| Author | Message | ||
| Grant Thiessen (Busshawg)
Registered Member Username: Busshawg Post Number: 85 Registered: 10-2007 Posted From: 206.45.93.160  Rating: N/A |
I have heard a few different opinions regarding this. Here is my question. I have a 1984 MC9 with a 8V71 in it. It has the direct drive alt. I want to do some welding on the bus near the back. Do I need to disconnect anything? I welded in all of my supports from where I removed my windows without disconnecting anything. I also cut and replaced some of the exsisting framing. Just kept the ground from the welder very close to where I was welding. I later have been told I just got lucky. What are your thoughts? | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 158 Registered: 11-2008 Posted From: 74.13.197.93  Rating: N/A |
Hi Grant - Whenever somsbody is going to weld on my bus, the first thing they do is disconnect the batteries. Don't ask me why because I don't know... I just know that's what they always do. FWIW - Nellie Wilson | ||
| Tony LEE (T_lee)
Registered Member Username: T_lee Post Number: 45 Registered: 11-2007 Posted From: 41.214.153.245 Rating: |
I would have thought that leaving the battery connected would provide a low impedance shunt in the unlikely event that welding imposed a high voltage on to the DC rail. Best way to eliminate potential problems would be to have an earth lead with a couple of clamps spaced about a foot apart. Fix a earth clamp on either side of the weld and no extraneous voltages or currents should appear anywhere on the rest of the bus - PROVIDED also that shore power was unplugged AND any earthed tools are not touching any metal on the bus. | ||
| Chuck Newman (Chuck_newman)
Registered Member Username: Chuck_newman Post Number: 288 Registered: 1-2005 Posted From: 76.246.254.144 Rating: N/A |
Most welders, at a minimum, will disconnect the battery. This "open circuits" the battery and cabling from any transients or long term current surges that may affect them, or components connected to the battery such as radio, ECM, etc. For those with DDECs: The Detroit Diesel DDEC III installation book states "System power and ground and the VIH (vehicle interface harness)must be disconnected prior to any welding on the vehicle. SERIOUS DAMAGE TO THE ECM(S)AND DDEC COMPONENTS MAY RESULT FROM WELDING IF ALL ECM CONNECTORS ARE NOT DISCONNECTED. The emphasis is theirs. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 688 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
PAY A WHOLE LOT OF ATTENTION TO WHAT TONY SAYS ABOUT DISCONNECTING SHORE POWER!!!, and grounded tools! In the (Upper) hemisphere, we call them ground leads, HA, HA. The potential for damage is the same, regardless of the latitude. That DOES mean NOT welding on your bus using your own generator! G (Message edited by George Mc6 on January 19, 2009) | ||
| Grant Thiessen (Busshawg)
Registered Member Username: Busshawg Post Number: 88 Registered: 10-2007 Posted From: 206.45.93.160 Rating: N/A |
Tony said "Fix a earth clamp on either side of the weld" . I appologize for my ingnorance , but by this do you mean a ground strap? And do I simply just use a vise grip and attach it , and then bare the other end of the cable and bury it in the ground? Thank you | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 689 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Grant, The "British" call what we call [ground], [earth]. So what Tony is saying is to use two standard welding ground clamps, one on each side of the weld. Maybe one on each piece being welded together would be more specific? The advice on disconnecting DDEC is also right on. Real electrical damage will occur when one side of the secondary transformer winding is touching the primary, and welding current tries to return thru the shore power, generator ground, OR SOME OTHER PATH! You are doing the right thing by keeping the ground clamp very close to the work, and my suggestion echoes Tony's, add a second ground clamp between the pieces being welded. The whole point of this exercise is to keep all of the welding current flowing between the two leads of the welder, and nowhere else. HTH, G | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1472 Registered: 12-2000 Posted From: 76.66.16.72  Rating: N/A |
And disconnect your inverter, equalizer, converter, isolators, and all the rest of anything in the coach that might have electronics in it. For instance, pull the plug on the microwave. If they aren't connected, lots harder for some stray high energy electrons to mess with them. happy coaching! buswarrior | ||
