X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 29 Jul 2013 11:23:26 -0400 Message-ID: X-Original-Return-Path: Received: from mail-gg0-f182.google.com ([209.85.161.182] verified) by logan.com (CommuniGate Pro SMTP 6.0.5) with ESMTPS id 6395122 for lml@lancaironline.net; Mon, 29 Jul 2013 11:16:35 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.161.182; envelope-from=pjdmiller@gmail.com Received: by mail-gg0-f182.google.com with SMTP id h13so219300ggd.27 for ; Mon, 29 Jul 2013 08:15:59 -0700 (PDT) X-Received: by 10.236.178.5 with SMTP id e5mr27150810yhm.180.1375110959461; Mon, 29 Jul 2013 08:15:59 -0700 (PDT) X-Original-Return-Path: Received: from [192.168.1.137] ([68.202.59.203]) by mx.google.com with ESMTPSA id 66sm84948653yhe.20.2013.07.29.08.15.58 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 29 Jul 2013 08:15:58 -0700 (PDT) From: Paul Miller Content-Type: multipart/alternative; boundary="Apple-Mail=_AA90AF86-9B7A-4D29-8220-059F635C1C5A" X-Original-Message-Id: Mime-Version: 1.0 (Mac OS X Mail 6.5 \(1508\)) Subject: Re: [LML] Re: Potential Problem-Engine Vibration X-Original-Date: Mon, 29 Jul 2013 11:15:57 -0400 References: X-Original-To: "Lancair Mailing List" In-Reply-To: X-Mailer: Apple Mail (2.1508) --Apple-Mail=_AA90AF86-9B7A-4D29-8220-059F635C1C5A Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=big5 One thing to keep in mind is that the prop balancing on the ground is = not as accurate as when the scimitar is loaded in flight. This comes = directly from one of the SX300 guys testing one of the Scimitars for = Hartzell on his Lyc 580. What he did was run the cables through the = heat duct and perform the balance in flight conditions. He reported = that balancing the scimitars was not easy. I had a hard time finding a = good balance on the ground on the Legacy but it was passable. I may try = the in-flight balance next time at the 2300 rpm mark. Our Legacy = scimitars are simply cut shorter than the longer bladed scimitars for = ground clearance. Second, the engine and cowl moves a lot and the clearances are very = tight in the Legacy. At 2700 RPM and low airspeed the cowl is different = shape than at cruise and the engine is in a different position relative = to the mounts that at 2300. The torque on the engine mounts is much = different at 2300 versus 2700. I found a lot of interference showed up = as the RPM came down from 2700 to 2300 and then the engine and cowling = were slightly separated so that the banging was transmitted. I believe = at other settings the engine was up against parts of the cowl and the = actual vibration was transmitted. I had the nose gear interference as = well plus the baffling hit the prop governor cable in cruise. Lots of = areas where interference fits are really tight. My point is that there = are many factors that can affect vibration with changing throttle and = RPM and it isn't just the prop/crankshaft combo that can be at issue. I = was seeing almost two inches of cowl movement between rest and flight at = certain locations. Thats a lot. Not to take anything away from the issue under discussion except to say = that, in my Legacy, vibration amplitude did change with varying RPM as a = result of mechanical interference. Paul Legacy --Apple-Mail=_AA90AF86-9B7A-4D29-8220-059F635C1C5A Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=big5 One = thing to keep in mind is that the prop balancing on the ground is not as = accurate as when the scimitar is loaded in flight. This comes directly = from one of the SX300 guys testing one of the Scimitars for Hartzell on = his Lyc 580. What he did was run the cables through the heat duct = and perform the balance in flight conditions. He reported that = balancing the scimitars was not easy. I had a hard time finding a = good balance on the ground on the Legacy but it was passable. I = may try the in-flight balance next time at the 2300 rpm mark. Our = Legacy scimitars are simply cut shorter than the longer bladed scimitars = for ground clearance.

Second, the engine and cowl = moves a lot and the clearances are very tight in the Legacy. At = 2700 RPM and low airspeed the cowl is different shape than at cruise and = the engine is in a different position relative to the mounts that at = 2300. The torque on the engine mounts is much different at 2300 = versus 2700. I found a lot of interference showed up as the RPM = came down from 2700 to 2300 and then the engine and cowling were = slightly separated so that the banging was transmitted. I believe = at other settings the engine was up against parts of the cowl and the = actual vibration was transmitted. I had the nose gear interference = as well plus the baffling hit the prop governor cable in cruise. = Lots of areas where interference fits are really tight. My = point is that there are many factors that can affect vibration with = changing throttle and RPM and it isn't just the prop/crankshaft combo = that can be at issue. I was seeing almost two inches of cowl = movement between rest and flight at certain locations. Thats a = lot.

Not to take anything away from the issue = under discussion except to say that, in my Legacy, vibration amplitude = did change with varying RPM as a result of mechanical = interference.

Paul

Legacy

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