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Old 08-30-2012, 04:11 PM   #16
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The way I look at is, the more steering angle you require to make the same turn, following the same line at the same apex speed, the more the car is pushing. Whether the driver senses it as tight or not, its sliding the fronts and creating more heat than necessary. Now although my pit observations aren't very scientific yet, I've overhead guys that I'm racing (which I'm close in speed to) talking about tire temps. Now granted temp tools certainly vary, but it sounds like I'm routinely 12-15*F cooler at the end of a run. Their 112-115 to my 97-103. I'd be interested to hear what other folks are temping their 17.5 TC rubber tires (Sweep 32 or the like) on carpet. I'm generally .3 -.6 back of the fastest guys locally.
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Old 08-30-2012, 04:15 PM   #17
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You're trying for the ideal energy-saving scenario. With a pushing front end, you can apply more power. Less efficient, but faster.
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Old 08-30-2012, 05:07 PM   #18
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Originally Posted by Steve S View Post
That is a bad crutch to rely on in my opinion.
Why is that? I got the idea from a racer who won many championships. It's no different from Nitro guys running slow servos for throttle to not cause the car to lurch so hard...it's all about more control.
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Old 08-30-2012, 06:20 PM   #19
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Why is that? I got the idea from a racer who won many championships. It's no different from Nitro guys running slow servos for throttle to not cause the car to lurch so hard...it's all about more control.
Isn't the nitro thing because sudden throttle changes can cause a flame-out? I'm not a nitro guy, but that was my impression. If that's case, it's more of a safety feature than a driving aid.

Having a servo speed limit seems to introduce inconsistency in the car's response to your input. ie. If you steer slowly, the servo very closely follows your input. But if you steer faster than the limit you set, the servo no longer follows your input. Plus if you do need that quick response on occasion, it's no longer there for you. It's similar to what others are saying about steering throw: It's better to have full throw available and use smaller inputs. But that makes me a hypocrite since I'm usually at 85% dual rate

However, if it works, more power to ya. Just not my personal approach. I always suggest to newer drivers to not try to correct handling issues by adjusting their radio.
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Old 08-30-2012, 06:36 PM   #20
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I have my 2nd D/R set at 100% and it's assigned (push=on; release=off) to the grip button on my 3PK (underneath my middle finger). Very convenient location for an on the fly adjustment.
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Old 08-30-2012, 09:04 PM   #21
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Guys, I normally set dual rate to 84% (3PK adjusts in increments of two, so I cannot achieve 85%, which is what I prefer) and set the steering throw to where the wheels almost touch the shock bottom (full throw). My dual rate setting tones down the aggressiveness of full dual rate. Makes it feel more linear. I don't use any expo or steering speed settings. I like to work off of a more neutral / natural feel to the car. I learned, that, if I need to move the dual rate more that 2 - 4 clicks in either direction, then my set-up is off. I like to rely on the set-up on the car as opposed to the radio. I believe the radio settings are just for fine tuning.
Ok, so on to why I ventured into this thread, in the first place. I'm curious about everyone's view on Ackerman adjustment and what the settings (moving the link forward, backward, up, down) do?
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Old 08-30-2012, 11:01 PM   #22
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kendawg, I think that you and I are on the same page. My intent is to use almost the full mechanical lock on the transmitter on the tightest parts of the course-with the caveat being that the car is setup to make all the turns with very little front tire scrub.

It's good to see the variety of approaches--and shows that beneath the surface, there is a lot more going on regarding the settings on cars even if they are on similar pace.

This will be a bit of a digression, but I was going to segway into this eventually, but it seems that, at least when I was helping with FSAE in the past, that we preferred as little ackerman as possible; zero would have been great if we could get the c-hub/kingpin geometry just right. The theory we subscribed to was that at full cornering load most of the weight has already transferred to the outside front, and because of the tire's slip angle, you would want the outside wheel turned more towards the middle of the turn anyway.
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Old 08-30-2012, 11:02 PM   #23
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First, not to call anyone out, but saying 85% dual rate means nothing. Max mechanical throw is accurate and may be achieved with 48 or 117% dual rate depending on the mechanical travel needed which varies with every car, every radio, servo, and linkage setting. It is very important to make sure your servo is not attempting to pull further than the linkage is capable. Also zero expo will actually yield a more sensitive response around center since the circular rotation of the servo horn yields the highest throw at 90 degrees and approaches zero at 180 degrees. But this isn't a discussion about linkage setup, its steering inputs vs. throw.

