[NSRCA-discussion] Fw: Serious Torque on the Nose of the Model- RESUBMITTED

Wed Dec 5 09:16:31 AKST 2012

I agree with Chris. I've personally had thousands of flights with nose
mounted motors with rear supports and never had so much as a hint of
failure. If you count all the flights I've seen Andrew fly with his nose
mounted, rear supported motors as well as countless others at the practice
field and on the contest trail, the number probably reaches into the tens of
thousands. 

The only time I've ever witnessed a catastrophic motor induced fuselage
failure was while I was judging an FAI pilot flying an Axi-equipped Smaragd
a few years back. Following a turnaround, there was a short, deep, rumbling
sound that sounded a little like flutter with heavy bass followed by the
departure of the motor and a significant section of the nose of the fuse.
The motor was nose mounted and had no rear support. 

My best guess, and it is just a guess,  was that the prop arc coupled with
the forces of the looping turnaround, set up a harmonic, or flutter if you
will, that the fuse couldn't contain. The rumble was very brief before it
came apart. 

I have no engineering data to report, just practical experience. A nose
mounted motor without a rear support is a disaster about to happen. As Chris
said, it's just a matter of when.

Verne Koester

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Chris
Sent: Wednesday, December 05, 2012 12:50 PM
To: Bob Kane; General pattern discussion
Subject: Re: [NSRCA-discussion] Fw: Serious Torque on the Nose of the Model-
RESUBMITTED

Early in the electric transition, many of us found out the hard way that
nose mounted outrunners without a rear support would lead to structural
failures with nearly 100% certainty.  My nose mounted Genesis lasted 1 1/2
flights before failure.  Others had many more flights but even the best
cases I know of had nose structure stresses and cracking due to the
unsupported nose mounting.  Jerry Budd and I did a lot of testing and
posting about this issue back in 2006 or 2007.  Newer designs have
reinforced noses which help but bottom line, don't nose mount an electric
motor without rear support. It "might" last 1 or 500 flights but 501 won't
be as successful.

Chris

On 12/5/2012 12:38 PM, Bob Kane wrote:

Great observations.  I am curious about the numbers myself, maybe in my
spare time (ha!) I'll pull out my old physics books and crunch some numbers.

Bob Kane
getterflash at yahoo.com

  _____  

From: ehaury  <mailto:ejhaury at comcast.net> <ejhaury at comcast.net>
To: mike mueller  <mailto:mikemueller at f3aunlimited.com>
<mikemueller at f3aunlimited.com>; General pattern discussion
<mailto:nsrca-discussion at lists.nsrca.org> <nsrca-discussion at lists.nsrca.org>

Sent: Wednesday, December 5, 2012 11:02 AM
Subject: Re: [NSRCA-discussion] Fw: Serious Torque on the Nose of the Model-
RESUBMITTED

I don't know what caused Charlie's failure, we've discussed possibilities -
obviously forces occurred that were beyond what the structure could handle.

Torque & precession have been with us since we stuck engines & props on the
front of airplanes. They really haven't changed much with the advent of E
power - actually went down with the use of lighter props.

I'd just like to offer that the Hacker Q80 design doesn't change much. The
rotating outer member (Q80-14) weighs about 100g and rotates up to 7K rpm
with an 1 1/2" radius. The rotor in a C50 also weighs around 100g, but it
rotates up to 40K rpm on a 3/8" radius. The latter, with the gearbox, can
probably apply torque quicker than the outie. Most other popular outrunners
fall somewhere between these. (Be neat if someone actually made the calcs.)

I've lots of flights with the Q80-11 without issue (the Q80-14 is less
powerful). It is firmly front mounted with also a solid rear mount. I think
we all know the importance of a nose ring on a YS and there's been no
success running inrunners without a rear support. While some have had
success running the Q without a rear support (bet the prop was light), these
things really need a more sturdy rear support (or very stout front mnt /
fuse nose) than may be obvious.

Essentially something slightly different that adds to the learning curve,
hopefully Charlie's experience and these discussions will prevent further
occurrences.

