weighted a 1:10 RC gearbox lately but I doubt it would be anymore than half of the motor weight (since you say the frame etc is separate I am only including the rotating parts of the gearbox) so even using that as a basis the motor and gearbox would equate to around 17% of the total car weight.

In 1:1 (depending on which series you base it on but since we are comparing TC), its hard to find specifics as a lot of racing people are pretty secretive, but even the bespoke (and therefore light) engines/gearboxes used in DTM still represent around 16% of the total car weight. For other categories, such as V8SC in Australia, it can be as high as 19% of the total weight. So your assertion that the motor and gearbox in a 1:10 car is considerably more of the proportional weight compared to a 1:1 car is not just flawed it is incorrect and therefore any claims you make based on that assertion are also incorrect.

Of course I am basing all this on the rules I have to run to here in Australia. You may run to different rules and this may skew this slightly but not significantly enough to change my point.

The biggest issue with gaining traction in a FWD (or any layout for that matter) 1:10 car is down to 2 things - power and weight transfer/balance. It is extremely difficult to make a FWD drive car transfer the weight back onto the driving wheels when the weight of the motor, and even the effects of its rotation, are trying to force the suspension to do the exact opposite. Some cars try to use this leverage to "increase" traction but they tend to have more issues in fast corners as the weight hanging so far forward changes the characteristics of the grip/slip circle and the front wheels simply lose grip sooner. Moving weight over the centreline of driving wheels is one of the holy grail's of chassis design and its no different in 1:10 or 1:1, but just moving the motor with no thought to suspension dynamics and weight balances etc won't provide a miracle cure.

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My experience with FWD is that having the motor anywhere except in front of the front axle is disastrous because it's impossible to get any traction to accelerate with. (even with the motor overhanging the front axle it's still hard to get traction, hence the reason for the part-time-4WD car I built.)
Your part time 4WD car is simply "cheating" by using 4WD when its advantageous (under power out of a corner or off the start line) and then going 2WD the rest of the time. Its essentially a version of how we used to run all 4WD cars when we used a series of one-ways, before we realised that brakes were important too.

When mini classes first moved to lipos (and lower weight) a lot of people struggled with car balance and handling and it wasn't until they added the weight back they had lost from going to the lipo battery that they got on top of it again.

My experience is that time and again people underestimate the importance of the rear suspension in a FWD car. In a 1:10 FWD car the battery (which comprises around 14-15% of the total RTR weight btw) is placed in the middle or even towards the rear of the car so the rear suspension actually has a lot of influence on how the car turns and handles. The only time it's useless is under power as the front does almost everything.
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Old 01-16-2016, 10:10 PM   #609
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So just got back from a race with my 3racing FF2015 car. Cannot tell you how much fun this thing is. I was lumped in with the touring car class in 17.5 and held my own very well. I turned better and was able to be on power more than they were but they did have the edge with acceleration off the line that's where I lost time. I stuck with light oil and did not like the way the heavy oils felt in the car. I settled on 10k with heavy springs up front and mediums in the rear, tamiya BB springs. Battery positioned all the way to the back. And a few geometry changes here and there and it was hooked. Gotta give it to 3racing in this one. Cars built like a tank and solid performance. I will be purchasing their 4wd as well. Was in 3rd place for the whole C main and then front body clips popped off hitting a barrier and had to drive careful after that and finished 6th. Not bad for FWD and there was a D main as well so gotta give it up for the FWD. great car to drive and will be using it more.
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Old 04-13-2016, 01:49 PM   #610
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https://www.youtube.com/watch?v=AfBQ...ature=youtu.be

FF-Class bump...

my way of providing more FFWD awareness. looks like some good racing..... over there.
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Old 04-13-2016, 03:57 PM   #611
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I'm putting together an FF-03R. Dunno if I'll ever run it though. Mostly I just wanted to build one. Right now I'm having great fun running my XV-01 FWD rally car.

Quote:
Originally Posted by ShadowAu
Of course Physics scale ... they have whole series' of classes they teach in physics at school about scaling laws and how to apply them. They may not always be simple as 1+1 but they do scale!
Yes, there are formulas, but they aren't as simple as "double the size of something and all the forces double as well", which is what most people think "scaling" consists of. I took physics with calculus for 2 years in college as part of my engineering degree, and in the process I learned to assume most people don't understand how physics works, but I have to be able to communicate with them at their level of comprehension anyway -- hence my statement "physics doesn't scale". I could say "the exact nature of the rules change as things get bigger/smaller, faster/slower, hotter/colder, etc.", and list off formulas, but I've done that before and people's eyes glaze-over almost instantly.

Quote:
Originally Posted by ShadowAu
Your part time 4WD car is simply "cheating" by using 4WD when its advantageous (under power out of a corner or off the start line) and then going 2WD the rest of the time. Its essentially a version of how we used to run all 4WD cars when we used a series of one-ways, before we realised that brakes were important too.
I know very well how it works, thanks. I'm the one who designed it to work the way it does. It is vaguely similar to a 4WD car with a one-way bearing in the front, except that instead of rendering the front wheels useless when braking, the front wheels do *all* the braking -- instead it's the rear wheels that freewheel when braking, which means when it skids, it skids in a straight line instead of spinning-out. Still not quite as good as 4-wheel braking, but way better than rear-wheel braking. Super-sharp FWD steering, strong 4WD acceleration, and pretty good braking -- what's not to like?

Last edited by fyrstormer; 04-13-2016 at 04:42 PM.
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Old 04-13-2016, 07:48 PM   #612
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https://www.youtube.com/watch?v=OHz612xqo_0

more FFWD fun... wish we could get this class going as good here in the 'States?
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Old 04-14-2016, 02:50 PM   #613
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very interested in this thread and FF cars in general. just a few questions that peaked my interest as I'm unfamiliar with the designs. that prototype reminds me somewhat of the yokomo yr4 f2 car. is there a benefit to the trailing arm like design vs the independent suspension we see in our 4wd counterparts?

also as mentioned and discussed, but why do most FF cars have their motor hanging in front of the drive axles instead of behind for better weight distribution and handling? is the additional weight in front of the axle that important for increased traction for our little 1/10 cars?
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Old 05-02-2016, 09:10 AM   #614
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Originally Posted by OSherman View Post
https://www.youtube.com/watch?v=OHz612xqo_0

more FFWD fun... wish we could get this class going as good here in the 'States?
FWIW, FWD cars are legal to run in USGT
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Old 05-02-2016, 09:36 AM   #615
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Yes.. I'm dialing in a car to run that class..

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