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Downline Braking : ESC set up query

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Downline Braking : ESC set up query

Old 08-09-2009, 11:44 AM
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Capiche
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Default Downline Braking : ESC set up query

To anyone that can help.

I have a Sebart WIND 110 with the recommended Hacker motor / esc etc.

The ESC is in default settings incl brake off.

I have been surprised at the lack of down line braking. I have it set to "tick over" at low throttle (rather than stop) but I think the airflow is increasing the rpm in the down lines and therefore failing to control downline speed. This has been a bit of a disappointment because I had expected that motor to hold the rpm that is being requested by my input : not speed up under air flow pressure.

I am hoping that I can alter this with changing the ESC set up but it did not come with instructions ! Although I suspect that this is a wider more general question : are my expectations unreasonable ? Should the motor be able to resist "winding up" on these downlines and just run at the rpm I call for ?

Old 08-09-2009, 06:52 PM
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Default RE: Downline Braking : ESC set up query

You might try increasing the idle RPM you have set, but my experience you will need the brake.
Old 08-10-2009, 05:17 AM
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David Kyjovsky
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Default RE: Downline Braking : ESC set up query

In both the Master and Spin (Hacker/Jeti) esc you can set the level of braking. Interestingly, too much brake can be less efficient than the "right" amount of brake (probably the prop blades turn too slow, with stalled airflow..). In my case, Hacker C50 XL13, the sweet spot is between 20 and 26%.
Old 08-10-2009, 02:38 PM
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Capiche
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Default RE: Downline Braking : ESC set up query

I am not sure I follow.

You suggest setting the brake control on will enable me to set a low rpm at idle which will avoid the airflow speeding it up ? Whereas with the brake off then at low power the airflow will cause the motor to rotate faster than the ESC is commanding ?
Old 08-10-2009, 05:08 PM
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Default RE: Downline Braking : ESC set up query

Without some kind of proportional brake (many times called F3A brake), you will nearly always experience that a model with an outrunner accelerates downwards. Setting an idle using the ESC will usually not be enough to stop the motor from spinning up going downwards. If you are using one of the Hacker X-series of controllers I don't think they have proportional braking, but the Spin controllers do, if you have the spin prog box.

With an inrunner using a gearbox, setting a low idle will in some cases work, this is due to the mechanical advantage of the gearbox. When the wind tries to spin the prop it will have to spin the motor with an RPM that is the prop RPM multiplied by the gearbox ratio, meaning that even a small amount of braking on the motor will be more effective. On the outrunner you don't have the mechanical advantage of the gearbox during braking, here the ratio is 1:1.

Hope this makes sense...
Old 08-10-2009, 05:44 PM
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Default RE: Downline Braking : ESC set up query

Capiche, with the brake on the motor will not tick over at an idle but will stop on the ground, in the air it will continue to spin as a result of the airflow and a light brake setting (of course set high enough the brake will stop the prop.) If brake is on and the motor is ticking over the brake will not engage on my Spin.

I set a switch to maintain an idle up to takeoff; once in the air I switch on the brake just to avoid stopping and starting the motor while taxing.
Old 08-15-2009, 06:47 AM
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Default RE: Downline Braking : ESC set up query

Mola - that does make sense thank you.

So the bottom line is that;
With the idle setting that I have already : this will not stop the prop speeding up.
With the brake on : this will not stop the prop speeding up.

The only way to improve the situation is to get the Spin ESC and prog box and programme proportional braking -although based on the argument about mechanics it seems that this will not totally solve the problem ? or is it worth the expense ?
Old 08-15-2009, 07:35 AM
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Default RE: Downline Braking : ESC set up query

The problem with the brake feature on many of the less advanced ESC's is that you can only adjust it in relative coarse steps. In most cases the brake is too strong and will stop the propeller turning, which will not give any significant slowing down of the model. We want the ESC to be able to brake the prop so that it compares to a low idle when going downwards, this will give maximum braking effect. If the brake is too weak or disengaged completely the prop will be allowed to spool up, and although more effective than a stopped prop it will not give the desired braking effect. This is where the finely adjustabe F3A brake comes in handy, since you will be able to adjust the amount af braking to your liking.

Depending on the ESC the F3A brake can be adjusted via a prog-box (Hacker/Jeti Spin), via a prog card (e.g. YGE), via a PC interface (Castle I think...?) or via the throttle curve (Schulze). In the first three cases you will have to try different percentages between flights to fine tune the braking to your liking. On the Schulze you can use the gas trim-lever to adjust the amount of braking in the air since it works a bit differently. Chad has described this in detail in another thread here on RCU.

When using an F3A brake you will be able to get plenty of braking on an outrunner as well.
Old 08-15-2009, 03:34 PM
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Default RE: Downline Braking : ESC set up query

Looks like if you want to fly EP F3A seriously, there are no shortcuts. Hmmmm ... time to check the bank balance so that I can purchase a proper ESC for my Wind 110 too. But really, can we live with not using the brake for the downlines? Does the plane speed up that much? I mean, I did not really feel it on my Angel. It does speed up a bit but not too much.
Old 08-16-2009, 03:27 AM
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Default RE: Downline Braking : ESC set up query

I don't know about the Wind 110 since I haven't tried it, but most of the F3A designs I have flown benefit from a slight amount of braking in the downlines if you would like to fly constant speed. I would not be surprised if there are some designs that are so draggy that the F3A brake is not needed, however I have just not tried these.

Especially in the figure 9 in the present P-09 schedule the brake is a nice thing. You have to do two opposite ½ rolls in a downline, and here the model can really speed up on the downline with too little braking.

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