Thread: All Aluminium large trailers

Was asked what size the "I" section is. I think 8mm on the skirt and 5mm on the flanges, with another 4m of 9x127 flat bar welded along under chassis where axle plates are to be mounted.
WA appears not to get the access to same sections of Ali as in East, lot of what we wanted was "special order" ex east, but showed as general stock in East.
Went with what we could get, but was looking for 200 "I".
Chassis is integrated into the draw bar and central solid rail piece extends through the internal rigid frame through to hitch without weld (until it reaches the hitch area of course).
From what some have suggested, might look to some gussets across underneath all chassis/draw bar intersections for extra rigidity.
Seems we shall have to be vigilant for any stress cracks, but I expect it will not be overworked.

Originally Posted by vbrab

Yes, should have clarified, electric over hydraulic, 6 x 10" discs, with the usual auto shut down option if it detaches.
.

Got me buggered why we don’t see more electric over hydraulic set up........I had it on a 1200kg trailer, it’d be my first choice on a big multi axle trailer

Originally Posted by Homestar

Looks good. We use heaps of Aluminium trailers at work for a lot of small equipment like mini excavators and mini skid steers that are quite heavy, so we can keep the combination under 2,000KG - makes hiring them much easier as they only need over ride brakes. We also have some larger ones that bigger genset s sit of that gross 3,000Kg.

All made by a manufacturer here in Melbourne who make a very good product. With the abuse they cop in the Hire game, we do see cracks turn up in them - the Mechanics are trained to carefully go over them before every hire and we do see cracks turn up where the drawbar meets the trailer and where the hitch plate is welded to the draw bar. Easy fix, a quick zap with a spool gun and you’re away again. They last around 8 to 10 years before the metal is fatigued beyond repair and you can’t keep up with repairs at which point they are scrapped, but I’m talking getting used almost every day here and they are always loaded close to their limit, so with domestic use, you should get a very good run out of it.

Certainly seeing more and more small aluminum plant trailers.......to get max. Payload

Spring rates will make a significant difference to the fatigue life eg if too stiff particularly when unladen or lightly loaded will speed up cracking if it has to bounce down the road.


Have you considered air bags or even an air bag helper with a light leaf setup? I think it will be a great trailer and some form of load adjustable suspension would really finish it off.

What are you doing for floor plate?

Have gone with ALKO axle systems as they are integrated and independent as well as low loading (which I want for stability when loaded).
No springs.
The axles combined capacity is 4.5 tons, but being licensed for only 3.5t as don't want to pull any more (or pay rego for more).
Floor height will be about 450 off the road with wheels intruding through an internal floor box about 100mm.
Have floor space to spare, so not fussed to achieve a "flat" floor (which I started off chasing).
Seems aluminum sizes/thicknesses not all available in WA either, so have had to change (reduce) the planned drawbar box due to weight and not wanting to increase tow ball weight.
Will still have my rollout BBQ, but somewhat less storage on draw bar.

VBRAB

Two points that hopefully your engineer would have noted according to VSB1:

# Your maximum permissible ATM will actually be 3625kg. (I know you mention you'll only register it for 3500kg so this is no problem)
In close coupled axle groups (non load sharing such as ALKO indies) each axle of the group must support 120% carrying capacity at max ATM. 1450kg rated axles, 120% rating to 1450kg gives each axle a load rating in close coupled configuration of 1208kg. Total ATM three by 1208 is 3625kg.

#If you were planning on using a 50mm ball coupling - with your chassis design as pictured and a projected deck height of 450mm you will need to mount your coupling midway between the top and bottom flanges of the drawbar beams. 50mm ball couplings require a mounting height of 350-420mm. If you mount a 50mm coupling to the top of the chassis it will be too high and if you plated and mounted it to the bottom flange it would be too low!
If you had intended to mount it to the top of the chassis beams (what I would choose to do) the quickest legal methodology would be to use a 70mm ball coupling and 70mm ball and tongue. The extra capacity isnt going to hurt and will keep the rig in specification as per VSB1.

As a question regarding the design - what is the transition between box and a-frame going to look like.
I have only really spent time around aluminium boat trailers - up to 4T jobbies. They bend like bananas but as the beams run from axle group to hitch with no real hard transition they have that inherent flexibility that no problems seem to happen. The best marine aluminium trailers are bolted construction - largely due to weld failure in HAZ which is accelerated in the marine environment.
Your design is obviously fully welded (less flexibility and HAZ weakness) so I would be interested in how your engineer is going to taper the loads across the transition zone from load carrying box to A-frame. I can see some huge forces applied to those three junctions where the deck becomes a-frame.

Regards,

Steve

A good way of increasing the rigidity of a relatively light drawbar is to truss the underside with a suitable length of flat steel bar in tension. Bolt it at each end and have an adjustable prop (nut and bolt in a short tube as pivot under the drawbar) in the middle where it meets the frame, adjust the tension here to stop flex.

I totally agree BeeUtey
I imagine that some fancy trussing will be in order on the underside to smooth the transition from very rigid box to flexible a-frame
Especially considering that the beam junctions will be welded introducing a stress riser at the transition.

S