I don't know about welding.

I did a little bit when I worked in the Los Angeles Harbor, but I wasn't very good.  You might consider using "right angle brackets" with tek self drilling self tapping screw to hold your steel tubing together.  You did not mention how big the tubing is (height & depth, not length).  You would probably want to use 4 screws for each connection to keep finished benchwork from flexing.  It might also be a good idea to put a thin film of JB Weld on the inside of the brackets before installing the screws, especially if you don't have enough clearance to use more than 2 screws in each corner.

How not to proceed.

    Learning to weld can be a hobby unto it's self. I learned long ago in high school shop class and built go-karts, race cars, sailboat hardware, etc.,last thing I welded up was lumber racks for my truck. Even with my experience I wouldn't consider welding up benchwork for a layout, wooden benchwork is so simple to build that it's just not worth doing it in metal. . You'd need a welder and protective gear, a way to cut the metal, clamps to hold it while welding, a fire proof place to work, ventilation for the smoke and fumes, etc. Not something that should be done in a 9th floor condo :> ) . You can buy modular metal rack components if you really want metal  or commercial bolt together wooden benchwork which would be more sensible, or maybe measure you space and design your benchwork for wood framing and have someone cut all the pieces off site then you can bring them home and assemble them with screws. Another sensible possibility is to buy ikea style bolt together base units like book shelves or cabinets (which would add useful under the layout storage)then put hollow core doors/foam sheet  or other simple benchwork on top.....DaveB 

You can bolted

I'm an iron worker.

I have build my wokrbench with tubes; they are rectangular tube of 15mm x 40 mm

It's simply four tubes with 4  lateral cross members ( see pictures) and two small frame which support a laminated white board for working surface. 

The lateral cross members are angle welded on little plate with two holes ( see second picture); the plates are bolted to the 4 feet (rectangular tube) at strategic height, the small frame which support the working table and the upstair rack are  also made of iron; they can be dissasembly in half to win space  and are bolted to this angle on the flat side, this give a well rigid assembly when everything is bolted

Course some piece were welded, but the whole workbench is bolted and by the way his disassembly is possible  any time you ask for; this way my workbench is with me in Quebec after a travel on the Atlantic

My workbench is a two level table, a work table and a uptsair level where I can put may boxes of models and stuff needed; this upstair level conceal also the lighting (leds) of the work table area.

This construction is extremly strong, you can walk easily on the workbench, and the upstair rack can support for sure more than 150kg.

All the tubes are cut in form, the skeleton is bolted together with 6mm diameter bolt and nuts.

The working surface is width enough to receive different small rack to store paint, brushes, small hardware, soldering unit, and all the necessary stuff to build models.

The working area was cut to be ergonomic, meaning I have cut it curved to manage a better working area.

If some are interessted I can do a plan and publish it.

Sorry for the messy workbench, but this was just before I move to Quebec

Here are  picture

1" square

Sorry, I didn't mention all the dimensions, I was planning on 1" square steel tubing. 

I've got a balcony to work on, it's fireproof (everything's tile, metal or cement out there).

Wood is not so easy to get here as metal. I don't know if this city has a proper lumber yard at all. None of the houses are stick-built, for example, everything's either poured concrete or cinder block. Home Depot has about 1/4 of the choice of wood that a US Home Depot would, and none of it any good.

I'm in Mexico, in case everyone forgot. That makes hiring someone to do the welding for me lots cheaper, for that option. 

One other option would be to have pieces welded together in two dimensions only, and then bolt the long horizontal pieces that run parallel to the aisle to the uprights and shelf pieces. 

Another option would be perforated square steel tubing and lots of bolts. Probably a lot more expensive that way.

@ Eastwind / Bolts and nuts / Square tube

Bolts and nuts cost nothing, I buy for this project a box of 100bolts and a box of 100 nuts

They cost me 7 euros or around 9$, and had more than necessary bolts for this project

I still use them here and there for other project

They are 6mm diameter nuts and bolts; the nuts are self washer type so they can't move when tightened.

I would not use square tube but rectangular ones for better stability and rigidity.

Welding can cost more because it's a quiet slow process and it need to be done properly on light tube; the tube you are using have a very light thickness, meaning you need some good practice to weld it without burning the tubes. .

If you go in the process of welding, make small parts and enginer a design which allow you to easily dissasemble the structures, the way I do, I saved this workbench severals times after move and this give me the opportunity to bring it with me in Quebec from Europe.

What about aluminum?

Back in the 1970s Model Railroader built the portable N-scale Clinchfield project layout. They used aluminum channel for the framework, a far more yielding material that steel. If you don't have much call for lumber in building construction around you, then perhaps they carry aluminum channel for wall studs.

