Build Steel or Aluminum Trailer?

[p40whk]

Hi all,

Been lurking for quite a while and am just beginning my serious foray into building my own teardrop. I have welding skills and am a licensed aircraft mechanic so building is preferable over buying for me. I've been debating on the pros and cons of an aluminum trailer over a steel trailer and wanted to get the input from people here who may have experience.

The obvious pros are weight savings, easy to tool, and corrosion resistance. The cons are the equipment and technique needed to weld aluminum, the cost is higher, and durability could be lower if not built correctly.

Was wondering if cost was not an issue for you and you had the skills and equipment to construct an Aluminumk trailer, would you go that route and why or would you choose steel and why?

Thanks!

[Redneck Teepee]

Hi all,

Been lurking for quite a while and am just beginning my serious foray into building my own teardrop. I have welding skills and am a licensed aircraft mechanic so building is preferable over buying for me. I've been debating on the pros and cons of an aluminum trailer over a steel trailer and wanted to get the input from people here who may have experience.

The obvious pros are weight savings, easy to tool, and corrosion resistance. The cons are the equipment and technique needed to weld aluminum, the cost is higher, and durability could be lower if not built correctly.

Was wondering if cost was not an issue for you and you had the skills and equipment to construct an Aluminumk trailer, would you go that route and why or would you choose steel and why?

Thanks!

Welcome to the site P40. You have got it figured correctly about needing special equipment/skills, not to mention expensive for constructing an aluminum trailer.
A properly engineered steel frame trailer can be built very strong and light with minimal materials with various wall thicknesses used in the appropriate places.

If you look at the old Kenskill and or Kit frames, they were very basic bare bones frames and are still being drug down the road today with no issues 70 years later.

My theory in life now that I am in my senior years is that it only has to outlast me

[tony.latham]

if cost was not an issue for you and you had the skills and equipment to construct an Aluminumk trailer

I'd seriously consider it. But during that process, I'd also ask myself (if I was yourself) why experimental taildraggers are being built with 4130 steel frames and not aluminum. And I don't have an answer. It's been a decade since my EAA membership expired, so perhaps it's being done these days. Dunno.

T

[KCStudly]

Fatigue resistance. I chose to build in steel.

Rule of thumb, aluminum is about 1/3 the weight of steel, but steel is about 3 times stronger, so shape for shape, in structures like a trailer frame steel gets this job done better, IMO, for all of the reasons you stated.

Now if you want to build a monocoque design, like RandyG started to do on his Aluminum Frame RD, where the geometry of the structure is incorporated into a unit body construction, then I can see how aluminum would be the better choice than steel. Or if you are building a really large trailer (think 30 ft toy hauler) where the weight savings can mean a significant difference in hauling capacity or weight category, then maybe aluminum would be worth considering.

There was a recent build, an Atma Traveler clone, that had a home designed aluminum trailer, but I don't think it has enough mileage on it yet to validate durability.

IIRC, Shadow Catcher's Compass Rose has an aluminum chassis that needed structural repair shortly after commissioning (before the roll over damage repairs?).

[KCStudly]

Forgot to mention, aluminum also looses a lot of its strength when welded due to the annealing effect.

[alaska teardrop]

To reiterate what Redneck, Tony & KC have said and add important considerations to their thoughts.

Size.
Weight goal.
Type of suspension.
Tongue length.
Proper welding where the tongue rails meet the cabin framing.

Andrews tongue strength page: http://www.angib.pwp.blueyonder.co.uk/t ... tear84.htm

Bryants build that KC mentioned in which there is a discussion about aluminum tongue rails: viewtopic.php?f=7&t=61645

My idea of a simple lightweight chassis that could be done in aluminum: viewtopic.php?f=35&t=12220

Fred

[Shadow Catcher]

To correct the previous, we did not have a failure, I did however learn of the first one built by Eye4Design and which we owned first. Quite frankly I was concerned and reinforced the tongue. I am still not happy as there is more flex than I like. Aluminum has a finite modulus of elasticity but certainly there are DC3's still flying. 4130 or more correctly 4140 is what is used for fork lift forks and crane hook it has a very high modulus of elasticity. I can see, most parts are forged as it is very difficult to weld.
Just completed is the replacement of the right side of the trailer which had sustained minor damage in the accident. In the repair process it was discovered that joints had never been properly sealed and the luan backing of the Filon had gotten wet causing disbonding... However because it is aluminum there is no rust... if the frame had been wood there would be rot.
The frame as pictured is 1 X 1.5 X .06 and is strong enough for me to stand on. Aluminum welded correctly is as strong as the parent metal

[angib]

Aluminium is a fine material - if you have years of experience of building trailers from it, or you have a team of aeronautical stressers to design it. For everyone else, it is a bit of a gamble.

Most trailers don't fail on one-cycle strength (one enormous load) but on fatigue strength (many little jiggles) when cracking starts. Most aluminium alloys have the disadvantage, compared to steel, that they do not have a fatigue (or endurance) limit, so even if the jiggles are tiny, if it is jiggled for long enough, in the end the aluminium will fracture. This graph from Wikipedia shows the effect:



So in steel as long as the jiggles are less than about half the maximum strength, it doesn't matter if there are one million or one billion of them, the steel won't start cracking. But with aluminium alloys, there is no such limit.

DC3s were built before the much stronger age-hardening aluminium alloys (Duralumin was the first, I think) had been discovered, which is why many DC3s are still flying when younger planes aren't. It says diddly squat about the long term strength of an aluminium trailer frame.

Welders often like to quote the 'stronger than the parent metal' claim, but they rarely say 'failure will occur in the parent material in the heat-affected zone right next to the weld', as that isn't such good advertising. And they are talking about one-cycle strength, not fatigue strength, which is often much lower for welds.

The Australian trailer rules go so far as to recommend that tongues/A-frames are not welded to the front cross member of the trailer at the point where they cross it, so that the lower fatigue strength of the welds do not start cracking - and the Aussies have a lot of washboard roads, which are the ideal 'jiggler' to cause fatigue failure, so they have more experience of this than most.

Clearly, it is possible to build a strong, long-lasting trailer frame from aluminium, but it isn't guaranteed.

[p40whk]

Thanks guys,

I went to the Travel Sports and Boat show this weekend and looked at some aluminum trailers. As mentioned above, you basically have to over build them for them to hold up and the weight savings is not that substantial.

I've decided steel will be my material of choice.

It was good to see the aircraft analogy (I'me a licensed aircraft mechanic) but what most people don't realize is aircraft are typically a monocoque structure where the loads are distributed throughout the skin of the aircraft, can't really do that with just the trailer.

I've got more research to do before I make all my decisions final but the trailer material is done so I'm one step closer!

Thanks for the help!