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Welding to inside shell of a skoolie skewl-bus mike 10-1-03  
A friend an i are converting an '85 ford b700 bluebird into an rv. we would like to make some frame supports on the inside of the bus so that we can use the walls and roof as rigid mounting surfaces.

i've seen plenty of people build wooden frames inside the bus and nail/screw/rivet them to the sides and roof.

has anyone ever welded aluminum frames to the inside?? what should i consider, and is there any prefered technique?

any info is always helpful. thanx.
Re: welding to inside shell of a skoolie Casper 10-2-03  
I see no reason you couldn't weld mild steel to your bus interior. Standard structural steel shapes such as angle-iron, flatbar, channel-iron and I-beams are made of ASTM A-36 steel, which is very mild and is weld-compatible with almost any ferrous metal (Like the roof bows in your bus or example).

One concern when welding on a vehicle is disturbing the metallurgical state of the material that you're welding to. For example, truck frame rails are often tempered for increased strength. If you weld to a tempered frame rail, the heat of the weld will anneal (soften) the area right around the weld. This will weaken the material, and can lead to cracking and eventual failure. As far as I know your roof bows are just square tubular steel, with no special metallurgical preparation. You should be able to weld to them.

Experienced bus-heads correct me if I'm wrong on that last point please.

Unfortunately, your idea about welding aluminum to your interior will not work unless the material you're welding to is aluminum as well. The aluminum you're welding in has a melting point about 1,000 degrees lower than the steel in the bus, and they will not weld together. Crown buses were largely made of aluminum, so that would probably work. If you have a Bluebird or Thomas body, or just about anything else, you're not going to be able to weld aluminum to it.

If you've really got your heart set on aluminum walls, one way to attack the problem would be to weld in small pieces of steel angle to your bus body, then drill holes and bolt your aluminum wall studs to the steel tabs.

Another possibility to look at would be the use of "Steel lumber". Due to fire codes, most commercial building construction nowadays is done with "lumber" made from steel sheet. The stuff is made in standard lumber dimensions such as 2x4, 2x6 etc. This stuff is remarkably strong and lightweight. The material is galvanized, so unless you are parking your bus on the beach year round, rust shouldn't be a problem. The stuff is surprisingly easy to work with, and you can cut it with tin snips and screw-bolt-weld it together any way you please.

To weld any of this stuff in, I would recommend the MIG process. MIG is quite easy to use and the equipment is getting cheaper. It could be done with a conventional stick welder, using 1/16" 7018 rod, but that requires more skill. Be sure to clean all surfaces to be welded, removing any paint, grease etc.

That's my story and I'm sticking to it. Let us know what you decide to do please.

C
Re: welding to inside shell of a skoolie mike 10-4-03  
Sounds good. i understand your point of not welding alum. to steel.

my idea is to basically use angle iron to weld a "universal" framwork for support and for fastening to. i'd rather not drill and bolt through the body a million times when installing a head,beds,side tables, and bar.

what about corrosion? i know mixing two metals creates an anode and cathode, and rust relentlessly results. will welding astm a-36 steel angle stock prevent and electrolytic potential? also, what should i consider when actually bolting through this angle iron? any good anti-corrosive beddings out there?

thanx for your help!
Re: welding to inside shell of a skoolie Casper 10-5-03  
Hi again Mike,

Electrolysis happens when there is electrical continuity between 2 dissimilar metals, and then the assembly is exposed to a corrosive atmosphere. The material in your bus is probably AISI 1010, or maybe 1018. This material is chemically similar enough to the A-36 that you shouldn't have a problem with corrosion. Be sure to paint your frames with a good coat of rust-oleum and you'll be fine. If you're really worried about corrosion, fabricate your frames with galvanized angle, then paint all of the welds with zinc-chromate after they've cooled. The chromate is almost like "Spray on" galvanizing, and will protect your material well.

As for how to bolt these things together, your biggest concern in this application is vibration. The trick to assembling to withstand vibration is to minimze the amount of "slop" between the holes and the fasteners, and to keep the fasteners tight.

To minimize the "slop", cut and fit your materials in place where you want them and secure with a C-clamp, then drill the holes to net size and insert and tighten the fasteners. By net size, I mean that if you're using 5/16 hardware (which is about the size that comes to mind in this application) you would drill 5/16" holes. You may have to tap the bolts in with a mallet, but you'll have almost zero slop.

To keep the fasteners tight, I've had great success with serrated flange cap screws and nuts. They have "teeth" under the heads that bite into the base material and hold better than normal lockwashers. The trade name is "Whiz-lock" nuts and bolts. look at this:

http://www.mcmaster.com/library/6/670282/92323A533s.gif ($8.04 for a 50-box)

and this:

http://www.mcmaster.com/param/asp/psearch.asp?FAM=nuts&FT_153=60971&FT_1455=61825&FT_137=31621&FT_255=7174&session=desc=Nuts;nuts;153=60971;1455=61825;137=31621;255=7174 ($5.97 for a 100-box).

You can order these online from www.mcmaster.com, or check your local hardware store.

This should do ya'

Note for the record that I have not converted a bus yet. I'm an ex-machinist/fabricator who went back to school for an engineering degree, and I'm currently making a living doing equipment design and engineering for a really big chemical company. I'm looking forward to applying some of what I've learned to building a safe-reliable-low cost motorhome for my family. I've learned a lot from reading this board, and I like to help with some non-bus specific tech help when I can.

Good luck and keep us posted,

C
Re: welding to inside shell of a skoolie Casper 10-5-03  
Let's try this:

Bolts

Nuts

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