X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-gw0-f52.google.com ([74.125.83.52] verified) by logan.com (CommuniGate Pro SMTP 5.4.0) with ESMTPS id 5071962 for flyrotary@lancaironline.net; Tue, 02 Aug 2011 16:45:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=74.125.83.52; envelope-from=dale.rog@gmail.com Received: by gwj15 with SMTP id 15so178259gwj.25 for ; Tue, 02 Aug 2011 13:44:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:content-type; bh=wqMMKkCKIwiJEOBe+fihEKzv7DiUrn/sqsyRTV9Uw6Q=; b=bESx208k0sdnGfqChCiGZp59l+mCf7FlVC0QIkd2HiJboZpuStG/BSWhXxnjgNYJdp EsMctaGNptyraZ+Wp2xWAr9zaBGzUa0YJoeQkRSf9oduDURCMKOTTCLkfH1f9yKtxGym fUScDDY8kBLVqy8EbRyqFN+mlsEG90OQ8f7Q4= Received: by 10.142.224.15 with SMTP id w15mr3864262wfg.159.1312317881350; Tue, 02 Aug 2011 13:44:41 -0700 (PDT) Return-Path: Received: from [192.168.1.107] (ip72-201-24-223.ph.ph.cox.net [72.201.24.223]) by mx.google.com with ESMTPS id y18sm79104wff.8.2011.08.02.13.44.39 (version=SSLv3 cipher=OTHER); Tue, 02 Aug 2011 13:44:40 -0700 (PDT) Message-ID: <4E3861B5.20001@gmail.com> Date: Tue, 02 Aug 2011 13:44:37 -0700 From: Dale_R User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:5.0) Gecko/20110624 Thunderbird/5.0 MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Flywheel Machine Work References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------070208030204050604050303" This is a multi-part message in MIME format. --------------070208030204050604050303 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Bill, Dunno how that one slipped past me; I could blame my 30 year old R-S calculator, but ultimately, I'm the responsible party -- I should have run the numbers twice. And it isn't just a misplaced decimal, either; although would have been close. But that just shows how much ~more~ important it is that the flywheel balance be done correctly. Best regards, Dale_R On 8/2/2011 1:27 PM, wrjjrs@aol.com wrote: > Dale, > I think you got a term wrong there. I get 807.34 rpm @ 60 > mph. 25" x 3.14=78.53in > 78.53/12=6.54ft. 60mph=1mile per minute. 5280'/6.545=807.34 > RPM > Bill Jepson > > /Connected by DROID on Verizon Wireless/ > > > -----Original message----- > > *From: *Dale_R * > To: *Rotary motors in aircraft * > Sent: *Tue, Aug 2, 2011 18:02:27 GMT+00:00* > Subject: *[FlyRotary] Re: Flywheel Machine Work > > On 8/2/2011 5:05 AM, David Leonard wrote: > > ... I am starting to think that the whole science of balancing is > > just a gimmick. Despite the old balance hole being mostly drilled > > away, the new balance holes are on the opposite side of the > flywheel. !?? > > > > Dave, > > Balancing is a procedure that falls right on the edge between > science and black art. At high RPMs, changes "out of plane" can > become > critical. > > As an example, when I started balancing wheels all we had were > bubble (static) balancers, and - because the weights had to go on the > rim edges - we would find the amount of weight, then split it, > e.g. two > half ounce weights, one on the inside and one on the outside. > ~Most~ of > the time it would put give good freeway speed balance. Sometimes, > though, we'd still get an out-of-balance wobble in the wheel due > to the > imbalance being off center of the c.g. plane of the wheel. > > Then affordable (for a small shop) dynamic balancers came along, and > we discovered that, most of the time, less weight was required on one > side of the wheel than the other, often not even opposite each > other, to > bring the center of balance the same as the center of rotation. > > Drilling balance divots on only one side of something like a wheel > can create a similar situation - where the static balance is > correct but > the center of balance is no longer the same as the center of > rotation. > It takes sophisticated equipment and an equally sharp operator to > get it > right. > > BTW, FWIW ... For an average car tire with 25" diameter at the > tread, at 60 MPH, the wheel is turning ~7950 RPM. > > > -- > Dale_R > Cozy MKIV #497 > > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > -- Dale_R Cozy MKIV #497 --------------070208030204050604050303 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit Bill,

   Dunno how that one slipped past me; I could blame my 30 year old R-S calculator, but ultimately, I'm the responsible party -- I should have run the numbers twice.  And it isn't just a misplaced decimal, either; although would have been close.

   But that just shows how much ~more~ important it is that the flywheel balance be done correctly.

Best regards,
Dale_R


On 8/2/2011 1:27 PM, wrjjrs@aol.com wrote:
Dale,
I think you got a term wrong there. I get 807.34 rpm @ 60 mph. 25" x 3.14=78.53in
78.53/12=6.54ft. 60mph=1mile per minute. 5280'/6.545=807.34 RPM
Bill Jepson

Connected by DROID on Verizon Wireless


-----Original message-----
From: Dale_R <dale.rog@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Tue, Aug 2, 2011 18:02:27 GMT+00:00
Subject: [FlyRotary] Re: Flywheel Machine Work

On 8/2/2011 5:05 AM, David Leonard wrote:
> ... I am starting to think that the whole science of balancing is
> just a gimmick. Despite the old balance hole being mostly drilled
> away, the new balance holes are on the opposite side of the flywheel. !??
>

Dave,

Balancing is a procedure that falls right on the edge between
science and black art. At high RPMs, changes "out of plane" can become
critical.

As an example, when I started balancing wheels all we had were
bubble (static) balancers, and - because the weights had to go on the
rim edges - we would find the amount of weight, then split it, e.g. two
half ounce weights, one on the inside and one on the outside. ~Most~ of
the time it would put give good freeway speed balance. Sometimes,
though, we'd still get an out-of-balance wobble in the wheel due to the
imbalance being off center of the c.g. plane of the wheel.

Then affordable (for a small shop) dynamic balancers came along, and
we discovered that, most of the time, less weight was required on one
side of the wheel than the other, often not even opposite each other, to
bring the center of balance the same as the center of rotation.

Drilling balance divots on only one side of something like a wheel
can create a similar situation - where the static balance is correct but
the center of balance is no longer the same as the center of rotation.
It takes sophisticated equipment and an equally sharp operator to get it
right.

BTW, FWIW ... For an average car tire with 25" diameter at the
tread, at 60 MPH, the wheel is turning ~7950 RPM.


--
Dale_R
Cozy MKIV #497


--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html


-- 
Dale_R
Cozy MKIV #497
--------------070208030204050604050303--