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Author Topic: Can electric motors withstand crashes?  (Read 2004 times)

Offline Joe Ed Pederson

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Can electric motors withstand crashes?
« on: February 22, 2019, 03:14:57 PM »
I thought of going Electric, but I keep crashing from time to time, and my last face plant with an IC motor filled the venturi with mud (not the first time).   I fly RC electric and can't imagine electric motors surviving my abuse.   And I wonder if you can get all the dirt/mud out of an electric motor.   What solvents would you use to get dirt/mud out of an electric motor: water, denatured alcohol, …..?

I've cleaned up many an IC engine after a crash, installed a new NVA when needed and kept on flying the engine.  Although NVA's aren't free, they are a lot less expensive than a new electric motor.

Am I wrong in thinking that electric motors are much more susceptible to crash damage and more difficult/impossible to clean?   Am I wrong in waiting until I rarely crash to switch to electric?

Joe Ed Pederson
Cuba, MO

Offline Tim Wescott

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Re: Can electric motors withstand crashes?
« Reply #1 on: February 22, 2019, 03:19:16 PM »
I have had this conversation with regards to planes for my wife.  The answer I got was to mount the motor on an aluminum "L" bracket.  You crash, the bracket bends, the motor is fine.

It varies from brand to brand, but at least some motors are easy to take apart.  I suspect (but will have opportunity to find out once my wife is out of school and wants to fly) that you can clean a motor in water if you then immediately bake it to drive the water out of the bearings -- I'd go for 180 degrees, unless someone tells me I can go higher or lower.  If you try it and the magnets fall out, it's not my fault!
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline James Mills

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Re: Can electric motors withstand crashes?
« Reply #2 on: February 22, 2019, 04:22:19 PM »
We have had several motors that Ben has crashed several times that keep going.  We normally use a spinner and do fly over asphalt almost all the time. 

James
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Offline John Rist

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Re: Can electric motors withstand crashes?
« Reply #3 on: February 22, 2019, 04:34:22 PM »
I have crashed several electric motors.  Destroyed one.   Straight in on asphalt.   (lost the up line).  Motor did not survive.   Also lost a battery in that crash.  The motors I use are Cobra's at about $40 to $60 each.  Cheep compared to new nitro engine.  The other crash was a bent shaft.  Easy to replace.  The third crash broke a prop, motor OK.  Hope this helps.   #^

Their are cheaper and more expensive motors but the Cobra line of motors have been a good bang for my buck.  If you are a world class stunt champion I am sure the cost of a top of the line motor is necessary.  But it's cost still pails compared to cost of the airplane.  And besides top flyers crash a lot less then I do!   LL~   LL~
John Rist
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Offline Perry Rose

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Re: Can electric motors withstand crashes?
« Reply #4 on: February 23, 2019, 05:17:48 AM »
The sudden stoppage may ruin the ESC.
I may be wrong but I doubt it.
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Offline Tim Wescott

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Re: Can electric motors withstand crashes?
« Reply #5 on: February 23, 2019, 01:17:49 PM »
The sudden stoppage may ruin the ESC.

A KR timer should help that.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline John Rist

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Re: Can electric motors withstand crashes?
« Reply #6 on: February 23, 2019, 05:53:01 PM »
A KR timer should help that.

I use the KR timer.  And yes it has protected everything during a prop strike.   A really good product.  Can be used with a cheep ESC.  Doesn't take a computer to program.  Is easy to change settings such as RPMs at the field.  #^
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Offline Martin Kuehschelm

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Re: Can electric motors withstand crashes?
« Reply #7 on: March 25, 2019, 02:13:44 PM »
Hallo,

this are my method for protecting my motor and ESC from damage:

1. Using a CW Propeller. If the propeller touch the ground, the propeller can untighten the mounting nut from the motor shaft.
2. Using a timer with rpm control (as e.g. KR timer). If the timer detect a blocked motor, it stops the motor.
3. Using a ESC with current threshold or limiting (as e.g. Castle Creations). By blocking the motor the current will rise to the threshold and the ESC stops the motor.

I use it all, but I have no solution against the mechanical impact by a crash.

Martin
« Last Edit: March 25, 2019, 02:34:44 PM by Martin Kuehschelm »

Offline Ken Culbertson

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Re: Can electric motors withstand crashes?
« Reply #8 on: March 25, 2019, 03:07:56 PM »
I have gone straight in on asphalt with no damage to the esc/timer/motor.  The Castle ESC cut off the motor.  The battery on the other hand went from 5" to 3" and crazy as it sounds was still working and in balance.  I use the same theory that car mfg use.  A weak collapsible front end.  I build in as much twisting strength in as I can and as little forward to rear strength I can get away with and use plastic spinners.  Plenty strong for flying and it crushes on impact saving the electronics and the rest of the plane.

Crashes suck just as much with Electric as they do with IC.  I don't see much difference in damage.  Just as likely to get a bent shaft on either.  Dirt will find a way to get into anything and the cost is about equal.  Biggest difference is that with Electric, you don't have to get all of the oil off of the parts you repair!  Oh, one other thing, without the engine noise you actually hear the snapping of all those pieces of balsa that you spent hours patiently sanding to perfection.

