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Reversible electric motors and CBs

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raymondj(at)frontiernet.n
Guest

Posted: Thu Jan 07, 2010 7:37 am Post subject: Reversible electric motors and CBs

Just thinking, would there be any value in having CBs on reversible 

motors.  I'm considering: flap motors; trim motors; gear motors; 

variable pitch electric propellers.  Perhaps being able to move the 

motor in the other direction might have some value or trying again after 

a mistake like deploying at too high a speed or in a condition where ice 

might have caused an overload.  I recognize the low probability of these 

things occurring but thought they deserved mentioning in the current 

discussion.



Raymond Julian

Kettle River, MN

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jan 07, 2010 8:03 am Post subject: Reversible electric motors and CBs

At 09:21 AM 1/7/2010, you wrote:

 	  Quote: 	
		  



Just thinking, would there be any value in having CBs on reversible 

motors.  I'm considering: flap motors; trim motors; gear motors; 

variable pitch electric propellers.  Perhaps being able to move the 

motor in the other direction might have some value or trying again 

after a mistake like deploying at too high a speed or in a condition 

where ice might have caused an overload.  I recognize the low 

probability of these things occurring but thought they deserved 

mentioning in the current discussion.


	


    Careful my friend, you'll be accused of doing

    FMEA . . . it's addictive.



    What you've hypothesized is a potential for

    nuisance tripping the circuit protection in

    non-normal or extra-ordinary operations.



    My sense is that there are very few motors

    at risk for jamming due to environmental

    conditions. Flaps and trim surfaces are away

    from ice-accretion spots. Ice might gather

    close to the hub of a prop blade but those

    motors tend to be highly geared and capable

    of producing much more torque than is necessary

    to move the blades. I think virtually all

    OBAM aircraft with retractable gear use hydraulics

    where the motor is not subject to "overload" . . .

    pressure relief valves generally address that

    issue. Further, large demand devices like

    motor driven hydraulics are protected with very

    robust protection devices like current limiters.



    Extending flaps against cruise speed air-loads

    MIGHT be a case where you could pop a fuse . . .

    but loads on most flap systems start out low

    and ramp up as the flap extends into the

    wind. Behavior of the airplane during the first

    few degrees of extension would no doubt get

    the pilot's attention long before current

    demands by the motor put a fuse at risk.



    But one can always UP-size a fuse and feeder

    to the flap system. PM motors draw so much

    current in a stalled state that if you doubled

    the size of the fuse (very fast) to accommodate

    some perceived transient overload condition

    you would not put the motor at risk for other

    fault conditions.



    That brings up another thought. We know that

    unlike breakers, fuses are subject to "wearing"

    caused by short term operations at or just above

    the fuse's ratings. So if your flap system normally

    calls for a 5 or 7A breaker, you would be on

    solid ground for upsizing to 10A.



    The goal is to provide a solid, trip free

    source of power. PM motor inrush currents

    are spectacular. Breakers are much slower

    than fuses and are pure I(squared)*R sensors.

    Fuses can slowly degrade over time when

    hit repeatedly with transient "overloads".



    Good thoughts . . .



    Bob . . .

mrspudandcompany(at)veriz
Guest

Posted: Thu Jan 07, 2010 9:17 am Post subject: Reversible electric motors and CBs

I think virtually all

    OBAM aircraft with retractable gear use hydraulics

    where the motor is not subject to "overload" . . .

    pressure relief valves generally address that

    issue. Further, large demand devices like

    motor driven hydraulics are protected with very

    robust protection devices like current limiters.

The Falco, which I am building, is one OBAM aircraft which uses a motor and

jack screws to deploy the LG.  There have been many complaints of the

breaker popping when raising the gear.  Some owners have set the limit

switches so the gear does not retract fully, and finish the last little bit

of retraction with the hand crank.  I believe there is a fundamental design

flaw in the retract mechanism, but have not seen a good fix.



Roger

raymondj(at)frontiernet.n
Guest

Posted: Thu Jan 07, 2010 9:50 am Post subject: Reversible electric motors and CBs

I always apply a probability to an adverse event, even if it is a WAG

just to help keep my perspective.  You're right, it can be addictive.



Raymond Julian

Kettle River, MN.

Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>

 

 At 09:21 AM 1/7/2010, you wrote:

> 

>

> Just thinking, would there be any value in having CBs on reversible 

> motors.  I'm considering: flap motors; trim motors; gear motors; 

> variable pitch electric propellers.  Perhaps being able to move the 

> motor in the other direction might have some value or trying again 

> after a mistake like deploying at too high a speed or in a condition 

> where ice might have caused an overload.  I recognize the low 

> probability of these things occurring but thought they deserved 

> mentioning in the current discussion.

 

    Careful my friend, you'll be accused of doing

    FMEA . . . it's addictive.

 

    What you've hypothesized is a potential for

    nuisance tripping the circuit protection in

    non-normal or extra-ordinary operations.

 

    My sense is that there are very few motors

    at risk for jamming due to environmental

    conditions. Flaps and trim surfaces are away

    from ice-accretion spots. Ice might gather

    close to the hub of a prop blade but those

    motors tend to be highly geared and capable

    of producing much more torque than is necessary

    to move the blades. I think virtually all

    OBAM aircraft with retractable gear use hydraulics

    where the motor is not subject to "overload" . . .

    pressure relief valves generally address that

    issue. Further, large demand devices like

    motor driven hydraulics are protected with very

    robust protection devices like current limiters.

 

    Extending flaps against cruise speed air-loads

    MIGHT be a case where you could pop a fuse . . .

    but loads on most flap systems start out low

    and ramp up as the flap extends into the

    wind. Behavior of the airplane during the first

    few degrees of extension would no doubt get

    the pilot's attention long before current

    demands by the motor put a fuse at risk.

 

    But one can always UP-size a fuse and feeder

    to the flap system. PM motors draw so much

    current in a stalled state that if you doubled

    the size of the fuse (very fast) to accommodate

    some perceived transient overload condition

    you would not put the motor at risk for other

    fault conditions.

 

    That brings up another thought. We know that

    unlike breakers, fuses are subject to "wearing"

    caused by short term operations at or just above

    the fuse's ratings. So if your flap system normally

    calls for a 5 or 7A breaker, you would be on

    solid ground for upsizing to 10A.

 

    The goal is to provide a solid, trip free

    source of power. PM motor inrush currents

    are spectacular. Breakers are much slower

    than fuses and are pure I(squared)*R sensors.

    Fuses can slowly degrade over time when

    hit repeatedly with transient "overloads".

 

    Good thoughts . . .

 

    Bob . . .

jay(at)horriblehyde.com
Guest

Posted: Thu Jan 07, 2010 10:15 am Post subject: Reversible electric motors and CBs

This is an area that I have used to 'placate' one of my clients whose

aircraft I am building.  He really wants to see breakers but I talked him

around to fuses and non-inflight changeable ones at that... But, to get him

to accept that I agreed that the hydraulic pump might 'overload' and hence

you might want to reset that breaker, so we put in a breaker for that

circuit and fuses for everything else.  It's a perception thing, but here

there was a good compromise.



Jay



--

jimw_btg(at)earthlink.net
Guest

Posted: Thu Jan 07, 2010 11:08 am Post subject: Reversible electric motors and CBs

If you have visual access to your Fuse Block or Blocks, mine I have a light

smoke plex cover indicator led show quite well, with the ATC/ATO fuses and

the Led that lights when fuse is blown you can quite quickly determine,

first something is of malfunction, two its XXXXXX and three where the fuse

is to replace.  Quite Quick and cost effective.  On pre flight you can

glance at the block or blocks in seconds determine there all functioning.

All for $0.448 cents.  You can get them from Wayteck, Digikey, Auto Zone

.....etc.  Something that gives visual and replace able with no extra

wiring or circuit.  This listing is from Wayteck.  Just another thought.

Take care.



LED BLADE TYPE FUSE ATO/ATC 

Category: Circuit Protection 

Sub Category: Blade Fuses And Accessories 

Sub-Sub Category: ATO/ATC Fuses-Light When Blown 

    

Description: LED BLADE TYPE FUSE ATO/ATC 

  10 AMP RED (12 VOLTS) 

    

Selling U/M: EA 

Weight: 0.0032 

Price: $0.4480 

Min Order Qty: 10  



Quantity Discounts:  

Quantity Price 

100.00  0.3808  

500.00  0.3360  

 

 

 



For larger quantities then shown, 

contact Sales at quotes(at)waytekwire.com. 



Qty:    

     

 

   



Click here to view catalog.  

