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Motorsport Fabrication Fundamentals: Step 4: Welding

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Step 4: Welding


00:00 - In this last step, we're going to cover the assembly and welding process of the fuel tank.
00:04 While we'll be discussing the TIG process used for the welding briefly, we're not focusing on the specific details of the welding within this course.
00:13 If you do want a deeper dive into TIG welder setup, as well as the welding technique that we use here, then this particular fuel tank construction is also covered as a worked example in our Practical TIG Welding course and you can check it out there.
00:27 Before we get into the assembly, we do need to mention that the same company who cut our raw material, also CNC bent the material as per our Fusion 360 model, meaning that we didn't need to do this in house, saving us another job and further ensuring accuracy.
00:43 If required though, this job could have easily been completed on a sheet metal bender or with a press brake attachment in a vice.
00:51 We got started by assembling and tacking the bottom section of the tank which also includes the internal baffle plates.
00:58 Obviously being non ferrous, magnetic clamping aids aren't much help to us with alloy, however due to the design of the tank, the individual parts fit together quite nicely and require little support.
01:10 The exception is the in fill panel that welds to the body of the tank at an angle.
01:15 In order to support this during the tack welding phase, we use kapton tape.
01:19 The end panel also required a little support in particular ensuring that the remainder of the tank was properly aligned prior to welding so that the panels align nicely with minimal gap.
01:30 To achieve this, we made use of a pair of clamps.
01:33 This is one of those normal situations where a variety of techniques can be applied to get the result that you want.
01:40 Fortunately, due to the accuracy of the laser cut sheet and the fact the part was modelled in CAD, the fitment was guaranteed to be good which makes our job easier when we're setting everything up.
01:51 Initially all we want to do is apply a small tack into the corners while we confirm and adjust fitment.
01:57 We want to make sure that the parts are aligned correctly so that we end up with a nice 90° edge between the two adjoining panels and this gives us a nice valley that we can then fill in with weld during the welding process.
02:09 With the base of the tank tacked together, we can then tack the angled in fill panel onto the rest of the fuel tank base.
02:16 Next we can flip the tank over and tack the end panel in place, ensuring that we manage the alignment of the various panels as we go.
02:25 At this stage, the top of the tank is just being held in place temporarily to aid alignment and we don't want to tack that in just yet.
02:33 We've now got the majority of the tank tacked up and we've gone through and added some additional tack welds about every 200 mm which will help ensure nothing moves or pulls with the heat when we perform the full welds.
02:46 Before we add the top to the tank, we need to take the opportunity to stitch the internal baffle plates to each other as well as to the outside of the tank.
02:54 There's not requirement for strength here but rather we're just preventing them from moving relative to each other in use so a few short stitch welds is more than sufficient.
03:03 This is also our last opportunity to access the inside of the tank so it's a great chance to give it one last thorough clean out.
03:11 Now we can prep the top of the tank and this requires the threaded machined adapter to be welded to what will become the inside of the tank.
03:17 This part doesn't do any sealing of the fuel so it just needs to be securely tacked rather than fully welded.
03:25 We do want to ensure though that the threaded holes correctly align with the holes in the lid of the tank so before welding this in place, we temporarily bolt it in place.
03:33 We're just going to stitch weld this to the tank lid in 4 places evenly spaced around its perimeter.
03:41 Once it's welded, we can remove the bolts and assemble the lid into location.
03:45 The internal baffles locate into slots cut into the tank lid and a little gentle force is required here to positively snap everything into location.
03:55 Now it's a case of tack welding the lid into place, initially at the corners before placing tacks every 150 to 200 mm along the edges.
04:04 Next we can weld the baffles to the lid along each of the slots.
04:08 Lastly, it's time to commit to the external welds on each edge of the tank.
04:12 There is around 6 metres of total weld length in this particular tank so sufficed to say there's a lot of time spent on the torch.
04:20 One of the issues with so many welds on a thermally conductive material such as aluminium is controlling the heat between welds and cooling it back down.
04:29 Waiting and allowing the parts to cool naturally is going to take a long time with aluminium so between the welds we used a fan to help circulate air through and around the tank and speed up this cooling process.
04:41 The fan we're using has a large shroud around it and this was big enough to support the whole tank so by simply sitting the tank on the fan for a few minutes, this was enough to cool the tank back down to a manageable level.
04:53 This of course also means that care is required any time we're handling the tank to reposition it as the heat from the weld will be conducted through the rest of the tank very quickly and even areas that are quite a distance from the weld location can be much hotter than you'd expect.
05:08 Our TIG welding gloves here should offer sufficient protection to allow the tank to be handled between welds though.
05:15 So at this point we have a complete fuel tank that's ready for test fitting into the vehicle before pressure testing.
05:22 It's always a good idea on any job of this size to take a final look over each of your welds, looking for any potential imperfections or impurities that may need to be addressed.
05:32 Any pin holes or porosity for example could be a potential leak and these will need to be addressed.
05:38 If you have any questions on this worked example, please ask these in the forum and we'll be happy to help you out there.

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