Enclosed "Off-Road" trailer ideas, looking for input.

R_Lefebvre

Expedition Leader
I've been considering getting a camping trailer for a while now, ever since I got this truck which will allow me to tow something substantial. I've looked at the Adventure Trailer type setups with unfolding tents, but... other than providing a hard floor, and cargo capacity, I don't see how they have much advantage over a regular tent. Also, I'd really like to be able carry a couple of dirt bikes, and everything but the Kimberley Kamper aren't really ammenable to that.

I've looked at the Fleetwood Evoloution type pop-ups, but those can't really be taken off-road due to their size and weight.

And then there's always cost. I don't have that kind of money lying around right now.

A few posts on this forum got me thinking about building a teardrop style off-road trailer. Only, it wouldn't be teardrop shaped, because I don't think that really looks very good behind a modern vehicle. Here's some of the idea I had, and just wanted some input.

- Shape will be very similar to my Discovery 2. Intent would be to have it follow the exact same hole punched in the air as my truck. I figure this should allow for a very generous size, while still allowing low fuel consumption? Net result would be you could almost stand up in the thing, since the Disco is so tall. It might also allow a bunk or two to be mounted crosswise inside the cabin for young'uns.

- The "footprint" would probably be about 5x8. The intent is to use the same wheels and tires as my truck, with the same track width. For obvious reasons. I'd intend to have the wheels tucked into the body with only a small amount of flare sticking out.

- Axle would probably be a 3500lb axle with hub adaptors to get to the LR bolt spacing, unless there's a better way. I'd use 2000lb springs or whatever else would be suitable. I personally like torsion axles, have them on my Seadoo trailer, but I think leaf springs would be more reliable, easy to fix, whatever...

- I think the axle would be 5/8ths or 3/4 of the way back, leaving a 2-3 foot rear overhang. This might result in a bit of a high tongue weight, but I'm trying to reduce rear overhang. I was also thinking of maybe having the rear frame have a kick-up, at least 6", for even better departure angle.

- Intend to mount two rails cross-wise on the tongue which could support a motorcycle. I'm a little concerned about the resultant tongue weight. I also thought I could put one rail in front, and use a plug in rack on a rear mounted reciever for the second. That would balance out the weight better. I already have one of these racks and use it in my reciever on the truck and it works. The other big issue with one, or two bikes on the front tongue, is they are long (and mounted width wise), and could restrict manoeverability via jack-knifing. Though, I'd be unlikely to use the camper off-road, with the bikes at the same time. It would sort of be an either-or affair.

- The space in the body in front of the wheel wells would be used for water tanks. In the rear, storage cubby holes.

- Another crazy idea I haven't seen done before... put a washroom on top of the tongue just ahead of the main cab. The height of the body might be such that one could take a shower standing up, and/or have a chemical toilet in there. I haven't quite sorted it out yet, but having facilities for a shower sure would be nice. At the least, I'd like to find a place for some sort of toilet. This space would extend the overall length of the body to 10', but it would be pinched in at the front to follow the angle of the tongue.

- Alternatively, maybe build a platform on the tongue, and make provision for a fabric "shower curtain" enclosure to be installed. The portable toilet could be sat on the same platform and the curtain used as well.

-For styling, and maybe utility, put a rack on top to match the rack on the truck. I was thinking about putting a kick in the roof as well, but that might be too much effort for styling. However... if the kick was actually facing backwards, it could help with wind drag.

Thoughts?
 

R_Lefebvre

Expedition Leader
That's what's inspired me, already saw those. Was just looking for some input on further evolution. The main question is, if I make it the same size as the Disco, will I get the extra space, with no extra drag?
 

jcbrandon

Explorer
... if I make it the same size as the Disco, will I get the extra space, with no extra drag?

Short answer: no.
More useful answer: That's probably the best way to do it.
Since the tow vehicle is not shaped like a tuna, the air immediately behind the rear is significantly disturbed. Lots of turbulence there. Since you cannot practically marry up the skin of the trailer to the skin of the tow vehicle, the front of the trailer will continually crash into this turbulent pocket of air at the back of the tow vehicle. This will increase drag.

This increased drag could be minimized by careful sizing and shaping of the trailer. But that would reduce interior volume on an already minimal box. It would also require sophisticated CFD modeling tools not readily available to most home designers.

Since you are already driving a pretty much square box with rounded corners, I think the return on investment in trying to minimize drag won't pan out.

I'd suggest just building something about the size you want, that looks the way you want it to, and smile at the result.
 

Hilldweller

SE Expedition Society
I saw the perfect thing the other day but have no idea who makes it. It was a large enclosed utility trailer like a haulmark, but not quite as tall. Had rear door and one side door; I think I also saw a vent on top.
Looked like the owner had replaced the axle with a big one with full-sized wheels and tires.
All it needed was windows, a few shelves, batteries, water tank, and a bed...
 

ntsqd

Heretic Car Camper
For the tongue weight & axle loading treat the side view to a simple Shear-Moment Diagram. Include the usual distributed & point loads etc., nothing new there. That is one of the basic premises of this book: How to Design and Build Trailers — Vol. 2 I've referred to it on several trailer builds and I've found it to be helpful. I do not have Vol. 1, but out of curiosity it is on 'the list.' I wish that I had a starter value for the trailer tire sidewall stiffness variable in Vol. 2's Critical Speed Prediction formula (predicts constructive interference minimum speed) as I think that would be a handy calculation to know the results of.

FWIW my granddad's very unscientific RoT was that the unladen tongue length be at least 1/3 of the distance from the ball to the axle. The two trailers that I know that this was applied to (one he built and one I built) tow excellently, laden and unladen. Applying the RoT to the S-M diagram for the one that I built made the numbers look good there too. The one that I built has been stability tested by a friend to 80 mph on the way to San Felipe. ;)

I've found that "filling the hole" behind a very brick shaped tow rig ('66 Econoline Extended body Van) does aid fuel economy, even if what fills the hole is not terribly aerodynamic. Flat towing the fiberglass dune buggy behind that van actually slightly increased the fuel economy at the same road speeds. That said, I concur with JCBrandon in that a trailer of the same frontal size probably would not have done that. The DB has a considerably smaller frontal cross section than did the van.

HTH
 

riprod

New member
Afrispoor Trailers

Have you guys seen the Afrispoor Off Road trailers.

As far as true Off Road Tent Trailers go, I think that it is pretty impressive. Super high ground clearance. Full kitchen, fridge, 12v batteries, optional generator and tent that expands out to about a 15 x 15 area with queen size top bunk bed.

Any thoughts on these ? The website is afrispoor.com
 

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