| Grant Thiessen (Busshawg)
Registered Member Username: Busshawg Post Number: 90 Registered: 10-2007 Posted From: 206.45.93.160 Rating: N/A |
Thanks guys! The earth thing was throwing me off, ha ha I guess I'm not very well travelled yet. A ground on each side,and everthing unpluggedis it. I was worried about my alt. but I gueess that's a non -issue | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 665 Registered: 10-2006 Posted From: 69.19.14.28 Rating: N/A |
For those that worry some of the items (and more) could be harmed with stray electrons, the following are at risk. (Ed. This list may not be complete). Propane Refrig thermostat and control board All heaters & furnaces with more than just an on off switch TV , clock radio, computer power supply and most anything with a transistor in it. Many genset speed controllers. Some inverters , equalizers , chargers and converters are at risk. The hassle , unlike a truck is the frame and AC power are grounded in common. This is usually at the noisemaker, where code requires it . Even the AC auto transfer switch is at risk. Weather the welding will or will not result in nonworking camper parts is very difficult to guess at. The "best" solution is to wire the camper with electric boxes and plug all the users in so they can be unplugged when needed . DC is harder but for a big $$$ inverter I would disconnect the leads (AC & DC), disconnecting JUST the battery ground may not work. FF . | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 703 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Now I have to ask a question, as I thought I knew a LITTLE about welding...? I always thought that TIG meant Tungsten + INERT GAS. (The tungsten makes the arc, and you feed the material into the hot INERT area with a stick.) Then, MIG had to mean Metal + INERT GAS. (The metal is the spool of wire fed out by the machine, into the hot INERT area.) The wire may be flux-core, which will provide some inerting when vaporized, or maybe that's why there's a cylinder of Argon or Tri-Mix and a hose and reg? Argon is inert, as is Helium, which are the two main components of Tri-Mix. Gas welding is Oxygen+Acetylene, right? Lets don't mess this up with MAPP, propane, or other fuel gasses, because it isn't my point. Point is: Oxygen is the pure definition of an oxidizer, and air is about 20% oxygen. So, why do we use flux core wire in MIG, and/or Argon or Tri-Mix gasses in both TIG and MIG? Couldn't be to prevent the material from oxidizing by displacing all the air around it with inert gas could it? Buses do have a lot of stainless and aluminum don't they? | ||
| Clint Hunter (Truthhunter)
Registered Member Username: Truthhunter Post Number: 9 Registered: 1-2009 Posted From: 24.129.235.190 Rating: N/A |
Well George...yes, it is as a sheild gas to prevent Oxidation reaction in the welds and also has a effect on promoting and maintaining the plasma arc. Hope I underdtood your simple question corectly. | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 480 Registered: 7-2006 Posted From: 75.209.85.115 Rating: N/A |
Hmmmm.......Define "simple"......scientific (fact) or innuedo? And to think I once owned a steel fabrication company....(yep we did all the other metals too). And the beat goes on...  RCB | ||
| Clint Hunter (Truthhunter)
Registered Member Username: Truthhunter Post Number: 23 Registered: 1-2009 Posted From: 24.129.235.190 Rating: N/A |
Oh Bishop C.R ease up (or not) it's your way that counts most to you: "simple" was in reference to the degree implied by the Toddster the sixth's bang on assumption about the "gas cloud" ; as employer of metallurgists, I am sure you know the complexity that could be included in a detailed answer when one approached the electron bonds at the sub-atomic level. Hope you won't always require connotation clarification, I could send you a formula for skin as tough as steel if you wish. hahahahah not really on that last part, it's not patented yet! I do not compete, if you remember just this one thing, you will know my connotations. Now that is simple ! | ||
| Cullen Newsom (Cullennewsom)
Registered Member Username: Cullennewsom Post Number: 7 Registered: 2-2009 Posted From: 98.201.161.214 Rating: N/A |
FWIW, I've used my 200 Amp welder to "jump" engines off with. | ||
| Cullen Newsom (Cullennewsom)
Registered Member Username: Cullennewsom Post Number: 8 Registered: 2-2009 Posted From: 98.201.161.214 Rating: N/A |
