Turnigy motors

[Mike Hardy]

I am going to use the Turnigy SK3 3536 but I have seen reference to the SK 3536 are they the same motor?

I have read with disquiet on this forum that motors can achieve full throttle when controls are set at zero. Fail safe or not, when the final semiconductor switch fails full power is applied to the motor. So I think there is a case for a 'fail safe' link placed in the battery supply lead to the ESC accessible from outside the fuselage. this can be opened as soon as the model has come to rest and 'armed' just before takeoff assuming all safety checks have taken place beforehand.

Mike.

[GrahamC]

Posted by Mike Hardy on 26/02/2013 09:39:25:

I am going to use the Turnigy SK3 3536 but I have seen reference to the SK 3536 are they the same motor?

Probably! - 35 = Diameter 36=Length.

Some of the big brand motors use a different system for refering to different size motors, but Turnigy, along with the motors from 4-Max, certainly some Overlander and the XYH motors Giant Shark use this generic numbering system.

The main thing is that you get the right KV rating for the application.

And... It's also worth considering how you want to mount the motor. I prefer to uses the system where a prop adapter bolts to the can of the motor - as per the XYH motors mentioned.

As for your comment about motors running - First thing I do with an electric aircraft after landing is disconnect the battery. That's why its quite important to have a good hatch. Even these size motors can bite [I was bitten by a WOT 4 foamy - 3536 motor of about 900KV] - and it was my fault.

You could make a closed link Deans plug to use as a switch - to break the circuit when removed - but you would be adding another potential failure point to the model. If the Deans were to fail [It can happen] or the link were to become dislodged...

[Mike Hardy]

Thanks Graham, I take your point another weak link in the chain but at least you may have a broken aircraft and still retain all your fingers!! Quite scary to a newbie in electric flight.

Mike.

[Olly P]

I have read with disquiet on this forum that motors can achieve full throttle when controls are set at zero. Fail safe or not, when the final semiconductor switch fails full power is applied to the motor. So I think there is a case for a 'fail safe' link placed in the battery supply lead to the ESC accessible from outside the fuselage. this can be opened as soon as the model has come to rest and 'armed' just before takeoff assuming all safety checks have taken place beforehand.

Hi Mike.

If the motor achieves full throttle with the controls set to zero there must be any 2 of 3 conditions

1) The main power battery must be connected (in all cases!)

AND

2) The throttle channel requires reversing on either the Tx or the ESC (not available on all ESC's)

OR

3) The Failsafe is set to the incorrect throttle position.

The best way to avoid this is to set the model up correctly with the prop removed, in the comfort of the shed/workshop/living room.

Firstly, when you first bind/power the Rx ensure the throttle is on minimum. if the ESC starts emitting a sequence of beeps, and does so continuously, then it is in programming mode, showing that it thinks the throttle is high. Disconnect power from the Aircraft, reverse the throttle on your Tx and then repower the aircraft.

The ESC/Motor should emit a short sequence to indicate the system is armed correctly.

I now check the throttle response, up and down.

More in the next post!

[GrahamC]

To be honest, most of the danger in electric flight comes about from daft mistakes, and you can minimise the danger.

A few suggestions.

1] When fiddling in the work shop with ESC's and motors in a air frame, always remove the prop. [Cross posted with Olly]

2] Always conduct a failsafe check after binding. Get an assistant to safely restrain the model, and turn off the transmitter. Check that the motor doesn't run.

3] Always have some means of restraining the model while you connect up the battery. We are used to restraining IC models, but not electric. A club member has a flight box with a model holder on top. He always places his electric models in the holder to connect and diconnect batteries. If it for some reason the model were to go wide open throttle, nothing will happen. It's easier too!

4] Never connect / diconnect with your hands or other bits in the prop arc!

5] Never charge Lipos on your bed or under the Sofa or in the back of your car!

