Lightening trailer floor cross beams ?

[CompoSimmonite]

I've got one of the ubiquitous folding 8' x 4' trailers that are popular in US (mine came from Northern Tools UK). It is a bolt together design and isn't a rigid frame but has some "twistability" like HGV chassis.

It's time for a refurb. as the Chinese paint is flaking so intend making some improvements at same time.
Originally it was sold as a bare frame as above to which customer then acquired their own 3/4" ply top. This was quite heavy so I replaced it with some thinner Buffalo board and now need to replace the single cross beams on each 4' x 4' section with two to reintroduce some support.
The metal is 3mm thick in a folded 70mm channel so I've bought lengths to 30mm & 40mm angle to weld together instead for the new beams.
I'd like to keep weight down so need to add lightening holes to the proposed fabricated beams out of the 30 & 40mm angle. Drilling something like 50mm holes is going to be hard work even with my pillar drill so am considering cutting alternating triangles with angle grinder before the two pieces are welded together.
First off does this sound OK ?
Second how close to top and bottom of the beam plus how close together should such triangles be ? As a guess I'm thinking around 10mm from top and bottom with 25mm between each triangle.

The reason why I want to keep weight down is the original ply weight made folding very difficult so whilst my improvements include ability for a winch to do most of the work.
This is how they fold -

This is power folding -

Cheers.

Paul H

 

[Shox Dr]

Hardy worth the effort, is it? How much weight do you think you will save? 2-3lbs cant be much more.

 

[MoreWellie]

don't know the theory but it sounds to me that the points of the triangles would be stress points that you wouldn't get with a circle

if a winch is doing most of the work then the small amount of weight saved wouldn't make much difference

 

[cianh91]

1 getting the channels folded and drilled by an engineering company would have been a better option as your just adding stress points with your method
2 I'd be more looking at the winch system than the weight. As stated already your weight savings are going to be very minimal so I'd look at an upgraded winch setup

 

[moose]

You don't say what the trailer is used for?

 

[Migmac]

No idea about what you want to do - sorry
A clever idea if your short of space and need a trailer, I would soon get bored with it though. What weight can it take ?

 

[Justme]

Those trailers look a right faff.

Re lowering weight, think hole cutters & a former to step them if the material is thin.

Or do what they do with I beams & cut castles then offset to make the beam taller for the same weight. So you could reduce the size you plan on using.

 

[CompoSimmonite]

Cut the steel roughly to size earlier as 6.0 lengths are difficult for me to store. Each new beam is going to be lighter than expected so now probably won't bother with any holes etc.
The trailer is rated at 750kg as unbraked. In US exactly the same trailer is 1 ton ! Mate has borrowed it and collected 1 ton bags of sand a few times .
I use it for quad bike, motorbikes (I've got 6), Class 3 mobility scooter, ride on mowers, microcars, collecting / moving chassis (will carry a Land Rover item), 8' x4' sheets of ply, plasterboards, fencing panels, 12' lengths of steel, scaffolding & timber, furniture moving (under clean / new tarp), trips to tip and much more. I've also got a little Erde trailer and used to also have a wide track Sankey - but that got nicked.

 

[Justme]

1 ton bags of sand dont hold 1 ton of sand. They are rated to hold 1 ton weight SWL for safety.

Sand is not sold by weight as you would be paying for rain water most of the time.