Frame materials: S.S. Vs. Al Vs. Steel

[TD Beej]

My current design thinking has the frame largely embedded in the structure. The implications are that repairs and maintenance would be problematic. And I haven't priced out material which may cause me to change my thinking entirely but since I don't think there should me much material I don't know how much of an effect this will have.

Stainless Steel
- Pros: No rust, no dialectic, no fatigue,
- Cons: Pricey.

Aluminum
- Pros: Light, No rust
- Cons: Fatigue, dialectic issues

Steel
- Pros: Cheep, no fatigue
- Cons: Rust

Any thoughts? SS seems the most appropriate for the long term and I am a do it right the first time type but each material has its own merits and I may fooling myself at the value SS over the others.

Thanks,
Beej

[danlott]

Not a metal expert here, but I believe that a steel frame properly primed and painted will far out last the trailer that you build on top of it.

Dan

[Ageless]

SS in dimensions for a frame is going to be very expensive. The time spent properly prepping steel will be a lot cheaper.

[asianflava]

How about welding? A nice TIG setup and a person who knows how to use it is necessary for SS. Just about any rig will weld steel tube.

Steel painted with something like Rust Bullet or POR15 will definitely allow the frame to outlive the box you plan on putting on it.

[dreadcptflint]

What about the weight factor?

[boxcar]

If rust is your major issue with mild steel. Build your frame then take it to a galvanizer and have it diped. Just make sure the frame is properly ventilated... Or just treat it with PAR 15. It will out last you using iether method. Stainless is expensive it does suffer fatige cracks and is heavyer. It can be welded using all methods / but tig is the best when dealing with stainless..... Just my thoughts...Boxcar...

[Corwin C]

Al and SS need to be handled differently than regular steel. They aren't necessarily harder to work with, but they are definitely different and require different methods/tools/fluxes to cut and weld. They are also going to cost more, be prepared for the price tag.

In my opinion, I would use conventional steel unless ...

a. your build is very weight critical ... consider Al.

b. your build will be continuously subjected to an extremely corrosive environment (saltwater, road salt, etc.) ... consider SS.

I think that most have found that properly coated, regular steel will last for 50 years or more with no problems in most situations. Even longer with regular maintenance.

[kennyrayandersen]

just a comment that steel is not immune from fatigue, and properly sized and designed aluminum also shouldn't experience any fatigue problems.

Aluminum if you really 'must' save weight, steel if you don't. SS, if you are just flaunting your money or you have a 'real' need.

[Shadow Catcher]

SS because of the amount of chromium (what makes it SS) is some what more brittle and as stated rather expensive and welding is much more difficult TIG is best. Aluminum does have a finite modulus of elasticity but there are DC3's still flying that are older than I am and it is light weight and can be MIG welded. Steel, there are alloys other than common 1018 steel that can be fabbed up. If you want the ultimate, Titanium would be it but lots of $$$$.
I went after an aluminum frame and out Mega-Mini is larger and lighter weight than most conventional framed comparable trailers i.e. Camp Inn. The LG Silver Shadow is about the same weight and shorter narrower and has few of the amenities.

[angib]

Aluminum does have a finite modulus of elasticity but there are DC3's still flying that are older than I am and it is light weight and can be MIG welded.

Don't get caught out by this - DC3s were build before age-hardening aluminium alloys were discovered (Duralumin being the most wideknown), so they don't have the fatigue life limitations (and lighter weight) of pretty much all subsequent planes.

Andrew

[vrodjason]

Powder coated steel

[2bits]

Steel. +1 on the comments, not sure I would even consider either of the other choices.