6] Remember that TX straps can catch the throttle. I always hold my thumb accross the throttle when carrying out a 'live' aircraft.

Electric flight is very safe as long as you understand the risks and are sensible.

Edited By GrahamC on 26/02/2013 11:10:05

Edited By GrahamC on 26/02/2013 11:10:28

[Olly P]

OK. So assuming all has gone well above we need to set the failsafe. Follow the instructions for your Tx/Rx combination for this. I do not know them all so cannot list them!

Once this has been set to zero throttle (the minimum legal requirement). Switch on the system normally (power on Tx, power on aircraft, prop still removed) and then turn off the Tx. If the motor spins to life then something hasn't set correctly, and it should be re-done.

Switch the Tx back on, and check control is restored. assuming all is well I now advance the throttle to 1/3rd of max throttle setting - remember there is no prop. I then switch off the Rx, and the motor should stop, again if it does not check the setting of your failsafe has worked. Switch the Tx back on and the motor should spin up again, depending on your Tx/Rx combo you may need to reduce throttle and then advance it to restart the motor.

OK possible other things:

Some ESC's need you to advance the throttle to full and then return it to nil before they recognise the throttle movement - if no response to any throttle inputs then check this is not needed.

Think that covers it!

 

EDIT: Forgot to say - if in doubt make sure the battery is disconnected and remove the prop before fiddling with anything. An Electric aircaft with a battery on should be treated the same as an IC one with the fuel in and glow plug attached - it can and will start up!

Olly

Edited By Olly P on 26/02/2013 11:25:05

[Simon Chambers]

Posted by Mike Hardy on 26/02/2013 09:39:25:

I am going to use the Turnigy SK3 3536 but I have seen reference to the SK 3536 are they the same motor?

If I recall correctly, the Turnigy SK3 is the newer version of the original Turnigy SK series.

I have read with disquiet on this forum that motors can achieve full throttle when controls are set at zero. Fail safe or not, when the final semiconductor switch fails full power is applied to the motor.

A brushless motor controller needs to switch the MOSFETS (the semiconductor that does the switching) on and off to move the motor (to perform commutation - i.e. it emulated switching the motor windings on and off as the brushes of a brushed motor will do). If a MOSFET fails and gets stuck on, it'll drive one of the windings with the full battery voltage. As the resistance of our motors are very low, this is almost a dead short. So in this state, any part of the powertrain will let go - the PCB tracks, the other MOSFETs, the motor windings, the connectors or even the battery cell tabs.

However if the MOSFET is a stuck on, it can't switch on and off (obviously), so the motor won't turn.

Brushed controllers on the other hand will go full throttle if a MOSFET should fail on.

Si.

[Mike Hardy]

Thanks Guys, I can see safety is an issue with electric flight possibly more so than IC flight! I note a few months back the Mag published a letter from a guy who had injured his hand from a spinning prop when he thought everything was safe and advocated an arming/disarming link assessable from outside the fuselage. With all the safety features built into the system why do we still get reports of injury - we can't all be 'reckless'.

I have a Aurora 9 which has not being fired up yet; but note the set-up instructions are extremely complex. No wonder accidents happen.

Mike.

[Olly P]

Mike - I think the thing is when an IC model is 'live' we tend to start her and the noise reminds us to take care....

With electric they can be live and silent, therefore we can easilly forget.

Personally I seperate setting up of the TX and setting up of the aircraft until I know what I am doing - i.e. I will set up the profile, reverse the throttle channel (futaba), and test it with some servos before I trust it to anything in an airframe.

Once in the airframe I will use a stand alone battery to set up all surface movements before connecting the throttle or putting a prop on.

finally i connect the ESC and set up throttle and ensure everything is safe before adding the flight battery, still with no prop.

As I and others have said - electric is no more dangerous, you simply need a safe routine for working with it. I intend to write out a checklist for when I do the bigger aircraft I have planned as these will have lots to connect up so I don't want to get anything wrong!