X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 13 Jun 2011 07:50:04 -0400 Message-ID: X-Original-Return-Path: Received: from mail-fx0-f52.google.com ([209.85.161.52] verified) by logan.com (CommuniGate Pro SMTP 5.4.0) with ESMTPS id 5018167 for lml@lancaironline.net; Sun, 12 Jun 2011 14:04:16 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.161.52; envelope-from=msteitle@gmail.com Received: by fxm6 with SMTP id 6so2342513fxm.25 for ; Sun, 12 Jun 2011 11:03:39 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=TQV7QA11sAxj5LbfHMO1YguhJQ49keiit4MjARfMLndtfPhxS467lCUl/44bRdtmFu CO202FXmaKKjRejqZyk1W1v5jwO5XhAmjCVmXrrgRMjWrUATIfSxle5C2rt359Q00rt1 sPo4WeYsAXNAgdiCZSBY3csJqCINGd/Lm+YPo= MIME-Version: 1.0 Received: by 10.223.111.132 with SMTP id s4mr2094229fap.6.1307901819217; Sun, 12 Jun 2011 11:03:39 -0700 (PDT) Received: by 10.223.100.12 with HTTP; Sun, 12 Jun 2011 11:03:39 -0700 (PDT) In-Reply-To: References: X-Original-Date: Sun, 12 Jun 2011 13:03:39 -0500 X-Original-Message-ID: Subject: Re: [LML] Re: L-IV Choice of Engine From: Mark Steitle X-Original-To: Lancair Mailing List Content-Type: multipart/alternative; boundary=001636c5a2eb55e94304a5879f0d --001636c5a2eb55e94304a5879f0d Content-Type: text/plain; charset=ISO-8859-1 Brent, Mazda was "better enough" to win the 1991 24 Hours of LeMans with their 4-rotor (26b). The only Japanese brand to ever achieve that feat. Quote from Wikipedia - "The Mazda's 787B, powered with a rotary model 26B Wankel engine , won in 1991, overcoming reliability issues in the older manufacturer cars. It was the first (and so far the only) Japanese manufacturer to win Le Mans, as well as the only non-piston engine car to ever win." You gotta admit that's pretty impressive. And rotaries are still racing, and winning. Mark S. [edit ] On Sun, Jun 12, 2011 at 11:52 AM, Brent Regan wrote: > Ted asks: > > << Is there an instrument that can be attached to the engine somewhere that > will measure frequencies to assess likely nodes of "don't run there?" > >> > > The short answer is no. > > Imagine a rod with an accelerometer mounted half way down its length. > Excite the rod at its second harmonic and the accelerometer will see no > acceleration or displacement as it is sitting on a "node". If the rod were > 360mm long the nodes are at 0mm, 180mm and 360mm with the points of maximum > displacement and acceleration at 90mm and 270mm. These will also be the > points of maximum stress, unless the ends or the rods are fixed, then the > maximum stress will be at the ends. > > Someone experienced in these matters and with a detailed knowledge of the > engine system would be able to put some accelerometers on the engine at > various locations and use a spectrum analyzer to determine the vibrational > energy distribution versus frequency and then connect a shaker to the engine > and see what "buzzes", but this is a lot closer to art than science. > > In response to my comment <<< After more than 100 years, the prime mover of > choice still has a piston, rod and crank. There may be a reason for that.>>> > > William observes: <<< The piston engine was invented first.>>> > > True, but the Wankel engine first ran February 1, 1957, 54 years ago. > Actually, to be accurate, Wankel's pure rotary design DKM 54 (Rotor and > housing rotated) ran on that day. Froede's epicyclic configuration, the KKM > 125, what we now recognize as the Wankel engine, first ran on July1, 1958. > > If the Wankel engine is superior it has had plenty of time and opportunity > to prove it. I have a collection of rotary engines including ones for model > aircraft, powered hang gliders, snow mobiles, lawn mowers and race cars > demonstrating that the Wankel has been exposed to all these markets yet has > failed to dominate any of them. > > In the last 50 years entire industries based on new technology have come > and gone. While I love the round motor it is hard to reconcile the claim of > rotary superiority in an environment where significantly better technology > quickly conquers the market. > > The Wankel may be the better engine, just not better enough. > > > Regards > Brent Regan > > -- > For archives and unsub > http://mail.lancaironline.net:81/lists/lml/List.html > --001636c5a2eb55e94304a5879f0d Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Brent,=A0

Mazda was "better enough" to win the= 1991 24 Hours of LeMans with their 4-rotor (26b). =A0The only Japanese bra= nd to ever achieve that feat.=A0

Quote from Wikipe= dia - "The=A0M= azda's 787B, powered with a rotary model=A026B=A0Wankel engine, won in 1991, overcoming reliab= ility issues in the older manufacturer cars. It was the first (and so far t= he only) Japanese manufacturer to win Le Mans, as well as the only non-pist= on engine car to ever win."
You gotta admit that's pretty impressive. =A0And rota= ries are still racing, and winning.

Mark S.

[edit]

<= /span>



On Sun, Jun 12= , 2011 at 11:52 AM, Brent Regan <brent@regandesigns.com> wrote:
Ted asks:

<< Is there an instrument that can be attached to the engine somewher= e that will measure frequencies to assess likely nodes of "don't r= un there?"
>>

The short answer is no.

Imagine a rod with an accelerometer mounted half way down its length. Excit= e the rod at its second harmonic and the accelerometer =A0will see no accel= eration or displacement as it is sitting on a "node". If the rod = were 360mm long the nodes are at 0mm, 180mm and 360mm with the points of ma= ximum displacement and acceleration at 90mm and 270mm. These will also be t= he points of maximum stress, unless the ends or the rods are fixed, then th= e maximum stress will be at the ends.

Someone experienced in these matters and with a detailed knowledge of the e= ngine system would be able to put some accelerometers on the engine at vari= ous locations and use a spectrum analyzer to determine the vibrational ener= gy distribution versus frequency and then connect a shaker to the engine an= d see what "buzzes", but this is a lot closer to art than science= .

In response to my comment <<< After more than 100 years, the prime= mover of choice still has a piston, rod and crank. There may be a reason f= or that.>>>

William observes: <<< The piston engine was invented first.>>= ;>

True, but the Wankel engine first ran February 1, 1957, =A054 years ago. Ac= tually, to be accurate, Wankel's pure rotary design DKM 54 (Rotor and h= ousing rotated) ran on that day. Froede's epicyclic configuration, the = KKM 125, what we now recognize as the Wankel engine, first ran on July1, 19= 58.

If the Wankel engine is superior it has had plenty of time and opportunity = to prove it. I have a collection of rotary engines including ones for model= aircraft, powered hang gliders, snow mobiles, lawn mowers and race cars de= monstrating that the Wankel has been exposed to all these markets yet has f= ailed to dominate any of them.

In the last 50 years entire industries based on new technology have come an= d gone. While I love the round motor it is hard to reconcile the claim of r= otary superiority in an environment where significantly better technology q= uickly conquers the market.

The Wankel may be the better engine, just not better enough.


Regards
Brent Regan

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