Help me design an aluminum frame please.

[JimGolden]

You guys have really got me thinking on this now. I'm going to research this deeper. Not just this specific trailer, but aluminum framed trailers in general. I see them all over the place and assumed they must be OK as they're so common. Heck, Mack Truck used to offer aluminum frame rails on their rigs. I don't know if they do now or not. I would have thought airplanes take more beating than trailers, but I could be wrong on that.

I'm going to dig into this. Report back when I have something.

Thank you for the info.

[Inland RV Center, In]

Originally Posted by JimGolden

You guys have really got me thinking on this now. I'm going to research this deeper. Not just this specific trailer, but aluminum framed trailers in general. I see them all over the place and assumed they must be OK as they're so common. Heck, Mack Truck used to offer aluminum frame rails on their rigs. I don't know if they do now or not. I would have thought airplanes take more beating than trailers, but I could be wrong on that.

I'm going to dig into this. Report back when I have something.

Thank you for the info.

Airstream construction methods are similiar to aircraft, but not the same.

Aircraft methods of construction methods are called "monocoque".

Airstream methods of construction is called "semi-monocoque".

"Monocoque" is defined as a "load bearing shell".

Aircraft do not have a frame, Airstream does.

Airstream has an incomplete shell, since it has a frame. The overall performance of the shell is therefore somewhat compromised, as opposed to an aircraft.

Accordingly, a semi-monocoque method of construction, since it's partially dependent on a frame, can punish that frame as the shell twists when in motion.

Aircraft twist in motion, but since they do not have a frame, there is no deleterious shell behavior, at least within the confines of the designed "G- force" limits.

The bottom line is very simple.

An aluminum framed travel trailer, "WON'T WORK," without sustaining severe structural failures.

Andy

[at_wanderer]

Jim,

I don't know if this information is correct, but it could help in your research. I was told that General Motors also put aluminum frames under their busses. Somewhere between 1948 - 1956(?) or even up to 1962 on the 4102 - 4106 models.

Sorry that is sketchy second-hand info, but it is something to look at to possibly see what their experiences were.

Brent

[A-Merry-Can]

it would cost a lot more, but what about stainless? at least the tongue and rear section? she'd bling like a new quarter!



jp

[Action]

I believe there would be a way of building a stronger enough AL frame. Just not in the same thickness as steel not in the same manner as steel. There are small (up to 25') power boats out there that work. And huge yachts that are made of that light stuff. The issue usually is cost for a production unit. Huge yachts are custom and one off so price while is some what of an issue it's not usually the only one. And this has to be considered after the thing is engineered. Or in this case since Skip doesn't have a lab to work in, I would suggest it needs to be over-engineered to survive.

And why do it?
To prove it can be done? OK knock your socks off.
To do a replacement on a unit that wasn't maintained and it rusted through? Just weld in a steel patch and move on. 'Cause if you don't, your off time may be spent entirely making something untried work. And camping is so much more fun than that.

>>>>>>>>>>>>>>>>>>>>>Action

[at_wanderer]

Carbon Fiber, anyone?........Hey, I'm not joking!

[JimGolden]

Now you're talking! We could do a new shell out of it too, and pressurize it. No more uncomfortable camping high up in the Rockies

Composites don't fatigue, have triple the strength of steel, don't corrode, are light and extremely stiff. Oh yeah, it just costs twenty times as much as aluminum...I knew there had to be a downside in there somewhere

Man it'd be cool though!

[till]

Now I would pay to see a carbon fiber shell Airstream on a Stainless steel frame with gold plated rims. But all the name plates will have to be aluminum.

[Action]

We would have to change the name from Silver Bullet to Bullet proof.

>>>>>>>>>>>>>Action

[scottanlily]

Hello everyone , Well it is interesting to know that airstream did attempt
to utilze an aluminum frame ,testing and such .thanks Andy for that information ,too bad it was not sucessful .I agree on the twisting /flexing
would be detriment to the aluminum frame .As Jim golden pointed out with
riviting a frame instead of welding it.Had a jeep turbo 400 trans once with a
huge crack starting at 1 area of the bell housing going up over to the top side ,say 8 " long ,it was welded proffesionally and the bellhousing recracked
right on the weld and right along side the weld ,so both sustained cracks.a new case fixed the wagoneers transmission finally ,but I remeber that it was
quite a surprise to see that happen .aluminum is tricky and takes considerable
thought to fabricate somthing like a frame ,and to be successful .A frame is not a bellhousing ,but the stress on that cracked area was enough to rebreak it ,no loose bolts as I myself did the R&R of the trans both times , which was
what we thought must have happened before ,hard to say ,still broke.

