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  1. #1
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    Jun 2010
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    Default Enclosed Trailer Fitout

    I've volunteered to fit out an enclosed trailer to act as a mobile clinic. They've purchased this:
    IMG_0225.jpgIMG_0224.jpg

    Which it seems was originally for carrying motorbikes, hence the rear ramp, and then used as a tiny house.

    The first thing I did was weigh it, or at least weigh one wheel with the other side jacked up until it was level, and more or less balancing front to back. I got a weight of 525kg on one wheel, so 1,050kg all up, give or take, which seems surprisingly heavy as it's pretty much empty.

    What also surprised me was an ATM of 2,000kg on the compliance plate. The single axle has disc brakes mechanically actuated via cable by an over-ride coupling, but I thought at best you could only get to 1,400kg on a single axle? I haven't measured the thickness of the axle, but at a glance it didn't look particularly heavy-duty.

    My concern is that there is quite a bit to add to this trailer, including solar panels and storage batteries, as well as various bits and pieces inside. A 2T ATM gives plenty of room for all that, but I don't really believe that's a correct figure. If it's actually 1,400kg, I've got to be a lot more careful about weight.

    Anyone know if the 2T rating is plausible?

  2. #2
    Join Date
    May 2011
    Location
    Murray Bridge S Aust.
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    71
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    5,942

    Default

    I find it plausible as;
    Definition: GTM (Gross Towing Mass) is the mass transmitted to the ground by the tyres of the trailer when coupled to a towing vehicle and carrying the maximum load recommended by the trailer manufacturer or importer approximately uniformly distributed over the load bearing area.

    • Trailers that do not exceed 750 Kg GTM with a single axle require no brakes to be fitted
    • Trailers from 750 Kg up to 2 Tonnes GTM, require an efficient braking system to be fitted to at least one axle. Over-run brakes may only be fitted to trailers that do not exceed 2 Tonnes GTM. Except for over-run brakes, all brakes must be operable from the driver's seat. Over-run brakes may only be used on trailers that do not exceed 2 Tonnes GTM
    • All trailers over 2 Tonnes GTM must have brakes operating on all wheels. These brakes must have an electric controller and must also be fitted with an electronic breakaway system

    The above was found here, https://www.mullins.com.au/tc-axles-...-cap-chart.asp
    I find the weight you gave, a bit heavy for what it is, but without seeing/knowing it's construction, you could be right. Best bet is to take it to a weight bridge for a correct weight, you can also get a good estimate on the ball weight at the same time. You'll need to know that so that the layout can be planned properly.
    Weigh everything that needs to go in it, unlike someone I know, they built a gooseneck toy hauler that weighs around 5 tonne, it was supposed to be about 2.5 tonne.
    Hope this helps
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
    Join Date
    Sep 2021
    Location
    Western Sydney
    Posts
    262

    Default

    Quote Originally Posted by RustyArc View Post
    I've volunteered to fit out an enclosed trailer to act as a mobile clinic... If it's actually 1,400kg, I've got to be a lot more careful about weight.

    Anyone know if the 2T rating is plausible?
    You could always slap mudguards on the side of it , extend the axle and go dual axle with electric brakes , it would give trailer more stability when people walking around inside it using it as a clinic and safely carry all the extra weight.

  4. #4
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    Jun 2010
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    Canberra
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    Default

    I think I might have to take it over a weighbridge, as I can't quite accept that it weighs a tonne as it is.

    I'm in the process of stripping out the lining, which looks to be 4mm ply, so that wouldn't have added any real weight, the cladding is 3mm composite panel, the wall and roof framing looks to be 30mm RHS, the chassis 50mm and 40mm RHS, so not exactly over-engineered. There may be a bit of weight in the rear ramp, which is covered with 3mm chequer plate, which I can probably replace with a much lighter removable panel, as while access is occasionally required for large items, there's no need to be able to wheel anything in.

  5. #5
    Join Date
    Aug 2010
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    Toorloo Arm, VIC
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    39
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    1,270

    Default

    Quote Originally Posted by RustyArc View Post
    I think I might have to take it over a weighbridge, as I can't quite accept that it weighs a tonne as it is.

