Path: csiph.com!tncsrv06.tnetconsulting.net!usenet.blueworldhosting.com!diablo1.usenet.blueworldhosting.com!nnrp.usenet.blueworldhosting.com!.POSTED!not-for-mail From: Richard Smith Newsgroups: alt.autos.4x4.chevy-trucks,sci.engr.joining.welding Subject: Re: cracked frame Date: Sat, 18 Nov 2023 09:44:55 +0000 Organization: BWH Usenet (https://usenet.blueworldhosting.com) Message-ID: References: <08qdnULQ7pFMQwHeRVn-sw@comcast.com> <3qHnf.139001$Ph4.4250147@ursa-nb00s0.nbnet.nb.ca> <439F485D.2D7126A2@execpc.com> <439F8C75.11BDBE5C@execpc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: nnrp.usenet.blueworldhosting.com; logging-data="6054"; mail-complaints-to="usenet@blueworldhosting.com" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.1 (darwin) Cancel-Lock: sha1:keaiFgtySV/R1GciNqz8WakUD1s= sha1:ieXUOicdGR4F7U+Hthhzz5xsw5I= sha256:zWOOluwpqrvuGSZSi/yoeZUoSYmlzDxBjRCTYaz/NV4= sha1:GFY5QkoA7RWGLfphq4uDkGfCSTI= sha256:xC9c1F7cdFFWP+c1kMkoP9Z0zyICjrC2gNH34yGvUxg= Xref: csiph.com alt.autos.4x4.chevy-trucks:1999 sci.engr.joining.welding:13854 The Nolalu Barn Owl <gordie@nolalu.on.ca> writes: > On Wed, 14 Dec 2005 11:40:14 GMT, "Steve Mackie" > wrote: > >>> Fishmouths & shear ties are a way to blend stiffness between a box >>> section >>> >>> and a channel... which minimizes stress concentrations... Metal >> >>You just seem to be stating the same thing over and over. I have never used >>anything but plain rectangular plates and they have always met stress >>requirements. I want to read into the theory to see if changing the way I do >>it is worth it. >> >>Steve >> > > I have looked and looked for information on the NET about fish mouthed > re-inforcing plates and there isn't much to be had. > > Basically you can use a plate cut to form what looks like an open fish > mouth on each end. > > ------ >> < > ------ > > You can also use a diamond shaped plate to give the same effect. > > To weld the frame directly from the top to the bottom makes it likely > to crack again for reasons which I am not qualified to try and > explain. After over 30 years of working as a Millwright, I can say > that once a crack has been welded it quite often cracks there again so > a plate is used to bridge the repaired area and this plate is welded > with stitch-welding so as not to make a continuous weld. This way, if > one stitch was to crack it won't carry over to the next weld. The > fish mouth (or diamond) allows you to place welds that are not in a > direct line from top to bottom. > > Since my explanation is wanting, and I am just a DIY repairman, I have > cross posted this message to a welding NG to draw in some expert > opinions for you - and for me :) > > -- > Gordie > > There are tongues speakers who speak in an unknown language that actually > exists among the peoples of the earth. I recall one such incident in which a > tongues speaker got up and spoken in some unknown language. As it > happened, there was a priest in the audience who just happened to speak the > language this women was speaking as an unknown tongue. The priest asked > her if she knew what she was saying. The women had no idea so the priest > told her: "You were speaking my native language and what you were saying > was cursing God." > http://www.saint-mike.org/Apologetics/QA/Answers/Faith_Spirituality/f0404120221.html This looks to be a fatigue cracking matter... Geordie seems to know from practical experience what does and doesn't work to avoid fatigue cracks or how to repair them when it happens. Steve - you've read and all seems fine and from that basis you disbelieve and experienced practitioner. Steve - you could do Finite Element Analysis modelling to see the stress concentrations. FEA for the general region of the structure. Here's a somewhat comparable example of me probing a feature I met while actually out there as a welder http://weldsmith.co.uk/tech/finiteelement/1609_beam_tjn_sim/160927_beam_w_column_w-wo_stiffplts.html What I would bet is that you will see theory concurring with what Geordie is telling you already. Steve - you'd benefit from "treading the path" and seeing how where you come from can plug you into the deep knowledge out there. I take it you are proposing some feature with an abrupt "right-angled in every way" change in thickness and possibly direction. That will be highly fatigue-prone. Steve I think you are being given a chance to learn and you are not seeing it. As best I can tell from message trail so far...