Shopping for materials and designing

[Kody]

I have been working on my design for our TD and have begun to get prices for all the material. I am amazed at the difference in prices of steel. One place quoted $15.68 / meter for 35 x 65 x 3mm RHS and another quoted $8.53 for the same steel. What a huge difference in price and the steel is all made here in Australia. I found a place that sells trailer parts and they can supply axles above the standard length (6'-6")in increments of 1" to any size that I need. Wow, how great is that? I can also buy a sheet of 1/2" ply, made of hardwood, 5' x 10' long. The ply has a beautiful finish to it and it is water proofed (glue) and sold as genuine structural plywood. Things are now starting to look up. I still have lots of designing work to do with my CAD program and will begin building as soon as I finish off the jobs around the house that need to be done. I can also buy structural Cedar plywood, 4.5mm thick. It too has a beautiful grain and colour. There is lots of plywood needed for the TD and the best way to transport it is to make the trailer and then strap the timber down on it and bring it home. This will save heaps in transport and I get to inspect every sheet of ply that I buy. The 5 x 10 sheet certainly makes it so much easier and more economical for the floor sheet. The floor will be 11' long so a small piece added in will be easy. Everything is starting to look really good.
Kody

[mezmo]

Welcome, and be sure to start a build thread with a lot of pics !

It's very encouraging that you've found some good materials
sources.

I, myself, would be interested to find out if you'll be going
with a galvanized chassis/frame - as that seems to be very
common [and a smart idea, I think] over there down under.

Cheers,
Norm/mezmo

[Kody]

G'day Norm,
I have welded trailers made with Galvanized RHS and 16 gauge steel and I will never be doing this again. The zinc coating is extremely difficult to "burn" thru and the fumes are terrible. The smoke that comes off the weld is vaporized zinc and it collects on the welding filter and blocks the view of the job. (It's zinc oxide, a white powder). The biggest problem I had was to get a weld that had good integrity as the arc is not stable. The zinc will also combine with the steel and the results are less than what is wanted. To get a good weld, the zinc needs to be ground off with an angle grinder. This takes a lot of time that can be better spent. Even with all the preparation, the welds still need to be painted with Cold Galvanizing paint. A far better way to build is to use standard RHS that is supplied already painted. The paint is no problem to weld with and the weld joints are exactly how they should be. When finished and cleaned up, the best paint to use on the frame is Cold Galvanizing paint and apply two coats with a brush straight from the can. Some of the people who read this may wish to differ on the welding but this is how I will do it for my trailer frame. The galvanized RHS as supplied does not have a heavy coating of zinc. I think this is done to aid welding but it is still a pain to use. The last problem I have with painting Galvanized steel is that the surface must be cleaned and etched for the paint to adhere 100%. The paint as supplied on the RHS can be scrubbed with a wire brush on an angle grinder to clean the steel somewhat if needed before painting. I have never had any problems doing it this way.
Kody

[Ben]

We work a lot with Galv. Metal where I work and have found out if you spray wd40 on it before you grind the Galv coating comes off a lot easier!!! And you don't have all the dust either so you don't get the dreaded Galv flu either.

[mezmo]

Hi Kody,

I hadn't realized that you were going to be welding up your own frame. I've
heard that welding galvanized is all of the pain that you described as well as
health dangerous. I was thinking more that you were going to be purchasing
a ready built frame and I really think the extra cost would be worth it for
longevity and reduced maintenance. But then there is always that little detail
called "cost" ! Ha !

So of course your best path would be regular steel for the 'ease' of welding
and then the cold galvanizing paint you mentioned. I'm not familiar with that,
so I'll have to Google that.

Over the years, I've dealt with a lot of rusty trailer frames/chassis that have all
been a pain to prepare and repaint, thus my admiration for the Australian
penchant for galvanized trailer/caravan frames now-a-days. I also like their
independent trailing arm suspensions that I've seen on the web on the higher
end caravans [Kimberley Karavan et.al.].

Good luck with the build and fabrication.

Cheers,
Norm/mezmo

[webbaldo]

can you not just weld the thing up then get it hot galv dipped?

[Kody]

Hi guys,
I very much prefer to weld my own frame from scratch. By doing it myself, I know it has been welded correctly to my own specs and requirements. The RHS that I will be using is grade 350 and comes painted with a blue paint. It also comes as a galvanized product but the thickness of the coating is on the thin side. This is to help the welding process but I have found that it is still a pain in the neck to weld for all the previously expressed reasons. I certainly can get the frame hot dipped galvanized but this will cost an arm and a leg to have done. The factory where this is done is about 200 miles south from where I live and transport costs to get the frame there and back are just too expensive. There is nothing wrong with Cold Galvanizing Paint. This is a very dense spheroidal zinc rich medium that really works and lasts a long long time. I made some overhead lights many years ago for the State Gov. and the drawings stated that the finished job had to be coated with two coats of Cold Gal. Paint. The TD frame will not be subjected to salt water like a boat trailer so the Cold Gal. Paint will last a very long time. I have used the same paint on my boat trailer with fabulous results. The paint I use is about 90% zinc and it certainly works.
There are no trailer frames readily available here for a TD. If you want one, it almost always has to be custom built. There is a trailer making firm close to where I live and they have been very helpful in being able to supply me with all the running gear when I need it. I can't wait to start building my own frame. I expect it to be within 1mm on the diagonals for squareness and the overall "flatness" of the frame to be within 0.5mm. I made two workbenches, 8' x 42"' and the flatness of the benches was within 1/64 of an inch or better all over. This degree of accuracy was essential as I was building high performance wings for radio controlled aircraft but that's another story.
The next detail in the designing is how I will lay out the side panels for the least number of joints. The method of joining the panels will be to cut an 1/8" groove along each edge to be joined and fit a continuous tenon to bridge and fill the joint. I will post the drawings this coming week for you all to see.

Kody and Joe