Thread: Off road camper build

Flaps
First up I dont build offorad box trailers with tents - I do the offroad boat trailer thing!
But I have played a fair bit with things dragged behind 4x4 a bit and will make a few comments!

First up - your frame seems pretty solid
You could have saved some weight going to a lighter section but it certainly fits in with the "if in doubt beef it out" motto of most backyard engineers!!

Second - In its current state Im not in love with your hitch setup
You have used 100x50xstupid thick chassis rails resisting the killer force on all single axle trailers (ie verticle dynamic loads) and compromised that strength with some 10mm or whatever flatplate - At the very least run some gussets (call them sliders) of flatbar on edge along the underside of the hitch plate and along the a-frame 300mm or so - This is to transfer the verticle loads from the hitch into the Aframe

Third (and this one is a soft spot for me as I have been here before) is your swing arms!
-65SHS5 would have been my choice but irrespective of that
-The location of the spring mount (fulcrum) vs the contact of the tyre vs the chassis attachments is gonna lead to some super funky camber / bush loadings / tyre scrubbings / poor load control
-Sure go with it for now but WHEN not IF it annoys you - Cut up the swing arms and make a stepped axle then mount four links ; 2 outer chassis rails to underside of axle straight links then 2 inner chassis to upper stepped surface of axle triangulated links
-I also have slight fears for the strength of your stub axle flange (compare it to the flange used by LR or Toyota)

In honesty - the whole independent suspension thing is wayyyyyyyyyyy overdone by the trailer industry
On a single axle trailer you will never garner the benefits of independent suspension but will have to compensate for all the negatives (varying geometry with load and suspension height & non cross axle load sharing to name the most significant)

You know that now is the time to make changes to your build which makes you smarter than me - I just kept building junk and hating it till I learnt the lessons above

Steve

Man what u just said about the swing arms is very hard to understand u couldn't explain it any better could u. i was going to add a gusset under the hitch point but thought it would be strong enough but might just do it anyway its always better to over engineer.

cheers

That there is sorta what iv copied. Cruisemaster® Independent Coil Suspension

Looks cool.

the things I would look at:

Xmembers and outriggers - I never let the kids run Xmembers and outriggers into the chassis rail at different heights. When the trailer flexs it works the sidewalls of the chassis rails and they crack around the welds. We tend to run the same depth for the Xmembers and the main rails, but run the Xmembers in a lighter or narrower section. You've done it now, but perhaps looking at running corners of RHS between the rails to bring the forces from the sidewalls back in to the top and bottom plates of the main rails which is where the strength is in that plane.

Axle mounts. These look well braced, but I would run a flange around the plates that bolt together on both plates again to prevent flex at the corners of the plate and latter on fatigue cracking.

The upper spring perch - same, flange to prevent the plate from flexing and fatigue cracking all over it.

Front Xmember. For an offroad trailer, I'm not sure if a 50x50 Xmember will be strong enough. A great section drawbar by the looks of it, but the main load that goes through the draw bar is levered off the front Xmember. I'm not sure what section the draw bar is, 100x50? and if thats the case, the draw bar might be somewhere around 4x stronger than the Xmember (but the Xmember is loaded in a stronger way than the drawbar).

Front coupling plate. I would look at running that 10mm plate between the drawbar rails and mounting the coupling between the drawbar rails with the handle and ball receiver protruding. It will be a much stronger and fatique resistant setup if you want the coupling down low.


BTW, I still think it's cool.

Cheers man its good to get some feed back i am going to weld the axles in with a gusset once i get the wheels on then use some sort of caster correction to correct any toe in or camber. Like danny did his idea is good

Great tips on bracing and hitch mount Simon - I hadnt noticed the 50SHS cross member

Flaps I assumed the frame was not completed and gusetting was still to come

With regards to the swing arms - have a look at that cruisemaster setup
The bottom spring perch is located outside the outer suspension link

On yours the spring is well inside (I did this once too!!! my geometry was almost exactly the same as yours)
What this means is the camber load on your setup has the coil as the fulcrum and will lever between you chassis links
Camber will be very hard to control with the spring this far inboard

When I did essentially the same geometry as you I actually aimed for about 2 degrees of positive camber at ride height (I wanted 0 but figured it would load up so +2 would allow it to load back to 0) - but when loaded and driven it pulled down to nearly 4 degrees negative camber - This means flex in links and bushes was allowing 6 degrees of camber (thats a lot of load in what seems a "rigid" setup) So even though it looked okay (for a racing trailer) it scrubbed tyres - so a few trips later I changed it

I think there will be too much leverage and camber in your current geometry
All my rambling in the last post was that I modded my setup to a solid axle with "triangulated 4 link" search on google or look under a 200series rear axle to get the concept

The benefits beside fixed camber and castor were astounding
I was able to drop the spring rate as there was a measure of cross axle load sharing (you could do this with an anti roll bar)
The trailer was more stable at speed
The suspension worked just as well

Anyways I clearly need another coffee as I am now rambling!
Please dont get me wrong - I love that you are building and it looks very tidy
Just trying to save you the time of rebuilding it

Steve

both suspensions taken to the extreme-


note the wheels on the buggy are exactly upright at full droop
and again, at full compression


Flaps, these guys make it happen for exactly the same reasons as you,,,

Upper and lower links though Pedro - only way to control the wheels like that.
Or is that your point?

If I was to build another independent design on a trailer (but i wouldnt )
I would run upper and lower links - it really is the only way to control camber and caster

S