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

Wed Dec 5 11:04:28 AKST 2012

This would be an *excellent* topic for an article in the K-factor!

(hint, hint)

Peter+

On Wed, Dec 5, 2012 at 11:30 AM, Larry Diamond <ldiamond at diamondrc.com>wrote:

> As somebody who is trying to get back into Pattern and those like me that
> have Zero experience with high power electric setups, is there an article
> or a something posted that we can reference?
>
> Maybe something on the NSRCA Website that can be accessed by all under
> Tips an Set Up...Yada Yada Yada...
>
> Larry Diamond
>
>   *From:* Verne Koester <verne at twmi.rr.com>
>
> *To:* 'General pattern discussion' <nsrca-discussion at lists.nsrca.org>
> *Sent:* Wednesday, December 5, 2012 12:16 PM
>
> *Subject:* Re: [NSRCA-discussion] Fw: Serious Torque on the Nose of the
> Model- RESUBMITTED
>
>   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 <mikemueller at f3aunlimited.com>
>  *To:* Bob Kane <getterflash at yahoo.com> ; General pattern discussion<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 - 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
>
>
>
> _______________________________________________
> 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
>

-- 
Director, Fixed Wing Flight Training
Santa Clara County Model Aircraft Skypark
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20121205/923469d4/attachment.html>