| Author | Message | ||
     Dktechguy112 |
I have to drain the gas tank. As many of you guys know, my frame has a dent/ crack in it and i found a guy to weld it. He told me to drain the gas tank. I am going to do that this weekend. My question is, should i drain the gas tank, and then start the bike up to get the gas out of the fuel pump and fuel lines, or should i run it while i'm draining the gas tank? | ||
| Dktechguy112 |
anybody? | ||
| 98s1lightning |
Drain the tank then run the bike empty. Fill the tank with water before ever striking an arc. Remember that the fuel VAPOR is whats flammable and not so much the liquid fuel.If you want to test this theory throw a burning cigarette into a cup of gas and you will see it goes out. By filling the tank with water it will push the fuel vapor out thus making it SAFER to weld. A good welder should know this and good luck. | ||
| Dktechguy112 |
i was told by someone on the forum to fill the tank with argon through the drain hole. he said it would feed the welder and keep the coating on the inside of the tank from burning. I haven't actually talked to the welder yet, but he does a lot of baja stuff, and from what i hear he is very good. | ||
| 98s1lightning |
That could be, is there a coating on the inside? You have remember that the pin hole is going to fill very fast and the chance of it needing that much argon is not likely. Heat will be minimum has a Heliarc machine for aluminum welds a lot colder than steel. Its how I have done it and how I would do it if I were you. Have you priced a new frame? | ||
| Dktechguy112 |
a new frame is $1300, not to mention that it would take a long time to install it. The frame is slightly dented, you can't even see a hole, it just leaks ever so slightly. I'm not giving up on the frame until the welder does. As far as the coating i have heard conflicting opinions, some people say there is a coating, some people say there isn't. I think i'm going to give ebr a call tomorrow and see what they say. | ||
| Guard_rail |
I'm in total shock no one has answered you. | ||
| Jules |
I don't suggest you try this but just FYI I know (and have seen it myself) that some people (call them lunatics) fill the tank to the brim with fuel and seal it and than weld... As has been said it's the vapour that explodes/ignites so when it's full there's no room for vapour. I've seen a few racers (desert) do this to their auxilliary tanks (watching from a safe distance). Is your guy going to drill the ends of the crack first? The damage looks really minimal so i am sure it'll be fine (fingers crossed) | ||
| Jdugger |
Welding on used fuel vessels is testy at best, and very, very dangerous (deadly) at worst. Back-gassing with Argon is probably the safest bet since it will prevent any fuel residue from burning and displace the fumes. The volume of the gas tank is pretty small... even a 5 gallon tank is only going to require about a minute to purge at pretty modest back-gas gas rates. | ||
| Pdccd |
I'm with Jdugger. Argon all the way, but I have seen it done as Jules suggested. I'm not a fan of that method at all. Argon will provide the cleanest and most uniform bead characteristics inside the tank (backside). To do it right, the hole/crack should be excavated to remove any contaminates from the hole/crack or else additional porosity will result, and in my experience the problem will migrate. Drain as advised above, run it empty, apply purge through taped of gas fill low flow (argon will sink to the low points and fill from there), excavate, clean with isopropyl alcohol and gtaw. (Message edited by pdccd on May 06, 2010) | ||
| Stirz007 |
+1 on argon - I use this method when TIG-ing tubing. The other plus is that it will self-purge when you fill the tank with gas (the go-fast kind). I like to try to keep water out of the fuel system if I can.... | ||
| Jdugger |
Plus, with Argon you can get a decent breath of it and sound like James Earl Jones for about 5 seconds. | ||
| Stirz007 |
Jdug - I did not know that - kinda anti-helium. Now you've given me another great useless and time-wasting skill I can try. | ||
| 98s1lightning |
The use of water is primarily for its cooling properties, the added benefit is that it weep if theirs a pin hole still in existence thus allowing you to re-weld the area. As for getting the water out of the fuel system, easy, rinse with one gallon of fuel and let sit for about an hour. When you have the bike all back together fill the tank with fuel and pour a bottle of HEAT in the tank also, it will remove all moisture from the system and your good to go. | ||
| Jdugger |
> kinda anti-helium Both are inert, noble gases. One is quite light. One is quite heavy... | ||
| Stirz007 |
Got the noble gas thing down, just never thought to huff any argon. James Earl Jones - Cool. (what will neon or xenon do, BTW?) | ||
| Jdugger |
> what will neon or xenon do Same effect relative to air. If the gas is lighter, your vocal chords will be higher in pitch, and if it's heavier than air, lower. That said, Neon and Xenon are rare and expensive. Argon and helium, however, are quite cheap. Futzing around with Argon doesn't cost much. Oh... and I know you know this... but don't play around with Argon in a small shop without the doors open. Argon isn't toxic, but you will faint before you realize there's not enough oxygen in the room and then suffocate as a result. A fan, an open window, etc, all prevent this from happening. | ||
| Boogiman1981 |
thinking the argon too. the water will vaporize behind the weld site and can cause some serious issues as it boils off, corrosion porosity etc | ||
| 98s1lightning |
