BCM Community
Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Scott & Heather on October 07, 2012, 03:41:46 PM
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When we converted our coach from a passenger bus to an RV, we riveted 1/8 inch aluminum sheet to the sides where the windows used to be (after our 9" roof raise), but I would have loved to have smooth sides sans the rivets. Because I am completely dumb when it comes to aluminum alloy types and aluminum welding, I wanted to poke some of your brains on this. As some of you know, we have our sights possibly set on building a 35 foot aluminum box over a mild steel frame that we will mount to a stretched Kenworth truck/frame. Not exactly a toter, but rather a Semi Truck based Coach. I'm looking for out-of-the-box thinking...and ideas on welding the aluminum roof/sides/bottom to create something nearly hermetically sealed and bracketing the panels somehow to the mild steel tubing of the interior frame. Help me think out loud here. Have any of you attached your aluminum skin to your bus frame sans riveting?
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Welding it would be a gigantic hassle... thin sheets warp and expand in the weld area and it's almost impossible to make a smooth seam unless you have some really fancy welding equipment and know what you're doing.
Think Sikaflex instead. The stuff is amazing for skins....
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Welding it would be a gigantic hassle... thin sheets warp and expand in the weld area and it's almost impossible to make a smooth seam unless you have some really fancy welding equipment and know what you're doing.
Think Sikaflex instead. The stuff is amazing for skins....
Yep, Sikaflex.
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That is the purpose of rivets and nut and bolts welding a ferrous metal to a non ferrous is almost impossible
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Gotta agree with Clifford for the mount.
But, I have successfully welded two 12' long pieces of sheet aluminum together to make one piece using "Alumiweld."
It's basically a welding rod with a low melting point, (730°F), for aluminum.
I've also been able to easily connect aluminum to brass, copper and bronze.
It will not work with ferrous metals.
Google it, it's not cheap, but the learning curve is short and it works well.
That is the purpose of rivets and nut and bolts welding a ferrous metal to a non ferrous is almost impossible
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This project sounds almost exactly like what TomC is doing. You might ask him how the panels are attached on his unit.
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I figured the aluminum couldn't be welded to the steel frame...I had in mind welded brackets that could be used to bolt the aluminum skin to the steel frame with a layer of something in between to prevent electrosomethingorother corrosion. Sikaflex is like Eternabond? As a sealant, I'm a believer...but welding the six sides together to form a sealed 35 foot "tank" would be very nice. 1/8" aluminum is actually pretty thick stuff. The alumiweld stuff sounds interesting.. I'll check it out.
edit: I checked out the Alumiweld...looks too good to be true...what's your experience actually working with it?
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I used a Sikaflex look alike that is used in autobody attaching. I placed two 4X6 pieces of 16 Ga. cold rolled steel, butted together, over the two center window holes of my 06, with no more that 1/4 inch overlap all around.
The result was a smooth surface with no obvious attachment points and does not warp under any conditions.
All this was done 14 years ago and no leaks or any other problems since..Todays urethane adhesives are amazing and permanent.>>>Dan
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1/8th can be welded easy without wrapping with a good mig welder and the right shielding gas and wire I use Lincoln wire with a 75% Helium and 25% Argon gas JMW
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When Rob Gray made his original Wothahellizat he attached 2mm aluminum (slightly thinner than 1/8") to his steel framework with sticky tape! OK, it wasn't your typical stuff from Ace Hardware - it was 3M's VHB tape which is how lots of vehicle bodies are made these days: http://www.robgray.com/graynomad/wothahellizat/wot1/diaries/diary_23/index.php (http://www.robgray.com/graynomad/wothahellizat/wot1/diaries/diary_23/index.php)
If it's strong enough for an off-road vehicle that saw more flexing and abuse than any road-going truck conversion will ever see, it should be good enough for you! Grainger has a full selection of different types of VHB tapes: http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=3M+VHB+tape&op=search&Ntt=3M+VHB+tape&N=0&GlobalSearch=true&sst=subset (http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=3M+VHB+tape&op=search&Ntt=3M+VHB+tape&N=0&GlobalSearch=true&sst=subset)
His construction diaries are fascinating reading, and his designs and imagination are inspirational.
John
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There is a learning curve to it but it doesn't take too long to learn.
