Correct Head Speed

[scallybert]

Yeah, nitro engines have a power band where they only make optimum power at a certain RPM range. Unlike an electric motor that makes 100% torque the minute it starts turning.

That's not really the case.

What's probably more relevant is that if a BLDC motor's RPM drops, that makes more torque available - so you don't drop out of a power band and then bog. [But you might go over-current, instead...]

[scallybert]

[...]
I'm guessing that most people trial and error it to get it just right, but with my 7HV I'm running 60% flat line in governor mode to get my 1650 rpm and I would rather run it higher then that so that I don't stress out the esc/motor.

I think that the main point of this is that when buying a new heli, I would like to make an informed choice of what Kv motor to buy with out having to trial and error the head speed. As it stands at the moment, my 7HV is running a 470kv motor on a 13T pinion and I would probably have been a lot better off on a 440kv motor and running 75% in governor mode.

[...]

That 60% or 75% just refers to your input to the ESC, that tells the ESC what speed to run at ?

As such, I'm not seeing that there's anything wrong with 60%. It doesn't relate to 60% on the internal 'PWM throttle'. It's just a number you're passing to the governor to tell it what speed you want. If it were really low (eg ~5%) you might think you were running outside the intended range, but 60% seems fine.

Of course, I don't know your ESC; and if I'm contradicting the manual, believe the manual instead of me..!

[trillian]

That 60% or 75% just refers to your input to the ESC, that tells the ESC what speed to run at ?

As such, I'm not seeing that there's anything wrong with 60%. It doesn't relate to 60% on the internal 'PWM throttle'. It's just a number you're passing to the governor to tell it what speed you want. If it were really low (eg ~5%) you might think you were running outside the intended range, but 60% seems fine.

Of course, I don't know your ESC; and if I'm contradicting the manual, believe the manual instead of me..!

I think just about any ESC will have no problem with 60% throttle. I'll assume for the moment it's not a Jive because on the Jives 60% throttle is very near the optimum range (non calibrated, using +/- 100 in the TX) so 60 wouldn't be low at all on a Jive. But having said that, where some ESCs struggle is when you throw at it a high load AND low throttle. Even still, as you say, 60% is usually not in the danger zone. ESCs with active freewheeling generally handle low throttle better but if the low throttle equates to low headspeed then the load will be dropping considerably as well.

[Granpappy]

I think just about any ESC will have no problem with 60% throttle. I'll assume for the moment it's not a Jive because on the Jives 60% throttle is very near the optimum range (non calibrated, using +/- 100 in the TX) so 60 wouldn't be low at all on a Jive. But having said that, where some ESCs struggle is when you throw at it a high load AND low throttle. Even still, as you say, 60% is usually not in the danger zone. ESCs with active freewheeling generally handle low throttle better but if the low throttle equates to low headspeed then the load will be dropping considerably as well.

It's a Helijive 120+ HV.

[trillian]

It's a Helijive 120+ HV.

Per my PM, 60% is actually right where you want to be on that ESC. If you ran it much higher % then what would happen is that as the pack voltage drops during the flight at some point the governor would no longer be able to give you the headspeed you want. With most other ESCs this would equate to around 80% throttle from the TX.

[scallybert]

I think just about any ESC will have no problem with 60% throttle. I'll assume for the moment it's not a Jive because on the Jives 60% throttle is very near the optimum range (non calibrated, using +/- 100 in the TX) so 60 wouldn't be low at all on a Jive. But having said that, where some ESCs struggle is when you throw at it a high load AND low throttle. Even still, as you say, 60% is usually not in the danger zone. ESCs with active freewheeling generally handle low throttle better but if the low throttle equates to low headspeed then the load will be dropping considerably as well.

It turns out it is a HeliJive; so what do they interpret 60% from the Tx as actually meaning ? ie an instruction to do what ?

