Well, I broke it.

[canter tourer]

Nice workshop, will make the work ahead of you so much easier, good luck!
Split apart like that, it kinda looks like the makings for a super heavy duty trailer now

 

[pugslyyy]

Nice workshop, will make the work ahead of you so much easier, good luck!
Split apart like that, it kinda looks like the makings for a super heavy duty trailer now

I was pleasantly surprised at how easily it finally came apart - when I'm dealing with big heavy stuff I like to have a good plan and no surprises. You are dealing with a lot of weight so if anything unexpected happens it is usually not pleasant.

 

[Overland Hadley]

So, more or less, the subframe was holding the back half of the truck to the front half?

 

[pugslyyy]

So, more or less, the subframe was holding the back half of the truck to the front half?

That and the brake lines.

 

[westyss]

Looking at the pictures I see that the rear pivot point is quite aft of the rear wheels and in fact look like its actually mounted onto the frame extension, with that set up I sure can see why the frame broke and do hope that you re and re the mounting system to reduce the lever effect on the frame.
With most of the weight of the camper resting on that part of the frame I can definitely see where the stress accumulated simply driving normal road conditions and driving over a bump the load increase at that rear pivot pushing down, above the wheels static and providing the upward motion lets say and then simply the weight of the cab and motor pushing down resulting in the frame being bent, ie crowned then straightened in a continuous motions over the smallest bumps.
Not sure if that makes sense or not but out of that I see a need to get the bulk of the camper weight right above the rear wheels if you were to retain the pivot system or like others have commented on go with a fully supported frame and avoid the point loads to save the new frame.

Sure is a bummer but it looks like you have a great shop to get the work done and wish you the best of luck to get it fixed up and travelling again.

 

[pugslyyy]

The new frame is going to be about 200% stronger than the old one, and I intend to go to the spring mounts the length of the sub frame, with oak sandwiched between the frame and subframe.

 

[SkiFreak]

...with oak sandwiched between the frame and subframe.

Have you considered going with polyurethane? The main advantage with using polyurethane is that there is no possibility of rot, so less maintenance down the track.

 

[pugslyyy]

Have you considered going with polyurethane? The main advantage with using polyurethane is that there is no possibility of rot, so less maintenance down the track.

I have, but am not familiar enough with the properties and how to spec thickness, etc.

 

[Buckstopper]

Oak is pretty tried and true. Most commercial truck bodies are mounted that way. It is also cheap and not that herd to replace. I haven't had any issues with mine mounted with oak.

Note that you do have to secure it. Mine is bolted with a few stainless steel flat head bolts to the subframe. The heads are countersunk into the wood so no exposed metal to rub and no holes drilled into the top flange of the truck frame. I have also seen banding used but the bolts are a bit more elegant. I also oiled the oak really well then painted it before I installed it.

Buckstopper

 

[pugslyyy]

Oak is pretty tried and true. Most commercial truck bodies are mounted that way. It is also cheap and not that herd to replace. I haven't had any issues with mine mounted with oak.

Note that you do have to secure it. Mine is bolted with a few stainless steel flat head bolts to the subframe. The heads are countersunk into the wood so no exposed metal to rub and no holes drilled into the top flange of the truck frame. I have also seen banding used but the bolts are a bit more elegant. I also oiled the oak really well then painted it before I installed it.

Buckstopper

Thanks, that's what I'm planning on doing. What did you use for oil?

 

[SkiFreak]

Oak is pretty tried and true.

Just to be clear... I am definitely not saying that using oak is bad, as it's obviously been used for this purpose successfully for many years. I was simply suggesting a possible alternative.

 

[pugslyyy]

Just to be clear... I am definitely not saying that using oak is bad, as it's obviously been used for this purpose successfully for many years. I was simply suggesting a possible alternative.

Yeah understood - I would be interested in learning more about that approach, but have not been able to locate good subject matter expertise on alternatives to oak at this point.

Thanks!

 

[SkiFreak]

Polyurethane

Not being someone that intentionally goes about reinventing the wheel, I discussed this matter with a company that made polyurethane products when I was looking for for a solution for my truck.
They had done some jobs for fire trucks and it was suggested that a Shore A hardness of around 90 was ideal for the separator between the chassis and subframe, so that's what I went with.

I mounted the polyurethane using an encapsulated method, that being supports on either side. The polyurethane is secured to the subframe with bolts having a 200mm (8") spacing. The polyurethane was counter-bored so that there was sufficient clearance between the top of the bolt head and the face. There is a flat washer and a spring washer that give some tension to the polyurethane, but the primarily bolt securing method is Loctite 243, which stops any vibration undoing them.

 

[pugslyyy]

Not being someone that intentionally goes about reinventing the wheel, I discussed this matter with a company that made polyurethane products when I was looking for for a solution for my truck.
They had done some jobs for fire trucks and it was suggested that a Shore A hardness of around 90 was ideal for the separator between the chassis and subframe, so that's what I went with.

I mounted the polyurethane using an encapsulated method, that being supports on either side. The polyurethane is secured to the subframe with bolts having a 200mm (8") spacing. The polyurethane was counter-bored so that there was sufficient clearance between the top of the bolt head and the face. There is a flat washer and a spring washer that give some tension to the polyurethane, but the primarily bolt securing method is Loctite 243, which stops any vibration undoing them.

View attachment 235815 View attachment 235816 View attachment 235820

excellent, thanks! How did you determine the appropriate / maximum / minimum thickness for the polyurethane?

 

[SkiFreak]

Given that the polyurethane compresses very little, especially if spread out over a large area, the thickness is not that critical. As I see it, the thickness is determined by the fixing method that will be used.
I went with 25mm x 50mm (1" x 2") bars of polyurethane, as this allowed me enough thickness and width for the counter-bore when using M10 bolts with a flat and spring washer. The head of the bolt is about 4mm (5/32") lower than the wear surface and there is about 10mm (3/8") under the washers, which I think is plenty.
With this setup the top of my subframe is 75mm (3") above the chassis at the front.