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Batteries

  1. Lipo Batteries Explained


    How fast a battery can discharge is it's maximum current capacity. Current is generally rated in C's for the battery. C is how long it takes to discharge the battery in fractions of an hour. For instance 1 C discharges the battery in 1/1 hours or 1 hour. 2 C discharges the battery in ½ or half an hour. All RC batteries are rated in milli Amp hours. If a battery is rated at 2000 mAh and you discharge it at 2000mA (or 2 amps, 1 amp = 1000mA) it will be completely discharged in one hour. The C rating of the battery is thus based on its capacity. A 2000mAh cell discharged at 2 amps is being discharged at 1C (2000mA x 1), a 2000mAh cell discharged at 6 amps is being discharged at 3C( 2000mA x 3).

    The naming convention that allows you to decipher how many cells are in parallel and how many are in series is the XSXP method. The number in front of the S represents the number of series cells in the pack so 3S means it's a 3 cell pack. The number in front of P means the number of cells in parallel. So a 3S4P pack of 2100mAh cells has a total of 12 cells inside. It will have the voltage of any other 3S pack since the number of cells in series determines the voltage. It will have the current handling of 4 times the maximum C rating of the 12 individual cells. So say our 3S4P pack had a maximum discharge of 6C. That means that it has a nominal voltage of 10.8 volts (3x3.6) and a maximum discharge rate of 50.4 amps (2100mAh x 6Cx4P ).

    Information from

    http://www.rchelisite.com/lipo_battery_charging_and_safety_guide.php

  2. Charging Lipo Batteries

    Lithium Polymer or LiPo batteries have very specific charging requirements and MUST only be changed by specific chargers designed to charge lithium polymer batteries.

    A 1s or 1 cell LiPo battery has a nominal voltage of 3.7v. When fully charged it has a maximum voltage of 4.2v and when fully discharged, it should never go below 3.0v without risking cell damage.

    A 5s-4p battery pack means that the pack contains 5 cells in a series circuit and 4 cells in a parallel circuit.

    Since each cell is 3.7v (nominal) a 5s LiPo battery has a nominal voltage of 18.5v, a fully charged voltage of 21.0v and a maximum discharged voltage of 15.0v before damage occurs.


    LiPo Battery Charging Tips

    Always use a charger made to charge LiPo packs. Double check that the settings for the lithium polymer charger are correct for the pack being charged – this includes the cell count as well as the current settings. In general, most lithium polymer batteries should be charged to no more than 4.2 volts per cell or depleted to less than 3.0 volts per cell. There are new generation batteries available that can handle higher / lower voltages, but they are still new and thus are the exception to the rule. Ensure that charging leads are connected correctly. Reverse charging can lead to cell damage or a fire or explosion.Always charge LiPo batteries on surfaces that won’t catch on fire such as cement, steel, ceramic or stone. Wooden tables and carpeted floors are not recommended charging surfaces. Do not charge batteries near flammable products or liquids. Never charge a LiPo battery while inside your model or other electronic device. If it catches fire it can lead to total destruction of the item it is being charged in. LiPo batteries should be charged within a temperature range of 0C to 50C. Batteries charged outside this temperature range may experience leakage, heat generation or cell damage. Never leave a charging lithium polymer battery pack unattended. Do not charge inside an automobile, especially while driving. Do not store batteries inside an automobile. Do not charge a lithium polymer battery pack at a rate over 1C. Never charge a LiPo pack that has ballooned or swelled due to over / under charging or from a crash. Never charge a lithium polymer battery pack that has been punctured or damaged in a crash. Never, under ANY circumstances let the positive and negative battery leads touch. It can lead to cell ballooning, cell damage or fire or an explosion.Have a fire extinguisher near the charging area or a large bucket of dry sand. Do not try to distinguish with water. If you notice your LiPo battery pack is swelling, stop the charging process immediately, put the battery in a safe container and observe it for 15 minutes. Information obtained from

    http://www.rchelisite.com/lipo_battery_charging_and_safety_guide.php

    http://www.rcgroups.com/forums/showthread.php?t=209187

     


     

  3. Exploding Lipo Battery

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Transmitters

  1. Dual Rates And Exponential Explained

    by Ed Anderson

    aeajr on the forums

    Perhaps you are buying your first plane. Or perhaps you are thinking about upgrading your radio. You read all those feature lists and don't understand what they do for you. This may help you understand two of the features that are listed so you can get the radio that will really help you enjoy this new plane and future planes, whether electric, glow, gas or glider.

