Caravan jacking brackets - first project.

[GazArc]

Hello everyone

Just wanted to ask you seasoned experts out there if my project is sound from a design point of view, since it will be my first attempt at welding.

The plan is to build a pair of caravan jacking brackets (caravans are trailers right?), which are then to be bolted to the standard position on the AL-KO chassis of my 2011 Sprite caravan.
(Weight of caravan is around 1200kgs when loaded, ready to tow)

The idea was stolen from inspired by the Kojack system:

My brackets are to be fitted in the same place (circled in red), as recommended by the makers of the chassis - AL-KO:
(Those that know about caravans, will understand the difficulty of jacking a caravan without these brackets....on a flat tyre it's near enough impossible.... especially on the side of a motorway in Spain!)

I have spared no expense by creating a very detailed CAD model of these brackets:

Of course, by CAD I meant Cardboard Aided Design!

The brackets will be fillet welded entirely, and cut from a plate of 4mm mild steel.
My welder is a (very cheap) Clarke MMA/TIG 120, and I shall be using 2.5mm 6013 electrodes with the machine set to 80-90Amps.
(Click here to see some pics in my intro thread)

I have been practising every day for a week or so, and with more practice over the next few weeks, I think I'm ready for the final build.

Does my design look sound?
I realise that access to the top section (in contact with the underside of the caravan floor) might be tight, so I will probably only have outside fillet welds, since it will not be load bearing - merely to act as additional support and to counter any twisting of the chassis member.

The 'circular' piece is a locating boss (anti-slip feature) for the bottle jack (~40mm OD, 3mm wall).
My jack isn't a low profile one with multi-section telescoping pistons like the Kojack.
The height of this boss has been calculated to allow my taller bottle jack under it, when the tyre is flat.

So, what do you experts think?
Am I on the right track, or destined for a spectacular failure?
(I think if done properly mine will be much stronger than the Kojack, simply by virtue of being made from thicker steel)

Any helpful criticism or advice will be gratefully received.

Thanks,
Gaz.

 

[Cobbler]

Does your spare wheel carrier come out of the side, like a lot or all of the ALKO chassis? If so getting the spare out either is against the bank, or pulls out into the traffic lane & either impossible or dangerous. I discovered this when assisting someone in France some years back. Apparently it’s easy to remount the sliding carrier to pull out of the rear & make it safe.

 

[GazArc]

@Cobbler I have previously removed the under-slung spare carrier some time ago, for that very reason!
(My spare is relocated inside, under the fixed rear bed - close to the axle line)

I agree that it is potentially dangerous, and when I tried to remove the spare from ours, it jammed up, preventing the spare from being removed at all!

It's a terrible design, and our carrier is now collecting dust in the shed!

I would have used it for welding practice but I think it's galvanised, and I don't want to take any chances!

 

[Bobupndown]

Looks good. Ours is a twin axle with motor movers fitted in front of the front axle and the spare wheel carrier behind the ns rear wheel which prevents me from fitting these. In the event of a puncture I can just raise the van by driving or reversing the non punctured tyre up on a levelling ramp which will raise the punctured tyre enough to replace it. I carry a small bottle jack in the car as a back up. Good sturdy looking design.

 

[GazArc]

Looks good. Ours is a twin axle with motor movers fitted in front of the front axle and the spare wheel carrier behind the ns rear wheel which prevents me from fitting these. In the event of a puncture I can just raise the van by driving or reversing the non punctured tyre up on a levelling ramp which will raise the punctured tyre enough to replace it. I carry a small bottle jack in the car as a back up. Good sturdy looking design.

Thanks @Bobupndown for the encouragement.

I had considered your method of using a levelling ramp - I would have to roll the flat tyre up the ramp however, and slide the jack under the axle, since my caravan is a single axle.
Unfortunately having rheumatoid arthritis in all joints (especially bad in my knees), kneeling/grovelling under a caravan is something I simply can no longer do!

I really need an alternative and the Kojack brackets looked like they ticked a lot of boxes, but they're a bit pricey and difficult to find in stock in the usual, trustworthy places.
Plus, I wouldn't need the jack anyway....I carry my 5 ton bottle jack, plus a small, 2 ton trolley jack....belt and braces perhaps, but you can't be too careful!

So there it is....why not make the brackets?!

(Although, I seem to have spent more money on all the welding stuff than the cost of the Kojack system! But then I wouldn't have the fun of learning a new skill, and the satisfaction of building something really useful)

 

[bricol]

Save some material - anything below the lower bolt hole isn't doing very much, and the top plate only job appears to be to hold dirt and crap against floor?

Won't your trolley jack go under the axle itself, provide the lift right where it needs it, rather than jacking weight off the spring first, then lifting the wheel?

 

[chrismac]

Looks good. Ours is a twin axle with motor movers fitted in front of the front axle and the spare wheel carrier behind the ns rear wheel which prevents me from fitting these. In the event of a puncture I can just raise the van by driving or reversing the non punctured tyre up on a levelling ramp which will raise the punctured tyre enough to replace it. I carry a small bottle jack in the car as a back up. Good sturdy looking design.

Have you needed to do this with a puncture? its a great idea, so easy, I was lucky never to have had a puncture when caravanning.

 

[bricol]

Have you needed to do this with a puncture? its a great idea, so easy, I was lucky never to have had a puncture when caravanning.

Wonder what happens when its the front axle with a puncture?

I had a twin axle van with a mover on one axle - works well until you take enough weight (going up a drop kerb) or traction (over loose gravel) off a driven wheel, then you start to get unintended turning.

 

[GazArc]

Save some material - anything below the lower bolt hole isn't doing very much....

Fair point, perhaps I could modify the design....although I have thought about extending the lower edge further down (beyond the edge of the lower chassis rail)....to maybe accommodate a trolley jack....sort of best of both worlds.
It would need some reinforcement, but shouldn't be too difficult.

....and the top plate only job appears to be to hold dirt and crap against floor?

Perhaps, but I'm basing my design directly from the Kojack system, if it's good enough for them, it's good enough for me.
Besides I think it's there as extra support for the chassis member, to prevent undue twisting.

Won't your trolley jack go under the axle itself, provide the lift right where it needs it, rather than jacking weight off the spring first, then lifting the wheel?

It will....but I cannot get down to place it under the axle (aforementioned ailments).
My 5 ton bottle jack will have plenty of lift, so I'm not worried about taking weight off the spring first.... I'm sure it'll manage.

Is it perfect? No, of course not, but I really need a more accessible jacking point, and this design (the 'borrowed' Kojack design) will make life a lot easier if I get a puncture.

Thanks for the comments.

 

[Bobupndown]

Have you needed to do this with a puncture? its a great idea, so easy, I was lucky never to have had a puncture when caravanning.

No, fortunately not but confident this would work on firm level ground.

Wonder what happens when its the front axle with a puncture?

Tow or reverse the rear wheel onto a leveller.

Wouldn't recommend trying it using the movers alone, which obviously wouldn't operate correctly with a front axle puncture anyway.

 

[Keithmac]

I bought the Kojack kit, works really well.