Return-Path: Received: from [199.185.220.223] (HELO priv-edtnes51.telusplanet.net) by logan.com (CommuniGate Pro SMTP 4.3c2) with ESMTP id 760809 for flyrotary@lancaironline.net; Sat, 26 Feb 2005 15:54:38 -0500 Received-SPF: pass receiver=logan.com; client-ip=199.185.220.223; envelope-from=haywire@telus.net Received: from Endurance ([207.81.25.155]) by priv-edtnes51.telusplanet.net (InterMail vM.6.01.04.00 201-2131-118-20041027) with SMTP id <20050226205352.ROKS13238.priv-edtnes51.telusplanet.net@Endurance> for ; Sat, 26 Feb 2005 13:53:52 -0700 From: "Todd Bartrim" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Belts Date: Sat, 26 Feb 2005 12:53:14 -0800 Message-ID: <00d101c51c45$3193ad10$0201a8c0@Endurance> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00D2_01C51C02.23737A50" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook CWS, Build 9.0.2416 (9.0.2910.0) X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Importance: Normal In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_00D2_01C51C02.23737A50 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Good point about the pulleys. My statement about never having a failure with a serpentine wasn't entirely true. I did have the tensioner pulley on a Ford Powerstroke fail. It was still under warranty and I was only ~a 1/2 mile from the dealership so I just drove it over. They replaced the belt with the new tensioner pulley but I kept the old one as a spare because there was nothing wrong with it (still have it). But Marvs post does bring up something important about belt tension. Belt slippage can lead to premature belt failure. Most older automotive V-belt installations have no automatic tensioner, while the newer serpentine belts usually do. This could be a large factor in the increased life of serpentine belts since they should always have the correct amount of tension. In the case of my aircraft alternator belt, which I have a multi-rib belt it doesn't have a tensioner pulley so it will not have any greater chance of proper tension than if I'd used a V-belt. Belt design has also improved dramatically as well. I recall in the late '80s we would never go on a snowmobile trip into the mountains without bringing at least 2 spare drive belts and we often needed them. My sled today has close to twice the HP with much higher load due to increased traction and yet I've never blown a single belt. Of coarse this is also helped by much better clutching design. So Tracy is definitely correct in his statement that reliability isn't a big reason to eliminate the belt driven accessories, but IMHO weight reduction is. Todd Good points. I can't get excited about eliminating belts because I have never seen even a hint of a problem with them * when properly installed *. This includes all experience with cars and aircraft. I *have* seen them fail when pulleys were not properly aligned, debris or damage caused the pulley to wobble, they were overloaded, or other installation errors. Belts are a very mature and reliable technology. There may be good reasons to replace a belt but reliability is not one of them. Tracy Crook ------=_NextPart_000_00D2_01C51C02.23737A50 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Good=20 point about the pulleys. My statement about never having a failure with = a=20 serpentine wasn't entirely true. I did have the tensioner pulley on a = Ford=20 Powerstroke fail. It was still under warranty and I was only ~a 1/2 mile = from=20 the dealership so I just drove it over. They replaced the belt with the = new=20 tensioner pulley but I kept the old one as a spare because there was = nothing=20 wrong with it (still have it).

But=20 Marvs post does bring up something important about belt tension. Belt = slippage=20 can lead to premature belt failure. Most older automotive V-belt = installations=20 have no automatic tensioner, while the newer serpentine belts usually = do. This=20 could be a large factor in the increased life of serpentine belts since = they=20 should always have the correct amount of tension. In the case of my = aircraft=20 alternator belt, which I have a multi-rib belt it doesn't have a = tensioner=20 pulley so it will not have any greater chance of proper tension = than if I'd=20 used a V-belt.

Belt=20 design has also improved dramatically as well. I recall in the late '80s = we=20 would never go on a snowmobile trip into the mountains without bringing = at least=20 2 spare drive belts and we often needed them. My sled today has close to = twice=20 the HP with much higher load due to increased traction and yet I've = never blown=20 a single belt. Of coarse this is also helped by much better clutching=20 design.

So=20 Tracy is definitely correct in his statement that reliability isn't a = big reason=20 to eliminate the belt driven accessories, but IMHO weight reduction=20 is.

Todd

Good points. I can't get excited about eliminating = belts=20 because I have never seen even a hint of a problem with = them *=20 when properly installed *. This includes all experience with = cars and=20 aircraft.

I *have* seen them fail when pulleys were not properly aligned, = debris or=20 damage caused the pulley to wobble, they were overloaded, or other=20 installation errors.

Belts are a very mature and reliable technology. There = may be=20 good reasons to replace a belt but reliability is not one of = them.

Tracy Crook

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