So the water tanks that need to go into the luggage bay are huge – I suppose my eyes were larger than my appetite, because after I got the tanks I realized that they were about an inch higher than the gap between the deck of the bay and the frame rails. After a little bit of hydraulic jack assistance, I was able to squeeze two of the tanks between the rails.
After this however, you can’t just (in good faith, anyway) leave them there and fill them up. Each tank when full of liquid is 390 LBS. Two of the tanks will be clean, and two are waste (gray). Technically, all four could be full, with a combined tankage weight of 1560 lbs, which is 3/4 of a ton.
That’s a lot of weight!
This is a 3/4 ton “pickup truck”, which means that what is pictured below is what’s required to haul 1500 lbs around in the bed safely. Yes, that is a gross simplification – I know that truck can carry more…
Anyway, after crunching some numbers and throwing about numbers related to young’s modulus, moment of inertia, and point loaded cases, I came up with a design to cradle the tanks off the frame rails that makes me happy enough.
Here it is pictured with the tanks and the chassis frame rails. The three across is towards the back of the vehicle. Not pictured are the cross members of the truck frame.
Here’s a simplification with the tanks removed to see the cross beams. Most of this assembly is in tension, so it’s more about hanging below than supporting. I have not built a lot of suspension style assemblies like this.
And here’s a picture of just the bits I want to assemble. Not shown are the fasteners and assembly join plates so I can actually put it together in the bus. Each truss section is individually built, and the cross-legs are then bolted onto the truss sections.
All in all, it’s a compromise – cost, weight, ease of assembly… I would have wished to have added the structure outside the luggage bay but it would require complete deconstruction of the bay floor. The bus is pretty low at the belly already as well.
The dynamics of carrying water are daunting, from all the movement, to the fact that it’s riding along in a moving vehicle and bouncing/sloshing is sort of scary.
I have a materials quote available, so maybe in the next week or so I’ll get my pile of steel and get to putting this monsterpiece together.