Anyone experienced with aluminum welding?

[Scott & Heather]

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?

[boogiethecat]

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....

[Oonrahnjay]

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.

[luvrbus]

That is the purpose of rivets and nut and bolts welding a ferrous metal to a non ferrous is almost impossible   

[Just Dallas]

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   

[belfert]

This project sounds almost exactly like what TomC is doing.  You might ask him how the panels are attached on his unit.

[Scott & Heather]

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?

[Utahclaimjumper]

 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
                     

[luvrbus]

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  

[Iceni John]

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
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

His construction diaries are fascinating reading, and his designs and imagination are inspirational.

John 

[Just Dallas]

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?

[luvrbus]

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 $$$

[belfert]

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.

[junkman42]

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

[Iceni John]

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