If I were a welder, a welding on your vehicle. Would I disconnect your batteries? Everything that I've heard on this subject is monkey-see-monkey-do, as far as I can tell. I can think of a few good reasons to disconnect electrical things before welding. 1. If I don't do it, you'll ask me why I didn't. Then I'll have to explain to you why I didn't, and why it doesn't make any difference. It isn't worth arguing with you; because you won't believe me (because of something you read on the Internet). I don't want you calling me next week and telling me that I gave your computer a virus. (It's been slow like this ever since that guy welded on the bus.) 2. If I do, it might cause you to busy yourself unplugging your "sensitive electronic equipment" and thus not getting in my way whilst I'm working. I am trying to imagine scenarios where welding can damage properly installed electronics. So far, they all involve poorly designed circuitry, and accidentally welding on them. I'll try to explain. How are electronics damaged? Integrated circuits can be damaged when their forward or reverse voltage ratings are exceeded, or when too much current is allowed to flow (in this case they overheat and melt). They have other failure modes as well, such as gravity, hammers, other forms of violence (though usually not verbal abuse), water, etc. But we're talking about damage from electricity. What do I mean by "poorly designed electronics"? I mean that a competent designer or engineer would be negligent to design an input or output circuit that could be damaged so easily (learn to use reverse-polarization-protection diodes, you hacks). That doesn't mean that they aren't out there, or that they never worked at GM building DDEC ECMs. What do I mean "so easily"? While it may look scary, arc welders don't output more than 50 volts (typically less). Even considering the (normal) case of welding with "DC Straight Polarity" (Ground is Positive), and even considering a reverse breakdown voltage of a typical transistor may be around 40V (2n3904), the welder electrode needs a very low resistance path to your "sensitive electronic equipment" and your "sensitive electronic equipment" needs a very low resistance path to "ground" (the welding machine ground). Despite the impressive display of sparks, Ohm's Law remains in effect. In other words, you have to touch the welder electrode to something that's directly connected to a piece of shoddy electronic circuitry, to have a chance at destroying it. Would disconnecting the battery help? I think the chances that it would help are infinitesimally small. What would help? Assuming there is any risk at all, one could completely disconnect and remove susceptible devices. tl;dr Weld close to your "ground" clamp and you should be fine. If anyone can show me some damaged electronics, I would like to see them. -Cullen | ||
| Cullen Newsom (Cullennewsom)
Registered Member Username: Cullennewsom Post Number: 9 Registered: 2-2009 Posted From: 98.201.161.214 Rating: N/A |
George, You can use solid wire in MIG welding if you use a shield gas. Us flux core if you don't have gas. -Cullen | ||
| niles steckbauer (Niles500)
Registered Member Username: Niles500 Post Number: 906 Registered: 11-2004 Posted From: 173.78.29.189 Rating: N/A |
******* If I were a welder, a welding on your vehicle. Would I disconnect your batteries? Everything that I've heard on this subject is monkey-see-monkey-do, as far as I can tell. I can think of a few good reasons to disconnect electrical things before welding. ******* The only reason necessary for you to disconnect your electronics, etc. = because the manufacturer requires it - Although, when welding (DC current) there is less resistance than AC current - the impedance level must match for current to flow without resistance - Now can you calculate the impedance of each weld/ground location? - Could someone please ship him a fried ECM - FWIW | ||
| Cullen Newsom (Cullennewsom)
Registered Member Username: Cullennewsom Post Number: 19 Registered: 2-2009 Posted From: 98.201.161.214 Rating: N/A |
Niles, I am sorry if my "monkey-see-monkey-do" comment hurts anyone's feelings. But, if we habitually perform some task without understanding why we do it, or (having a good reason), well that exactly defines "monkey-see-monkey-do". Note that all welding is not DC. The Lincoln 225 which many refer to as a "crackerjack box" is AC only; and may be the most common welding machine in recent history. Also note that I haven't addressed special cases like TIG welders, Plasma Arc Welders, or Plasma Cutters. I'm talking about good ol' common "stick" welding. I'm not exactly sure that I follow your meaning here.
