X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 11 Jan 2011 17:24:28 -0500 Message-ID: X-Original-Return-Path: Received: from raven.ravenwebhosting.com ([72.9.254.67] verified) by logan.com (CommuniGate Pro SMTP 5.3.11) with ESMTPS id 4670984 for lml@lancaironline.net; Tue, 11 Jan 2011 10:41:13 -0500 Received-SPF: none receiver=logan.com; client-ip=72.9.254.67; envelope-from=paul@tbm700.com Received: from 111-57.202-68.tampabay.res.rr.com ([68.202.57.111]:57127 helo=[192.168.1.102]) by raven.ravenwebhosting.com with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.69) (envelope-from ) id 1PcgKr-00037Y-Qe for lml@lancaironline.net; Tue, 11 Jan 2011 10:40:37 -0500 From: paul miller Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: multipart/alternative; boundary=Apple-Mail-77-773138403 Subject: Re: [LML] Re: Legacy Main Gear Countersunk Screws X-Original-Date: Tue, 11 Jan 2011 08:40:34 -0700 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <8E41B73A-362F-4742-B9B5-E46E745EC0D2@tbm700.com> X-Mailer: Apple Mail (2.1082) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - raven.ravenwebhosting.com X-AntiAbuse: Original Domain - lancaironline.net X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - tbm700.com X-Source: X-Source-Args: X-Source-Dir: --Apple-Mail-77-773138403 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii I'm confused but I don't understand where the higher numbers are = justified. In the Lancair manual the replacement nuts MS21042-5 show = 60-140 range of torque (inch-lbs) depending on shear/tension. That's = only 5-10 ftlbs. The material specifications are 160,000 psi tensile = strength and 450F. I agree Grayhawk's SAE grade 8 specification would = suggest a much higher torque value (20-28 ft-lbs) is applicable for a = 5/16 bolt also 160,000 psi rating but there are also footnotes showing = 50% reduction for lubricated fasteners (wax etc). But MS manufacturers of these nuts show a maximum torque of 60 inch-lbs = (Spiralok). Another aerospace manufacturer talks about clamping (I = believe this is a clamping connection) where there must be a smooth flat = surface which is questionable here. Coastpac writes that in clamping = situations use 85% of ultimate tensile strength: For applications requiring high installation torque values and using = standard NAS bolts: achievable torque is dependent on plating, length of thread engagement, class of mating = threads and lubricant (if any). For maximum fatigue resistance and clamping force in the bolted assembly, we want to produce = a level of installed tensile stress that is just below the yield strength of the bolt material (typically around 85% of the = ultimate tensile strength). The manufacturer goes on to suggest a 5/16 bolt would torque to 330 = in-lbs for 160k tensile bolt--a much higher figure than shown in the = Lancair default schedule. So, it appears 60 in-lbs is on the low end = but is the default Lancair value but a higher number seems to be more = reasonable for this application. I'd like some additional thoughts from = the experts please. Main gear fork attachment hardware is a key element = in safety and the lack of any specific torque value leaves the builder = to se the default schedule. I note that the nose strut bolts where the = tow plate is attached is indicated at 10-12 ft-lbs by Lancair which is = higher than the default schedule. Paul Legacy RG 186 On 2011-01-10, at 12:10 PM, Sky2high@aol.com wrote: > 5 lb feet does not sound like enough torque for this application where = one is definitely concerned about tension as well as shear. Check = again. Even a mere 1/4" grade 8 bolt is 13 and 5/16 is 27.=20 > =20 > Grayhawk > =20 > PS: I'd make the sucker tight so it doesn't fret or move in cross wind = landings or bumpy surfaces.=20 > =20 > In a message dated 1/9/2011 4:57:24 P.M. Central Standard Time, = paul@tbm700.com writes: >=20 >=20 > i did the product upgrade with hardware from Lancair. The original = bolts were rubbing the new Desser tires. When I removed the forks I = found a small amount of what appears to be corrosion, possibly some = fretting. A few of the bolts were not very tight when I removed them. = On the Legacy manuals there are no special TRQ for these bolts so I used = the table value of around 60 in-lb. I will retorque after a few = landings. I suggest checking these for torque if you have this Type II = gear because the mating surface is slotted to allow the tire to toe-in = and this fork could rotate about the strut if the bolts are not secure. >=20 > Paul > L2K-186 --Apple-Mail-77-773138403 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii I'm = confused but I don't understand where the higher numbers are justified. =   In the Lancair manual the replacement nuts MS21042-5 show 60-140 = range of torque (inch-lbs) depending on shear/tension.   =  That's only 5-10 ftlbs.  The material specifications are = 160,000 psi tensile strength and 450F.  I agree Grayhawk's SAE = grade 8 specification would suggest a much higher torque value (20-28 = ft-lbs) is applicable for a 5/16 bolt also 160,000 psi rating but there = are also footnotes showing 50% reduction for lubricated fasteners (wax = etc).

But MS manufacturers of these nuts show a = maximum torque of 60 inch-lbs (Spiralok).    Another aerospace = manufacturer talks about clamping (I believe this is a clamping = connection) where there must be a smooth flat surface which is = questionable here. Coastpac writes that in clamping situations use 85% = of ultimate tensile strength:

For applications requiring = high installation torque values and using standard NAS bolts: achievable = torque is
dependent on = plating, length of thread engagement, class of mating threads and = lubricant (if any). For maximum fatigue
resistance and clamping = force in the bolted assembly, we want to produce a level of installed = tensile stress that is just below
the yield strength of the = bolt material (typically around 85% of the ultimate tensile = strength).
Sky2high@aol.com wrote:

5 lb feet does not sound like enough torque for this application = where one=20 is definitely concerned about tension as well as shear.  Check=20 again.  Even a mere 1/4" grade 8 bolt is 13 and 5/16 is = 27. =20
 
Grayhawk
 
PS: I'd make the sucker tight so it doesn't fret or move in cross = wind=20 landings or bumpy surfaces. 
 
In a message dated 1/9/2011 4:57:24 P.M. Central Standard Time,=20 paul@tbm700.com writes:


i did the product upgrade with hardware from Lancair.   The = original=20 bolts were rubbing the new Desser tires.   When I removed the = forks I=20 found a small amount of what appears to be corrosion, possibly some = fretting.=20  A few of the bolts were not very tight when I removed them. =  On the=20 Legacy manuals there are no special TRQ for these bolts so I used the = table=20 value of around 60 in-lb.   I will retorque after a few landings. =  =20 I suggest checking these for torque if you have this Type II gear = because the=20 mating surface is slotted to allow the tire to toe-in and this fork = could=20 rotate about the strut if the bolts are not secure.

Paul
L2K-186
=

= --Apple-Mail-77-773138403--