Thread: Chassis build for "box" trailer

I know I know
updates been a bit slow. . . you see there has been important things like fishing getting in the way of the build Show day Friday saw the freezer get a little healthier with a good catch of coral trout!

Anyways, a few photos of the little things!
First is is the bracketry to hold the air springs. The springs we have used have plenty of travel which is good but also means that I needed to optimise the position of the top and bottom mounts.

1/ Bottom mount is easy. This is the bottom spring mount tacked to a temporary axle (purple). By placing the bag behind the centre point of the axle two things are achieved, less overall travel and less load on the bag (no big issue as travel is plenty) This also means the bottom plate can be attached to the axle directly without a perch of some sort and the bottom retaining bolt just fires straight on up, through the plate, through the piston and into the bag. Obviously I will gusset around the back edge of the bottom plate back to the axle. Will also most likely incorporate the lower damper mount into the gussets.

2/ Top air spring mount is a little trick - sorry about bad pic image was taken upside down. Later Ill take more pics if wanted.
The theory is I didnt want to have to space the top mount plate down a huge amount to enable access to air lines and top mount fixations.
So I have mounted the top plate ~10mm below the top of chassis rail, That only gives 10mm of clearance between floor of box and top of mount. I then have a removable plate mount that is hard bolted to the top of the bag, air line exits from some clearance holes. So to install the bag, you bolt this mount plate to the bag, attach the airline adaptor (hard tube with brazed gas fittings) and and then slide it up into the actual bucket mount that is welded to the chassis. The plate is locked in with some tangs that engage in the bucket and a machine screw, Once load is on gravity will do the rest.

3/ Other photos are of the stub axle arrangement. I have ended up using multiple different tojo parts to get this to work. Pics 3 is of the components laid out prior to welding (Left to right) First is the flange that will be welded to the axle proper (You may notice a cut down axle is welded to the centre of the flange - this can then be engaged with the freewheel hub to act as the hand brake), then the disc brake mount that I removed off a the swivel housing and machined up, and then the standard stub axle. The second pic is the setup assemblied minus the brake caliper and the bottom flange to axle plate.

Sooo not too much big progress but essentially it is now ready to just weld up the axle (all hub/brake caliper/stub axle machining is done) and then glue together some links and voila!

Steve

Do you have more pics of the chassis and how did the side rails cut/bending/braced at front?

I want to build a chassis for a 130 tub with additional stuff on front and still thinking about best way to dot eh chassis/side rails to draw bar.

Pics and tips appreciated
Skiboy

Chassis is from 100PFC so essentially hot rolled channel 100 in the web, 50 wide flanges.
Flanges are about 5mm thick web is 3-4mm. A great section for HDG and correlates roughly with 100x50RHS 4mm but is stronger in the x axis less so in the y axis. But it is actually lighter than 4mm RHS so pretty good alround section for a trailer that will GTM 1.5T.

The draw bar is 100SHS4. This is the section you will find on ~2T boat trailers with a single drawbar. Just followed their lead. The draw is attached using heavier channel to the angled PFC. Suspension links will be mounted at the change in chassis angle to act as bracing.

Ill rustle some more pics up. Hopefully make it clearer. Chassis to draw bar is important as I am sure you are aware - not only large point loadings but also the area of most flex within the chassis.

S

Dear Roverrescue

For the uninitiated out there like me who got lost after RHS - ie I don't follow the short hand such as

• PFC
• 100 in the web
• Flanges are about 5mm thick web is 3-4mm.
• HDG

This seems fairly heavy duty - I thought box trailers were 2-3mm thick

SKiboy

Sorry,
PFC - parrallel flange channel. A section of steel that is rolled hot in the foundrey.
The top flange has parrallel faces as does the bottom flange. So think a square c witht he top of the c and the bottom of the c all square. The web (left side of the c) measures 100mm, the two flanges measure 5mm in my case. The inside corner is rounded.

HDG - hot dipped galvanized.

Yeah most box trailers are 2-3mm. But they are not getting abused like I know this one will. Wanting to galvanize it also changes the chassis design. If you do the maths on the chassis between say 100x50x3mm and what mine will weigh the difference is not huge but the quality well - this one will still be around for the customers kids I imagine

Sure weight is bad but I dont ever want a return on this one and I know the guy who is gonna flog it to death all over the country side!

One other consideration is he wanted the boxes out of folded aluminium. This will offer no rigity in the y axis to the chassis. On a "standard" camper trailer with the sides welded to the chassis there is strengthening added to the chassis by the rigid addition of the box section of the trailer. This build the two boxes will essentially float on the chassis

S

Hard to see from the images but looks like there may be edges on that upper mount that could cut into the bags on full compression??? (could be wrong).

yeah Ben,
I am a little worried about the upper rim. It is currently a band of 50mm wide FMS welded to the OD of the mount plate. There 15mm of space miniumum to the bag wall at compression but obviously I cant dynamiclaly load it yet.

the plan is to drive this thing hard before HDG if ther eis even a feint touch on the bag then the mount will get modified. Depending on your thoughts maybe I should thin up that lip to say 25-30mm which would remove the lower edge from the moving part of the bag? 25-30mm should still give enough bracing?

What sort of clearances would you llike to see about the top edge of a rolling sleeve bag?

S

Thanks for the tutorial - I am learning slowly - sorry did not see in pics that was C section

I am trying to figure out the right balance between weight and durability. I rebuilt my boat trailer before and like the A frame design like you have done rather than adding an A under a ladder chassis like most do. But not seen many do box trailers this way hence interest in yours.

Will keep watching.
Skiboy