PeteB wrote:Logic for leaving the stripped load bed was 1) simpler and quicker build, 2) suspect it must contribute to chassis strength, 3) will be strong and stiff enough to support a composite cabin.
Re recent post on Ivan's Tramp Build thread.
1) +1 with Ivan - definitely.
2) It does, but it's a moot point. The chassis doesn't need this augmentation. It'll perform just fine fully naked - or when incorporated with a (well designed and built) pivoting subframe (which allows full chassis deflection).
3) A qualified 'yes'. The bare load bed does NOT deflect very much at all under full cross-axle loads. I measured it crudely, Beep-Beep Tom measured it, well... like Tom does. Hopefully he'll pop up and take due credit, otherwise he did at one point post the work on his Beep-Beep blog (it may still be there).
With the completely standard chassis-to-loadbed mounting arrangement, it's just plain sensible to build a very sturdy box - which is why I specified my own panels with peripheral frames and (partially) interlocking rebates.
NB To relieve the torsional stress passed from the chassis to the load bed, I've also slightly tweaked the front chassis-to-loadbed mount. Not strictly necessary, perhaps, but it makes me feel better.
From what I've seen of my own and other builds, I suspect (but obviously wouldn't be so reckless as to guarantee) that a somewhat flimsier box might still be OK with the perfectly standard chassis-to-loadbed mounting system.
If required, I'd be reasonably confident in suggesting that the front chassis-to-loadbed mount could be further tweaked to allow still more articulation if combined with a further mod. That mod being: the second chassis-to-loadbed mount (a static nut and bolt) being removed and replaced with a (very conservative) opposing-spring arrangement - perhaps allowing a max of 10mm of separation at that point.
This combination would further isolate the standard loadbed's torsional stress.
All this said, my box is heavier than it strictly needs to be and we can still hit 7.5t. NB part of the solution is to keep wife-space to a minimum.
To qualify: wife-space is literally any space clumsily left available by the builder, into which a wife is genetically predisposed to quite literally cram utterly useless and wholly unnecessary items to be transported thousands of miles for absolutely zero logical purpose: actual or imagined.