Thread: A problem for all the budding engineers

Originally Posted by walker

I am just planning the build for my off-road trailer. It is going to be basically a 6x4 box trailer with lid but I am also building a rack above it to mount the Howling moon roof top tent I have.

Now the problem:

I have an annexe with the roof top tent which I would like to use when we stop for longer periods. This means that the base of the rooftop tent has to be above head height. (about 1900 to base). I don't want the tent up this high when towing as it would be higher than the roof of the Disco. I would like to be able to lift it up when we are stopped but keep it all as simple as possible.

My first thought was to have supports/legs in all 4 corners and have a smaller piece of square tube run down inside a larger tube and put bolts through to hold it in place when lifted up. I am a bit worried that doing this will cause too much movement when sleeping up there and that it might be too hard to lift up. the tent weighs about 60kg but the tube would have to be a fairly tight fit.

Any ideas?

If you carry a high lift jack, a base plate and slot for raising if it is within the range of the jack.
For stability, drill holes and weld nuts so the bolt can be tightened against the far side of the inner tube.
And weld a small piece of rod to the bolt head so you can do it by hand.
Just some thoughts!

Originally Posted by harro

If you carry a high lift jack, a base plate and slot for raising if it is within the range of the jack.
For stability, drill holes and weld nuts so the bolt can be tightened against the far side of the inner tube.
And weld a small piece of rod to the bolt head so you can do it by hand.
Just some thoughts!

I was thinking along the same lines,
Another would be to use a pulley system on each corner a cable boat winch on the trailor and locking pins on each corner.

I think you would need 2 high lift jacks to lift either end at the same time.

But I reckon you are right about welding on nuts and then use a wingbolt. I just onder if the whole thing will have too much flex/movement in it. I guess just use big heavy tube.

Originally Posted by dobbo

I was thinking along the same lines,
Another would be to use a pulley system on each corner a cable boat winch on the trailor and locking pins on each corner.

Not sure I understand that, but then I'm no engineer. To use a pulley, wouldn't you need a solid fixing up high to "pulley" off?

Not to knock you down.... but I have found that a neat to slightly loose fit will give you problems for several reasons.

Firstly, moisture will get in and cause oxidation which will jam the sleeves onto the poles.

Secondly, even if you could lift the thing on one side, it will cause the posts to go off vertical. Overcome this by mounting with bolts so that they pivot? Then the whole thing lays over without any vertical support whatsoever!

If you make the sleeves a loose fit, it will rattle, move in the wind or when you roll over in bed, and still be too heavy to lift.

You could try some heavy duty gas struts but then there would be a problem when trying to pack it up.

How about some wind up support legs, same as they use to stabilize the factory made campers?

I do not suggest cable or electric ones as there can be problems with batteries, cables/pulleys etc.

A couple of portable hydraulic rams to do the lifting and then a physical pin/ latch arrangement may work.

Originally Posted by walker

Not sure I understand that, but then I'm no engineer. To use a pulley, wouldn't you need a solid fixing up high to "pulley" off?

Yes you would four poles with pulleys on top and cables running,


I forgot height is your enemy.




Hydraulic or Pneumatic rams would be expensive but would do the job.

I'll go back to sleep now.

Originally Posted by walker

I think you would need 2 high lift jacks to lift either end at the same time.

But I reckon you are right about welding on nuts and then use a wingbolt. I just onder if the whole thing will have too much flex/movement in it. I guess just use big heavy tube.

A couple of attatchable angled bracing rods should do the trick.
They can be light gauge and should not much trouble to carry.


Even box, say 20mm x20mm and use the wingbolt as a one of the mounting points

the bracing could even be male- female like those cheap tent poles
for minimising carry space.

Now it's all just getting too hard.

The top legs will have to slide out about 500-600mm. I think we could lift it ok with 2 people...maybe. I wonder if I could coat the poles in plastic or teflon so they dont seize up. Or use something else other than tube for the posts....I just don't know what.