Aluminium might be an option

In Australia 1" aluminium square hollow section is often used.  It's called Qubelok and Connect-It here, maybe there is something similar elsewhere e.g. Brunner in the US.  6 metre lengths.  Easily cut. I used a mitre handsaw.  Can be joined with knock-in strong plastic joiners, but a screw-in metal bracket would add strength.  A simple 4' x 2' x 6" box shape structure was strong enough to support my weight of 12 stone without flexing.  One section type has a tongue, good for dropping in an extruded foam or other type of board.

There is a bit more about it here -

https://forum.mrhmag.com/magazine-feedback-was-ezines-891776

or google "qubelok model railways"

Bolt-able sections

Doing it in bolt together sections might make sense for several reasons.  First, if you ever need to move it will be a heck of a lot easier to get out.  And second, if you hire someone to do the welding, and that someone has a shop with a nice workbench and all the tools and supplies right there, you may get better results than if they try to lug up just the minimal number of tools to the ninth floor and work on a balcony with no workbench.  And third, you’ll have pieces that fit in the elevator nicely, without having to do any 3-stooges piano on a pulley type operations.

Welding...

Can you teach yourself to weld?  Yes, of course, thousands and thousands of people have done just that, including me. I wouldn't buy a welder just for a layout, but if you plan to do other welding, it might be worth doing. You can get a nice small MIG welder for under $1k and after a couple of days welding scrap pieces you should be fine. I would use gas, and not flux core wire. I don't like welding with flux core myself. You can get a buzz box stick welder for less than a MIG unit, but your learning curve is going to be a bit steeper. 

I did all my welding in my shop, on a nice flat table with square sides, and then screwed the components together in my layout room, which is what I would suggest to you.  I don't get a warm fuzzy feeling  thinking about welding high up in a finished and occupied multi-story apartment building.  I don't recommend that. 

In addition to your 1" square tubing, buy some 1"x1" angle. Cut the angle into 1" lengths and assemble your benchwork with that angle and some self-drilling screws. I've done that in several areas on my benchwork and it works fine and you won't have to do any welding. Get a local welder to weld up your supports and whatever major components will fit into the elevator.  

Randy

No Welding

I would not consider welding up in your condo,...and particularly if you don't have the experience,....possible flash burn to the eyes, and fire hazard from sparking, etc.

I would consider square alum tubes like those I used in constructing my outdoor helix,..
https://forum.mrhmag.com/post/multiple-staging-areas-access-to-them-perhaps-subloop-in-the-helix-12209513
Those are 3/4 inch tubes, and they are utilized in LOTS of stairway and porch railings here in FL, and likely many areas. I found 2 different wall thicknesses, and ended up using primarily the thicker of the two so I would have a robust thickness to drill and bolt thru.

Somewhere I have pics of those 2 different ones, but don't know where at the moment.

There was also a Swiss gentleman who posted some interesting alum benchwork pics on one of my discussions about metal benchwork, but I don't know specifically where that is at the moment. If I recall properly he purchesed his product directly from one of the big box stores in Europe (but I think it was one we have in the USA as well)

NOTE: just found that reference to the aluminum deck railing pieces,...
https://forum.mrhmag.com/post/metal-benchwork-12207979

Metal Benchwork 'Images'

BTW, have you googled 'metal benchwork' and selected 'images',....lots of interesting possibilities

Steel studs?

Steel studs normally used for wall construction are another option. See my blog or search the site. Several folks here use them for benchwork. No welding required. Not sure if they are available in Mexico but they are used in many parts of the world.  

Jeff

Unistrut

Have you considered something more along the lines of Uni-Strut.  They have different sizes, finishes etc.   But for you the best part might be the connectors they offer to attach pieces together. All bolted connections that way.  Plus they offer bolt on and bolt in accessories you might find useful. Or even easier light gauge metal framing like used for walls.  It is available in gauges, widths and lengths to fit almost anything you can dream up.  Depending on the gauge you used the material can be cut with snips.  All of it can be screwed together and make a solid benchwork.

 I weld quite a bit but sure would not want to for something like this in an occupied condo. Not without a major amount of prep work for safety.   The fire risk is substantial, if your building is smoke alarmed or sprinkled you have a strong risk of setting those off.  The smoke alarms for sure.   Keep in mind to weld up a framework it will need cut and a grinder to clean up the welds after.  

 I'm all for alternative benchwork ideas, hopefully you can come up with something that will work for you. Keep us posted.

220 voltage available?

I have absolutely no welding experience, skills, credentials, but, don't most (if not all) welders require 220 voltage? If so, is that even available anywhere in your condo's complex to take advantage of? Let alone your specific condo?

