Isuzu npr 4wd

[SkiFreak]

Basically... if you want to totally remove the possibility of wood rot, avoid using wood.

I should add that buildup of moisture at the floor level does not necessarily mean that you have water leaks.
This could also be caused from things like cold bridges, or simply having humans in the habitat, which can result in increased condensation inside.

 

[gator70]

Auto manufacturers stopped using wood (except for decoration) in about 1950.
There is no wood in my expedition vehicle builds. There are better materials.
Cheers,
Peter
OKA196 motorhome

Interesting

All the van builds have wood floors.

And I have seen wood on all Lance truck campers

 

[gator70]

@SkiFreak Gave me the idea to hang a tank off the subframe

I want to hang a medium Aux freshwater tank there.

Does anyone have any good practice advice?

Seen below is the idea, concept example

 

[rruff]

Does anyone have any good practice advice?

Don't use wood...

 

[SkiFreak]

I don't know what the rules are in the US, but I always design my tank frames to withstand a crash impact.
There is a lot of dynamic weight in a tank full of water.

 

[gator70]

When calculating the habitat clearances over the cab roof and mounted to the truck frame. I left 4 inches of clearance to the cab roof. The frame will twist and based on my articulating subframe there is movement. More so further down the frame over the rear axle. Never-the-less I left 4 inches of clearance.

 

[SkiFreak]

I left 4 inches of clearance to the cab roof.

I probably would have left a bit more than that, but it's your build...

 

[gator70]

I probably would have left a bit more than that, but it's your build...

I calculate a side to side movement by the cab of 2.5 inches.

(rear "subframe" springs only allows a 5 inch movement)

So:

• Bed length: 14 ft = 168 inches
• Twist amount at rear: 5 inches
• So, the twist angle:
  θ=tan⁡−1(5168)≈tan⁡−1(0.0298)≈1.71∘\theta = \tan^{-1}\left(\frac{5}{168}\right) \approx \tan^{-1}(0.0298) \approx 1.71^\circθ=tan−1(1685)≈tan−1(0.0298)≈1.71∘
• At the front, the vertical offset is:
  Offset=distance from twist×tan⁡(θ)\text{Offset} = \text{distance from twist} \times \tan(\theta)Offset=distance from twist×tan(θ)
  For the front corner directly above the wheel in the ditch:
  =0(the twist happens at the rear)= 0 \quad \text{(the twist happens at the rear)}=0(the twist happens at the rear)
  But if you mean the diagonal opposite front corner:
  Then the twist is spread corner-to-corner, so the opposite front corner is lifted:
  Movement=5 inches (diagonal)\text{Movement} = 5 \text{ inches (diagonal)}Movement=5 inches (diagonal)

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✅ If the bed is allowed to flex evenly front and back:
Then the front mount takes half the twist:

• So the front corners could move about ~2.5 inches up or down relative to the frame.

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✔️ Answer summary​

It depends on the mounting:

• If all the twist is absorbed at the back: Front movement = 0 inches
• If twist is equally shared front and rear: Front movement = ~2.5 inches

 

[Ultimark]

I'm not 100% sure of your figures as mathematics is my weakest subject, plus my NPS has a shorter wheelbase (medium) in Isuzu land.

Sometimes what you work out on paper is fine, but sometimes there is, or there can be, an exception. No doubt you will find this out as did a close friend who has done something very similar to your proposal, but on a European truck. His remedy was to lift his camper by about 30mm from memory by using spacers of some kind; it did work and after about 8 years, it's still running well.

Attached is something you may have seen before, this is my NPS with the front and rear axles running right to their limit, but in opposite directions, thereby inducing chassis rail twist. My tray is attached to the chassis rails in a very similar fashion to your set-up, as you can see, the cabin is twisting in tune with the front of the chassis rails, while the tray, containing the bolted on camper, is more in tune with the rear section of the chassis rails.

Our suspension set-up allows the live axles to swing in a 600mm arc from the very top to the very bottom of the arc. Looking at the cabin in relation to the camper it does appear that your calculations may be pretty good, but do remember I have a shorter wheelbase and therefore shorter chassis rails, at least I think my chassis rails are shorter as I cannot remember what your base truck is.

Mick.

 

[gator70]

I'm not 100% sure of your figures as mathematics is my weakest subject, plus my NPS has a shorter wheelbase (medium) in Isuzu land.

Sometimes what you work out on paper is fine, but sometimes there is, or there can be, an exception. No doubt you will find this out as did a close friend who has done something very similar to your proposal, but on a European truck. His remedy was to lift his camper by about 30mm from memory by using spacers of some kind; it did work and after about 8 years, it's still running well.

Attached is something you may have seen before, this is my NPS with the front and rear axles running right to their limit, but in opposite directions, thereby inducing chassis rail twist. My tray is attached to the chassis rails in a very similar fashion to your set-up, as you can see, the cabin is twisting in tune with the front of the chassis rails, while the tray, containing the bolted on camper, is more in tune with the rear section of the chassis rails.

Our suspension set-up allows the live axles to swing in a 600mm arc from the very top to the very bottom of the arc. Looking at the cabin in relation to the camper it does appear that your calculations may be pretty good, but do remember I have a shorter wheelbase and therefore shorter chassis rails, at least I think my chassis rails are shorter as I cannot remember what your base truck is.

Mick.


View attachment 886059

Thanks 100X for the comments

My wheelbase is 176. (crew cab)

And honestly I will not enter into that type of ditch you chose to enter into. My rig is not designed for jeep only type trails. There is millions of trails with less than that erosion in the western USA and Canada.

 

[gator70]

My rear spring mounts - 9 inches of spring length

5 inches after compression.

(needs mods before the finished product is mounted on the truck frame)



Point of reference - Australian brackets shown below (for sale)

 

[gator70]

Spring bracket mods

Instead of washers I will use these

 

[gator70]

One guys opinion about spring brackets (interesting)

 

[rruff]

So the front corners could move about ~2.5 inches up or down relative to the frame.

If your subframe rests on the chassis, then the subframe can only move up from the chassis... not down.

I like this video for showing how much twist is possible. This probably used springs with the rear fixed.

 

[gator70]

If your subframe rests on the chassis, then the subframe can only move up from the chassis... not down.

I like this video for showing how much twist is possible. This probably used springs with the rear fixed.

Extreme conditions - and it depends on the erosion ditch you are willing to enter. That ditch shown is 48 inch deep.

You will never see me do that.