Frame flex fundamental question

GR8ADV

Explorer
I spent two days done at ATW and did not pay attention to that. Can someone explain how it works. I did see one of the spring mounts. How many more are there and how is the frame isolated. Thanks.
 

GR8ADV

Explorer
Yes I have seen these and this is similar to what is in the alpha. I do not understand how his isolates the box. Can you explain?
 

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DzlToy

Explorer
I do not understand how this isolates the box
I don't think that it does isolate the box, hence my original post here about rigid mounting a box and using a properly designed suspension.

Rob Gray is no dummy, so maybe he knows something I don't, but I just don't see that a few springs and some plastic as the answer.
 

k9lestat

Expedition Leader
Robs design allows the frame to flex without the box binding the frame, or the frame stressing the integrity of the box.

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GR8ADV

Explorer
Robs design allows the frame to flex without the box binding the frame, or the frame stressing the integrity of the box.

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I don't understand how with this design. I am not questioning, I just have questions. Please explain how this minimal gap does that. Thanks.
 

k9lestat

Expedition Leader
On the three point system you have two mounting points on on end of the box. During the frame flex these points move with frame. The other end has a single point centered between the rails. Which does not move with the frame, this way there less stress placed on your camper box.

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k9lestat

Expedition Leader
Did that help. The reason I referred you to robs build is its got visual aids to help explain

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GR8ADV

Explorer
W
Ok I am almost getting smarter. The concept is very sound. I am having trouble of how it functions in the real world. In the pic below which is pretty typical and is the same in the side of the ATW

image.jpg

These are not shown on the sketch in the link I don't believe.

image.jpg

My headache is that these appear to limit the great frame movement in the sketch link to less than one inch to the frame. Thus when the frame drops to the left as shown the left spring (not shown) extends and the right side spring (not shown)!contracts. But it can only contract until the apparent very small gap is covered and it hits the frame in the right side ( way less than one inch or less) then it is business as usual with no spring benefit. I can't see a meaningful benefit. Now in the sketch link it shows a tremendous amount of frame flex before contact. Now this makes sense but does not jibe with what I 'think' I am seeing. But I really think I am missing something.

Sorry to be such high maintenance....
 
Last edited:

k9lestat

Expedition Leader
It's been awhile since I read his build but I don't think these were in his final set up let me go read. The spring here from what can gather is to let springs allow for movement. But it looks like those springs for force to allow movement. I'm not a mechanic. But if you had camper box on that system it be subject to more stress than with the three point system.

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k9lestat

Expedition Leader
This article discusses spring mounts well.

http://www.truckcampermagazine.com/off-road-expeditions/the-overland-fuso-truck-camper

I think that the camper box reduces frame flex and the spring mounts just allow enough flex to reduces point loads from occurring. I don't think you need to allow as much flex as a bare chassis allows - they expect there to be something to be mounted there after all...
Yeah what he said

Keep reading the next few days of the build diarie. I think it'll become more clear.

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GR8ADV

Explorer
This article discusses spring mounts well.

http://www.truckcampermagazine.com/off-road-expeditions/the-overland-fuso-truck-camper

I think that the camper box reduces frame flex and the spring mounts just allow enough flex to reduces point loads from occurring. I don't think you need to allow as much flex as a bare chassis allows - they expect there to be something to be mounted there after all...
I can see that mounting a rigid box directly along the frame would change the stress pattern along the frame. However that is how they intended them to be attached. So yes it will change it but exactly how they intended. If it is mounted per fuso with several u bolts and wood there arenvirtually no point loads so I am not sure what you are referring to. The only point loads on the frame rails that exist are the ones created by the side spring mounts???

Not sure if I need more sleep or more coffee or more beer. I am starting to feel pretty thick as I am apparently the only one who does not understand this. Thanks for humoring me.
 
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