A few very important differences between real cars and r/c. A few have been mentioned already so this may be slightly redundant.

1) Sheer speed. Take for example Silverstone. 18 turns with a lap record around 1:30. Even the massively fast F1 cars get a whooping 5 seconds/turn avg where an r/c might negotiate an 18 turn track in 20 seconds (or less). That's 1.1 seconds/turn avg. That means your reaction times essentially need to be 5 times faster than F1. (its late and this is super generalized so don't pick this comparison apart too much)

2) Disconnect of not being able to feel the car react to your inputs. This is made worse if your vision is not perfect, the car gets farther away, and the quality of your equipment.

I feel these are the two biggest reasons why we need the helping factor of turning lock to lock to be able to get around a corner with a reasonable amount of consistency. I would prefer a transmitter that would have a good 180-270 degrees of rotation in the wheel to allow a finer input with max throw still available but thats not available so we adjust to what we have. However, this may be a problem because if you get too much wheel turn, that 1.1 seconds/corner may get to be too fast to get the wheel to the other side quickly enough and with some amount of accuracy.

To add to my previous reasons I would also like to know how the scrub angles we run at differ to full scale. To start, with zero scrub you need X amount of degrees to get around a turn but you can gain traction up to a certain scrub past the minimum, X+n. It seems to me that our reduced scale leads us to be able to use a higher scrub angle without as significant loss in traction as a full scale vehicle. This could possibly be because the ultra light weight (when compared to full scale) make the comparative tire compounds significantly harder than full scale. Hence, no tire marks when we spin off into a corner. Anything else I can think of now is pure speculation so I will just stop.

Last edited by gubbs3; 08-30-2012 at 11:14 PM.
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Old 08-30-2012, 11:34 PM   #24
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Default A little clarity..

I said, "85%" in my post, thinking that those of us viewing this thread would have the understanding that it was out of 100% - on ANY radio. I have yet to encounter any racer using a percentage above 100, but that's not to say its not being used - just extremely uncommon in these neck of the woods. I would have to say that there's definitely a set-up issue with the chassis that's not being addressed, with that kind of d/r setting. I think we all would definitely benefit from each other's input if we can stick to the script. No right or wrong, here. Just what you do and why you do it? Maybe, throw in: how you achieve it?
Also, the exponential and steering speed setting would be set at the default / neutral position, which could be 100 or zero. Just depends on you radio. I'm simply saying, that, I don't change it.
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Old 08-30-2012, 11:55 PM   #25
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Originally Posted by TwoWheel View Post
It's good to see the variety of approaches--and shows that beneath the surface, there is a lot more going on regarding the settings on cars even if they are on similar pace.
I find this very interesting. I'm amazed at how you can have two different set-ups and drivers be equally fast. I'll have a friend drive my car and he'll say, "your car has a lot more steering than my car, but his lap times are almost identical!
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Old 08-31-2012, 12:27 AM   #26
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I run offroad, 1/8 buggy. I enjoyed reading through this thread, even though it is short. It is nice to see people in the hobby actually thinking and dissecting the mechanics/physics of the handing of rc cars.

