[NSRCA-discussion] Fw: Serious Torque on the Nose of the Model- RESUBMITTED
Chris
cjm767driver at hotmail.com
Wed Dec 5 11:04:39 AKST 2012
Larry,
A rear mounted outrunner (on a firewall) or a nose mounted outrunner or
inrunner with rear support are all safe ways to go. Find your budget and
get suggestions of combos that are currently ( that's funny) in use and
are successful and copy the working setup EXACTLY. 99.99% of problems
from new electric guys are when they start experimenting or want to try
something different - don't. Just copy what works and you will have
success, and please don't rely on the many faceless experts on RCU etc.
Guys on this thread like Earl and Verne and Mike have tons of experience
and can lead you to a working setup from day 1.
Electric is not that difficult at all but you need to learn a new
language and that takes a while so rely on any good teacher here on the
list.
Chris
On 12/5/2012 2:30 PM, Larry Diamond 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 <mailto:getterflash at yahoo.com>
> *From:*ehaury mailto:ejhaury at comcast.net
> *To:* mike mueller mailto:mikemueller at f3aunlimited.com; General
> pattern discussion mailto: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
> <mailto:getterflash at yahoo.com>>
> *To:* Generalpatterndiscussion
> <nsrca-discussion at lists.nsrca.org
> <mailto: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 <mailto:getterflash at yahoo.com>
> *From:*mike mueller mailto:mikemueller at f3aunlimited.com
> *To:* Bob Kane mailto: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
> *To:* mailto:vicenterc at comcast.net
> mailto:vicenterc at comcast.net; General pattern discussion
> mailto: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 <mailto:getterflash at yahoo.com>
> *From:*mailto:vicenterc at comcast.net mailto:vicenterc at comcast.net
> *To:* General pattern discussion
> mailto: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
> <mailto:charliebarrera at consolidated.net>>
> Sender: nsrca-discussion-bounces at lists.nsrca.org
> <mailto:nsrca-discussion-bounces at lists.nsrca.org>
> Date: Tue, 4 Dec 2012 07:02:47
> To: <nsrca-discussion at lists.nsrca.org
> <mailto:nsrca-discussion at lists.nsrca.org>>
> Reply-To: General pattern discussion
> <nsrca-discussion at lists.nsrca.org
> <mailto:nsrca-discussion at lists.nsrca.org>>
> Subject: [NSRCA-discussion] Serious Torque on the Nose of the
> Model -
> RESUBMITTED
>
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