 

Comments: 

 

 

Jim Wickert

Tel 920-467-0219

Cell 920-912-1014



--

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jan 07, 2010 11:29 am Post subject: Reversible electric motors and CBs

At 12:10 PM 1/7/2010, you wrote:

 	  Quote: 	
		  

This is an area that I have used to 'placate' one of my clients whose

aircraft I am building.  He really wants to see breakers but I talked him

around to fuses and non-inflight changeable ones at that... But, to get him

to accept that I agreed that the hydraulic pump might 'overload' and hence

you might want to reset that breaker, so we put in a breaker for that

circuit and fuses for everything else.  It's a perception thing, but here

there was a good compromise.


	


    We wouldn't do that on a King Air . . . the motor

    supply circuit would be protected with a ROBUST fuse,

    i.e. a current limiter.



    Besides, how does he get the gear down if the motor

    craps?



    Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jan 07, 2010 11:43 am Post subject: Reversible electric motors and CBs

At 11:11 AM 1/7/2010, you wrote:


<mrspudandcompany(at)verizon.net>



     I think virtually all

     OBAM aircraft with retractable gear use hydraulics

     where the motor is not subject to "overload" . . .

     pressure relief valves generally address that

     issue. Further, large demand devices like

     motor driven hydraulics are protected with very

     robust protection devices like current limiters.



The Falco, which I am building, is one OBAM aircraft which uses a motor and

jack screws to deploy the LG.  There have been many complaints of the

breaker popping when raising the gear.  Some owners have set the limit

switches so the gear does not retract fully, and finish the last little bit

of retraction with the hand crank.  I believe there is a fundamental design

flaw in the retract mechanism, but have not seen a good fix.



     There IS a fix . . . but it's not common to the

     OBAM aircraft industry. Some years ago I participated

     in the development of a line of electro-mechanical

     landing gear actuators. They were controlled over

     a serial data line and needed only +28 and a

     communications line to hook up.  These had micro-

     controllers driving brushless dc motors. As "smart"

     actuators, they knew when they were approaching

     limits and would slow down to a crawl . . . the

     stroke drove to hard mechanical limits in the gear

     mechanism. The microprocessor sensed the up-tick

     in current and shut the motor off. No limit switches

     needed.



     One of my clients has a line of 'smart actuators'

     based on a universal controller with only the motor,

     drive transistors, and actuator mechanical details

     tailored to the task.



     A few years ago, I built some fast electronic

     current limiters for a builder who wanted to use

     independent actuators at each wheel of a Lancair.

     They were not fast and the mechanisms could tolerate

     driving to hard stops without tearing up the gear

     train. The electronic current limiters prevented

     motor inrush and "limit" spikes.



     Don't know how that project worked out. Don't even

     recall now who was building it.



     Bob . . .

jay(at)horriblehyde.com
Guest

Posted: Thu Jan 07, 2010 12:29 pm Post subject: Reversible electric motors and CBs

He used to fly King Airs.. 

The gear comes down without power using a hydraulic release valve- which is

why I say its perception thing- he knows that he has a manual backup but he

wants a breaker or two on the panel; it's a compromise of sorts..

--

mprather(at)spro.net
Guest

Posted: Thu Jan 07, 2010 1:47 pm Post subject: Reversible electric motors and CBs

I say give him a breaker which powers a switch driving a noise maker of

some sort.  Flip the switch up for the light and noise, down for none. 

Maybe a "ding alarm."  Pull the breaker to disable.  Label it "Retro

Encabulator" with apologies to Rockwell Automation...

Matt-



do not archive



[quote] 

 He used to fly King Airs.. 

 The gear comes down without power using a hydraulic release valve- which

 is

 why I say its perception thing- he knows that he has a manual backup but

 he

 wants a breaker or two on the panel; it's a compromise of sorts..

 --

jay(at)horriblehyde.com
Guest

Posted: Thu Jan 07, 2010 11:13 pm Post subject: Reversible electric motors and CBs

Actually, what you need is one of these....



http://www.youtube.com/watch?v=Z86V_ICUCD4



--

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jan 08, 2010 3:06 pm Post subject: Reversible electric motors and CBs

At 01:10 AM 1/8/2010, you wrote:

 	  Quote: 	
		  



Actually, what you need is one of these....



http://www.youtube.com/watch?v=Z86V_ICUCD4


	


   Pretty cute. I'll have to get the details on

   it. Be a good project for my oldest grandson

   this summer. I've got a bucket-load of model

   servos left over from a project.



   Bob . . .

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