Throttle curve set up 101
By Brian James
Usually we set up the pitch curve first, but it really doesn’t matter what you do first. There will be a different set up for nitro and electric throttles as they work differently.
Here’s the set up for Nitro!
1. Build the throttle linkage to exactly what the manual states. This is important. Ideally, you’ll want the servo linkage 90 degrees to the servo horn. This ensures equal travel in both directions.
2. Turn on your transmitter. Scroll to the “throttle curve” screen and notice that there are points usually 5, and the all have an assignable percentage. For example point 1 is 0% and point 5 is 100% (of the servo’s travel). We first want to ensure that when the throttle/collective stick is at it’s mid point (point 3) that the engines carburetor is exactly ½ or 50% open. This is crucial to easy set up. You may have to loosen the throttle arm on the carburetor for this to happen. So put the throttle stick to ½ and see where the carburetor opens to. On most popular engines today there is a mark that shows the halfway point. If it is not quite ½ way open you can use sub trim to make it so, but you don’t want to use too much. Too much sub trim can make further set up more difficult.
3. Move the throttle stick to full throttle . The servo should open the carb to full open. If it opens less you can increase the end point in your radio so that it opens a little further, and if the servo binds (keeps wanting to move but the throttle is fully open) you can decrease the endpoint, but ideally you want the endpoints as close to 100% and 100% as possible.
4. If you are experiencing the need for more servo movement, try moving the ball link out one hole on the servo arm, and conversely if you need much less servo movement, you can move the ball link one hole in.
5. Once you have this set up in normal mode you’ll have to start and fly the helicopter to determine whether you need more or less throttle, but from what I’ve found this is a good starting point on most 50 and 90 size helicopters.
6. Setting up for Idle up or stunt mode is a little different, as you’ll want full throttle on either end of the stick. So scroll to the idle up menu in your radio, and you’ll again find points such as 1,2,3,4,5. If you do not have a governor you have to set up a fixed throttle curve that controls the throttle. If you have a governor, please follow the set up instructions from the manufacturer. Without a governor you’ll rely on the throttle curve to control the engine rpm while you’re managing the collective stick. Make points 1 and 5 100%. Make point 3 50% Then you’ll want a friend with an optical tachometer to observe the headspeed of your helicopter. Refer to the manual for your specific helicopter to determine what an acceptable headspeed should be for your model.
7. If the headspeed is too low (and with a value of 50% at point 3 it should be a little low) then increase the value of point 3 by 5% increments until you get the headspeed you desire.
Electric Helicopter throttle curve set up is a little easier than nitro because there’s no linkage to set up.
1. Ususally in idle up mode people will run a nearly flat throttle curve on small micro electric helicopters such as the Trex. That means 100% at points 1 and 5, and maybe a small “v” down to 85% in point 3. Many people run 100% at all points.
2. Larger electric helicopters will require a “v” curve to avoid overspeeding the head, maybe a “v” curve with 70%. This will require a friend with a tachometer to determine the proper headspeed as indicated in your helicopter’s manual.
3. Normal mode can be done similar to the Nitro throttle curve for normal mode. It is up to you the end user to adjust the headspeed to what you feel comfortable with and what is recommended by the manufacturer of your helicopter!
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