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Not sure how that process works exactly. I asked the racers choice guy and he makes molds, then casts off the molds. The mold is the expensive part. I do not remember the other company but their web site states custom tanks. Just as expensive as racers choice. Been considering making a cardboard templates and having a custom ss tank made . I'd feel better with a pex lined tank but ss would be safer then aluminum. The current tank can be mounted as seen in the pics. Looks bad but it fits at that angle. The round tank can go back in until I can get a custom tank made too. Having one made is my only option. I am tolerating welding to finish this project and barely. Using a new better helmet that does help too! Diff color screen and that made a difference. After what I welded sun my eye was dry and a small pull on it.
Your tank is the mold the way I have it done. (It also assures a perfect fit.)That is why you would need to send the tank to me before paint and no to powdercoat. All fab work would need to be completed first as well.
So if this is a real possibility , I will have a tank made. I assume aluminum would be fine since the bladder will be the real tank?? Could have it made out of 14g 3003 aluminum.
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There are a couple considerations. First and foremost the welded seams need to be "professionally" done with TIG. What I mean by that is the welder must be capable of having smooth seams on the inside,no dingle berry shit.I do not recommend a 1 piece tank like mine because of that possibility. I won't do a 1 piece again. It is best to make the tank with a removeable lid so it can be welded inside and out.
If using fill plate with pickup and return fittings integrated,do not do a cutout for it at this time. You will do that after rotomolding. If using a separate fuel level sender do a cut out for it and make a plate for plugging the hole after the PEX powder is added.
3003 is perfect material . I use .090 3003 h13 You will to make a pair of hold down straps that can be bolted down to the roto table that won't allow the tank to slip.
The rotomold process is pretty simple. You will need to calculate the surface area of the tank and they will calculate the volume of PEX granules to give the desired approximate thickness . They fill the tank,cap the fill port,bolt it to the roto table. Then it is off to the oven where the roto table turns 360 degrees and rotates in another axis 360 degrees. The PEX granules melt and crosslink into a consistent thickness in the tank covering all areas. The heat is removed ,tank continues rotating until the pex has hardened into a very tough bladder fitting your tank perfectly.
Crosslinked polyethylene (PEX) is much tougher than regular polyethylene and cannot be repaired by heat welding. Once melted and brought up to temperature the cross linking occurs and it will not melt again and is much more chemical resistant the regular polyethylene.