    Dual rates and exponential allow you to change how responsive the plane is to your stick movements. If you have them set-up on a switch, you can make these changes while the plane is in flight. This might be useful as you move from take-off to normal flight. Perhaps an instructor has a trainer plane she would like share between new pilots and more experienced pilots. It would be convenient to be able to change the plane's behavior depending on the pilot without having to move the linkages.

    Changing how the plane responds might be useful if we move from normal flight to highly aerobatic flight. The large throws for aerobatics might make the plane "twitchy" or hard to control during normal cruising around. Dual rates and exponential, when tied to a switch, or some other trigger can be changed while the plane is flying. They are used for similar reasons but accomplish the task in different ways.

    DUAL RATES

    Of the two, dual rates has been around longer and is simpler to understand.

    Dual rates are based on changing how much a surface can move. Let's use rudder set-up to illustrate this.

    If your instructions say to set 1" of throw left and right, that would be the recommended surface movement at full stick movement. When you move the stick 1/4 of the way, you would get 1/4" of rudder movement. At 1/2 stick you would get 1/2" of rudder movement. You get a direct, proportional and linear relationship between stick movement and surface movement. At 100% stick movement you get 100% of the maximum surface movement that you have set. In this case 100% stick equals 1 inch.

    With dual rates we can change to a second maximum at the flip of a switch.

    Let's assume you have the standard throw set as the high rate. Then, using the procedures outlined in your manual, you low rate, say 50%. At this setting, when you move the stick all the way over you will only get 1/2" of surface movement. However stick movement and surface movement remain proportional. So at 1/2 stick movement we will get 1/2 of the 1/2 inch maximum or 1/4 inch of surface movement. Your rudder movements remain directly proportional but are now based on a smaller maximum.

    We can say that control and response are both proportional and linear. Thatis, all the way through the stick movement the rudder will move with us in a linier fashion. If we move the stick 20% we gets 20% rudder. Move the stick 62% and the rudder will move 62% rudder movement. If we plotted a graph with stick movement on one axis and rudder movement on the other, the graph would have all points along a straight line at a 45 degree.

    How does this effect the handling of the plane?

    Continuing the example above, we have high rate, at full stick movement equals

    1" and low rate set at 1/2" maximum rudder movement.

    On low rate, for each small movement of the stick, we get less movement of the tail surface. So, on low rates the plane will be less responsive to the same amount of stick movement. This may make it easier to fly as we can make smaller adjustments when we move the stick. We have finer grain control. On high, we get more movement of the rudder for each unit of movement of the stick. We get a faster response from the plane for the same stick movement. If you have ever worked with a precision tool or instrument, this is like having course adjustment and fine adjustment.

     As new flyers often have a tendency to over control the plane, it is not uncommon to set-up the plane with smaller throws so that the pilot is less likely to get in trouble by over controlling the plane. Later when she gains confidence and the right feel for control, surface movements can be increased to make the plane more responsive. Originally this had to be done on the plane. Many RTF planes come set-up this way. They are set for mild response for initial flights. Then the manual explains how to increase the rates as the pilot gains experience. Some RTF planes now include a dual rate style control on their radios.

    With dual rates on the radio, this can be done at the radio rather than working on the plane itself. This is much more convenient. Dual rates can even allow the instructor to take control, flip to high rates and pull the plane out of a tough situation that the student could not handle. Dual rates can be very helpful during training.

    Of course we can always have it the other way where the low setting is the "standard" recommended by the instructions and a high setting might be our aerobatic setting or our 3D setting where we want 1.5" of deflection at full stick. This allows us to take the plane from mild to wild at the flip of a switch. However having it set to high might make the plane uncomfortable for "normal" flying so we switch to low.

     OK? You with me so far? If not, go back and read through it again as the next section is based on your understanding of dual rates. Imagine how your plane will behave on high and low rates. When you are comfortable then you can go on to the next section.


    http://www.wattflyer.com/forums/showthread.php?t=934

  2. Dual Rates

    Of the two, dual rates has been around longer and is simpler to understand.

