Okey-dokey
let me refer to a previously-discussed water-heating device. see pics?
In the one with the pipes you are looking at the stubs of the wetback plumbing, the 40mm BSP galv bends, the copper pipe and the "starkie" unions attached to the wetback. I designed and built the wetback myself, making it out of 10mm 316 stainless. It is specifically sized to heat the contents of a (standard) 180-litre hot-water cylinder over what I think might be the average evening "burn" for a fire like this, five hours. it's the product of the evolution of three previous wetbacks I have used over 30-odd years and the experience gained in running them. I figure 180L of water at about 90 degrees is an optimum result - the cylinder is in no danger of boiling and I don't have to run hot water to waste.
In the one with the ugly circular register, the funny-looking copper-coloured hinge pis and the odd latch, what you are looking at is the firebox door (in its functional-but-unfinished stages). the components of the latch are essentially the 14mm threaded stub off am Hitachi angle grinder and its disc-retaining nut. I have used these items for all sorts of applications where the conditions are a bit harsh and have found that - whatever alloy they are made from - it's durable and never rusts, seizes up, gets burred over time or anything like that. plus I enjoy recycling them as they come from dead grinders
There is a lot of years of experience behind the placement of the register at the point it is situated in the door in relation to the height of the grate etc etc, and there's a whole 'nother story around the hinges and pins and their material - as there is in the whole stove and the selection of 10mm, 12mm and 16mm mild and corten steel in the build of its many parts
but we'd be here all day . . .
The point I am making is I am quite capable of making a "better" hot water heater . . .
BUT I derive a lot of enjoyment from my "free" shower from something I knocked up one afternoon in the workshop when the boss was away, which cost almost nothing, has no moving parts and works really well
As you say, each to his own