Well I broke it, in Canada

[gait]

What would capture the fore and aft movement of the camper? You need to restrict motion. Something like this:View attachment 409152

I have 6 of something like those, in a length of about 2m towards rear of chassis. Then two spring mounts at the front of sub-frame.

I've forgotten the end of the calculations, a 5 degree twist over 4m (length of the sub-frame) is twice (in mm) that over 2m.

I used to have three point mount, with solid mounts about 1m from front of sub-frame. Pivot at rear of chassis. Extra spring mounts in between.

There was twisting evident at the fixed mounts, which would have resulted in sheared bolts (like Puggles but in different place) without some occasional maintenance. Current system is many kg lighter as I overdesigned the pivot. Current system seems to be maintenance free, though nothing is inspection free.

Both work in decoupling body from chassis. Both constrained end to end as well as side to side movement.

Re-inventing wheels is fun. One-off projects are fun. Until, as Owen insists on pointing out, it goes wrong.

During design, ensure that everything is accessible and maintainable. So far I've been lucky.

 

[gait]

This is definitely the type of mount that would give fore, aft and lateral support.

My only concern with this specific mount design is the tolerance between the sides of the upper and lower mount, which looks pretty tight in this photo.
When the chassis flexes (twists) it will change the vertical axis of the mounts. This is even more relevant on the FG if you have mounts in front of the step as well as behind it, as the mounts would also be on a different plane.
There needs to be sufficient clearance in the mounts to allow for this.

very important .... take note. Its the equivalent of me saying my original fixed mounts had twisting applied. Different way of saying it.

 

[The Artisan]

Thanks for all your feedback. After researching it sounds like your guys spring design is the way to proceed. In my case my bed frame would be be taking the twisting forces, as my camper is removable. I have have not found the answer but is there an advantage going with a single, dual or 4 spring setup. What spring rates are most using, and how heavy are your campers? I assume you are using die springs. BTW, the vibration mounts I posted are $1,100.00 each, made for he industrial applications.
Kevin

 

[kerry]

Not sure if this as any relevance at all, but many garbage trucks around here have those spring mounts.

 

[The Artisan]

Seems like this is popular
http://www.svitrucks.com/wp-content/uploads/2016/05/body-mount.jpg
http://www.svitrucks.com/wp-content/uploads/2016/05/sub-frame.jpg
Kevin

 

[gait]

Thanks for all your feedback. After researching it sounds like your guys spring design is the way to proceed. In my case my bed frame would be be taking the twisting forces, as my camper is removable. I have have not found the answer but is there an advantage going with a single, dual or 4 spring setup. What spring rates are most using, and how heavy are your campers? I assume you are using die springs. BTW, the vibration mounts I posted are $1,100.00 each, made for he industrial applications.
Kevin

the difference between single and dual springs is finding the space so multiply design time by a factor (its nice if the same mount can be used in all locations else multiply everything by a bigger factor), multiply holes, bolts, washers, nuts, spring retainers by two, multiply mounting holes, nuts bolts washers by a factor, multiply manufacturing time by a factor, multiply assembly time by a factor.

basically time, money, and I can't perceive any significant engineering advantage.

"die spring" isn't terminology I met. But all the design considerations that implies were part of the overall design (will it fit and work) and the discussions with spring manufacturer (wire diameter, number of turns, spring rate, etc.). My mounts are welded rather than formed, so little things like welds can be stronger in compression than tension. There's a tendancy to over design for one-off projects.

 

[The Artisan]

Gait,
Thanks. Nice thing about my FE is that my tank sits between the frame rails, so its easy to access all the swiss chz...... Thoughts were 3 sets on each side
Kevin

 

[gait]

Gait,
Thanks. Nice thing about my FE is that my tank sits between the frame rails, so its easy to access all the swiss chz...... Thoughts were 3 sets on each side
Kevin

I have water tanks between the rails, fuel tanks both sides. There are places in Aus where one fuel tank is insufficient.