Scott

[wahoonc]

however, I spent a fair share of my adult life working with metals. It possibly could be done. Cost effective I doubt it. There have been great strides in composites and metal alloys in the past 35 years. But if you really want to go first class...and light weight... why not titanium

Aaron

[SkipS]

any idea how much the material cost for a 22 foot titanium frame would cost for the materials? -seriously- how much weight would it save over steel? I see there is a kit aircraft using titanium for the fuselage tubes, maybe that is the way to go?

looks like aluminum has been done and failed. at least this is more fun than actually building a bad idea.

[JimGolden]

Titanium is really hard to machine. Other than that, it's pretty good stuff. Weighs more than aluminum, but still a lot less than steel. Very expensive though. Unless you've got the inside source

Realistically though, you don't have to machine it very much. If you've got the pipeline, it's worth looking into!

[till]

Also make sure that it is not pure titanium. The pure stuff is very flexable.

[Althea68]

I am an A&P as well and I can attest to the frequency of Aluminium failures in many many jets. We inspect them though on a required regulated schedule and replace the questionable components. If you were into that kind of inspection and maintenance ritual you would probably be ok. However, what would you use for fasteners i.e. nuts and particularly bolts? You would certainly wind up with dis-similar metal corrosion at your fastener points. I don't believe you could find or use Al bolts that could hold up to the load and stress of the road.

[nickcrowhurst]

Boatdoc's stainless steel frame is well documented here:
http://www.airforums.com/forums/f36/...ame-29294.html

If the cost of stainless is excessive, I would consider building a galvanized steel frame as used in the European Airstreams. (Is this still not available in the USA?). When I built my 6 ton wooden sailing yacht in the 1970's, all the fittings were hot-dipped galvanized, and they are still corrosion free, after 35 years in a salt water environment. If the local galvanizing tank is too small for a full frame, I would construct the frame in small sections, just small enough to go in the tank. Put it together with galvanized bolts, with electrolytic insulation between the frame, bolts and aluminium shell, and it will outlast most of us.
Nick.

[nickcrowhurst]

Further to my discussion above, I've checked with the American Galvanisers' Association, and there are three galvanizers with tanks (kettles in their parlance) that would take your complete frame. They are in Miami, Tampa, and Jacksonville, so you're spoilt for choice. Here's the link:
American Galvanizers Association

Nick.

[nickcrowhurst]

Here's a few points to consider when preparing steel for hot-dip galvanizing:
1. Any completely sealed sections must have sufficient access holes made so that air is not explosively trapped, and the zinc must coat all sides of the steel.
2. Any holes drilled after galvanizing will breach the protective coating, so these should be minimized. However, the electrolytic nature of the protective layer means that the zinc gradually erodes at any scratches or breaches, rather than the steel.
3. Heat distortion of the frame can occur because of the high temperature in the kettle. Be prepared to check for this, and be prepared for some imaginative use of hydraulic jacks and levers. I don't know how relevant this will be in an Airstream frame, but the European Airstreams are built this way.
4. The frame and shell can be separated with a dielectric gasket and or paste, such as zinc chromate. Bolts can pass through dielectric bushes, such as nylon.
5. The steel must be bare of all coatings before dipping. If in doubt, I get the galvanizer to shot-blast the steel. They usually offer that facility.
Nick

[Action]

Thanks Nick for your input. However the original poster only posted 3 times on this website. All 3 being in this thread and all 3 being over 4 years ago.

I wonder if he is still in the info gathering process?

>>>>>>>>>>>>Action

[skipnsb]

I am the original poster. Unfortunately, my Airstream project is being used as storage for some of my other projects. Which is ok for since my retirement/travel plans have changed, but now that the government has told us the recession was over....

Seriously, I appreciate the responses to my original post, and continue to dream. SkipS