Sso not like I really needed another project but I have made the decision to build a bigger trailer, my box trailer is good but I find its limits every now and again.
I picked up a used, steel ute tray from a single cab ute that will be modified and turned into a trailer. Building trailers is not my area of expertise so those more knowledgeable feel free to offer guidance.

I have a fair idea on most of the design but haven't started the build yet or bought my components so nothing is yet set in stone.

So the requirements
- Need to keep the floor height low, lifting things on and off the trailer is easier if it's lower. Have seen some ute tray to trailer builds where the floor ends up way to high. To keep the height low this means that I will be recessing the wheel arches into the tray floor, like you see on some utes / one tonners
- as there will be wheel arches in the tray floor I want to have at least 1,250mm between the arches so can hold pallets, full sheets of material ect
- single axle only, not uncommon for me to have to move the trailer around the yard manually, sometimes loaded with stuff and single is much easier to turn
- 1,400kg rating minimum, this should net me about 1,000kg carrying capacity, want to be able to carry most of my machines in it if needed.
- 1,200mm drawbar

Components so far
1,400kg or 1,600kg kit if I can find one
- 45mm square axle solid, either ford slimline bearings at 1,400kg or Parallel bearings at 1,600kg
- eye to eye leaf springs
- hydraulic over ride disc brakes, while electric would be preferred it's likely that others will borrow the trailer so need a generic setup and hydraulic discs seem to be the pick of that category
- ford hubs, sunraysia rims, running 185r14 LT tyres, 850kg each load rating should net me 1,700kg rating on tyres, keeps diameter down and width down
- other generic stuff to complete the build, jockey wheel, coupling, LED lights, ect ect

At the moment the bottom of the tray looks like this
Attachment 388565

Basic dimensions that I'm starting with from a quick measure
Total width - 1,915mm
Width between rails - 1,830mm
Total length - 2,385mm
Headboard to back length - 2,340mm
Front to back chassis rails are 65x35x3 RHS
Side to side rails are 50x20x2.5 RHS
tie rails are 27mm round
side tray rails 40mm SHS
Floor is 3mm checkerplate
front to back rails are spaced 1,060-1,080mm measured outside to outside (not totally parallel)
side to side rails outside to outside, front to back are 450, 875, 1460, 1895 & 2120

Plan is something like this
Ute tray underbody hacked.jpg

Red - remove old mounts, remove section of 50x25 RHS where wheel needs to go through, remove section of floor for wheel
Purple - weld in 50x25 RHS to brace around wheel well where section was removed
Blue - 100x50x4 RHS chassis rails & drawbar, drawbar attached at front spring hanger
Brown - 65x35x3 RHS laid on its side so it's 65 wide and 35 high.

Cutout for wheels would be with 255 wide, allowing 185 for wheel / tyre, 3mm each side for sheeting, 30mm gap either side and a couple mm for mismeasurement, should give me just over 1,300mm between the wheel wells.


From there it should just be fit suspension, brakes, wiring, ect

I have had a quick look through the build regs but need to check again as I'm sure I read something prior that specified where the wheel had to be in relation to overall loading area, like % in front of axle vs behind. From reading couldn't really see anything that specified frame strength but I'm thinking that should be strong enough, would rather not put in a chassis rail in the centre as more work and would like the option to use it to store a ramp if I decide to build a ramp for it in the future.

Questions for those more experienced with trailer building
- Have I missed anything obvious or is this not a good idea?
- Suggestions on suppliers, probably best to pick up to save on high postage costs, happy to travel within say 2 hours of Toowoomba, so Brisbane, Sunny or Gold coast
Attached Images




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