Tuesday, July 30, 2013

Tuning with your transmitter: Steering

Have you ever been to a race and thought if I could just get that little bit more “this” or a little more “that” from your car but didn't want to change anything either because you,  A: Might screw up how good your car is now. B: The changes you make might be too much or not enough or C: Not know what to change to make the car do what you want it to do to improve it?

   I learned many years ago that we could manipulate the settings on our transmitters to make the car work better or simply just drive better and / or easier. On today’s TX’s there are so many settings that most drivers don’t know what they do or what they are for, let alone utilize what they are capable of to help you tune and dial in your car for better performance.

    In this post I will touch on the basis of helping you tune your car by explaining what some of the adjustments are for, what they do and how you can use them to gain more performance to get your R/C to do what you want it to without picking up a wrench. (OK you might need a wrench to start with)

Let’s start with the basics for steering and assume that you have everything straight. This means that your servo arm is straight up and down (or in the factory specified position) that your links are equal length side to side for camber and tie rods and that the sub trim/ trim settings are not too far from center. The basics are EPA (End Point Adjustment) , Sub Trim and Trim and D/R (Dual Rate).  Others include EXP/EXPO/Curve (Exponential), Speed and Punch. (Punch can be found on KO Propo Radios)

Sub-Trim/Trim:  These settings allow you to set the servo exactly in a neutral (or otherwise) position to allow the car to drive straight. Sub-Trim allows you to make adjustments within your Trim setting to allow the trim to be set as close to “0” as possible. This makes a difference with some Transmitters where the Sub trim moves the servo in larger movements per click than compared to the Trim which is the finer setting. Some radios allow you to adjust the movement or rate per click within the Trim setting.

EPA/Highpoint: This setting allows you to independently set the maximum throw of the servo from left to right. This eliminates the binding of the servo once it reaches full throw and to give you maximum operating range for your model’s steering.

Dual Rate: Dual rate is simply a means to control your end point adjustments together to either gain or lessen the throw of your servo. Even if your EPA is off from one side to the other the Dual Rate will add or subtract the same amount of EPA from both sides at the same time. Tuning Tip: Some Transmitters will allow you to go to 120% or more with Dual Rate. For beginning drivers I will set their Dual Rate this high before setting the EPA and then back down the D/R until it’s back to 100%. This decreases the steering which makes the car a little easier to drive as well as makes the new driver slow down more to complete a corner. Once the new driver becomes more skilled a simple click of the D/R switch gives them more throw. Once you explain to them that they can turn up the D/R a click here and there even if they go Max their servo is safe.

EXPO/Curve/Exponential: Exponential is one of those settings that was created to compensate for the arch of the servo arm to allow the driver/pilot to get back the feel of linearity for a particular control. For many years we have used EXPO to help in getting that feel that we are looking for both with Linearity of the steering and with Control. Without a graph I will try to explain. You can manipulate Expo to give you a slower or faster reaction off of the neutral point of your steering. Minus EXPO numbs the initial output of the servo versus your input on the steering wheel. It does not slow down the entire throw. Gain or Plus EXPO will do the opposite. It will make the steering react quicker in terms of feel but not speed up the servo. Your transit time stays the same from 0 to your end point. (Example: You have a Mustang and a Turbo Honda that both run 11.0. They will both get to the end at the same time however the Mustang (Plus EXPO) will leave the line quicker where the Honda (Minus EXPO) will make up it’s time later in that 11 seconds.) So, Plus EXPO will feel faster or twitchy from center and Minus Expo will feel slower or lag off from center but both will reach the End Point at the same time. Tech Tip: You can use EXPO to help tune the reaction of your car. In example if it feels like it needs a little more steering going into or initiating a corner add more “Plus” Expo to your transmitter or If your car feels twitchy and hard to drive straight dial in some “Minus” Expo.

Speed:  On some transmitters you can lower the speed of your servo. However you cannot add to the speed. Your servo will only perform to its specifications reliant on the voltage that is being input. Why would you turn down speed? One instance would be for a beginner or when changing from a NiMH to a Lipo battery on a gas car or buggy. Other examples would be for a sweeping layout where no tight or quick corners require fast steering which makes for an easier drive especially in a long main event.

Punch:  (KO Propo term) This setting allows you bypass a portion of the initial input of the curve (whether linear, EXPO + or EXPO-) all the way up to 100%. In example of you where to dial in as much as 50% Punch as soon as you input steering up to 50% of your throw the servo will bypass any EXPO setting you have until 51% where it will then resume the EXPO setting. Tech Tip: If you are familiar with the Motorcycle Road Racing term “Flick” you will understand what Punch does. Flick is the term used when a rider moves the handlebars extremely rapid to get a bike to turn in very hard in some cases I have seen black marks on the pavement from the front tire! Punch can be used for this reason but I have never effectively used anything past 5% and that is on the radical side in my opinion.


In my next installment we will cover the uses of these terms and others for the throttle and brake tuning from your transmitter.

Posted by: JIMMY WRIGHT
http://www.teamtrf.com/index.php/my-blog/blogger/Jimmy%20Wright/

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