    I'm in the process of stripping out the lining, which looks to be 4mm ply, so that wouldn't have added any real weight, the cladding is 3mm composite panel, the wall and roof framing looks to be 30mm RHS, the chassis 50mm and 40mm RHS, so not exactly over-engineered. There may be a bit of weight in the rear ramp, which is covered with 3mm chequer plate, which I can probably replace with a much lighter removable panel, as while access is occasionally required for large items, there's no need to be able to wheel anything in.
    I think you'd be pretty close. My unbraked 8' x 4.5' box trailer is about 270kg - but it has no brakes, and a crappy angle iron drawbar (and chassis) instead of the solid looking affair yours has. Looks like maybe 75x50 on the drawbar? Assuming a 2mm wall, and 5m of steel in the drawbar, that'd be 18kg vs the 9kg of mine. If its 2.5mm 75x50, add another 4kg.

    Rough figures assuming 30x30x1.6 framing on the ramp and it being approx 1.5m square gives me about 66kg for the ramp alone (guessing you meant steel chequer plate). Make it 30x30x2 (or 25x25x2.5) and you can add 3kg, repeat for every half mm thicker.

    That aluminium toolbox will be at least 25kg.

    3mm Alucobond is 5.9kg/m2, and assuming the trailer is about 2.5m long by 2m tall and 1.8m wide, I make the 2 sides, the roof and front to be 18m2 - or 106kg. Add the same area at approx 2.25kg/m2 for 4mm marine ply (only spec I found), for another 40kg.

    So taking the 270kg figure for my trailer, and adding the best case figures from above, you're already up to 516kg. That's without considering the brakes, the heavier chassis, probably a heavier duty axle, the framing for the walls, 3 windows (if they're glass they'll be surprisingly heavy), and if someone has used for example 3mm wall thickness somewhere along the way that will add a considerable amount, as will adding half a metre to the length (and by eye I wouldn't be surprised if it's more like 3m long).

    Truly a death by a thousand cuts, lots of little bits do add up. Those awning mounts (?) on the roof probably add 5kg, looks like there's a water tank hidden somewhere on the front right, a kg or two for the jerry can mount, etc, etc.

  6. #6
    Join Date
    Feb 2018
    Location
    Sydney
    Posts
    33

    Default

    Hi

    Yes, you can do 2t ATM on a single axle. The axle should be 50mm with a set of springs rated for the weight. In my case its 9 leaf springs (60 X 7mm). Hope this helps.

    Cheers
    Frank

  7. #7
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    Jun 2010
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    Canberra
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    Default

    Thanks for the comments - the axle is 40mm with 7 leaves on the spring, so I'm not sure what's going on there.

    Since I don't do this kind of thing often, I went and modelled the trailer so I can do most of my mistakes on the computer before I go cutting bits of steel too short.

    APCS Trailer 4.png

    The chassis comprises all 50x50 section, except for the floor cross-members that alternate 50x50 and 25x50 at 350 centres. The claim is that this was at first a motorbike trailer, but that floor seems a lot beefier than I'd have thought you'd need for that application. The walls up to 1400 are 30x30, then there's been another 400mm added on top using 25x25, and the roof is 20x20. The added 400 top bit extends out the front an extra 300mm

    I've stripped out most of the internals:
    IMG_0250.jpg

    I think I'll also rip up the floor, and remove this front wall:
    IMG_0233.jpg

    I'd hoped to reuse the wiring, as most of the power points and lights were in the right spots, but now I've removed the old lining, I'm not convinced this was done by a sparky:
    IMG_0234.jpgIMG_0235.jpg

    Fortunately one has come forward to volunteer his services.

    I'm thinking about what to use to line the interior. I plan to use 9 or 12mm ply for the floor (there's mild steel sheet there already, making me think 9mm might be OK) and 7 or 9mm on the walls and ceiling. I had toyed with using composite panel on the inside, as it'd have a nice glossy white finish, but adding support for the edges of the sheets where they meet the corners looked like a lot of work, whereas the stiffness of plywood might make things simpler.

    I also plan to move the front wall forward 300mm to remove the existing overhang, and add valuable storage space, although not sure how much weight I can put there, given how far forward it is...

  8. #8
    Join Date
    Sep 2021
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    Western Sydney
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    Default

    Quote Originally Posted by RustyArc View Post
    ...I'm thinking about what to use to line the interior. I plan to use 9 or 12mm ply for the floor (there's mild steel sheet there already, making me think 9mm might be OK) and 7 or 9mm on the walls and ceiling. I had toyed with using composite panel on the inside, as it'd have a nice glossy white finish, but adding support for the edges of the sheets where they meet the corners looked like a lot of work, whereas the stiffness of plywood might make things simpler...
    Are you putting in any insulation between the sheets ? to keep in cooler and warmer ect . Imo composite sheets will look better than ply , u could always laminate them to ply to stiffen them up on the edges rather than add bracing to the frame, composite = no painting , easy to clean and looks modern. I buy panels from sign places up here cheaper B grade quality i.e have a few minor defects and odd colours but does the job.

