2022-12-05 - New Motors & ESCs, Move to 12S

Change Description

Description of Change

We would switch the vertical lift motors from the current 6S MN5008 340KV motors to 12S T-Motor V505 260KV motors, keeping the current props. This change will result in ~2.45x more thrust per motor, going from 3.556kg to 8.741kg. The new motors will also lock in position in line with the frame while not spinning, reducing drag. The rear push motor will be switched from the current 6S Propdrive 5060 270KV on a 21x5.5” prop to a 12S T-Motor AT4130 300KV motor running a 16x8” prop. This will result in slightly more thrust than the current setup (~20% more? This isn’t very accurate as no test data is provided by HobbyKing, I had to calculate theoretical thrust), but the prop will be able to clear the lift props and the ground. The four lift ESCs will have to be replaced with 12S ESCs, the push motor already has a 12S capable ESC. The ESC of choice is the APD 120A F3, one of the few 12S ESCs which support DSHOT. The only other option is the FlyColor 80A ESC, but I have heard bad things about FlyColor (Anni had a FlyColor ESC catch fire on a personal project). A new Pixhawk power module is also required, we are maxing out the reading on the one we have now at 100A.

Implementation

The mounting pattern of the new motors is the same as the current ones, no redesigning or manufacturing will be required to attach them. The current batteries can be connected in series instead of parallel to achieve 12S voltage. Everything else should be a drop-in replacement.

Reason for Change

Our current motors are underpowered for the airframe. On December 4th we conducted a test flight of the aluminium comp frame. While hovering in loiter mode facing into the wind the two rear motors were at 100% throttle and the drone was not easily controllable. This log data is attached in the flight test page. At one point we were commanding full ascent, but the drone was descending due to force on the wings from the wind. In the current state it would be very difficult, if not impossible, to land on the required 36” landing pad for the competition because the drone is not easily controllable.

Priority

High

Impact of Not Responding to Change

The drone will not be easily controllable in low wind, and not flyable at all in high wind.

What Groups, People, Sub-teams Need to be Notified?

• Mechanical

• Electrical

• Systems Integration

Change Impact

Additional Parts/Resources Required and Costs

Cost (in CAD, tax + shipping included) will be roughly $830 for 5 lift motors (4 for use, 1 spare), $165 for the push motor, and $700 for 4 APD 120A F3 ESCs. We already have one 12S ESC. The motors would be purchased from T-Motor, the ESCs from GetFPV. A new power module for the pixhawk, the PM06, which supports up to 14S and an ADC (Analogue - Digital Converter), the ADS1115, would be needed to regulate voltage and measure power for the Pixhawk. The combined cost of these two components is $40. Total cost is ~$1735. With the recent sponsorship(s) we have enough money.

Impact on deadlines

Once the parts are received it could be changed over in a day on the aluminium test frame. These motors would be installed on Icarus from the beginning.

Alternatives and Recommendations

The alternative is higher KV motors on 6S, or doubling up current motors (adding identical motors on the bottom). I suggest against this because higher KV motors on 6S will draw significantly more amps. We are already drawing ~130A from the battery at the peak. Bigger motors could push this to around 190A assuming 60A per vertical motor, 2x what they draw now. New ESCs would be required for this regardless. Motors with these specs are also hard to find, I could not find any motors like this. Adding more motors underneath would have the same issues with current draw and more ESCs would also be required. Coaxial configurations like this have a ~25% efficiency loss.

Comments

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Status

Accepted / On Hold / Rejected / More info Requested

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