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Date:         Mon, 9 May 2011 23:41:55 -0400
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: 2.1 rebuild - new nuts for case halves-thoughts for all
              bolted connections.
Content-Type: text/plain; charset="US-ASCII"

Here are two links that give some good information. One is how a clamped or bolted connection works and is indicative of case main bearing bolts and rod bolts. The other is the relative strengths of various grades of fasteners. Note the difference in strength of the A2 or A4 stainless as compared to property class 10.9. This class is the most common class used on the Vanagon. The real important stuff can be 12.9. In order for these bolted connections to work the nut and if used washers need to be matched. The nut has to be strong enough to stretch the bolt and get it under tension. The washer has to carry that load. If the washer distorts then the connection becomes loose.

In addition to the strength of the material, finish, (zinc, black oxide, chrome, cadmium, organics) and lubrication, (oil, anti-seize, sealants, Loctite) will affect the torque required to reach a given clamp load. Black oxide, organics, and cadmium are often used on high strength fasteners as they provide more consistent torque tensioning. Zinc is sometimes an issue as it may cause hydrogen embrittlement. Some lubricants or wax coatings can reduce required torque by 40% or more. Consider that when thinking of never seize on your lug bolts.

Many engine problems or failures come down to fluid problems or fastener failures. Internal head leaks, (gasses in coolant or coolant in cylinder) if not due to an actual cracked head are really a fastener failure. A problem is that engines will often be repaired or rebuilt without addressing the failed part.

Dennis

http://www.unified-eng.com/scitech/bolt/clamping.html http://www.tessco.com/yts/customerservice/techsupport/whitepapers/pdf/bolt_g rade.pdf

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Daniel Rotblatt Sent: Thursday, May 05, 2011 12:05 PM To: vanagon@GERRY.VANAGON.COM Subject: Re: 2.1 rebuild - new nuts for case halves

There have been several discussions on other forums about this. Essentially, if it's a torqued nut then the torque setting is defined by the type of nut and stud - stainless (or different grade nuts for that matter) require different to torque settings. Saying "stainless is not as strong" is incorrect - like different grades of nuts, it depends on the alloy of the stainless. I imagine that standard stainless nuts may be "less strong" then standard non-stainless nuts, but that is still a generalization. The alloys used in stainlesss (and there are many many alloys) give the metal different properties then carbon steel. There is even a problem changing the strength class (using grade 8 nuts/bolts when grade 5 are specified) - some nuts/bolts are specified because they are supposed to fail at a certain stress to prevent further damage to the engine - and of course there's that torque issue again.

The upshot, is that if it's a torqued nut, use the manufacturer specified if possible. If you replace with stainless when not specified, you take a chance that the nut will fail. Doesn't mean it will, just that it may or may not be within proper specifications (thus Franks observation that he uses stainless hardware and does not have failure).

Dan Los Angeles, CA '85 Westy Weekender

On May 5, 2011, at 2:33 AM, Frank Condelli wrote:

> I beg to disagree. All engines I have rebuilt here get > stainless hardware everywhere possible. Never seen any problems > related to the use of stainless hardware on the engine cases or > elsewhere. See here > http://www.frankcondelli.com/21engpcs.htm > > > On 2011-05-05, at 12:00 AM, Automatic digest processor wrote: > >> I sure would not be putting any stainless fasteners on it. >> they are not as strong .. >> stainless is not titanium or 'fautless' like people want to think it >> is. > > > > Cheers, > > Frank Condelli > Almonte, Ontario, Canada > '87 Westy & Lionel Trains (Collection for sale) Frank Condelli & > Associates - Vanagon/Vanagon Westfalia Service in the Ottawa Valley > Vanagon Stainless Steel Exhaust Systems BusFusion a VW Camper camping > event, Almonte, ON, June 09 ~ 12, 2011


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