Impedance must match for current to flow with minimal resistance (and minimize reflections etc). This is a reasonable thing to say when dealing with higher frequencies. At 60Hz there's not a lot of complex impedance stuff going on. 60Hz is the frequency that "crackerjack boxes" operate at. Furthermore, to be clear here, I am assuming that we're all grown folks and understand the risks (ie replacement cost of some electronics, plus labor to install, etc).
That's fine. There's nothing wrong with following recommended procedures. My point is to try and gain some understanding of the subject, and if possible, dispel some of the mythology that runs amok. For example, why should anyone disconnect the batteries? Batteries are not "sensitive electronic equipment". You can even weld with only a car battery (though, it is foolish); yet many people advise that you should disconnect them. What's the reason? I think a much greater risk is presented by welding near lead acid batteries. Vapors from the battery may be ignited and explode. In which case, batteries should be removed completely from an area where welding is to occur. Yet, somehow it wouldn't surprise me to see some one welding near batteries (which they have taken care to disconnect).
There are techniques available to do exactly that. Though, I have to admit that modeling so many variables is time consuming and difficult, and to do a thorough job one needs to work very hard, and might still fail.
I would like to see an ECM, or any electronics that have been damaged by welding, especially if it is accompanied by a detailed procedural account of the welding. I would happily post anything I learned here. I'll even pay the shipping. If you read carefully what I wrote, you'll see that I haven't said it's impossible to damage something. I said it's unlikely (based on my understanding of how things are damaged; a hypothesis which I explained previously.) I also said that a better way to protect yourself (assuming that there is a risk) is to remove the allegedly susceptible device completely before welding. -Cullen | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 765 Registered: 1-2003 Posted From: 67.142.130.11 Rating: N/A |
Cullen, now that I know what coach you have, let me give you some unsolicited advice. Your Neoplan has both a DDEC ECM and an Allison ECU. A replacement ECM will cost you between $1,000 and $2,000, depending on whether you can find a working used take-out (from, for example, a seized engine) or have to get a new one. That ECM will have the wrong program for your engine, so next you will need to have the correct program downloaded from the only place it can be, the mother ship at Detroit Diesel. That will cost you another $2,000. You seem pretty handy, so I am guessing that you could swap them yourself, even without the manual. On my coach, a bunch of things have to come out first, before I can even get to the ECM. If you had to pay a shop to do it, it might cost perhaps $200-$300 to install your new ECM. So a fried ECM could cost you as much as $4,000 or so, and probably a minimum of $2,500. Detroit requires you to disconnect the ECM completely before any welding. The reason is simple: ECM's have, indeed, been fried by welding that was done, in some cases, at the very opposite end of the coach. Remember that there's a harness for controls and sensors that runs the length of the coach, which will happily carry even a tiny amount of, for example, reverse voltage, back to the ECM. Pretty much everything I just wrote about the ECM applies equally to the ATEC ECU, although the specific numbers differ slightly. So, given the above, I suggest you follow the recommendation of both those manufacturers and disconnect the modules before you weld anywhere on your coach. But, as you say, you're "grown folk" -- and now you know the replacement cost of your electronics. FWIW. -Sean http://OurOdyssey.BlogSpot.com | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 746 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Cullen, Now that this thread has come back to life, it is interesting to note a couple of things. 