Earl

----- Original Message ----- 

From: mike mueller <mailto:mikemueller at f3aunlimited.com>  

To: Bob Kane <mailto:getterflash at yahoo.com>  ; General pattern discussion
<mailto:nsrca-discussion at lists.nsrca.org>  

Sent: Wednesday, December 05, 2012 8:26 AM

Subject: Re: [NSRCA-discussion] Fw: Serious Torque on the Nose of the Model-
RESUBMITTED

Very cool video. I've learned a lot of neat things watching Youtube video's.
Thanks Bob

From: Bob Kane <getterflash at yahoo.com>
To: Generalpatterndiscussion <nsrca-discussion at lists.nsrca.org> 
Sent: Wednesday, December 5, 2012 7:07 AM
Subject: [NSRCA-discussion] Fw: Serious Torque on the Nose of the Model -
RESUBMITTED

Charlie was spot on with his comment on torque, but there are two torque
vectors at work, the first is the obvious force required to turn the prop
and the "equal but opposite" torque the motor transmits to it's mount. If
that was all we had to worry about, the single mount would probably be fine.
But there is the other torque (gyroscopic precession)  resulting from
attempting to move a rotating mass in the pitch or yaw axis.  Here is a good
youtube video demonstrating the effect . .. .  

http://www.youtube.com/watch?v=ty9QSiVC2g0

Bob Kane
getterflash at yahoo.com

From: mike mueller  <mailto:mikemueller at f3aunlimited.com>
<mikemueller at f3aunlimited.com>
To: Bob Kane  <mailto:getterflash at yahoo.com> <getterflash at yahoo.com> 
Sent: Tuesday, December 4, 2012 4:34 PM
Subject: Re: [NSRCA-discussion] Serious Torque on the Nose of the Model -
RESUBMITTED

Say what?

"a large reactionary force called gyroscopic precession"

 I feel infinitlty smarter

 Is it violent warble?

 What prop were you running????

 Mike

From: Bob Kane  <mailto:getterflash at yahoo.com> <getterflash at yahoo.com>
To:  <mailto:vicenterc at comcast.net> "vicenterc at comcast.net"
<mailto:vicenterc at comcast.net> <vicenterc at comcast.net>; General pattern
discussion  <mailto:nsrca-discussion at lists.nsrca.org>
<nsrca-discussion at lists.nsrca.org> 
Sent: Tuesday, December 4, 2012 7:54 AM
Subject: Re: [NSRCA-discussion] Serious Torque on the Nose of the Model -
RESUBMITTED

The Q80 has a large diameter rotating mass, and it brings with it a large
reactionary force called gyroscopic precession when it is spinning.  In
laymen terms it will strongly resist changing direction in yaw or pitch.  A
rear brace would help keep this force in check. 

Bob Kane
getterflash at yahoo.com

From:  <mailto:vicenterc at comcast.net> "vicenterc at comcast.net"
<mailto:vicenterc at comcast.net> <vicenterc at comcast.net>
To: General pattern discussion  <mailto:nsrca-discussion at lists.nsrca.org>
<nsrca-discussion at lists.nsrca.org> 
Sent: Tuesday, December 4, 2012 8:27 AM
Subject: Re: [NSRCA-discussion] Serious Torque on the Nose of the Model -
RESUBMITTED

I understand that a rear brace is a must for this motor.  

Vicente "Vince" Bortone
Sent via BlackBerry by AT&T

-----Original Message-----
From: "Charlie Barrera" <charliebarrera at consolidated.net>
Sender: nsrca-discussion-bounces at lists.nsrca.org
Date: Tue, 4 Dec 2012 07:02:47 
To: <nsrca-discussion at lists.nsrca.org>
Reply-To: General pattern discussion <nsrca-discussion at lists.nsrca.org>
Subject: [NSRCA-discussion] Serious Torque on the Nose of the Model -
    RESUBMITTED

_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

  _____  

_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion 

  _____  

No virus found in this message.
Checked by AVG - www.avg.com <http://www.avg.com/> 
Version: 2012.0.2221 / Virus Database: 2634/5437 - Release Date: 12/04/12

_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20121205/c255ef73/attachment.html>