[As an example of how arbitrary these values can be, a CC in 'set RPM mode' uses the Tx throttle value to select one of 3 pre-programmed headspeeds. So 30% is perfectly valid - it just means 'Speed 1' {which might not even be the lowest of the 3 speeds.}]

As I'm sure we're aware, the internal PWM throttle (or however it's implemented) is a completely different matter. Running that at an overly low value, is usually indicative of a set-up issue, and can cause problems.

[trillian]

It turns out it is a HeliJive; so what do they interpret 60% from the Tx as actually meaning ? ie an instruction to do what ?

[As an example of how arbitrary these values can be, a CC in 'set RPM mode' uses the Tx throttle value to select one of 3 pre-programmed headspeeds. So 30% is perfectly valid - it just means 'Speed 1' {which might not even be the lowest of the 3 speeds.}]

As I'm sure we're aware, the internal PWM throttle (or however it's implemented) is a completely different matter. Running that at an overly low value, is usually indicative of a set-up issue, and can cause problems.

Yeah the Jives (not counting the Jive pro as I'm not familiar with them) have a little different interpretation of throttle % than most ESCs. So to get around 80% PWM you run them between 60 and 65% throttle on the TX. Any higher and they won't have enough governor headroom.

[scallybert]

Yeah the Jives (not counting the Jive pro as I'm not familiar with them) have a little different interpretation of throttle % than most ESCs. So to get around 80% PWM you run them between 60 and 65% throttle on the TX. Any higher and they won't have enough governor headroom.

As a contrast, on 3 of the 4 governor modes on CC ESCs, there is absolutely no relationship between the Tx throttle input, and the PWM percentage.

The exception is 'simple mode', where you control the PWM to find the headspeed, then the ESC takes over and governs to that speed.

In the other three, two modes map Tx throttle percentage to 'electrical RPM' ; the other is 'Set RPM', where the throttle is an RPM value selector.

From CastleLink

Simple Governor Mode
Simple governor mode is designed to be the easiest to use out of the box. 　You simply throttle up as if you were in heli-Fixed mode. The throttle stick is directly controlling the power to the motor, and NOT specifying 　rpm. Once you get to your desired rpm, leave the stick at that position for 1.5 seconds and the ESC will lock onto that RPM. If you move the throttle, the head-speed will change accordingly. 　The only drawback to this mode is you do not know your exact head-speed.

Governor Low
Governor low translates the throttle input to a pre defined head-speed. This mode will allow the motor to be governed at ELECTRICAL RPMs from 10,000 to 64,000. 　Note that electrical rpm is the RPM seen by the controller before taking into account gearing and motor type. You can determine what throttle value you will need for a desired head-speed by using the desired Head Speed inputs below. If governor low does not provide the speed you desire, switch to governor high and work your way up through the throttle until you achieve the desired speed.

Governor High
Governor high translates the throttle input to a pre defined head-speed. This mode will allow the motor to be governed at ELECTRICAL RPMs from 50,000 to 210,000. Note, that electrical rpm is the RPM seen by the controller -- before taking into account gearing and motor type. You can determine what throttle value you will need for a desired head-speed by using the desired Head Speed inputs below. If governor high does not provide the speed you desire, switch to governor low and work your way up through the throttle until you achieve the desired speed.

Set RPM Governor Mode
Fixed RPM will allow you to set 3 distinct head speeds that you would like to use. 　Simply enter the head speed and some vehicle setup information and Castle Link will do all of the work to set up the controller for you. 　The first head speed is used for throttle inputs between 1.1ms and 1.5ms (up to 50% throttle). 　The middle head speed is used for throttle inputs between 1.5ms and 2.0ms (between 50% and 99% throttle). The last head speed is used for throttle inputs greater than 2.0ms (greater than 99% throttle).

[Mike656]

I always thought the Jives pretty simple to set up. Mode 1 to learn the throttle end points, mode 4 for helis, then mode 9 on the helijive if you need ksa. If your tranny goes -100 to +100, a flat line at 60 equates to 80% throttle. I tend to use a slider on the side of the tranny to move the flat line up or down, so I can adjust the head speed in flight. Kontronik governors are pretty solid, so I Just bypass the esc's internal governor.