1. The post I was referring to has disappeared. It was a suggestion to carry and use an OXY-Acetylene torch on a bus to avoid electrical damage... It would work fine in welding mild steel, but the whole point of using either flux core wire to give off inert gas, or just plain using inert gas is to avoid oxidation from the oxygen in the air, when welding either aluminum or stainless. Adding an inert gas to a torch would put the flame out, not to mention the whole point of adding inert gas to electric welding is to displace the oxygen in the air from the weld site. 2. It is obvious from your post that you understand the welding process, and I was too obscure in what I posted. Since the post I was referring to is gone, I won't offend anybody by asking if anyone had success welding either aluminum or stainless with a torch? (This is a question that doesn't merit an answer.) I agree with you on monkeys, and I think the reason people disconnect batteries is because it makes them feel good, but this will just stir up more slag. Regards, George | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 541 Registered: 7-2006 Posted From: 75.211.63.169 Rating: N/A |
I believe...not sure...that a couple of manuals I have retained say specifically to disconnect batteries prior to welding on a coach....there is a bunch of stuff in the archives about this subject, as well. Consequently... as a matter of decorum (?) I do it....just because....and life's experiences have always taught me to..."do what you are told"... . When you get to be as old as I am, you'll understand  !!! Just my way. RCB | ||
| Kyle Brandt (Kyle4501)
Registered Member Username: Kyle4501 Post Number: 459 Registered: 9-2004 Posted From: 65.23.106.193 Rating: N/A |
I think what is being missed is the induced current flow resulting from the electric welding process. It is this unintended & uncontrolled current that is the likely cause of fried electronics. Disconnecting the bateries is one of the easiest ways to minimize paths for the induced current. I have been shocked when welding before. It was hot & my shirt was soaked with sweat & it didn't seem to matter the arc was closer to the ground clamp than I was. . . I still got shocked. The inert gas does far more than just displace oxygen, some shield gas mixes actually have oxygen added to reduce carbon buildup in the weld. Then there is arc stability & filler metal spray transfer improvement. . . . BTW, welding stainless with an oxy Acetylene torch has certain advantages. . . but it is like any other welding, you have to have the right tools. The oxy Acetylene flame is easily changed from carbonizing (aka reducing), neutral, or oxidizing depending on what is needed. Some things that reduce the quality of any weld- wrong shielding gas wrong filler alloy wrong heat setting wrong size rod wrong flux wrong travel speed poor welp prep unclean metal surfaces etc | ||
| Cullen Newsom (Cullennewsom)
Registered Member Username: Cullennewsom Post Number: 21 Registered: 2-2009 Posted From: 98.201.161.214 Rating: N/A |
Sean, Thanks, I reckon it's better to spend a few minutes disconnecting all of that garbage than it is to reward Detroit, Allison, et al for lousy design. George, I guess I missed a lot of context from the other thread. R.C. My Neoplan has a sticker in the battery compartment "DISCONNECT BATTERIES BEFORE WELDING ZOMG!" I think it was put there by whomever fitted the battery converters. As a general matter, I see notices everywhere, that are meant to scare me off. "No User Serviceable Parts inside" for example. I appreciate, and respect your viewpoint. But ,I am one of those smart-alack pain-in-the-neck folks that has to know "why". Kyle,
I have no idea what you just said.
