ALIGN 450L Dominator S3 vs S6 (long version)

[Ben M]

I have read several publications talking about the two different versions of the ALIGN 450L Dominator where the S3 version seems to be very good and the S6 is extra powerful. Guided by this information I bought the S3 version because I was not interested in extreme 3D flight so I thought I didn’t need “super power”.

I want to share my experience with the aim of helping somebody else to avoid my error.

I bought my S3 version and after few flights where I only tried to keep the helicopter hovering 1 metre high I started to have problems. The motor stopped in the air at the same time that it made a strange noise (pitched whine). It happened intermittently in several flights until the day the motor got burned.

After a thorough study in technical forums I found other people with the same problem and all of them had the S3 version. None of them had the S6 version. This was strange because the S6 version is more popular. Most of the people buy the S6 version so I was expecting that someone with the same problem had the S6 version. Especially because I was pointing the ESC as the responsible of the problem.

My conclusion after quite some time (and money) spent is that the problem was not due to any faulty component. It is just a matter of wrong design. The S3 version’s motor draws too much current and the components that provide that current (ESC and battery) cannot support it.

The S3 version has a 32,000 KV motor which is different from the S6 version’s motor which has 18,000 KV. The S3 version’s motor gets its power by drawing a lot of current with low (11.1V) voltage and the S6 version’s motor gets its power from the higher (22.2V) voltage (with less current).

The ESC is the same for both and it has a feature (security system) called “Battery Protection” that detects if the battery voltage is under a certain threshold in which case it stops the motor.

Telemetry information shows that even for a very gentle hover the S3 motor can draw quite some current (around 20 amps constantly). As the helicopter flies the voltage of the batteries goes down very fast passing from 12.6V to less than 11.1 in 1 or 2 minutes (in some flights). This voltage change makes the motor increases its need of current to keep the power constant and here is when the whole electric system collapses because the battery voltage drops even faster until the moment when the ESC stops the motor.

This problem occurs intermittently and there are several factors than can affect such as:

• ESC settings.
• Radio settings.
• Gyro settings.
• Flying style.
• Batteries
• Environmental temperature.

By finding the right settings in the ESC and the radio some people with this problem could get rid of it at least for some time. I did it and I thought it was solved until the day the motor got burned after stopping. This day the telemetry information indicated during more than one second the motor drew more than 730 watts which is its maximum instantaneous power limit. There was a moment when it drew 117.29 amps and the battery had 8.18 volts which made 959.43 watts (31% over the instantaneous limit).

Talking about limits I remembered something interesting in my study. The S3 motor can draw more power than the S6’s one however its specifications has lower power limits which is something I cannot understand. The maximum continuous power limit in the S3 version is 500W while the same limit in the S6 version is 650W. And the maximum instantaneous limit in the S3 version is 730W vs the 970W the S6 version has.

Moreover, the S3 version has a motor pinion with 12 teeth and the S6 version has a motor pinion with 11 teeth. This means that the S3 motor has to push harder to make the main rotor head turn once. This extra stress makes the motor draw more current. If the S3 version had the same pinion as the S6 version theoretically it should need less current. The only reason I can think of why ALIGN may have chosen that pinion for the S3 version is to get similar rotor speed in both versions. In my opinion, it is an error because they are raising the risk of electrical problems when the people who buy the S3 version are expecting to have less flying power than the S6 version.

Finally I upgraded my S3 version to the S6 version and now the helicopter flies with current flows between 8 and 14 amps (with more active flights) with the exact same ESC (I didn’t change it). The only component I changed was the motor, the motor pinion and the batteries.

In summary, the S3 version brings its electrical components to their limit which has a high risk of problems. And the only way to be get rid of them (with peace of mind) is by choosing the S6 version or upgrading your S3 version to the S6 (if you already bought the wrong one).

My experience in the RC world is short (only 1 year) so I do not have sense of what is normal voltage for a battery and what is an extra powerful battery. If I read in several sites that S6 is extremely powerful and 3S is normal then I believe it. However, as in many other sides in life things are relative. In the case of the 450L dominator the S6 battery is not that much, it just what it needs to fly.

I may be wrong in any of my thoughts. If somebody has different experiences please share them so that all learn from them.

[Dave Bran]

Hi Ben,

Sorry you have had issues!!

Here's a few thoughts and points off top of head..........................

1. The motors involved are not as you state, they are 3200kV and 1800kV

2. Its conventional to state cell pack count as 3S or 6S, etc. (3S is 3 cells internally connected in "S"eries so 3x3v minimum, 3x4.2v fully charged, nominal 11.1v)

3. The combination of a 3S cell pack of around 2200mAh capacity and a motor around 3000kV is the arch typical format for a 3D capable 450 class Heli of pretty much any make dating back to when Fred Flintstone flew them, i.e. ooodles of knowledge base and experience.

4. Yes, the gearing will alter between the two formats Align have chosen to use. The head speed will be different, but not hugely so, so with very different motor rotation ratings 3200/1800, the gearing is adjusted to get the correct rotor speed.

5. Its not a good idea to run any ESC at well below its rated max current. (or of course over!) I don't think I'd like to try to calculate and install a single ESC that would deal fully with those two very differing mech's, though obviously I don't know the correctness of the mech setup affecting their actual current draws at all flight stages.

