Thread: Learning the right way to go about building a trailer?

Hi , is there any good reading on the How too"s of trailer building ?
Or good web sites ? That any one knows of .

Rob

What I am thinking of building is a 5 x 8 or a 6 x 10 dual axle with electric brakes and possibly a 4 x 4 type hitch , if that's the correct name for it [ Hitch ] ?

I wouldn't mind over building for strength as I want to load and haul some heavy woodworking machinery . Have points to winch from mounted within ,for a block and tackle. Ramps maybe.
And It would be nice to be able to drive up and down the hills on a country block of land behind my Troopy with loads of wood.

Should I look at plans for that size and beef it up a little ?

Rob

The first place to start is VSB01...linked above.

Some of the trailer parts sites have usefull information.

As for this beefing up...well that gets out of hand realy quickly.

There are plenty of trailers out there that are neither use nor ornament, because they have been beefed up to the point where that can carry no payload before being overloaded.


Plenty of trailers out there working on the basis of steel and plenty of it..big heavy sections and not a lot of smarts.

A light strong trailer will have side members that actually form a truss.

As I say...the weight can get out of hand pretty quickly.

cheers

This forum is about the best website on the net. Heavy material is not stronger than a well designed trailer. Start with drawing your plan.

You should be able to calculate the weight of the trailer before you buy a single inch of steel.

All steel manufacturers publish "mass & bundling data", this tells you how much each steel profile weighs..as well and how it comes bundled.....imperitave if you are transporting steel.....realy useful if you are building in steel.

cheers

Ill have a read of that vsb1 .
When I say beefed up , yeah I don't mean going over board on it. If I compare to trailers I have taken notice of ,comercial made ones , there seems to be these light weight ones I see second hand for sale which are all rusted through and they look ten years old , and there are older one's going back to the early eighty's maybe that are a step up in thickness and solid . of course condition has to do with how its stored . but avoiding the rust traps if possible would be nice.

Is it possible to avoid rust between the tray and the frame ?
Or mabey a better way of asking is what is the best way to fix the tray to the frame , fully welding it in?, or just the standard 19mm weld every 300 mm , this is just a guess.
Then fill in the un welded part with some modern sealer to keep out moisture ?

Or can a tray be glued down with the sealer in between then welded at the correct spacing ?

These questions have probably been asked here before , but where?

Rob

Appart from being left out in the weather full of grass clippings, the single biggest reason fro rust in trailers is a failure to paint properly.

Many...I would say most...commercially built trailers are slashed with a single, thin, cheap, top coat with no proper surface preparation.....certainly no paint protection in vunerable areas.

If you paint striaght over mill scale, anti-spatter, lumps, bumps and cavities, with a cheap enamel....rust is inevitable.

If you want to keep thye rust away, it all starts when you cut the steel....make sure you do not leave any swarf or filings inside hollow sections and clean down all the areas adjacent to the welds.....after assembly you may not get back in there easily.

If working with black materials like angle or flat remove all the mill scale before you weld..its easier to do this with the pieces while they are easy to handle than afterward.

I'm realy keen on flap disks on a grinder....they clean stuff up pretty well without taking too much material off or leaving a rough finish.

Weld spatter leaves places whenthe finish can be compromised.....if the spatter is not well adhered, it may come off later leaving a hole in the finish.....if the spatter Is well adhered, it leaves a sharp bump that will penetrate the finish or leave an imperfection where dirt or moisture can lodge....or a lump that allows the finish to be rubbed off.

After assembly.....if I am beeing fussy...I will go over the whole job with a flap disk a go back to bright metal.....the crevices and closed bits can be got at with either a die grinder or a hand sand blaster.

I do not believe the blue paint that comes on steel material is an adequate undercoat or primer.

If sand blasting..ya got get ALL the sand out....that is easier said than done.

For a good durable paint job on steel some sort of etch primer or etching under coat is important....I like "wattyl superetch"
I will generally get into the fiddly bits with a brush before spraying.....If being particularly fussy I will rub the fist coat of super etch in with a brush....not being particularly concerned with good coverage..but more a rubbed into the grain key coat....then I'll spray over...be reasonably generous with the primer..within reason.