You were shocked because 1. In arc welding, the arc is not a constant. 2. The sweat lowered your body's resistance, and the resistance normally provided by your gloves. You were probably also leaning against the work. | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 771 Registered: 1-2003 Posted From: 67.142.130.11 Rating: N/A |
You're welcome. BTW, whether or not the design is "lousy" depends on where you sit. My guess is that from Roger Penske's desk, the design was fantastic. Allow me to elaborate by means of an example. A longer time ago than I care to admit, I was a telephone switching engineer with Bell Laboratories. In those days, phones were polarity-sensitive. They were pretty robust -- you'd not likely damage one by connecting it backwards, but it certainly would not work. Anyone who was a phone phreak like myself had figured this out by the age of ten, because we all wired our houses or whatever for ten extra extensions, had "found" phones to put there (you could not "buy" a telephone then), and even figured out how to kee Ma Bell from detecting that you had "illegal" extensions (disconnect the bell). So it was not surprising that many yay-hoo engineers (and note that we can't write "yahoo" anymore without possibly being misunderstood) who came to the Labs suggested that we could fix this oversight by adding a diode rectifier to the circuit inside the phone, and why hadn't the idiots who designed phones already thought of this. To finally understand the answer to this simple question, for a new engineer at the Labs, was like drinking the proverbial Kool-Aid. You had to look at the bigger picture: 1. The cost of the parts (diodes, wire, additional space on the "network block", etc.) might have been perhaps a quarter, which seems cheap. But Western Electric was churning out perhaps 20 million telephone sets per year -- a quarter per each would add up to $5 million or so. As the saying used to go, a million here, a million there, and pretty soon you are talking real money. 2. The diodes would drop about half a volt. While that is, again, small on a 48-volt system, it meant the phone would not work as well as far away from the Central Office as it's unprotected brethren. That could be a real issue for some rural subscribers, at the end of miles and miles of twisted pair. Moreover, multiply the power loss in the diode assembly for one phone by the number of phones off-hook at any given moment -- as many as 50,000 in a Central Office during, say, a civic disaster, and you're talking real power, which would mean even more batteries (all telephone switches are battery powered). 3. While it would seem beneficial to add such idiot-protection, so that even idiots could install phones, at that time, only Bell System installers could legally install phones. Since we completely controlled and trained the installation and maintenance workforce, even down to exactly what tools they carried, it was a trivial matter to keep them from incorrectly connecting telephones -- much, much cheaper than adding the diode block or extra batteries. Now, I have never, in my engineering career, worked for an engine or transmission manufacturer or designed ECM/U's, but I am guessing that much the same discussion takes place around their water coolers. The cost of adding even simple diodes to every polarity-sensitive connection may be only a few pennies, and a few mm of board real estate, but multiply that by millions of units produced, and it's real money. Besides that, every such item added draws power, and engineers are constantly constrained by a power budget dictated, in many cases, by legacy issues (why ECM's are all 12-volt, even on 24-volt coaches, for example). Simpler and cheaper to mandate that mechanics working on these units be properly trained to connect them the right way, and to issue a bulletin that says disconnect the darned thing when you weld on the vehicle, something which is done only infrequently after the vehicle enters service. So, yes, from the point of view of the consumer (and maybe even the mechanic), the design might be lousy, but, unless that diminishes customer good-will, from the point of view of a shareholder it is not.
Your Neoplan very likely has a Vanner battery equalizer. This, too, is not polarity-protected, and usually does not have a separate disconnect other than the battery cables themselves. I would venture a guess that this is the principle reason for the sticker in the battery compartment. BTW, you can (and should) download the manual for the equalizer in PDF format from the Vanner web site. The equalizer is also very picky about the sequence in which its three leads are connected and disconnected. Getting it wrong can fry the unit. FWIW. -Sean http://OurOdyssey.BlogSpot.com | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 551 Registered: 7-2006 Posted From: 75.210.37.147 Rating: N/A |
Well, Cullen...while I acknowledge your point of view, I also know that when something is "out of warranty".........I'd rather take the high road...and say to myself, if no one else...."I did what I was told". Then when I make that move I can have some, if not much, peace of mind. Don't know about you,. but I go thru that scenario most every week in some mechanical thing or another. Experience is the best teacher,... for me! I have a PhD....in hard knocks.. I defer to FF. RCB | ||
| Kyle Brandt (Kyle4501)
Registered Member Username: Kyle4501 Post Number: 461 Registered: 9-2004 Posted From: 70.153.13.17 Rating: N/A |
I may have the vocabulary wrong, but what I refer to as 'induced' current flow is that which is caused when current flowing in one conductor causes current to flow in another conductor. Do you know how a transformer works? Think Maxwell's & Faraday's equations. . . Passing current thru a wire creates a magnetic field. A changing magnetic field can cause current to flow in a wire. . . . see? |