6. A high kV rated motor has comparatively little torque. It takes less extra mechanical loading to push it over the edge out of its "comfort zone". That is why it should have a smaller pinion to allow it to turn at its design speed while getting the right head speed. And why its a little more critical on any mechanical stiffness.

Lets ignore the gearing etc issues for a moment. A higher cell count provides more voltage, more voltage (akin to water pressure in a hose) provides the conditions to allow more current (water flow rate), provided of course that the hose isn't too small or kinked!!

Your figures above do not include head speed counts, but your text suggests that you (and from your comments others) have exceeded the safe load, possibly by over pitching the head. 20 amps though is not that high for a 3S Heli installation!

I do not have experience of the exact model(s) you state, but I do have more than 30 EP Helis and that includes five 450s, all running 3S 2200/2300mAh packs, three with the extra weight of scale bodies.

[Dave Bran]

Posted by Ben M on 09/01/2015 00:48:25:. The motor stopped in the air at the same time that it made a strange noise (pitched whine). It happened intermittently in several flights until the day the motor got burned.

This suggests the ESC was losing timing (it pulses the three windings to gain rotation). For this to happen at all there was something clearly wrong, and to continue to use the model without finding the reason and curing it was sadly always likely to end in tears. ESCs have user settable timing settings to adjust for differing motor winds. I doubt the Align ESC is any different. If an ESC cannot keep pace with the pulse rate you get a high pitch whine/scream.

Going off topic, but by way of explanation, I have a own design fast flying wing, tuned to the absolute limit. With a new pack, so high voltage, the ESC will lose timing if full throttle is held, but in order to get the absolute best from the set up over the pack capacity at normal output voltage I fly more conservatively for the first 30 seconds or so until the pack voltage drops to nearer nominal level, when its fine and giving all it can handle.

[Ben M]

Thanks Dave for your corrections and for your comments. They are very interesting.

I didn't know anything about "Overproping" or "ESC timing". I saw the ESC setting called "Electronic Timing" but I didn't know what it was so I followed the manual's instructions which were:

1. "6 or more poles should use Mid timing" (the 450L Dominator's motor has 6 poles)

2. "High timing gives more power at the expense of efficiency. Always check the current draw after changing the timing in order to prevent overloading of battery"

3. "When setting to the Quick throttle response speed, the accelerative peak current will increase."

The problem of the motor stopping while screeching is clearly related to an excessive current consumption. I would have never tried any setting that may potentially increase the current draw. So I did not pay attention to this setting and I used the default value "Mid timing".

 

This suggests the ESC was losing timing (it pulses the three windings to gain rotation). For this to happen at all there was something clearly wrong, and to continue to use the model without finding the reason and curing it was sadly always likely to end in tears. ESCs have user settable timing settings to adjust for differing motor winds. I doubt the Align ESC is any different. If an ESC cannot keep pace with the pulse rate you get a high pitch whine/scream.

 

Do you think that using a "High timing" value may help to avoid the motor stopping and screeching? How can it be if this increases the motor and ESC current and temperature?

 

Your figures above do not include head speed counts, but your text suggests that you (and from your comments others) have exceeded the safe load, possibly by over pitching the head. 20 amps though is not that high for a 3S Heli installation!

 

What do you mean with "exceeded the safe load"?

What make you think so? In my case I was just hovering very slowly and within a small area.

I have double checked the Telemetry data I got from the day the motor got burned. During the first 20 seconds of flight (take off) the motor RPM went from 0 to 30K. Taking in account its gear ratio of 10.08 (with the stock 12 teeth pinion and 121 teeth main gear) the main rotor head should be 2,975 RPM. After that the helicopter flew about 30 seconds (gentle hover) around 32K motor's RPM which should be around 3,174 head's RPM.

I would say that these values are very high for a gentle flight. The radio settings I had that day were:

• Throttle curve: 0% 75% 85% 85% 85%
• Pitch curve: 50% 62% 75% 85% 95%
• Pitch angle: 0º 2º 5º 7.1º 9º (Based on measures taken on the bench with each Pitch %)

In the moment of the motor failure the throttle stick should be just over the centre: throttle 85% and Pitch angle between 5º and 7º. I would say 6º. The diameter of the main rotor head is 710 mm.

Is this overloading?

Can I know if there is "Overproping" with this data?

 

5. Its not a good idea to run any ESC at well below its rated max current. (or of course over!) I don't think I'd like to try to calculate and install a single ESC that would deal fully with those two very differing mech's, though obviously I don't know the correctness of the mech setup affecting their actual current draws at all flight stages.

The ALIGN stock ESC for the 450L Dominator is rated to work with a max continuous current of 45A and a max voltage of 22.2V.

Does this mean that flying between 8 and 14 amps may damage the ESC?

 

6. A high kV rated motor has comparatively little torque. It takes less extra mechanical loading to push it over the edge out of its "comfort zone". That is why it should have a smaller pinion to allow it to turn at its design speed while getting the right head speed. And why its a little more critical on any mechanical stiffness.

This is why I think that making the 3,200 KV motor pinion bigger (more teeth) than the one in the 6S version makes the 3S version weak and prone to electrical problems.

 

Edited By Ben M on 10/01/2015 21:02:48

Edited By Ben M on 10/01/2015 22:27:43