My box uses the original Iveco mounts.
The box is built on 2 rails which are then bolted directly onto the Iveco mounts. I think I have 3 mounts down each side (I must confirm this) because it’s a LWB. The truck’s done 220 kkm around Africa, OZ and Europe with its 3 owners. It’s an all wood box and is still holding up fine.
When it was first commissioned the original owner took it round the LRE track at Solihull and all were pleasantly surprised; it wasn’t penalised by the box.
All that to say that you’ll get by with a simple subframe, and that the Iveco mounts are very good.
The next upgrade would be a tubular steel subframe (100 x 100 box section for example) still using the original mounts. That would seriously minimise the flex in the box. On the rare occasion that the chassis flex exceeds the mount travel, the subframe would end up working against the chassis flex (effectively stiffening the chassis) It’s not perfect, but it’s a step in the right direction without modifying the chassis mounts.
(for info, the Bremach has a welded tubular steel chassis. On the few campers that I’ve seen on Bremach, the box is bolted directly to the chassis. No mounts, just sikaflex mastic!)
If you’re a greenlining LR axle twister you need to be sure of the travel. To do this, if you have the time, you could knock up a frame which is bolted to two of the mounts and just sits on the other two (the box itself would probably do); load up to your MGVW with whatever crap you have around and drive one wheel up a ramp until another lifts. Now you can see the total travel necessary without having to do any sums ( ;-) ) I’m just lazy Roger, please don’t take offence.
If it’s less than the travel available with the standard mounts, you have the solution.
If it’s more, you can:
Either Install a chassis cross member on which you mount the original mounts closer together; the closer they are the less they will travel, for the same load capacity.
Or Fabricate a pair of long travel mounts, based on the same principle as the existing, replacing the rubber with springs and using a longer bolt (it’s possible that a commercial truck body builder has such a beast, or even that their standard model has enough travel for your application
Or go the 3 point Unimog route, raising the box up way too much.
Or the 4 point route: 2 mounts/pivots fore and aft on the centreline of the chassis, and 2 mounts left/right near the front spring hangers. On the Unicat and similar, the centreline mounts are in fact pivots, but IMHO that’s overkill, and a pair of normal mounts in the centre will happily take the twist we’re looking at.
It looks like you won’t need to twin up the rear, but if you can find some wheels with less offset the truck will look better (WM wheels?). And while you’re at it, make sure the box can clear a set of 9 x 16 (or metric equivalent). The gearing is short and they’d help. Even if you have no intention of putting them on yourself, one day you’ll probably sell the van and a future buyer might want to (apparently the front wings need mods to fit 9x16).
Oh yes, try and mount that silly little tank behind the axle. If you bolt custom tanks directly onto the box floor, you’ve gained the height of the subframe in capacity. Mine has a 130L tank on each side and the original 90L mounted behind the axle – means you can really be picky about where you fill up; and save! SWB might be less, but worth it.
Hope this helps.
Back to my other work avoidance tasks…