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Old 06-01-2007, 06:20 AM   #1
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Red face Expotential???

I was hoping someone could explain to me what expotential is and how to use it, thanks.
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Old 06-01-2007, 06:43 AM   #2
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I always using a simple rule, if your car oversteering just dial to negative exponential vice versa..
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Old 06-01-2007, 07:01 AM   #3
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Originally Posted by t4m1y4niac
I always using a simple rule, if your car oversteering just dial to negative exponential vice versa..
Really that is too simple a rule and in honesty is not the right way to use exponential anyway. Bad advice there.

OK here is the way the basic steering settings work. I'll get to exponential in a moment.

1. Dual Rate. This is generally a knob or switch on the transmitter that allows you to limit steering lock. THIS is the control you should use to reduce oversteer with the transmitter. However, to correctly set up the steering on your transmitter is should be set to 100% to start with.

2. End-points/EPA/ATV. This sets the total movement of the steering servo left and right. In the initial setup of thr car you should adjust these so that the car reaches full left lock at full left steering input, and full right lock at full right input, no more, no less. A finer adjustment is to make sure that the car turns equal radius circles left and right at slow speeds on the track, in which case some finer adjustment of EPA may be necessary.

After setting these two you will have a car that steers correctly.

Now onto...

3. Exponential/EXP. This is the steering "curve". At 0% the steering response will be totally linear, however sometimes you will find that the car is too twitchy with small steering inputs on the straights, in which case you may like to reduce the EPA to a small negative value, say -10%. This will mean that the servo moves less sharply closer to neutral, but moves more sharply as it approaches full lock. Rarely will you need positive EXP. DON'T use EXP to tame oversteer, use the Dual Rate.

With all of these settings avoid large variations from the normal setting. If you need EXP of -30 or -40% to make the car driveable, something else is significantly wrong with the car setup. Only use the transmitter for fine adjustments during running.

Also, avoid very small dual rate settings that mean your car cannot negotiate the tighter sections of the track. I always make sure the car can turn 360 within the width of the track.

Incorrect adjustment of high-end radios is something I see a lot of locally. You can actually make the driving experience worse than using cheap, unadjustable gear if you are not careful.

Hope that helps.
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Old 06-01-2007, 07:03 AM   #4
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PS I also want add add that your steering linkages should be set up correctly before you attempt any transmitter setup, ie geometrically even and with the correct toe-in and neutral position.
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Old 06-01-2007, 07:57 AM   #5
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very good information .
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Old 06-01-2007, 08:00 AM   #6
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So sosidge, if your suffering from a bit of udnersteer, would some positive expo help initial turn in?

Also, Ive heard of using positive throttle exponential on brushless motors to make them feel more like a brushed, does it work?
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Old 06-01-2007, 08:47 AM   #7
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Good read Sosidge!
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Old 06-01-2007, 09:30 AM   #8
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My exponetial is prgrammed into my finger!! Works with any radio i use


Good info sosidge
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Old 06-01-2007, 09:36 AM   #9
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Great explanations of the radio settings!


I would only caution against using radio settings like dual rate to change car handling. By reducing your steering throw, you will not really "cure" an oversteering condition, you just mechanically limit the amount of mistakes you can physically make with the steering wheel, and limit your actual turning radius. As a quick band-aid, it'll work for keeping you safe with a car that has changed handling quickly, but you shouldn't use it as a super fix to a handling problem. Your steering travel (EPA) should be limited on the workbench to the limits of the car's linkage design, and to not put stress on your steering servo, and none less.

Personally, I set my D/R at the start of the day to make a nice, tight radius within the width of the track, then leave it alone. In an emergency, I'll pull the D/R back a bit to keep the car off the walls, if I have to, but I will promptly change tires or suspension settings, then return the D/R to the original setting.


Radio settings should be set for driver comfort, not to adjust car handling.




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Old 06-01-2007, 09:37 AM   #10
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Quote:
Originally Posted by thecrow2k
So sosidge, if your suffering from a bit of udnersteer, would some positive expo help initial turn in?

Also, Ive heard of using positive throttle exponential on brushless motors to make them feel more like a brushed, does it work?
Re:understeer, I would say change the car setup to generate more steering, and back off the Dual Rate to tame it.

If the car is a bit unresponsive to SMALL steering movements around centre try some positive expo. EXPO IS NOT A CURE FOR OVER/UNDERSTEER! Expo is about feel.

Re: brushless feel, I really couldn't comment, personally I would rather keep the transmitter linear and program the ESC for the right "feel", ie go for a punchier profile.
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Old 06-01-2007, 09:42 AM   #11
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Quote:
Originally Posted by ApexSpeed
Great explanations of the radio settings!


I would only caution against using radio settings like dual rate to change car handling. By reducing your steering throw, you will not really "cure" an oversteering condition, you just mechanically limit the amount of mistakes you can physically make with the steering wheel, and limit your actual turning radius. As a quick band-aid, it'll work for keeping you safe with a car that has changed handling quickly, but you shouldn't use it as a super fix to a handling problem. Your steering travel (EPA) should be limited on the workbench to the limits of the car's linkage design, and to not put stress on your steering servo, and none less.

Personally, I set my D/R at the start of the day to make a nice, tight radius within the width of the track, then leave it alone. In an emergency, I'll pull the D/R back a bit to keep the car off the walls, if I have to, but I will promptly change tires or suspension settings, then return the D/R to the original setting.


Radio settings should be set for driver comfort, not to adjust car handling.




I agree entirely. I only ever use dual rate as a fine adjustment, if I need to change it by more than 10% from the "normal" setting (usually 90-100% for me indoors, maybe 70-80% outdoors) I know that the car needs a setup change, not the transmitter.
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Old 06-01-2007, 02:05 PM   #12
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Thanks Sosidge, thats exactly what I needed to know
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