May 23rd, 2018
Aim: To create an Aluminium Fuel tank, in 3 parts providing a seamless connection once finished.My main objective was to create the lid of the tank
The petrol tank form is quite a challenging yet simple design which requires a certain standard of skill and aluminium moulding processes, in order to provide the abnormal shape and definition of the model.In order to replicate the petrol tank a large amount of skill and knowledge from our previous tutorials i.e( bowl making, tray making & the blister techniques) ,were used in order to give the exact shape and sophistication of the tank.
Firstly, before creating the lid of the tank the petrol tanks form must be created in order to be used as a reference point for all three parts that are to be moulded.The process followed in order to achieve this model was as follows.
Measure up the tank in order to provide realistic dimensions which will be used to be put into the modelling program to form the mould.Once these dimensions have been established, using the RHINO digital modelling program the stencils to form the petrol tank mould are then designed using this program, to provide an exact duplicate of the petrol tank.(A KEY IMPORTANT FACTOR WAS ENSURING THE CURVATURES RUNNING UP AND DOWN & LEFT AND RIGHT MATCHED THE MEASUREMENT AND RADIUSES OF THE TANK, TO PROVIDE A SEAMLESS ROUNDED EDGE.)
Once the Rhino Slicer model has been finalised and matches the design requirement of the mould, using a laser cutting machine and 3mm ply, the stencils created in the program are then precisely cut onto the board to form a jigsaw puzzle of the tank.
Using the stencil cutouts, the pieces are then joined together to form the irregular form of the petrol tank.In order to strengthen the mould and prevent it from collapsing when moulding the aluminium, using a hot glue gun all the seams and joints of the stencils were glued, essentially providing a rigid structure for the tank to be formed.
The mould was then split into three quadrants which will effectively provide the greatest look when joined together.The easiest way decided in order to provide greatest efficiency was to seperate the sides into two pieces then the lid on the top.
PROCESS
Being responsible for the tanks lid, the following process was implemented in order to achieve the required form and design:
Step 1
Using tracing paper, trace the shape of the lid on to the piece of paper to provide a stencil for the sizing of the lid.Once traced the paper stencil is to be cut out using scissors, leaving approximately 10mm on each side for shrinkage and any minor mistakes.
Step 2
When the paper stencil has been cut and it suits the shape of the lid, trace the stencil onto the annealed piece of aluminium using a marker, followed by a sharp metal point in order to engrave the line clearer.Then using a sheet metal cutter or aviation snips carefully cut out the stencil ensuring a even smooth cut all the way around.After cutting the shape run a file or sandpaper along the edges to remove the burrs or any uneven edges.
Step 3
In order to create the shape and curve of the mould, using the ply stencil trace the curve of the lid onto a piece of 18mm plywood.Once traced onto the plywood, cutout the shape using a band saw then using a drum sander smooth the edges.Duplicate this process several times and drill all the pieces together with screws, until the stencil is wide enough to fit the aluminium stencil.
Step 4
Once the form has been made clamp it into a bench vice, and place the aluminium stencil on top.Then using a fibre glass hammer using strategic hits, hammer the aluminium into the mould until you receive the shape desired.During this process it is important that the stencil is securely held down to prevent the shape being irregular and not being able to match the mould.
Step 5
Then, due to the top half of the tank having a reversed bowl pro-form, using a marker mark the centre of the top top half piece of the tank and draw circles around the centre to be used as guidelines for moulding it into the bowl shape.Then using a sand bag and a fibre glass mallet begin to hammer the aluminium from the centre out , slowly moulding it and curving the edges to form the round outer-skin of the tank.
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Step 6
After, the bulk of the shape has been formed with the sand bag, then using a depressed tree stump and rounded fibreglass mallet, hammer the form into the mould at the correct angle for the full 360 degrees of the piece.By doing this it will essentially define the edges and curve of the top half of the tank to provide a greater seamless finish when joining it with the side pieces.It is also very important to continue matching the piece your moulding over the reference mould in order to prevent it from being incorrect.
Step 7
Once the top half shape has been formed, then using the same process as the rounded top half, however with more gentle curves, using a sand bag and depressed tree stump hammer the body of the lid to form the curve that essentially defines the length part of the tank.This is a repetitive process which requires strategic hammering, and continuous matching to the already made mould, to prevent distortion.It is important to ensure that during this process that you do not over hammer the aluminium as it will crack or bend and wont be fixable especially due to how delicate the curvature of the lid is.
Step 8
Then, after the shape of the aluminium suits the mould, it is then time to smooth out the lid.Using a english wheel gently wheel out the formed piece of aluminium removing the depressions formed by the mallet as well as providing smoother rounder edges for the lid.Again during this process it is important to continuously check the mould with the aluminium lid to prevent it from distorting as a result of the english wheel.Then, using a dolly and mallet smooth out the imperfections that couldn't be done with the english wheel.Essentially, properly done this will provide a professional tank finish with a seamless finish.
Step 9
Lastly, once completed joint the pieces together and using aviation snips cut out any imperfections or overhanging pieces of metal from the aluminium lid in order to allow the pieces to fit together perfectly.Once done the tank is complete.
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