One 16" stick will last quite awhile and this stuff is stronger than the aluminum it's welding. The main thing is to have clean metal and to clean it use a stainless brush that hasn't been used for anything else. Microscopic particles of steel in a regular used brush will inhibit the weld.
The 730°F temperature is nice because there is a lot less wrp and buckle of the aluminum, plus it means a low flame on the propane torch so the propane lasts a lot longer.
I was looking for a picture of the panels I welded together but must have lost them a couple of computers ago. I did find a picture of my first practice piece and I'll try to post it.
I figured the aluminum couldn't be welded to the steel frame...I had in mind welded brackets that could be used to bolt the aluminum skin to the steel frame with a layer of something in between to prevent electrosomethingorother corrosion. Sikaflex is like Eternabond? As a sealant, I'm a believer...but welding the six sides together to form a sealed 35 foot "tank" would be very nice. 1/8" aluminum is actually pretty thick stuff. The alumiweld stuff sounds interesting.. I'll check it out.
edit: I checked out the Alumiweld...looks too good to be true...what's your experience actually working with it?
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Scott,if you are looking for a nice smooth job for siding aluminum is not the way to go when the sun heats it that stuff is all over the place waving like old Glory on a windy day
Take a look at the GM buses the way it is attached, steel will give you a smoother better looking job or if you have deep pockets Stainless with the 3M tape like Newell uses $$$
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I agree that VHB tape or Sikaflex would be the way to go, but it sounds like Scott wants no seams for a watertight shell. Wouldn't you need seams for expansion/contraction anyhow?
My bus is built with flat aluminum panels adhered with some sort of tape or adhesive. So far they are all sticking after 17 years.
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Alumiweld and all of the materials with the same claim are not suitable for any decorative welding! The weld and heat affected zone will turn almost black and will not polish like the aluminum material You are welding! It is actually not a weld but a form of brazing or soldering! The joint strength is far inferior to a actual weld. As always if it sounds to good to be true it is probably not true! John L
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Alumiweld and all of the materials with the same claim are not suitable for any decorative welding! The weld and heat affected zone will turn almost black and will not polish like the aluminum material You are welding! It is actually not a weld but a form of brazing or soldering! The joint strength is far inferior to a actual weld. As always if it sounds to good to be true it is probably not true! John L
I used some of that aluminum solder a while back to fill some holes I mis-drilled in some 6061-T6 blocks, so I could then re-drill the holes correctly. I pre-heated the blocks with my oxy-propane brazing torch, then melted the aluminum solder into the holes until they were over-filled. As it cooled it shrank back down a lot, so I had to level it off with more solder. Whatever brand of rod I used (I don't know if it was Alumiweld or something different) seemed to melt very quickly, maybe at less than 730F, and it was quite soft when I redrilled through it, with a sticky feel to the drillbit even with Tapmatic cutting fluid.
Would I use it again? Probably not - I don't think it's anywhere near strong enough to be useful, but for non-critical low-load applications where appearance doesn't matter maybe it has its uses.
John
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I don't think Dallas was saying it was better or stronger than a wire weld or tig weld just easier for Scott
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Same as stated above,
Aluminum will grow and shring with the changing weather.
All my panels were secured with sikaflex. Good thing I didn't paint my coach
till a year later... Some of the sika seams tore apart in the hot sun.
I ended up riveting all the seams and covering the rivets with umbrella caps
just before the paint job went on.
They are still holding well after 6 years now.
Nick-
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... 3M's VHB tape which is how lots of vehicle bodies are made these days:
A friend of mine up here in MN built a Kinglsey clone. He used VHB tape to mount his aluminum panels to his steel frame. I've never seen anything attach so well!
His coach is incredible!! Really puts my bus to shame. Stretched Volvo chassis. 48 feet long. I think he put 3 slideouts in it. It's something else.
If I had known then what I know now, I would have used VHB on my bus with my Alucobond panels. I think that combination might be the definitive siding material
on a conversion.
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I have never welded aluminum with another other than a good TIG.
Cheers, John
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These new Mig machines and gas do a good job and so much faster plus cheaper
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I had no idea there were 3M or Sikaflex tapes that could be counted on to hold sheets of metal to metal ribbing. Some of you swear by this stuff...17 years and still holding? Wow. I don't think that I could restrain myself from popping in a rivet at least here and there just for security...
