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Old 11-12-2015, 08:19 AM   #1
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Steel to Aluminum frame

Aside from the initial cost of building a new frame out of AL, what would be the negatives? Is structural integrity going to be a problem? Has anyone done this yet?

Thank you!
Andy
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Old 11-12-2015, 08:44 AM   #2
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Will not be as stiff unless you upsize the members, which you could do given the weight savings.
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Old 11-12-2015, 09:14 AM   #3
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Steel to Aluminum frame

They discussed this on the VAP a couple of weeks ago. Collin Hyde stated that when they do things like this in the car mod world, they increase the thickness of the metal by 50% for added strength. It think it's a great idea overall.


I saw a post here on the forums where some one made a frame out of SS. Talk about a frame that will out live you!

http://www.airforums.com/forums/322122-post.html
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Old 11-12-2015, 08:26 PM   #4
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I do like the idea of the frame never touching the wood floor, since you asked for issue here are the ones I know.

Aluminum has the same issues with water as steel does. It is also more sacrificial next to zinc on the galvanic scale. There are stories of construction wire being left inside of aluminum boats, those boats develop leaks.

For strength aluminum needs to be thicker which tends to eliminate the weight savings.

From what I can see, AS construction issues are based on fresh water intrusion control (from all sides).
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Old 11-13-2015, 11:45 AM   #5
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What about carbon fiber? Will that bond or attach properly - could get strength and weight benefit
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Old 11-13-2015, 01:37 PM   #6
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The reasons for increased thickness of aluminum structures compared to steel are basically twofold: strength and stiffness. The yield strength of 6061-T6 aluminum (your most logical choice) is only slightly lower than the steel of the trailer, which I assume to be low carbon steel. However, aluminum is about 3x as "springy" as steel of the same thickness. Bottom line is that your trailer's body and other parts might bend excessively on an aluminum frame the same thickness of your steel one due to increased operational deflections. Likewise, your interior walls, floor, and other parts could also suffer from the increased movement. Therefore, you would likely increase aluminum frame thickness by a factor of 1.5-2, resulting in a potential weight saving of around 20-25% for the frame. I have to raise a question: why in the world would you want an aluminum frame?
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Old 11-13-2015, 02:15 PM   #7
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Exactly

Quote:
Originally Posted by biyak269 View Post
The reasons for increased thickness of aluminum structures compared to steel are basically twofold: strength and stiffness. The yield strength of 6061-T6 aluminum (your most logical choice) is only slightly lower than the steel of the trailer, which I assume to be low carbon steel. However, aluminum is about 3x as "springy" as steel of the same thickness. Bottom line is that your trailer's body and other parts might bend excessively on an aluminum frame the same thickness of your steel one due to increased operational deflections. Likewise, your interior walls, floor, and other parts could also suffer from the increased movement. Therefore, you would likely increase aluminum frame thickness by a factor of 1.5-2, resulting in a potential weight saving of around 20-25% for the frame. I have to raise a question: why in the world would you want an aluminum frame?
Stiffness, not strength, is the issue when replacing steel structures with aluminum. Steel modulus is 29E6 compared to 10E6 for aluminum.
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Old 11-13-2015, 05:49 PM   #8
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I always thought the reason for an aluminum frame was avoiding rusting. I have assumed that aluminum corrodes at a much slower rate than steel rusts. Is this correct?
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Old 11-13-2015, 07:19 PM   #9
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That is true, but if steel lasts thirty years in the worst of cases....


Brevi tempore!
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Old 11-13-2015, 07:26 PM   #10
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They make transport truck frames of aluminum so it is possible. Reason not to do it, mostly cost.

There is a trailer manufacturer near here that sends out all their chassis to be galvanized. You see galvanized trailers all over the place now, Home Depot sells them. You could probably get a new heavy duty chassis made by a trailer manufacturer and galvanized, it would last indefinitely.
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Old 11-14-2015, 07:06 AM   #11
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Thanks everyone. I am doing a frame off resto. It was just a thought about the AL frame. I have a buddy who owns an AL fabricating shop. That's why I asked. I spoke with him the other day and he said he just opened a steel shop also and moved to a bigger location for full fabrication/restorations. I am currently gutting the AS and pulling all the belly pans off. I work 10 hour days minimum so not much time in the evenings for more work. I'm trying to do the easy stuff and then when it comes to the shell, I'll leave it to him and his team. seeing as he will be making my new frame.

Thanks again for the info guys.
Andy Moreau
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Old 11-15-2015, 12:10 PM   #12
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Ist question - How long did the original frame last? How long do you want the new one to last?

A stock type steel frame, protected with the best rust proof paint, or the type of paint used on seagoing ships, will last twice as long as a stock one.

Have it galvanized and the life will be indefinite. Possibly 50 - 100 years.
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Old 11-16-2015, 05:59 PM   #13
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I will bring this to my welders attention when he arrives. May as well do it right the first time!
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Old 11-16-2015, 07:27 PM   #14
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Build it out of steel, once it is done and one Soild piece have the whole frame hot dipped galvanized. After that, acid wash it, and paint it with poor 15. That should last a little while!
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