Ken
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Offline Tim Wescott

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Re: Can electric motors withstand crashes?
« Reply #9 on: March 25, 2019, 04:06:49 PM »
... A weak collapsible front end.  I build in as much twisting strength in as I can and as little forward to rear strength I can get away with and use plastic spinners....

Picture?  I'm interested in how you achieve this.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Ken Culbertson

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Re: Can electric motors withstand crashes?
« Reply #10 on: March 25, 2019, 05:44:41 PM »
Picture?  I'm interested in how you achieve this.
Sorry that I only have ones from the start and finish but they tell the story.  First I use 1/16 plywood sides with the nose ring motor mount screwed into it then epoxy all over the place.  I don't use any bulkheads past the LE and no motor mount beams.  The rigidity comes from the "shelf" separating the battery from the ESC and the top blocks.  I don't try and make it too resistant to twisting.  Those electric motors put enormous torque on the front mount and I want it to have a little give about mid nose.  That is the reason that the bottom is a full removable hatch.

Now here is where it gets cute.  There is about a 1" gap between the motor and the battery shelf.  This is where it will snap off if it hits the asphalt nose first.  The motor is protected by the spinner.  Bob Hunt put me onto the open nose with the spinner recessed making an air scoop to cool the motor.  The one in the pix. is a 1 3/4 I use for fitting.  The real one is a 2". What I discovered in making the first one or these was that the spinner back plate on the ones I use (DuBro or Goldberg) would hit the motor mounting screws if I wasn't careful so I made it fit tight then pulled the prop up 1/16 before tightening the collet.  What happens in a crash was not planned but it saved the motor.  The spinner crushes and forces the rim into the motor ring which in turn snaps off the nose and saves the motor without ever putting any direct force on the motor itself.  By the time the nose is crushed there is not enough energy left and the plane survives to be crashed another day.  A metal spinner would more than likely have bent the motor shaft.

I am probably going to get slammed for this blasphemy but, it works for me!

Ken

PS - the last pic. is the rest of the ship undamaged after a direct hit under power with the asphalt.  The rest are of the rebuilding of the nose.  Sorry about the cluttered workbench!  And, the ship is in primer.  I fly my electrics before finishing them just in case there is a major construction flaw - there was. mw~
« Last Edit: March 25, 2019, 08:04:51 PM by Ken Culbertson »
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Offline Chris Wilson

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Re: Can electric motors withstand crashes?
« Reply #11 on: March 25, 2019, 06:06:26 PM »
With electric there is no reason why the old standard of having a tractor nacelle mounted engine should be manditory any more.

Surely there are some designs out there with the vunerable engine mid or rear mounted away from the impact zone and use the nacelle cone as ablative armour?
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Offline Paul Bray

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Re: Can electric motors withstand crashes?
« Reply #12 on: March 28, 2019, 11:40:19 AM »
Hi,

I probably crash more than most  ;D   ;D   ;D  but it is one figure that I practice regularly so I can do it well....

Bent a couple of shafts, few bearings gone 'notchy' (always check, surprising when the shaft gets a smack how often the bearings suffer), ripped the wires off and turned more props inot paint stirrers than I care to count but not written a motor off yet.

However, I have trashed 3 fairly expensive LiPo's which are probably more expensive than the motors which I was using and a couple of times the battery has taken most of the nose with it. Mount it more securely and it causes more damage when it bales out, mount lightly and it gets trashed when it hits the ground. I am thinking of some kind of protective sleeve for this summer although learning to fly with some ability and reduce the crashes may also help.

Paul

Offline Ken Culbertson

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Re: Can electric motors withstand crashes?
« Reply #13 on: March 28, 2019, 02:02:47 PM »
Hi,

I probably crash more than most  ;D   ;D   ;D  but it is one figure that I practice regularly so I can do it well....

Bent a couple of shafts, few bearings gone 'notchy' (always check, surprising when the shaft gets a smack how often the bearings suffer), ripped the wires off and turned more props inot paint stirrers than I care to count but not written a motor off yet.

However, I have trashed 3 fairly expensive LiPo's which are probably more expensive than the motors which I was using and a couple of times the battery has taken most of the nose with it. Mount it more securely and it causes more damage when it bales out, mount lightly and it gets trashed when it hits the ground. I am thinking of some kind of protective sleeve for this summer although learning to fly with some ability and reduce the crashes may also help.

Paul
I don't crash very often, not that I don't try, I just somehow don't.  But, when I do it mirrors your experience.

I think battery protection in a crash might warrant it's own topic.  The problem is that if you protect it you can't cool it.  If you mount it too far off of the vertical CG the plane fly's funny and if you don't it wipes things out in a crash.  I am sure some of the long time electric types have some things that might help or maybe the only answer is - don't crash.  One thing I never do is put the esc or timer in it's "crash path"
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