You onroad guys are alright lol.
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Old 08-31-2012, 12:31 AM   #27
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Old 08-31-2012, 04:22 AM   #28
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Quote:
Originally Posted by kewdawg View Post
Guys, I normally set dual rate to 84% (3PK adjusts in increments of two, so I cannot achieve 85%, which is what I prefer)
Increments are adjustable on this radio. Go to Func-Dial. It's on menu 2 if your radio is set to Level 2 or 3.
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Old 08-31-2012, 04:35 AM   #29
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Originally Posted by kewdawg View Post
I said, "85%" in my post, thinking that those of us viewing this thread would have the understanding that it was out of 100% - on ANY radio. I have yet to encounter any racer using a percentage above 100, but that's not to say its not being used - just extremely uncommon in these neck of the woods. I would have to say that there's definitely a set-up issue with the chassis that's not being addressed, with that kind of d/r setting. I think we all would definitely benefit from each other's input if we can stick to the script. No right or wrong, here. Just what you do and why you do it? Maybe, throw in: how you achieve it?
Also, the exponential and steering speed setting would be set at the default / neutral position, which could be 100 or zero. Just depends on you radio. I'm simply saying, that, I don't change it.
100% D/R should be full mechanical lock - it is impossible to run more than 100% dual rate. Set the D/R to 100%, use the EPA to set full lock, then decrease the D/R to get the amount of steering you need. I'm generally between 85 and 100% with a TC depending on track and conditions. Less than that and the car won't turn full circle within the lanes.

Anyway - to answer the original question about using less lock and less rear toe-in - the Tamiya TT-01 is set up like that. It has no rear toe-in and quite limited lock, and the handling balance is very nice. It is probably a second a lap slower than a full-fat TC with the same motor and tyres, but that is not just because of the steering and toe - the CG and other suspension geometry is a limiting factor as well.

Bear in mind that an RC car, although subject to the same laws of physics as a full-size racer, races under very different conditions. The time spent in corners is very short, the response to steering, acceleration and braking are very rapid, and the driver's feedback is purely visual - there is no "seat of the pants" feeling.

By all means experiment with limited toe and steering lock, but don't assume it will work better. It is no accident that the current setups have developed the way they have, it is the result of experience and testing.
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Old 08-31-2012, 04:21 PM   #30
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Originally Posted by gubbs3 View Post
A few very important differences between real cars and r/c. A few have been mentioned already so this may be slightly redundant.

1) Sheer speed. (edited...)

2) Disconnect of not being able to feel the car react to your inputs. This is made worse if your vision is not perfect, the car gets farther away, and the quality of your equipment.

I feel these are the two biggest reasons why we need the helping factor of turning lock to lock to be able to get around a corner with a reasonable amount of consistency. I would prefer a transmitter that would have a good 180-270 degrees of rotation in the wheel to allow a finer input with max throw still available but thats not available so we adjust to what we have. However, this may be a problem because if you get too much wheel turn, that 1.1 seconds/corner may get to be too fast to get the wheel to the other side quickly enough and with some amount of accuracy.

To add to my previous reasons I would also like to know how the scrub angles we run at differ to full scale. To start, with zero scrub you need X amount of degrees to get around a turn but you can gain traction up to a certain scrub past the minimum, X+n. It seems to me that our reduced scale leads us to be able to use a higher scrub angle without as significant loss in traction as a full scale vehicle. This could possibly be because the ultra light weight (when compared to full scale) make the comparative tire compounds significantly harder than full scale. Hence, no tire marks when we spin off into a corner. Anything else I can think of now is pure speculation so I will just stop.
Very good points. This is the type of discussion I wanted to get going.

While I agree with your points above, I will say that having some sort of marker, not necessarily a mechanical stop on the transmitter, but a point where we know if you have turned a wheel "enough," is more important than having a physical stop itself-it's easy to guage 45 and 90 degrees, but difficult to guage 21 degrees-which is why I also would like a transmitter that had more than the customary 70 degrees of travel.

I say that because of the ergonomics and limited rotation of your wrist, doubling the range to 140 degrees on the transmitter would be a good start--at least have the option on the higher end radios to be able to do this.

The best drivers, like Rick Howart, can drive at 100% mechanical lock AND 100% setting on the dual rate, which takes tremendous skill--and from watching him at the REEDY on-road race, his car is not set up "slow."

Not really to belabor the point, but I think that yes, one can just accept the fact that "it is what is" and just set up their car to push and very slowly learn to drive a "faster" setup (read--less push). There is only certain amount of expo, steering speed, etc...that you can dial in before the steering feels disconnected--for me, anything more than +/- 10% on the expo starts to affect my steering accuracy and consistency.
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