    Dual rates are based on changing how much a surface can move. Let's use rudder set-up to illustrate this.

     

    If your instructions say to set 1" of throw left and right, that would be the recommended surface movement at full stick movement. When you move the stick 1/4 of the way, you would get 1/4" of rudder movement. At 1/2 stick you would get 1/2" of rudder movement. You get a direct, proportional and linear relationship between stick movement and surface movement. At 100% stick movement you get 100% of the maximum surface movement that you have set. In this case 100% stick equals 1 inch.

    With dual rates we can change to a second maximum at the flip of a switch.

    Let's assume you have the standard throw set as the high rate. Then, using the procedures outlined in your manual, you low rate, say 50%. At this setting, when you move the stick all the way over you will only get 1/2" of surface movement. However stick movement and surface movement remain proportional. So at 1/2 stick movement we will get 1/2 of the 1/2 inch maximum or 1/4 inch of surface movement. Your rudder movements remain directly proportional but are now based on a smaller maximum.

    We can say that control and response are both proportional and linear. Thatis, all the way through the stick movement the rudder will move with us in a linier fashion. If we move the stick 20% we gets 20% rudder. Move the stick 62% and the rudder will move 62% rudder movement. If we plotted a graph with stick movement on one axis and rudder movement on the other, the graph would have all points along a straight line at a 45 degree.

     

    How does this effect the handling of the plane?

    Continuing the example above, we have high rate, at full stick movement equals

    1" and low rate set at 1/2" maximum rudder movement.

    On low rate, for each small movement of the stick, we get less movement of the tail surface. So, on low rates the plane will be less responsive to the same amount of stick movement. This may make it easier to fly as we can make smaller adjustments when we move the stick. We have finer grain control. On high, we get more movement of the rudder for each unit of movement of the stick. We get a faster response from the plane for the same stick movement. If you have ever worked with a precision tool or instrument, this is like having course adjustment and fine adjustment.

     As new flyers often have a tendency to over control the plane, it is not uncommon to set-up the plane with smaller throws so that the pilot is less likely to get in trouble by over controlling the plane. Later when she gains confidence and the right feel for control, surface movements can be increased to make the plane more responsive. Originally this had to be done on the plane. Many RTF planes come set-up this way. They are set for mild response for initial flights. Then the manual explains how to increase the rates as the pilot gains experience. Some RTF planes now include a dual rate style control on their radios.

    With dual rates on the radio, this can be done at the radio rather than working on the plane itself. This is much more convenient. Dual rates can even allow the instructor to take control, flip to high rates and pull the plane out of a tough situation that the student could not handle. Dual rates can be very helpful during training.

    Of course we can always have it the other way where the low setting is the "standard" recommended by the instructions and a high setting might be our aerobatic setting or our 3D setting where we want 1.5" of deflection at full stick. This allows us to take the plane from mild to wild at the flip of a switch. However having it set to high might make the plane uncomfortable for "normal" flying so we switch to low.

     OK? You with me so far? If not, go back and read through it again as the next section is based on your understanding of dual rates. Imagine how your plane will behave on high and low rates. When you are comfortable then you can go on to the next section.

    http://www.wattflyer.com/forums/showthread.php?t=934


     

  3. Exponential

    Exponential changes the relationship between stick movement and surface movement. When using exponential, stick movement and surface movement will no longer be linear. What does that mean?

    Exponential is going to allow us to shift some of the rudder response so that we get a different amount in the early part of the stick movement as compared to the later part. Let's stay with the rudder example above.

    At 100% stick movement we would still get 100% surface movement, but at 50% stick movement we might only get 25% rudder movement. This would be like having low rates on the first half of the stick travel and high rates on the second half of the stick travel. That would give us a "softer" response around the center of the stick area, and a faster response toward the end.

    How is this beneficial? This gives us finer control when we are making those typical small adjustments to the plane when we are cruising around, just like low rates. However if we suddenly want a big surface movement to get out of trouble, to respond to a gust of wind or to perform that big stunt, we still have the big surface movements we need without having to manually switch to high rates. One of the criticisms of using a low rate for "flyability, is that it limits the pilot's ability to get out of trouble when you are on low rate.