If doing a frame & sheet construction I can see a big advantage in a good prime coat on the frame before attaching the sheet......you can always clean away the areas you want to weld on...and rub some primer in later.....but all those voids where you have not welded have some paint on them..that has to be worth something.

If you are welding, you cant use a sealer......leave the voids open so they can dry out or be cleaned out.

If you are screwing down sheets....you can use sealer, but screw down on a good bed of sealer.....drill up and remove the swarf, before you actually fix.

Back in the 80's I built my first trailer.....its still with me.....I screwed down the tray with self drillers and bedded on no more gaps.....it worked...but I would not do it that way again.
It looks a bit sorry at the moment..mostly due to paint failure.

OH...leave the silicon alone.....if anything it promotes corrosion, if you are looking for a sealer, think of acrillic, polyeurathane or even the old favorite......butal mastic...That is..if you can find any.

Remember all this takes time.....and is a major fiddle....but if you want a metal object that lasts...that is how its done...attention to detail.

As for the top coat.....ya get what you pay for.

I have had a lot of sucess with Galmet Duragal....its a silver paint with high metals content and a good resin...not to be confused with their cold gal product...that is ground up zinc in resin (Galmet cold gal....hell what a thing....but it aint pretty).
If sprayed well, Duragal comes up like wheel silver and looks as good in the short term....log term it dulls off a bit.
But as an anti corrosive top coat its hard to go past..if you like silver/grey.

If you want colour, and you don't mind paying...look at the marine polyeurathnes....

cheers

OH..before you put ya first coat of primer on, don't forget a solvent scrub.

I get out there with a big paint brush and a bowl of thinners and scrub the frame, doctor seus style..... inside, outside and upside down.

That will get any oil or other contaminats off.

cheers

Originally Posted by soundman

doctor seus style..... inside, outside and upside down.



cheers

Thanks soundman

Just a note on the use of silicone. Silicone can be used if it is neutral cure. Neutral cure silicones are those intended for roofing or guttering.
Sikaflex is the pick of the sealants in my book as it sticks like the proverbial, takes paint really well and will not promote rust.
If stick welding your trailer, be sure to properly remove all slag. Slag will promote rust and compromise the paint coverage.
One of the best ways to really add strength to a trailer is to cap and weld all open hollow sections, (SHS RHS etc). If you must run wiring through the structural members, then seal around the wiring to prevent the ingress of water and dirt.
As others have posted, intelligent design will achieve far more than mass of steel. Make your sides work for you.

The problem with silicon is not just the acetic acid that comes from curing...and even neutral cure can promote corrosion on bare steel.

The problem with silicon is that it is not intimate with the surface.....over time, it shrinks, peels and water gets under it.
For silicon to provide a long tem effective seal it has to be clamped between surfaces.
I've pumped my fair share of silicon..and it has been the "go to" sealer for nearly 30 years.....but it has always had a string of problems.

There are a few that have stuck by good old butal mastic.

Plain old acrillic (no more gaps) has it over silicon in many situations.

And OH yes polyeurathane ( sicaflex) is a fabulous sealer in it role...and there are other brands of Polyeurathane sealer.

Less and less am I looking to silicon as a sealer.

cheers

I will do scale drawings after a few more decisions are made .

" A light strong trailer will have side members that actually form a truss."

So If I do sheet and frame sides , would the bottom drawing be the best ? and a truss as simple as that or more to it ?

I would guess the side frame material could be 35 x 35 x 2.5 or 3mm
or 40 x 40 x 2.5 ? What do you guys think

I have this Trigg Bros hitch

PB 750 3000 kg Non Over ride . what do you think of it? stronger than a standard tow Ball with more travel ?

and what is PB 750.
Rob

More on the Hitch. On one side it has PB 700 2000 Over - Ride

The Other side PB750 3000 Non Over - Ride

??
Rob

You probably have it already, but the Martin's Catalogue is very handy and can be downloaded here- http://www.trailerparts.net.au/catalogue

Looking at your drawing, the side diagonals are totally superfluous if you are using sheet for the sides.
Unless you are doing a lot of extreme off roading I would not use that hitch. They are a fair bugger to hitch and unhitch compared to the usual 50mm ball and you lose 500Kg rating as well.