The water cant vaporize as it is constantly circulating eliminating the possibility to boil. You have to remember that the frame is welded from the factory and its a practice thats been used on 1000's of different Aluminum tanks around the world. Corrosion and porosity will never be an issue. | ||
| Jdugger |
> The water cant vaporize as it is constantly circulating eliminating the possibility to boil. I've never had good luck welding with water behind the bead. It most definitely does boil as the heat from the arc and metal boil the local area faster than it can transfer the heat. When the frame is welded at the factory, it's done so on new, clean metal. | ||
| 98s1lightning |
A debate that can go for days. | ||
| Boogiman1981 |
lightning exactly how is this situation would said water be circulating? and even so water cannot absorb the heat and move it fast enough to prevent vaporization and the resulting cavitation caused erosion. and in factory situations it's clean metal so no need to worry about anything like fuel vapors or the like. | ||
| Johnbranx1 |
DKtechguy112, I had to drain the gas from my bike last year to get one of the seat subframe tabs welded back on. To drain the gas is easy..take off the front drive belt cover near the engine. Behind that you will see a small bolt that you backout and the gas will come out. The way the frame/tank is designed this is the lowest point and you will get all of the gas out. Don't worry about the fuel pump, if you hit the starter button the bike you will not get gas in the line/pump. I then filled the tank with water and my welder welded the frame. Empty the water put in gas and the bike started right up. | ||
| Dktechguy112 |
i am not sure about putting water in the tank. I'm going to talk to the welder, but i think i am going to put argon in it. also, i emailed ebr about welding the tank, they said that they do not recommend it, they said there is a sealant on the inside. they said the sealant could become damaged from the welding. Has anyone on here re-coated the inside of the gas tank with sealant? I'm not sure how to do this, or if it can be done? ebr recommended that i replace the frame. I kind of expected they would from a legal stand point. But my dad has already spent $1600 on fixing it up, he really does not want to spend another $1300 on a new frame. | ||
| 98s1lightning |
There are several sealants for the inside of a fuel tank. The bad thing is that you may need to remove the frame to get the sealant into the desired area. As E-B-R has said, "you may damage the factory sealant" Its already damaged via the hole/leak. I'm sticking with the water in the tank idea, this way you know when the tank is full and with argon being heavy it will push the gas vapor to the top where the welding is going to be. | ||
| Chevycummins |
I remember back when I was a kid my dad welded up a gas tank from an old VW, he took his van and ran the exhaust from it into the VW gas tank. It seemed to work well, no explosion and it dried the gas out of the tank with the hot exhaust. | ||
| Jdugger |
> with argon being heavy it will push the gas vapor to the top where the welding is going to be. Only if you don't fully purge the vessel. Once you have filled the volume with Argon, the vessel, provided it doesn't have a bottom-side leak, will push argon out the top, too. In welding school they taught us to use a simple volume calculation to estimate purge times: So, 5.3 gallon fuel tank at room temp is .7 cubic feet, that means at a low 1 CFM flow rate from the back-purge tube you need to about 45 seconds before welding. I took a quick look in my text book from Welding school, (http://www.amazon.com/Welding-Principles-Applicati ons-Larry-Jeffus/dp/1401810462/ref=pd_sim_b_4), and at least for SS work, only Argon and Helium are acceptable back purge. If you are doing any kind of chem, nuke or pressure vessel work, ANY other kind of back purge is specifically called out as improper. You might be able to get away with a water back purge on Aluminum -- and our gas tanks are aluminum -- but on SS you most definitely would not, under any circumstances. The resulting weld would never pass code or xray. For what it's worth, I've probably laid a mile of TIG bead on 6061 and 6063 in my lifetime, and Aluminum is pretty friggin' moody about what gets into the weld. An arc is going to cause electrolysis (http://en.wikipedia.org/wiki/Electrolysis_of_water) to happen to any water vapor making it's way into the shielding gas layer, and that's going to oxidize the weld. As I said before, I've had bad luck trying water as a back purge in the past, and would be suspicious of it here. My welding instructor use to say about Aluminum "if you won't lick it, don't weld it." In other words, clean, clean, clean. For what it's worth, the book also says "don't weld on fuel vessels"...  I'd fork out the $1300, honestly. (Message edited by jdugger on May 06, 2010) | ||
| Stirz007 |
If you want to really go old school, just rub a bar of soap over the pinhole...that will work for a little while. | ||
| Pdccd |
And water has hydrogen in it, a primary contributor of porosity. Honestly, there's only two ways to get the fuel that's trapped inside the crack itself that's leaked through already, grind it out, or burn it out, and burning it out is going to cause a huge mess. After you've ground it out, water is going to be pissing out of the hole. You cannot gtaw through water on aluminum. I don't care who you are. I just spent 10 hours today on a coast guard harbor tug in the rain trying to do it lol. Now i'm off to google how the factory uses water, if find this curious. X2 everything Jdugger has explained. (except huffing argon lol) (Message edited by pdccd on May 06, 2010) |