    Let's look at that aerobatic or 3D pilot we mentioned above. He has BIG surfaces and BIG throws set which makes the plane very responsive to small inputs. If he were to set exponential rather than dual rates, then he could have a very soft center to the stick. He could make fine adjustments when needed, but get big response when he needed it and there would be not need to flip a switch during the flight. Cool?

    Let's try some examples that involve numbers. The numbers I am going to use may not map directly to your transmitter as different manufacturers have different interpretation of exponential and what the numbers mean, but the overall impact on flying is the same. They just express it differently.

    Let's say that under standard set-up conditions exponential will be expressed as zero. This means we have the same linear response we have always had. Now, if I put in -50% exponential, that might mean that for a 50% movement in the stick I only want to get 1/4 surface movement but when I move the stick to 100% I want full 100% surface movement. An input into the set-up menu of +50% might mean that for the first half of the stick movement I want more of the total surface movement. This would make the center area very responsive while leaving find grain control at the ends of the stick movement. I am not sure where this would be used, but that is how it would work.

    It is important to note that exponential does not imply a sudden change in rate. Rather it is a smooth change in rate. So the further we move the stick, the faster we get more stick movement. If we were to plot the percent stick movement to percent surface movement we would not get a straight line as we normally get. We would get a curved line indicating that the further we move the stick the less linear the relationship between the stick and the surface.

    This is one of those things you are just going to have to try to fully understand. At first it seems it would make it difficult to predict how the plane will behave depending on how much you move the stick. However in fact most people tend to fly more by input/response rather than where the stick is in its travel. You move the stick and watch the plane. After a while you develop a good understanding of how the plane will respond to a given stick movement, but you know that it will be influenced by wind, air speed, and other factors.

    I typically set up my controls with about 35% exponential so that I have a softer response around the middle but gradually faster response as I move toward the extremes of stick movement. On my radio I have dual rates and exponential available and I can use them together. I can also set them by surface.

    Computer Radios

    While I have seen dual rates on a some "standard" radios I have never seen exponential. So for this discussion, we are going to assume that exponential is a feature of computer radios. If you don't have a computer radio, this might be a reason to move up to one.

    Whether you ever use dual rates or exponential is, of course, is up to you. However I would encourage you to give them a try if you have them. They are just tools and like all tools, it takes a little while to get the feel of how to use them. So, if the first time you try dual rates you don't see an overwhelming benefit, don't walk away. Try different settings.

    Most radios will allow you to set different rates to each surface. So, for example, my ZAGI flying wing slope glider has dual rates set up on the elevator. Tailless planes like this tend to be very sensitive to pitch, so under normal circumstances I find I like to have the elevator controls set on a low rate. However when I want to "crank it up" and get aerobatic that low rate does not give me the action I want, so I flip the switch and get the kind of pitch control I want for stunts.

    On my 3M sailplane I find I like to have high rates set up for launch where the plane can get in trouble very quickly and I might need a fast response, but then switch to lower rates for normal flying. I even have a third rate set for working thermals which is lower so I can make very find adjustments and more easily to get the most lift I can out of each thermal.

    On my electric planes, I tend to have a mild and wild set-up for cruising and for stunting.

    I have been experimenting with exponential and find that I like it. I could see myself going totally to using exponential and doing away with dual rates all together, but that is not the case today. Right now I am having fun trying out different settings to see what works for me. I encourage you to do the same. Information obtained form

    http://www.wattflyer.com/forums/showthread.php?t=934

     

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Servo Information

  1. Servo Connectors

    The below image depicts the two most popular servo connections "Futaba" & "JR" as well as a third "Airtronics" which is not commonly used with in Australia. 



    Information from http://www.geistware.com/rcmodeling/general_tips.htm


    An excellent source of information about servo brands can be found at 


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Electric Motors

  1. Which wires do I connect to the ESC

    Electric motors generally have three connecting wires attached. Some manufactures color code the wires and some leave them the same. It doesn't matter which of the three wires you connect up to the three ESC wires because the motor will still work. They don't need to connect in any particular way. However once connected  if your motor is spinning in the wrong direction and your ESC doesn't have the built in programing to reverse this then simple swap any two motor wires over and this will reverse the direction of the motor.

  2. Wiring For the Masses


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