Aluminum frame?

[deadly99]

I have a utility trailer that is an aluminum framed trailer. Debating building it into a tear drop style overland trailer. Seems everyone uses steel frames, am I going to regret using an aluminum frame? Appreciate any advice you may have, thanks.

 

[762X39]

I have a utility trailer that is an aluminum framed trailer. Debating building it into a tear drop style overland trailer. Seems everyone uses steel frames, am I going to regret using an aluminum frame? Appreciate any advice you may have, thanks.

There is nothing wrong with using an aluminium framed trailer as a base for your Teardrop as long as the suspension and load rating are appropriate for your project. Most "Bubba" fabricators can't weld aluminium and also are not interested in doing the engineering math to be sure that they have chosen the right thickness and dimensions of square or rectangular tubing for their project. I don't need a teardrop at this time but if I decide to build one it will be on an aluminium frame.

 

[TernOverland]

As John alluded to, many fabricators simply attempt to replace steel with aluminum without taking into account the engineering requirements. Aluminum welds do not generally handle fatigue as well as steel, so bolting and riveting for some joints that are subjected to high stress is a better option. The bottom line is that aluminum is awesome if used properly. Your utility frame may be require some reinforcement in critical areas, but may be fine. Get the advice of someone who knows what they are looking at!

 

[mtnbike28]

Ask Jim65Wagon - his TD - Crowswing is on a AL frame.
http://forum.expeditionportal.com/threads/68693-The-CrowsWing-Offroad-Teardrop-Trailer

I will say, if a light TD, I would have no problem with AL frame.

 

[deadly99]

Thanks for the advice, much appreciated

 

[KD702]

Just My $0.02. I have been talking about building one too with a good friend that is a fabricator. He brought up one point I am finding hard to look past. Say you are out and you do have some type of issue, such as accidental damage or failure of the frame, you can almost always find someone with a welder to repair a steel frame. Heck most farmers/ranchers or small repair shop in most small towns will have one (if not know someone who does). That being said, finding someone who can repair aluminum tends to be much harder, and if it is your frame that needs repair, you may be stuck. So on that note, my plan is to build my lower frame out of steel and the rest of the camper out of Aluminum and other light weight material.

 

[TernOverland]

Just My $0.02. I have been talking about building one too with a good friend that is a fabricator. He brought up one point I am finding hard to look past. Say you are out and you do have some type of issue, such as accidental damage or failure of the frame, you can almost always find someone with a welder to repair a steel frame. Heck most farmers/ranchers or small repair shop in most small towns will have one (if not know someone who does). That being said, finding someone who can repair aluminum tends to be much harder, and if it is your frame that needs repair, you may be stuck. So on that note, my plan is to build my lower frame out of steel and the rest of the camper out of Aluminum and other light weight material.

Your friend has a point, BUT, the kind of failures most likely to need welding are fatigue related. Those failures usually happen over a long period of time. They can be detected way in advance. Regular inspection should be routine for anyone spending time in the outback, or away from services. I will stress again that properly designed aluminum structures are extremely durable, and they do not suffer from corrosion related failures as often as steel. There are planes with aluminum airframes that have been flying for 50 years, and are still reliable. They do get regular inspections though.

Another approach to the problem is a steel / aluminum hybrid structure as you mentioned. I've designed many of them that use steel where welds are required , or in high flex areas, and aluminum for the rest of the structure. It makes fabrication easier, saves lots of weight, and those fatigue prone areas can be welded in a pinch.

 

[LikeABoss]

The latest generation light military trailer (M1101 and M1102) are aluminum with NO welds specifically for off road due to the fatigue issue. All joints are huck bolted. Check out Schutt industries trailers who is one of the makers. I'm building a rig using a LTT flatdeck extended from them. Though no expert by any means, I'm staying away from aluminum welds from what I have learned. I welded a steel frame which sits on the military platform then bolt and rivet the aluminum skin onto that.