Agree with Randy - don't think you want to be welding inside your condo. Is that even allowed for in your Condo Association By-Laws?

Too late...

Looks like he forged ahead with the welding:  

Randy

220

I've got a Miller that runs on 220 or 110.  It runs better on 220, but you can use it on 110. It works sorta ok on 110. I wouldn't want to weld my benchwork with it plugged into 110.  Most apartments have 220 coming in at the stove though, so...

Randy

It's impressive that you'd

It's impressive that you'd like to use steel.  I admire your energy.  Some engineering things to consider about the design, though, that will govern your results no matter how you build up your benchwork support:

1) Aluminum versus steel:  Aluminum is 3 times more flexible than steel, if all dimensions are the same. You want the benchwork to stay stable.  You'll need a nominal 1" wide by 2" tall aluminum tube of the same thickness as the 1" square steel to give the same stiffness.  Stiffness is measured as how much the layout will sag when there's a weight on top.  Like if you lean on the edge a bit to construct scenery at the back edge, or lean on the front edge to uncouple a car at the back edge.  Will cars on the track at the front roll or even derail if the benchwork sags.

2) Since either welding or bolting are going to be slow compared to working with wood, perhaps fewer joints would be a good thing.  To achieve this the length of a benchwork section could be as long as is reasonable.  For example, if the support legs are 8 feet apart and the tube is 1 x 1, and imagine someone leans on it with a 40 lb force (reasonable) then the front edge will deflect about 5/16 of an inch.  Not too bad.  If the span between legs goes out to 12 feet and the same person leans on the center of it with that 40 pound force, the deflection will be 1.375 inches - a whole lot more.  

3)  If you did the above experiment with aluminum tube of the same 1x1x1/8" thick, at 8 feet  long the frame would deflect down about 7/8", which seems like a lot.  If the legs are 12 feet apart, the deflection is a ridiculous 3 and a half inches.

Perhaps a good design would be to weld up some rectangular frames and bolt them together, with legs bolted close enough to give you the support you want.  Then put plywood or whatever top material onto those frames.  As long as you get the steel to support the perimeter you'll have benchwork you can build on.

Don't know if you can do this, but what about ripping plywood to make wood boards for the frame?  Perhaps 3/4 plywood, cut to the width of other wood available in your area, could substitute for buying "solid" wood?  I've used plywood ripped to 3.5 inches and 5.5 inches to match nominal 1x4 and 1x6 pine.  Since I don't know how to weld either this was a good solution for me.  Also, the plywood is MUCH less likely to warp in the direction of the cut edge.  If you build a frame with it, it will stay flat with changes in temperature and humidity.  Actually better than solid wood.  And you get to quickly build it with just ordinary screws and glue.

Welding thin material to get a respectable joint is not that easy.  1/8" is "thin" for most non-professional folks who weld.  But the good thing is a model railroad won't need much joint strength.  Any weld probably will be fine.  I'd be more concerned about having enough electric power available in your apartment to power the welding machine.  

Aluminum offers ease of cutting and ease of drilling.  If it's available near you, maybe that's a good way to go.  Just keep the support legs no farther than 6 feet apart.  Angle brackets bolted through the parts could hold it all together.  Just use some oil when cutting or drilling as aluminum wants to stick to steel tool surfaces.  

Best wishes constructing your new layout!!

Kevin

What Jeff said - steel studs

If climate is a problem, implying expansion /contraction and mold, and other things that live in damp wood, then steel studs will greatly reduce that problem.

Steel studs are extremely light, can be cut to size with hand shears, and fastened with self-drilling screws.  They have pre-made cutouts to pass through electrical wire.

The major drawback is, they have sharp edges.  You should wear cut-resistant gloves when handling steel studs.  Normally they are sealed inside a wall, concealing the edges.  If used exposed, you might want to put plastic edging on some of them. The kind of rubbery stuff that you can get for car doors so they don't scratch the car parked next to you.

@randy

Funny, I was jokingly going to say plug it into the oven or range. HA But you beat me to it.   I sure hope nobody tries it!

Steel studs to me would be the easy choice but I do that for a living so it is a biased choice.   It would not take long to figure out even for a rookie.  Much quicker learning curve than welding.  Much less welding aluminum if that was the plan for it too?    With steel studs a tape measure and square,snips, and a cordless drill will have you ready to go.  I’d suggest some cheap spring clamps or C shaped vise grips too but you can do it without.    Like someone mentioned they are punched for wiring and you can even get plastic grommets to protect wires that snap in the holes.    
 

good luck

Instead of square tubing use 3-4 inch aluminum angle.

