Aluminum Trailer Questions

Hey, pretty cool. Looks like air-ride bags for trailers. Good show. They look very well built, too.

Though aluminum is tempting I would lean toward mild steel instead. By weight the steel and aluminum are virtually the same stiffness. Of course aluminum will have better corrosion resistance but the steel can be painted easily. When in comes to joining though the steel has the advantage. Especially when you have towed your kayaks to some remote area, bent something on your trailer, and the only person close by that can weld it just has a 115 volt wire feed welder loaded with flux core wire. Eric

Jimbo1490: "Welding is often not a choice since not all alloys of Al are weldable. Even among the weldable alloys, the welds and immeditaely adjacent areas will be weaker than the unwelded parts if the stock was heat treated.

Aircraft are extensively riveted together. Until the latest generation of large aircraft, riveting was used exclusively to join aluminum panels together. This is still true of wings, which always serve as fuel tanks. Leaks are a very minimal problem even though kero is much slipperier than water. In aircraft, adhesive bonding is slowly replacing riveting. For the most part it is not being replaced by welding."

The Comet he mentioned was an early British aluminum airliner that broke apart in flight from unexpected metal fatigue.

--jsw

It is a bit more complex, at least for the Comet. In those days 2024, which is an unweldable copper-aluminum alloy was the most commonly used "aluminum" used for airplane construction (I think that may be true today).

2024-T4 has an ultimate tensile strength of 68,000 psi and 6061-T6 an ultimate tensile strength of 45,000 psi.

Looks like a functional duplicate of the ols Austin Mini suspension system - should work pretty good - perhaps a little "strong " for the application (designed for 800 lb trailer load)

Or beside the deck, with the suspension he is using.

Aluminum boat trailers are routinely welded.

All of the aluminum on my plane is 6061T6 - rivetted. All flight surfaces and flight structures.

What's the difference?

--jsw

The stuff on the plane is .016 to .030" thick. The trailer is minimum

3/16 inch - mostly 1/4 inch wall.

It's very difficult to weld any aluminum alloy above the 5000 series without creating a crack-sensitive joint. And 5000 series and below are not very strong. Besides that, 5052, which is used a lot in boats, has a "cracking peak" at 2.5% magnesium, so you need to use filler that will supply plenty of extra magnesium to be sure your weld doesn't hit the cracking peak after welding.

6061 is very crack sensitive if you use insufficient filler metal. Welds in 6061 are tricky because welding exceeds the artificial ageing temperature; your heat-affected zone will be a mess of varying hardness and ductility, and it will change over time.

It is almost impossible to produce a weld in aluminum that is as strong as the base metal. In contrast, mild-steel welds generally are close in strength and ductility to the base metal.

Thus, they don't weld aluminum on aircraft. They aren't welding the new aluminum car chassis, either.

The boat trailer is probably not made from 6061 aluminum :-)

The only welded aluminum parts on our plane are the fuel tanks. I believe also the only parts that are not 6061.

Actually, it is. See

A guess: 2219. Popular for welded tanks, and one of the few of the

2000 series that welds well.

My old partner in the machine shop had some that came into our shop to be modified for a new filler neck. We had no idea what it was, so we sent it out to our favorite welding shop. They had no idea what it was, either.

Apparently it's well-known among airframe mechanics.

I can't tell from the photo but I seriously doubt that a welded trailer would have been built from 6061T6 as the materials list shows.

If for no other reason than the area around every weld would have magically lost about half its strength (ultimate tensile strength). Why would one want to built a trailer of relatively high priced, high strength, aluminum and deliberately destroy the strength of the aluminum?

My son-in-law has an aluminum boat trailer made of 6061T651 - some parts are welded, some are bolted. Being a high end factory built trailer the weldments MAY have been heat treated - but T6 or T651 returns to about a T4 in less than a year after welding, and keeps getting better from there.

Which is partially true. Although it isn't quite that simple. The ageing/artificial aging process is largely dependent on the pre aging solution heat treatment. If you melt 606T6 it looses much of its pre welded properties and if the ageing process doesn't start from a maximum solution treatment than there is no way of telling what is going to occur See"

for a more in depth discussion with additional references.

And, while it is "probably good enough for a fish boat" as my Maine State relatives might say it could be a different story for a flying machine :-)

I ran across a blog by a guy building a submarine out of 6061, but I never did follow up to see how he did. The thing that got my attention in thiws thread was "Sea" kayaks. I don't know how well 6061 holds up to saltwater. Otherwise 6061 is really nice to work with. Cuts well (compared to 5052) and is pretty easy to weld.