 

[Silverhorse]

I was wondering this as well. I'm thinking about getting one of the Alum-line Sport/cargo units and modifying it with a large RTT but stress cracks are a concern. We have an older Airstream which are extremely well built but they use a steel frame... I'm a back yard fabricator and have been welding for years but have never welding aluminum. What i was always told when using aluminum for bumpers etc was- just double the thinkness of material.. I'll check and see what they're using for the frames...

http://www.alumline.com/products/sport-and-toy-haulers/multi-sport-camping-trailer
Camping Trailers Toy Haulers - CT 23

 

[flipmachine]

I use aluminum on some of my builds, good rule of thumb is double up material thickness from steel, if you use 1/8 wall steel for your frame usually, go 1/4 aluminum

 

[wandererr]

I use aluminum on some of my builds, good rule of thumb is double up material thickness from steel, if you use 1/8 wall steel for your frame usually, go 1/4 aluminum

So weight savings are negligible since steel is 2.5 times heavier then aluminum with doubled thickness you're almost there?

 

[downhill]

Low carbon "mild steel" weighs 2.97 x aluminum. Yield strength of typical astm 513 steel used in tubing is 72,000. Yield strength of typical astm A36 used in angle and
channel is 35,000. Typical yield strength of 6061-T6 or T651 aluminum used in tube, channel and angle is 40,000. You can typically save 35% to 50% by going to aluminum in simple structures.

Choosing the right material for the structure, joint design, fastener selection, etc. is a complex task.

 

[Hillbilly Heaven]

Here are some simple facts I found. I am speaking strictly from an automotive standpoint. I have used 2x3x0.083 steel for connecting subframes on unibody cars. If I was deciding on whether to build a trailer out of steel or aluminum this would be the steel of choice for me. Now if we follow the rule of doubling the wall thickness when going from steel to aluminum I find the easiest material for me to find locally is 2x3x0.250.
Comparing the two materials:
2x3x0.083 A513 steel weighs 2.7347 pounds per foot Ultimate Tensile Strength 87,000 PSI Yield Strength 72,000 PSI
2x3x0.250 6061 T6 aluminum weighs 2.646 pounds per foot Ultimate Tensile Strength 45,000 PSI Yield Strength 40,000 PSI
Not much weight savings unless you are using a lot of tubing.

This is where materials knowledge will prove useful or finding someone that knows structural strengths.
My thoughts and this is just my opinion I don't think it is enough weight savings.

Maybe stepping up to this might help. I don't know as it is just an assumption.
3x3x0.1875 6061 T6 weighs 2.474 pounds per foot. At almost 0.3 pound per foot weight loss again not much gain unless you use a lot.
There are bigger gains to be had by going with this:
2x2x0.250 6061 T6 weighs 2.0528 pounds per foot. Now we are talking weight loss of almost 0.7 pound per foot. This might add up to significant gains depending upon if additional bracing is require vs using steel.

To make an honest decision it takes someone who has been fabricating a long time in both steel and aluminum or a materials engineer. Anything else is just a guess that could lead to failure and wasted material.

One other possibility to look at is structural shapes like I beams. Using a combination of I beams for main rails and square tubing for crossmembers may net some usable weight gains without losing strength.

Keep in mind the bare frame may appear weak or springy but that is not a bad thing as some flex will help relieve stress fractures unless you always flex in the same spot. Same reasoning as why tall buildings actually sway. Remember your camper body (unless you fully float mount) and depending on type of axle chosen will add some rigidity.

First thing I would do is start out with napkin sketches of basic size you want and work up from there with some consulting from the experts.

 

[MrOffshore]

We use aluminum on EVERYTHING we build...we back our frames with a 3 year warranty, so without question, we are confident that they can handle real-world use. We find that the full aluminum, cage frame is better than having only an aluminum base frame...attaching stick and tin walls or bolting the walls on separately is not as strong as an entire cage.

 

[Roaddude]

Yep, from everything I can gather from researching the best made camping trailers out there right now, aluminum trailer frames are a great choice. That said, for DYI, might not be. Both Patriot (in Australia) and Schutt (in Wisconsin) use aluminum but have huge processing plants dedicated to creating aluminum frames. Patriot welds and hot-dip galvanizes their frames, while Schutt uses Alcoa's cool huck-bolt system, line-x's the hell out of their frames, and give a 10yr warranty on their trailers.

I like the Schutt frames a lot and have already sent for a quote request on their XVenture XV-2 trailer. They've been awarded contract after contract to make trailers for US military. I trust that a lot.

Here's a vid on their process: https://www.youtube.com/watch?v=ZPxK6Mr0LLQ