If you use the aluminum angle for the longitudinal pieces or 1 1/2-2 inch steel angle, it should solve any flex problems from someone leaning on the benchwork.  Use your square tubing for legs.  I would use flat stock for bracing to keep the benchwork from "racking".  Bolt it together with tek screws.  I would not recommend steel studs because the ones I have seen are made with thin sheet metal.  1/8 inch thick aluminum or steel would give you more thickness for the threads to bite into to hold things together.  With sheet metal if there are earthquakes, or any sort of stress on the joints and the holes "wallow" out then you would need nuts and probably washers to tighten everything up.  Tek screws self drill and then tap a thread into the material and hold everything together tightly in one operation.

Welding steel

I'm an iron worker, I have had my own small company in Europe, we were specialized in any welding work but also

any craftsman work in wrought iron.

So we were able to weld any pieces of steel together.

Welding with Mig or with arc or even Tig require experiences, this experience take time to come and need a lot of practice specialy if you ask to weld very thin parts together.

Second safety is very important when you weld iron, first course for your eyes, the light is powerful as solar light, much powerful as solar light in the case of use of Tig but also your clothes need to protect you and gloves are a necessity

A good welder is burnt a bit each days it's an evidence.

When you weld iron you need to do it in a very well ventilated area, fumes are just ….somewhat toxic.

Weldind iron is also a confirmed fire hazard by itself but specialy because of all the sparks the welding action produce, you need to do it in  a lone place were nothing  is able to burn and remember in the protective welding helmet you don't see the flame of a fire; the light of this fire is not powerful enough to be seen in the helmet.

Electricity power is needed even with the new inverter systems, 16 amp on the line seems to be a minimum.

Welding iron is really a work and not a play game, and is not so easy to do it

Before in this post I showed how I build my Iron worbench, but it has needed some welding and I believe these are out of scope of this thread for the most of us.

A bolted structures seems to me more affordable for all of you.

food for thought

I have been a custom fabricator for over 20 years I've worked with steel wood plastic fiberglass ect. I've been a model railroader over 40 years built 15 or more layouts some for private customers or store displays. All materials expand and contract in my experience the rail is the most vulnerable. So even with a steel frame you will still have a wood or foam roadbed that will expand or contract regardless of what you frame work does. Wood can be painted on all sides to decrease its vulnerability to the climate. I will say this for the investment in welding equipment you would come out far better to invest in some climate control. I have been working on a layout started in 1986, it's in a basement we have had one issues in all those years. We had some rail buckle during and extremely cold winter while my friend was recovering from heart surgery. The section was on an outside wall, the layout is old school L girder with 3/4 plywood sub roadbed. One other thing to consider when you build something using many different materials as we do in model railroading, that all expand and contract if you make one component extremely rigid it will only put more stress on the other materials when the expand or contract. Consistent Climate is the secret.  

Climate, climate control

Thanks for all the feedback, it's certainly generated a lot of cautions.

The space where the layout is will be air conditioned, 24 hours a day, every day. *But*, the power goes out occasionally, maybe once every 6 months for a few hours, and the air conditioning goes out sometimes all by itself. This seems to happen about every 2-3 months. It's a long story, but nothing I can do anything about, because it's a community system. 

So the net is that about every 2 months I have a few hours with no AC and the temperature rises and I usually open the doors and let the outside air in, along with the humidity.

In the apartment I'm in now (I'm renting one, and buying another that I will move into) there is a problem with air leaks from outside bringing in humidity constantly. I definitely plan to take more effective action against that in the new apartment than I was able to get done in the one I'm renting, but some humidity invasion is inevitable when you go out the door.

I'll give it some more thought, it's going to be a few months before I can start. I'm leaning towards having the welding done at a shop and bolting pieces together. 

Somebody had a layout where the benchwork support was made in the shape of a 'chair', actually just a lowercase h, no 3rd dimension. They got the h's to stand vertical somehow, and then they simply used spline roadbed to hold the 'h's together. I"m thinking maybe to get h's welded off-site, then bolt the horizontal-lengthwise pieces to them to create the front edge and back edge of the benchwork. I think that would address most of everyone's concerns.

If power outages are a problem, buy a Honda Generator.

The Eu10001kc puts out 2000 watts of power for less than $900.00.  It weighs 29#, and I have one that runs dead quiet.  You could carry it out to your balcony and run it in the event of a power outage.  Mine runs about 6 hours on a tank of gas (I'm not sure but I think the tank capacity is 1 pint).  If 1 is not enough power to keep your a/c & dehumidifier online, get a second one and the $43.00 parallel cable to allow you to run 2 of them in parallel.