  9. #9
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    Default

    Quote Originally Posted by Iron triangle View Post
    Are you putting in any insulation between the sheets ? to keep in cooler and warmer ect . Imo composite sheets will look better than ply , u could always laminate them to ply to stiffen them up on the edges rather than add bracing to the frame, composite = no painting , easy to clean and looks modern. I buy panels from sign places up here cheaper B grade quality i.e have a few minor defects and odd colours but does the job.
    I'm tempted to add insulation, but there's only a 30mm gap in the walls, and 20mm in the roof, and there's a lot of random blocks of MDF that have been glued there, which I'm not sure how to remove without warping/denting the outer cladding.

    I certainly like the idea of composite panel on the inside. Maybe laminating it with 4mm brace ply might do the job, but then I'm wondering how to fix it in place, as screws would look pretty unsightly.

  10. #10
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    Sep 2021
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    Western Sydney
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    Default

    Quote Originally Posted by RustyArc View Post
    I'm tempted to add insulation, but there's only a 30mm gap in the walls, and 20mm in the roof, and there's a lot of random blocks of MDF that have been glued there, which I'm not sure how to remove without warping/denting the outer cladding.

    I certainly like the idea of composite panel on the inside. Maybe laminating it with 4mm brace ply might do the job, but then I'm wondering how to fix it in place, as screws would look pretty unsightly.
    Use sikoflex or 3m double sided bonding tape to hold the panels on , no screws required but takes longer to fix them ! For insulation the self adhesive sheets of foam with silver backing work ok, better than nothing , lol

  11. #11
    Join Date
    Sep 2012
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    York, North Yorkshire UK
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    Hi Guys,

    When I did the camper van conversion, I used 6mm thick self adhesive peel off backing insulation with bubble and silver foil directly on the metal wall of the van which I then covered with 6 mm ply covered with glued on 3 mm thick felted carpet. the actual panels are secured by double sided tape to timber supports. The only screwed stuff is the roof ventilators and the roof panel.
    Best Regards:
    Baron J.

  12. #12
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    Jun 2010
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    Canberra
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    Quote Originally Posted by Iron triangle View Post
    For insulation the self adhesive sheets of foam with silver backing work ok, better than nothing , lol
    Bunnings flog polystyrene foam Foilboard in 10,15 & 20mm thicknesses. They may end up sponsoring this project, so that's definitely an option.

  13. #13
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    Quote Originally Posted by BaronJ View Post
    Hi Guys,

    When I did the camper van conversion, I used 6mm thick self adhesive peel off backing insulation with bubble and silver foil directly on the metal wall of the van which I then covered with 6 mm ply covered with glued on 3 mm thick felted carpet. the actual panels are secured by double sided tape to timber supports. The only screwed stuff is the roof ventilators and the roof panel.
    Double-sided tape is something I hadn't though of - it seems a lot more practical than using Sikaflex in terms of getting a consistent adhesive thickness - i.e. making sure everything ends up flat.

  14. #14
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    There was a random bit of chequer plate on the drawbar that I was keen to remove, but revealed some worrying sings of rust:
    IMG_0251.jpg

    That and the odd, undulating floor lead me to decide to pull up the flooring and check out what's happening underneath:
    IMG_0253.jpg

    Which revealed some large sections that looked to have been patched, although not clear why.

    So taking a deep breath, I decided to cut out the floor, in part to reduce weight, but also to see if there were hidden rust problems that might cause issues in the future:
    IMG_0254.jpg

    The plasma cutter got a good workout, and I discovered that plasma cutting through welds while on your back has many downsides, most of them burning and painful.

    IMG_0255.jpg

    All I have to do now is go through with a grinder and clean up everything. There's a fair bit of rust damage on the left of the front cross-member. Not entirely sure what to do about that.

    Once it's cleaned up, I'll lay down a new 12mm plywood floor, which should be considerably lighter than the old steel floor.

    Tossing up whether to glue and screw the floor, or just screw, and if I glue, whether I should pre-paint the underside of the floor.

  15. #15
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    Sep 2012
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    Hi Russel,

    I would make sure that all the cross members were clean and rust free before painting and then undercoating them. I put timber cross members under my van 12mm plywood floor, using the space to run water, gas and electric cables around. Since you don't have a sub floor, I would use plastic pipe to get any utilities from one side to the other. Secured with Ty wraps which won't be thick enough to lift the floor.
    Best Regards:
    Baron J.

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