Description of mount locations in earlier post. I have three sprung mounts within 2m. Extra spring support at front. But that's unusual, just me being cautious about twist. Convention seems to be three each side over length of sub-frame.

Fibreglass foam panel construction on steel sub-frame is about 250kg of panels and total less than 500kg plus 260kg water (tanks attached to sub-frame). Design aim was total less than 4500kg total. Things like solar on roof can add a lot.

On recent trip I got a bit too much above walking pace downhill through some alternating deep scallops - I discovered the resonant frequency at which the vehicle oscillates side to side, and the accompanying clunk as the spring mounts did their work and reseated.

 

[The Artisan]

Gait,
Under mount service boxes will hold my water, genset and batteries. I think I will be around 1500lbs when I add the polyurea coating to my pod. As stated previously, I wont be doing much off grid camping but as ski said better have it than not. Plus I need to convert it to 4x4 which will be a while.
Kevin

 

[SkiFreak]

I have have not found the answer but is there an advantage going with a single, dual or 4 spring setup.

ATW are arguably one of the most knowledgeable and experienced when it comes to mounting bodies onto Fuso/Isuzu light trucks. Their standard setup is 4 single spring mounts per side, but they go to 5 mounts per side on heavier builds.

Single or multiple springs on the mount is a totally different discussion. As Gait has already noted, a double spring setup will normally take up more space. Normally these mounts are wider but not as high, which could be beneficial in some setups.
Technically, as long as the combined spring force of all mounts is the same it should not matter how many springs you use. Multiple springs on a mount will give you a more "precise" spring movement, but I do not know how beneficial that would be, if at all.

Working out the correct spring rate is complicated and there is no "standard" for this, as it will be defined by the individual setup. One thing to remember is that the spring mounts are on the chassis, not the outer edge of the camper box or tray. This means that there is a significant increase in the leverage factor. A normal camper internal layout positions most of the heavy items against the walls, so, if you know anything about levers you would understand that this has a significant effect on the force applied to the mounts.

Basically, there is a lot to consider when it comes to designing the spring mount system that will be used. As with any design... the devil is in the detail.

 

[The Artisan]

Thanks Ski, yes I did consider the cantilevered distance from the springs locations and its effect. If you look at my design my weight is on the ends of the pod and the middle section is basically empty. Another option is hard mount the bed with ubolts and make the camper pod move. The mounts would be on the outer edge so not as much leverage. Am I looking for a spring that compresses or extends a few inches?
Kevin

 

[pugslyyy]

So back to the original subject of this post, me breaking my spring hanger bolts in the great white north...

I was able to beg/borrow (not steal) hardware to do a temporary repair on the Dempster, and then got some 1/2 inch bolts in Inuvik. tbh I'm not even sure what grade they are. I installed these when my "found" hardware started to fail on Top of the World, and now that I made it to Anchorage I have been able to procure better hardware (grade 8). As has been noted, the original bolts were M10 so the 1/2 (same thickness but different threads as M12) should be considerably stronger.

At this point it is still a trail fix that I am keeping an eye on, but I was able to catch the latest failure before everything came completely apart again. I also have replacement rear shocks on order that will hopefully come in tomorrow or Wednesday which will further improve things. Last year I replaced the front shocks but not the rears. The rationale for that decision made sense at the time, but eludes me now...

 

[SkiFreak]

The rationale for that decision made sense at the time, but eludes me now...

I can't count the amount of times I have encountered the same situation.

 

[pugslyyy]

I can't count the amount of times I have encountered the same situation.

Well there's only so much you can do... but as I watch $1000 of tyres get chewed up because I saved $200 not replacing the shocks...

 

[dlh62c]

So back to the original subject of this post, me breaking my spring hanger bolts in the great white north...

Glad your back on the road.

Geographically speaking, a road trip to Alaska from the lower 48, is all uphill.