How To Set Up Computer Radios

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Learning to fly a model helicopter in the first place can be one hell of a challenge. In fact I would argue that this hobby is 40% set-up, 40% skill and 20% having the balls to simply try it in the first place. If you do not have the basic set-up then you are stuffed, the model won’t run right, the head pitch range will be screwed the tail will kick out and it will all go pear shaped. It basically makes the learning and the skill bit all that much harder.

If you look at the top boys attention to detail on the setup is where it all begins.

Now there are really two schools of thought regarding setup depending on who you speak to and what your ultimate goal is. In this example I am going to look specifically at the basic setup and take these two schools of thought into account.

The schools of thought are really about where you have you pitch range and where your model should come in to the hover on the stick movement. For ease of use I’m going to use the basis of 20˚ of pitch travel, although commonly most modern machines have 26˚ plus of movement.

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The old school of thought is based around learning to fly and hovering and the old school FAI type flying. The basis of it is running -5˚ of pitch and 10û positive pitch, although you would run as much as needed to run according to your setup, but as explained, for simplicity we are going to use +/-10˚.

So with the above in mind you then set the model to come into the hover at the mid point of the stick/half-stick. If the model hovers on 5˚ of pitch and the max is 10˚ then you end up with 5˚ of travel from hover point (mid-stick) to full pitch (top-stick), this then means that you have 10˚ of movement from the middle to the bottom. What this enables the user to do is to have a very fine control of the pitch movement and is really considered a conventional set-up.

The problem with this setup in my opinion is that if you want to progress to 3D or even smooth aerobatics it becomes restrictive, even if you run idle ups it becomes restrictive as you then need to re-learn the pitch control and to get used it. The idea is great for basic usage but I have always found it difficult to repeat every singe time should you have a mishap and need to rebuild.

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The new school of thought is around a linear setup, or straight line pitch curve. So you would end up with the default standard set-up on your transmitter.

Now using this setup and plus and minus 10˚ of pitch you would end up with 0˚ of pitch at mid stick, 5˚ at 3/4 stick (the new hover point) and then top stick is again 10˚.

The advantage of this set up is that when it comes to any inverted flight or 3D flight the pitch curved is mirrored from the mid stick up and from the mid stick to the bottom. So you have a nice smooth linear pitch set up, the disadvantage if any is that you loose out on the fine control you get with the old school of thought set-up.

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You can actually use the new school set up to achieve exacting results on the old school set up allowing you to run a true linear 3D curve in idle up modes whilst also using the benefits of the old school set-up in the hover.

The above depends on the basic mechanical set up of the machine which we will run over now.

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The starting point for your set up is your servo, in this case we will look specifically at 120˚ CCPM but it really applies to all machines.

With a new machine and clean model memory turn everything on with the motor disconnected if its electric and if possible also set up a throttle hold (we can do this in throttle hold if need be. With a clean model memory and no sub trims etc put the pitch throttle stick to the mid point and make sure it’s exact.

Now put the servo arms on the servo and make sure they are as square as possible, this will normally mean they are horizontal as per the T-Rex 500, 250 etc, but with my MA Stratus the servos are actually completely vertical as the controls go thought a series of bell cranks.

If you can’t get the servo horns in to this position completely then you will need to sub trim the servos to the point they are complete square be this vertical or horizontal depending on your CCPM system.

If you have bell cranks then ensure that the connection to the bell cranks leave the bell cranks at 90˚ to the servo, if they are off then lengthen or shorten the links accordingly.

Follow up to the swashplate and make sure its level, if not level it with the control rods.

Now follow up from the swashplate to the lower mixing arms, these too should be straight and level, they should be horizontal and in an equal position, if they are not, adjust the rod lengths to make sure they are.

From here follow up the main shaft to see the upper mixing arms which again should be horizontal.

The last remaining part of the set-up is the main blades and the pitch; these should now be zero degrees pitch on both blades located all around the swash plate. If not adjust it so that it is.

Its worth noting that many manufactures will recommend this set up out of the box for the head set-up, but sometimes the instructions don’t quite replicate the exact set up that they should be so this is a worth while check.

You may find that different servos have different centre potions to the ones the manufacture tested the model with meaning that it’s the rods from the servos that can be out rather then from the swash plate up, but still, check it and follow the links through to get that perfect mechanical set up.

Now the mechanical setup is perfect the next bit is simple.

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Okay, so you now have the perfect mechanically set up model, with perfect symmetry. But you still want that old school feel in Normal idle up setting as you like your hovering and you want that fine set pitch control.

Okay, so if done correctly you should end up with minus and plus the same number of degrees pitch with zero degrees in the middle. If we use +/- 10˚ as the example we have the following out puts of pitch based on stick movement:

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Stick position % movement = Pitch reading

  • Low: 0% = -10˚
  • Quarter: 25% = -5˚
  • Middle: 50% = 0.00˚
  • Three Quarter: 75% = +5˚
  • High: 100% = +10˚

 

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So on this basis if you move the range up by 25% at the low point, you will get an output of -5˚, if you then up the middle to 75% you will get +5û pitch, this will in turn mean that three quarter stick will need to be taken up to 87.5% or just cleared out if your TX allows, this will then give you your smooth curve for learning and hovering whilst maintaining the same range and setup for your stunt or idle up curve.

You can then run your stunt/idle up pitch set ups with the standard linear line for the 3D curve.

Now the above is pretty simple but, you will need tweak it for your pitch range and set-up, however the same basic principles apply.

For me and for a stunt curve I run two set-ups, one running at 80% flat across the board and 100% in the other curve, this gives me a two speed set up on an electric machine and being electric we don’t need to worry about a pitch curve.

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