Motorsport Fabrication Fundamentals: Step 1: Planning
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Step 1: Planning
05.53
| 00:00 | - In this worked example, we're going to go through the design and construction process for a fuel tank to suit an off road truck project that we're building in house. |
| 00:08 | There's a few requirements that we need to keep in mind for this tank design and this starts with the physical location inside the chassis. |
| 00:16 | Due to the transmission location, there's insufficient room to fit the tank in the middle of the chassis in the stock location however there's plenty of room at the rear of the vehicle. |
| 00:25 | A consideration here is how the filler will integrate with the new tank location but there is sufficient room in our example to extend the filler to the tank without interfering with any other components. |
| 00:38 | The other requirements we need to keep in mind are the capacity of the tank and ideally we'd like to be able to hold around 50 litres of fuel to provide good range. |
| 00:47 | We also want to ensure the shape of the tank doesn't compromise ground clearance or more specifically the departure angle which is essentially a line from the rear wheels to the rear bumper. |
| 00:58 | This tank is for an electronically fuel injected engine so we need to be able to prevent fuel surge and always provide a constant supply of high pressure fuel even when the truck is moving or in an extreme angle. |
| 01:10 | To do this, we're utilising a universal fuel cell surge tank from Radium Engineering. |
| 01:16 | This incorporates a lift pump that pumps fuel out of the main fuel tank and into a built in surge tank. |
| 01:23 | From here, the high pressure fuel pump feeds the fuel forward to the engine. |
| 01:27 | This simplifies the fuel system since we don't need to incorporate an external surge tank and a separate fuel pump, everything is in one single unit. |
| 01:37 | The other advantage of this unit from Radium is that it uses the industry standard 6 x 10, 24 bolt fill plate bolt pattern so this makes it compatible with most fuel cells. |
| 01:48 | In addition, the Radium unit also incorporates a fuel level sender which is an essential for a street driven vehicle. |
| 01:55 | At this stage, we can develop some of our fundamental measurements which include the width between the chassis rails and this defines the maximum allowable width of the tank, this being 880 mm. |
| 02:05 | The length of the tank is limited by the location of a cross member at the front and the rear bumper at the back, meaning we have around 500 mm to work with here. |
| 02:15 | There are also some diagonal braces between the chassis rails and the rear bumper that will necessitate an angled section on each side of the tank to provide clearance. |
| 02:25 | The Radium surge tank that we've chosen is 200 mm deep which defines the depth of the tank as any additional depth will mean that the fuel can't be picked up by the lift pump. |
| 02:36 | Working with these dimensions, we can start to plan out the shape of the tank. |
| 02:40 | While there's no reason that we couldn't have designed the tank using graph paper and a ruler and pencil, in this instance we've chosen to use Fusion 360 to model the tank in CAD. |
| 02:51 | There's a couple of obvious advantages here in that we can easily manipulate the design and try out different shapes to see what fits our space best. |
| 02:59 | However the key advantage is that we can then use the sheet metal functions inside of Fusion 360 and send a file to a sheet metal working company and have the parts laser cut, saving time and insuring accuracy. |
| 03:13 | As part of the design, we also incorporated some internal walls within the tank which serve two purposes. |
| 03:19 | Firstly, by incorporating these walls with a series of holes cut in them, it will help reduce fuel slosh in the tank and help to keep the fuel around the lift pump pick up. |
| 03:29 | Secondly, these walls will be stitch welded to each other as well as to the tank internally and this will provide some additional strength and rigidity. |
| 03:37 | We do need to consider how these parts will be assembled though, so that we can stitch weld them together. |
| 03:42 | If we assemble the tank from the bottom up, then we'll be able to access the inside of th tank to weld these parts together but of course we wouldn't be able to stitch them to the tank top when that's in place. |
| 03:53 | To solve this issue, we incorporated a number of tabs on the internal walls and these locate into matching slots on the tank lid. |
| 04:01 | These can then be welded together externally. |
| 04:04 | We also need a threaded plate to accept the bolts for the Radium surge tank bolt pattern. |
| 04:09 | This part needs to be thick enough to be tapped for the bolts and this will be welded to the inside of the tank lid so of course it needs to be made from the same material as the fuel tank for compatibility. |
| 04:20 | The section that will make up the rear and the sides of the tank could have been made out of separate parts, however we can easily make this from a single section and bend the sheet as required into what will become the corners. |
| 04:32 | This simplifies the construction and reduces the number of parts as well as the number of welds that we'll need to complete. |
| 04:39 | It of course does require access to a bender though so depending on the tools you have available, it could still be constructed using separate panels. |
| 04:48 | Lastly, we incorporated an angle on the rear lower section of the tank to provide a better aesthetic look to the tank as well as to optimise the departure angle we already discussed. |
| 04:59 | Another advantage of using Fusion 360 is that we can use the software to quickly and easily calculate the volume of the tank which came out to be 54.5 litres although this will be reduced marginally by the volume of the surge tank when that's fitted. |
| 05:15 | Sufficed to say, this is going to end up above our 50 litre target so we're good to go. |
| 05:20 | With our design finalised in CAD, we also made a cardboard mock up of the tank so that we could physically confirm fitment as well as to get a sense of how the finished tank would look in the truck. |
| 05:31 | You could argue that the looks really aren't too important to the function of the fuel tank but whenever we're making parts for our vehicles, we usually want to produce something that not only works as expected but looks great too. |
| 05:43 | With the planning and design stage complete, we can now move on and select the materials we're going to use. |