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Any enclosed trailer that is screwless uses tape to hold the sides on. Any problems are usually due to poor prep by the trailer manufacturer.
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that's also not really true.
Many of the older Trailmobile trailers used aircraft grade aluminum and fasteners. Take a look at a DC3 or an F85... no rivets to be seen anywhere.
It's intersting that so many took umbrage to my post, although if you look at the MSDS and structural sheets for Alumiweld and 6061 Aluminum, the Alumiweld is much stronger and is more malleable.
Now I don't care one way or the other, I just report the facts as I find them. If the OP wants to use tape or glue or staples, it's his/her choice.
I like the Alumiweld and haven't had a failure from it.
Yes, I don't use it for structural stuff, but then I wouldn't use glue or tape for anything structural either.
Whatever the OP chooses to do is his choice, not ours.
Good Luck to him no matter what he decides.
Any enclosed trailer that is screwless uses tape to hold the sides on. Any problems are usually due to poor prep by the trailer manufacturer.
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that's also not really true.
Many of the older Trailmobile trailers used aircraft grade aluminum and fasteners. Take a look at a DC3 or an F85... no rivets to be seen anywhere.
The enclosed trailers I am talking about are the ones that you pull behind a pickup, SUV, or similar. Not semi trailers.
Screwless enclosed trailers are maybe a decade old. You'll find that 99% of them use tape to hold the sides on. You can get more information at any trailer dealer.
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This is wonderful info. Opening my eyes to some new realities in bonding tech. Justdallas, I have to say that I'm very intrigued by alumiweld and I plan on trying it out. I want to attempt a virtual hermetic seal on those seams and I think it's the right stuff for me. It does sound to good to be true, but that doesn't mean it isn't. Your experience with it tells a promising story. I'm looking forward to playing with it a little. I wonder if there are certain alum alloys it won't bond to.
Sent from iPhone via Tapatalk
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I haven't found any aluminum alloy it won't adhere to. I do have to add that I've only used 3 or 4 different types of alloy with it.
As others have said I would be worried about expansion and contraction of a single sheet as large as the side of a bus. If it were me, I would make the roof in 3 pieces with expansion joints and the sides in 3 or 4 pieces with expansion joints. (Basically a lap joint with polyurethane adhesive/sealant inside).
The idea of using the tape to attach with will also help you in many ways. It will provide a thermal break, lessening sweating, stop interaction between dissimilar metals, be a lot easier to attach, and provide an expansion joint between the dissimilar metals.
Think about it this way: In 1943 The USS Pittsburgh was launched. Design spec was 704'. That was at the Brooklyn Navy yard.
When it was in dry dock in Hawaii it measured 706'.
It gained a full 2 feet from thermal expansion. 40° in Brooklyn, 80° in Honolulu. That was steel and it doesn't expand and contract as much as aluminum.
Good luck!
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There are some pretty tough adheasives out there. The gruman aircraft company built at least three different aircraft with fue rivets and glue.
Brice
Sent from my SPH-M900 using Tapatalk 2
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Forget welding. You want smooth. Think sikaflex. See any rivets on newer busses lately?
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My trailer uses the 3M tape to fasten on all the sides - close fit is critical, no gaps. It's as close to hermetically sealed as I have ever seen, for a trailer. Two years, 20K miles and still perfect, FWIW. I used the alumiweld on a few projects, the end result of which was a Lincoln 175 Tig machine which does a wonderful job of welding aluminium. I make a lot of water/oil/coolant tanks for race cars and never have any leaks, but there is a long learning curve before you lay down those perfect "stack 0'dimes" beads. I wouldn't do a bus for love nor money. Between the alumiweld and the Tig, I did a bunch of oxy/acetylene welding of aluminium using flux-cored rod. I could do 1/8th inch, but 1/16" sheet mostly ended up on the floor - one very memorable moment saw a large drip of aluminium fall inside my deck shoe... Still have the scar to remind me to wear heavy leather boots when welding... Mig welding aluminium is absolutely possible, for best results you need a hot shielding gas and a spool gun, and a lot of amps so this is more trending towards an industrial process than a home process. Widely used in industry, all those aluminium framed bicycles up to the aluminium dump truck bodies and tractor trailer flat beds are Mig welded.
I heard once that the aluminium superstructure on some warships is explosively welded to the steel hull structure. Not sure explosive welding on a bus is a good idea... ;D
Brian