Crazyflie w/ Double Motors
Posted: Wed Jun 12, 2013 3:04 am
In order to put a micro camera/transmitter on my CF, I'll need extra SWaP (size, weight, and power). This will require more thrust and consume more battery power. I thought about doubling up the motors using the existing motor mounts (see pics) and using some of the extra payload capacity for a larger battery to compensate for the increased power requirements.
Wiring the motors:
Both propellers on each arm must be spinning in the same direction. Because the underside motors will be upside down, they must actually spin in the opposite direction as the right-side up motors so that when they're upside down, the propellers of both motors are spinning in the same direction. Therefore, for each arm, the black wire of the original motor must be twisted & soldered in parallel to the white wire of the new (underside motor) and both soldered back into the same power port that the original black motor wire was soldered into. Do the same for the white wire of the original motor with the black wire of the new motor. Repeat for each arm and wrap the wires loosely around the arm.
Connecting the motors in parallel means the second set of motors will be regulated equally by the stability chipset and consume/produce the same electrical/thrust power. Here's what I've put together from various other posts and some deductive reasoning.
Launch and recovery:
Use the center peg of a spool of CD-ROMs as a launch platform. The peg keeps the bottom props lifted off the ground, while allowing enough clearance for them to spin. Land the CF softly on carpet for catch it in your hand. Because the motors are loosely slid into the mounts, they may fall off during a rough landing, but are easily put pack in their mounts.
This photo shows the completed modification on a CD-ROM peg with a few coins attached on top as a test payload.
Stock Configuration (single motors)
Empty Weight: 14g
Total Weight: 19G (Empty 14g plus 170mAh battery 5g)
Operational thrust provided by 4 motors: 24g (weight 19g plus 5g payload)
Payload capacity: 5g unaffected, up to 10g degraded flight
Power consumption at hover: 5W for each motor power path (max capacity 15W per path)
Avg Flight time: 7 mins
Proposed Configuration (double motors with 350mAh battery)
Empty Weight: 21g (14g plus 1.7g X 4 motors)
Total Weight: 31g (Empty 21g plus 350mAh battery 10g)
Operational thrust provided by 8 motors: 43g (First 4 motors provide 24g plus second set 24g minus inefficiency due to prop turbulence (10%?)
Payload capacity: 12g unaffected, up to 17g degraded flight (Thrust 43g minus total weight 31g)
Power consumption at hover: 10W for each motor power path
Avg Flight time: 7 mins
Hypothesis: Double motors and a bigger battery will more-than double the payload capacity. This gives you a net increase of about 7G payload capacity (12g total payload capacity) for the same flight time.
Note: Payload power consumption (camera) will decrease avg flight time.
Calculations assume 10% loss of thrust due to prop turbulence. Anyone have experience with dual prop multi-coptors? Any thoughts on what actual power loss might be?
-Ryan
Both propellers on each arm must be spinning in the same direction. Because the underside motors will be upside down, they must actually spin in the opposite direction as the right-side up motors so that when they're upside down, the propellers of both motors are spinning in the same direction. Therefore, for each arm, the black wire of the original motor must be twisted & soldered in parallel to the white wire of the new (underside motor) and both soldered back into the same power port that the original black motor wire was soldered into. Do the same for the white wire of the original motor with the black wire of the new motor. Repeat for each arm and wrap the wires loosely around the arm.
Connecting the motors in parallel means the second set of motors will be regulated equally by the stability chipset and consume/produce the same electrical/thrust power. Here's what I've put together from various other posts and some deductive reasoning.
Launch and recovery:
Use the center peg of a spool of CD-ROMs as a launch platform. The peg keeps the bottom props lifted off the ground, while allowing enough clearance for them to spin. Land the CF softly on carpet for catch it in your hand. Because the motors are loosely slid into the mounts, they may fall off during a rough landing, but are easily put pack in their mounts.
- 2013-06-29 10.11.03a.jpg (68.57 KiB) Viewed 13892 times
Stock Configuration (single motors)
Empty Weight: 14g
Total Weight: 19G (Empty 14g plus 170mAh battery 5g)
Operational thrust provided by 4 motors: 24g (weight 19g plus 5g payload)
Payload capacity: 5g unaffected, up to 10g degraded flight
Power consumption at hover: 5W for each motor power path (max capacity 15W per path)
Avg Flight time: 7 mins
Proposed Configuration (double motors with 350mAh battery)
Empty Weight: 21g (14g plus 1.7g X 4 motors)
Total Weight: 31g (Empty 21g plus 350mAh battery 10g)
Operational thrust provided by 8 motors: 43g (First 4 motors provide 24g plus second set 24g minus inefficiency due to prop turbulence (10%?)
Payload capacity: 12g unaffected, up to 17g degraded flight (Thrust 43g minus total weight 31g)
Power consumption at hover: 10W for each motor power path
Avg Flight time: 7 mins
Hypothesis: Double motors and a bigger battery will more-than double the payload capacity. This gives you a net increase of about 7G payload capacity (12g total payload capacity) for the same flight time.
Note: Payload power consumption (camera) will decrease avg flight time.
Calculations assume 10% loss of thrust due to prop turbulence. Anyone have experience with dual prop multi-coptors? Any thoughts on what actual power loss might be?
-Ryan
