In recent years, I've made my metal tanks, not bought them.
It's another enjoyable part of the hobby -to me, anyway. seems that about 68 years ago a high school shop and several Classes involved forming sheet metal (including aircraft aluminum), or making wooden molds for sandcasting and various metal forming activities. Calculations and drafting for these things were included.
It's a gppd thing that he thin gauge tinplate we're talking about generally does not need specific bend radii for our uses,
Useful info:
Required tank volume (in fluid ounces, most often,)
Approximate 'space' for the tank in the model.
Orientation of the engine and any quirks the engine may have about "...tank height,,,"
Venting - kind of venting and locations of fill, overflow and venting tubes.
using the info:
Tank capacity in fluid ounces (VOLUME measurements not weights.) where ( 1 fl. oz.requires 1.80 cubic inches.), The volume needed lets you figure the dimensions. That can be simple, usually isn't.
The old Froom/VECO/?SIG/?Fox tanks = ostly 2" wide, 1"tall with about ab eigth inch web on the outboard wall, were sold as about 1 fl oz per inch of length. Fully rectangular tanks with 1"H and 2" W went almost 1.25 cu inch per inch of length.- in theory. Plumbing and soldered surfaces change capacity.
The tanks I setttled on were mostly 1" high, 2" wide rectangular with a square front and a half-height wedge as the back end, That shape can be laid out for easy forming with straight-line bends. The rear cap wedge is at a 90° and feeds VERY well.
Using an actual dimension drawing on papereasy even with pencil and triangles - (or printed from a drawing program. Spray glued over machinist's blue on - say - K&S sheet tinplate (about
,008" thick) Very ightly scribe through the blue on the paper.
Think carefully and make the bends in a sequence that won't be trapped by a bend that cannot be made halfway home.
The end caps 'flats' are prepared the same way.