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Date:         Sun, 16 Mar 2008 15:00:41 -0400
Reply-To:     Jim Akiba <syncrolist@BOSTIG.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jim Akiba <syncrolist@BOSTIG.COM>
Subject:      Re: WAS: building carrier bar..... NOW: Test Weld PIC
Comments: To: neil N <musomuso@gmail.com>
In-Reply-To:  <c4e7c5f90803160900g7be19333k4e6eb753422a1fb3@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

Hey Neil,

It can also be useful in these kinds of circumstances to build it to fail, but see exactly how it does it so you know where the important areas and the thresholds are... meaning, if it's possible for you to run a test cycle with the bar in full operation, don't fully weld it. Use longer tacks and space them out along the joins you might have in question, then watch carefully to see which ones start to fail first. This allows you to "hurry up" the cycle and see ahead of time what are the most critical joints, and help determine where you will need or not need gusseting etc. If done carefully/systematically it can be very effective in highlighting and answering questions without doing or knowing how to do the math or have it in CAD and calc the factor of safety. It's often faster to boot, since common sense will lead the way with your predictions as well. One of the problems for one offs, and folks that don't do it all the time, is to establish a more generic "sense" of what your weldaments/joins, and design can or can't do. So bringing it into the realm of the obvious by building it to fail just fast enough not to damage anything is a fast easy way to learn about both the design and construction at the same time. Either that or just overbuild it and watch it like a hawk(which you will likely be doing anyhow from what I know of you) so maybe my first suggestion is worthless in the end ha.

