Coreless Motor for Eflite UMX Aircraft

Heard some good things about the CL-0820-15-9T motor as a replacement/upgrade for the motors in the UMX series.  The video is highly entertaining (quite unusual for a motor spec video!), check it out.  They've got a pointer to 3drankin@rcgroups, who sells some UMX kits.

blogodex = {"idx" : ["motors", "UMX"]};

What's a "C Clip Support Thrust Collar"?

Turns out it's this thing, which keeps your motor from pushing the shaft out when it's installed in a rear-facing configuration.

Klique provided this picture and notes it should be all the way up against the C clip.

eCalc propCalc -- Propeller Calculator!

Courtesy of the most awesome brosius85, here's a great power system calculator that seems pretty comprehensive.  It has a large selection of motor data, nice charts showing the power curve, and warnings when some parameter is out of whack.  Thanks Brosius!!

Motor Balancing

Not just props, you should balance your motors too:

• http://www.rcgroups.com/forums/showpost.php?p=15936915&postcount=8839

Motor Math and Propeller Basics

A couple of nice articles which were pointed out by Superfly maven Tram.  It looks like there's a lot more interesting things there as well.

• Propeller Basics
• Motor Math

Balls of Steel, Scorpion Motor Edition

Scorpion HK-4525-520KV (Limited Edition):

"Each of the new HK-4525-520KV Limited Edition motor is wound with a single strand of 1.4mm wire for the highest possible efficiency. This motor is capable of running continuously at an input power of 4450 watts at 100 amps, and can handle peak inputs of 9600 watts and 215 amps for 2 seconds"

Predicting motor rotation direction

When connecting a brushless motor to an ESC, we are taught to apply power and switch two of the wires if the blade is spinning in the wrong direction.

Is it possible to predict the blade rotation by examining the ESC/motor hookup?

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Forget FPV!

This just posted on the HK twitter feed.  Forget FPV, I'm just gonna make my multicopter out of these and fly around looking at things with my own two eyes!

Pager Motors

Here's some links about 4mm and 8mm pager motors.

• recommending a GWS 2508 prop, with some data.
• different models at pagermotors.
• google for "namiki pager motors"
• lots on ebay, seems about $15 including shipping for 10 units.

Power Guidelines

Courtesy of PhilipA on RCGroups:

• 50 watts/lb: Minimum required for flight.
• 70-90 watts/lb: Trainer and slow flying aerobatic models.
• 90-110 watts/lb: Sport aerobatic and fast flying scale models.
•  110-130 watts/lb: advanced aerobatic and high speed models

He notes:

• 80-100w/lb nice target for many planes.
• The Blue Wonder maxes out around 85 watts on a 3S lipo and GWS 9x5HD (straight blade) prop. 
• Sufficient for up to a 16oz AUW plane with decent performance including a 4ch aileron version.

Changing an Outrunner Motor Shaft

Abridged from HeadsUp RC:

1. Remove firewall mount. Requires 1.5mm allen wrench (12 cents at Ace Hardware!). Sometimes can be quite difficult to remove.
2. Remove C-clip and washer at rear of the motor that retains the shaft. Removing washer can be most difficult part, as it tends to hang in C-clip groove.
3. Pull motor bell off of stator. (motor bell = outer part with the magnets, stator = inner part with windings). Do this by grasping motor tube with a pliers where the firewall mount was located, and pull on the motor bell with your fingers. There will be resistance from the magnets.
4. Remove flange from the motor bell by removing 10mm retaining nut on inside of motor bell. (May be asier to remove nut if shaft removed from the flange first. Loosen two set screws on front of motor bell, then drive shaft out of flange with hammer and small punch.)
5. Insert the new shaft with flange, and secure with nut on inside of motor.
6. Reinstall stator, washer and C-clip.

Heads Up RC Brushless Motor Guide

Heads Up RC has a great guide to brushless motors.

The legendary Blue Wonder motor

New, improved, and red:
Turnigy 2730 Brushless Motor 1300kv

• Dimension: 32mm x 27mm, 43mm(with shaft)
• Weight: 28g (not including connectors)
  Diameter of shaft: 3.1mm 
• Voltage: 2~3S
• Max current: 3.5~7.5A/20S
• Propeller: 7x3.5~9x4.7
• Pull: 250~470g
• For small parkflyer and gliders.

By The Numbers: Brushless Motors

Brushless motors have lots of numbers associated with them.  Let's use the popular TowerPro 2408-21 as an example.  It's very well documented.  Here's the HobbyKing, TowerPro, and TowerPro Motor Spec pages.





Most Important Numbers

• Kv -- measured in RPM, shows the maximum rotational speed per volt of input (bigger number = faster spin = more power required).
• weight -- typically measured in grams.
• max current -- measured in amps.  The maximum current draw this motor can handle for an extended period of time (important for picking your ESC.  The ESC Amps should be larger than this number).
• max loaded current (60s) --measured in Amps, and usually given with a timeframe (60 seconds is common.)  The maximum current draw the motor can take for a short period of time without burning up.

Other Numbers

• Battery - number of cells
• dimension - the physical size
• shaft diameter - more powerful motors need bigger, stronger shafts.  you need to know this number if you buy a prop saver. 3mm is a common value.
• poles, magnets -- not sure why these are important, maybe highter quality motors have more?
  

Thrust Calculation
(still in progress)

Relationship of ESC numbers to Motor Numbers

• ESC Amp number must be greater than motor Amp number, or you will burn up you ESC by pulling too much electricity through the circuit.

"Runner" Configuration

Brushless motors are either inrunner or outrunner. The Towerpro motor above is an outrunner.

• inrunner -- the motor is stationary and the motor shaft spins
• outrunner -- the motor shaft is stationary and the motor body spins

Motor Equivalency

If you need to see how equivalent two motors are, the two most important numbers to match are

• Kv -- they should be close to the same power output
• Weight - they should weigh similarly