Jim Akiba

On 3/16/08, neil N <musomuso@gmail.com> wrote: > Thanks Mike! :) > > > Neil. > > > > > On Sun, Mar 16, 2008 at 8:53 AM, Mike <mbucchino@charter.net> wrote: > > It's definitely a good idea to cut one cross-sectionally to demonstrate > > penetration. You do need 100% penetration; this can be achieved by > > V-notching the thickest parts before welding, even if it means laying down > > more than one bead to fill the gap completely. This is how the thickest > > metals are commonly joined by welding professionals. > > One way to judge if you've achieved 100% weld penetration, is to look at > > the backside of the joint; if you can clearly see an even, 'heated' stripe > > of discoloration in backside of the base metal, you've got it. > > If you have thick, rounded 'mountains' of filler metal standing above the > > base metal, there's not enough penetration, and the joint will be weak and > > will crack. > > If you have thin 'valleys' of melted base metal, there's too much heat and > > not enough filler; possibly undercutting and weakening, even to the point of > > 'blowing-through' in spots. This too will be weak and will crack. > > It's this delicate balance of proper heat, filler and penetration that > > takes lots of practice to achieve, and the procedure differs for > > butt-welding, lap-welding, corner-welding, vertical-welding, tube-on-tube, > > tube-on-plate, different thickness materials, thick -to-thin metals, TIG, > > MIG, oxy-acetylene, etc. > > Have fun and get lots of practice, and some critiqueing from experienced > > welders. > > > > Mike B. > > > > > > > > ----- Original Message ----- > > From: "neil N" <musomuso@GMAIL.COM> > > To: <vanagon@GERRY.VANAGON.COM> > > Sent: Sunday, March 16, 2008 11:07 AM > > Subject: Re: WAS: building carrier bar..... NOW: Test Weld PIC > > > > > > > Thanks again Gary. > > > > > > I've been pushing my welds. Was considering pulling so I could see the > > > puddle better, but I'll stick with the programme. Good tip on pre > > > heating. As for wiring etc., I don't use an extension, but I did find > > > that with the welder set to max. and my big fan on max, that the > > > circuit will overload! (can a guy weld in the dark? --- ;^) > > > > > > I can sort of "see" that the penetration on 1/4", even if welding > > > optimally, would be limited. I'll bet that at best, it's only going in > > > about a 1/3 of the way. I should cut open a 1/4" weld and see. > > > > > > Appreciate the help. And nice lookin' Vanagon bike racks! > > > > > > Cheers, > > > > > > Neil. > > > > > > On Sat, Mar 15, 2008 at 11:14 PM, Gary Lee www.vwrack.com > > > <gary2a@telus.net> wrote: > > >> Well gas will be cleaner than flux, but not necessarily stronger. If you > > >> only weld occasionally, I would not bother with renting or buying a gas > > >> bottle. > > >> Good you got lots of amps available. That makes a big difference. > > >> > > >> 120 volt welders can't produce enough heat to weld 1/4" 'properly'. > > >> > > >> To maximize the amount of heat a small welder will produce: > > >> - Heavy gauge extension cord > > >> - Hold tip as close to work as possible > > >> - Push the bead, as opposed to pull. Push = like driving forward. Pull > > >> = > > >> like driving in reverse > > >> - Preheat the piece with a propane or acetylene torch > > >> - Move torch slow, steady and smoothly. In a controlled motion. > > >> > > >> fwiw, I wouldn't be welding any trailer hitches with a 120 volt welder. > > >> > > >> If anybody in Calgary needs simple welding jobs like that done, I do it > > >> for > > >> free for local vanagon owners. > > >> > > >> > > >> Gary Lee > > >> www.vwrack.com > > >> > > >> > > >> > > >> ----- Original Message ----- > > >> From: "neil N" <musomuso@gmail.com> > > >> To: "Gary Lee www.vwrack.com" <gary2a@telus.net> > > >> Cc: <vanagon@gerry.vanagon.com> > > >> Sent: Saturday, March 15, 2008 11:44 PM > > >> Subject: Re: WAS: building carrier bar..... NOW: Test Weld PIC > > >> > > >> > > >> > Thanks for the pointers Gary. > > >> > > > >> > Yup. 120, MIG with flux but am running 12 gauge from a 20 amp breaker. > > >> > I found I could go quite slow on the 1/4" plate and will slow it down > > >> > more. Quite a contrast to the practice welds I tried on the scrap > > >> > exhaust tube. > > >> > > > >> > I may end up using 1/8" plate and angle instead of the 1/4". Those > > >> > were free scrap pieces so I gave it a whirl. > > >> > > > >> > I'm learning pretty fast, but there's lots to learn even with just > > >> > setting up correctly. Proper lighting, material and work position etc. > > >> > > > >> > It'll be nice to get set up with gas. The flux puts out too much smoke > > >> > and spatter. > > >> > > > >> > Thanks, > > >> > > > >> > Neil. > > >> > > > >> > On Sat, Mar 15, 2008 at 10:30 PM, Gary Lee www.vwrack.com > > >> > <gary2a@telus.net> wrote: > > >> >> >Now I KNOW I'll get this load bar done. Too bad I can't get > > >> material > > >> >> >til Tuesday! > > >> >> > > >> >> > http://tubaneil.googlepages.com/1stlargeweld > > >> >> > > >> >> >Thanks guys, > > >> >> >Neil. > > >> >> > > >> >> Neil, > > >> >> Looking at your picture, I'd say you are using a 120 volt MIG. > > >> >> Fluxcore? > > >> >> That would give you marginal penetration on material as thick as in > > >> >> your picture. Go slowly and weave back and forth. I hold the torch > > >> >> with two hands, one on the trigger and the other near the tip. Hold > > >> >> the torch close in to the material, as little 'stick out' and > > >> >> possible. Plug your welder in as close to the breaker box as > > >> >> possible. Avoid using extension cords. > > >> >> > > >> >> Gary Lee > > >> >> www.vwrack.com > > >> >> > > >> > > > >> > > > >> > > > >> > -- > > >> > Neil Nicholson. 1981 Air Cooled Westfalia - "Jaco" > > >> > > > >> > http://web.mac.com/tubaneil > > >> > http://tubaneil.googlepages.com/ > > >> > > > >> > > > >> > -- > > >> > No virus found in this incoming message. > > >> > Checked by AVG. > > >> > Version: 7.5.519 / Virus Database: 269.21.7/1329 - Release Date: > > >> > 14/03/2008 12:33 PM > > >> > > > >> > > > >> > > >> > > > > > > > > > > > > -- > > > Neil Nicholson. 1981 Air Cooled Westfalia - "Jaco" > > > > > > http://web.mac.com/tubaneil > > > http://tubaneil.googlepages.com/ > > > > > > > > > > > -- > Neil Nicholson. 1981 Air Cooled Westfalia - "Jaco" > > http://web.mac.com/tubaneil > http://tubaneil.googlepages.com/ >


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