While I do own a lathe and mill, the methods I will show you here do not require the use of them.  Some basic tools are all that are required, a drill, a saw, a few files, etc.  That said, if you want to make your own trucks you will need a lathe.  For the purposes of this article I’m assuming the use of purchased trucks and couplers. 

A welder is also an excellent tool to have.  If you don’t have the money to purchase one get together with a group of people from your local club and buy one as a group.  Set up your rules as to when it can be used, etc and the cost becomes extremely affordable.  I use a Hobart 135 MIG welder with a gas mixture of 75% Argon / 25% Carbon Dioxide.  You can use a flux-cored wire but the welds are not as clean. 

Not interested in doing the welding?  Cut all the pieces and take them to a welder.  The time to weld all the pieces together is minimal compared to the time cutting and fitting.  Many welders are happy to see they don’t have to fit the pieces and can focus on “gluing” the pieces together.  This also helps to keep the cost down.

 A Place To Start And Some Basic Math 

                           click any image to enlarge
Not sure where to start?  Head to your local hobby shop and pick up an HO scale ruler and a car that you’d like to build.

 Measure the dimensions on the car.  In this case our car is 50 scale feet long.  Now comes the hard part.  Multiply 50 by 1.5 and we get 75.  That’s it! We now know that the car we are going to build will be 75 inches long.  Measure all your dimensions and do the math.

 Now let’s say that you managed to find a set of drawings with the actual dimensions of the car and they show 50’ 3”.  Does the math have to be confusing?  Not a chance.  We’ve already figured out how long 50’ feet is.  Now comes the easy part.  We are working in 1/8th scale so every inch in 1:1 scale equals 1/8 of an inch in 1/8th scale.  So 3 inches equals 3/8ths of an inch.  The total length of the car would be 75 3/8”.

 Beginning Fabrication

 Now that you have your dimensions, cut the basic parts for the frame.  I use a design that has worked well for Mountain Car Company. 

 I start with a 1” x 2” thin wall box tube for the backbone.  Use your measurement from above and add two inches so that the coupler pockets stick out beyond the ends of the car.  The two cross members above the trucks are also 1” x 2” box tube centered 8” from the end.  I recommend and use Mountain Car Co. trucks.  As such I also add a 3” piece of 1”x 2” tubing on each side of the backbone.  These are what the frame rides on.  Note that some trucks such as Tom Bee trucks require an additional 3/8” plate below that as well.  Check with your trucks supplier to see what they recommend for height.  Depending on the length of your car you will want to add one or more cross members made from 1” square tubing.  Next, use 1” angle iron for the perimeter of the frame. 

Looking at the picture you will also see the bolts for the couplers and the trucks.  Measure 2” from each end of the backbone and drill a 3/8” hole.  These will be for your couplers. Now measure 8” from each end of the backbone and drill a 3/8” hole.  Next drill a 1/2” hole in the upper side of the box tube only.  These are for your trucks and the larger upper hole is to recess the bolt head.  I like to use a 3” long bolt and drill a hole in the bolt for a hairpin lock.  This setup facilitates quick changes should a problem develop.  If the hairpin lock did manage to find its way out, the bolt is still fairly secure and won’t drop out on the ground.  I also round the corners off of the truck bolt head so that I can keep the upper hole in the box tube as small as possible.  Since I won’t be putting any torque on the head (remember I’m using the hairpin lock) this doesn’t matter.

Let’s Build A Flat Car 

Once the basic frame is built almost any kind of car can be built from almost any material, a hopper made from steel or a boxcar made from wood.  In this clinic we will make a flat car since these are so versatile and can be put together quickly.    This is your end piece (see photo).  You will need to make two of these. 

This is the side piece.  The photograph only shows half of it but it is one long piece that looks the same at the other end.  The metal bar lying on the side piece is for a stirrup and you will see that later.  You will need two side pieces as well.

The pieces for the sides were cut from 1/8” steel, 3” wide and in this case 48 1/4” long.  The extra 1/4” is to overlap the end pieces.  I used a band saw to cut the pieces to shape and then used a flap wheel in an angle grinder to clean up the edges.   

The end pieces were cut in the same fashion.  The cutout over the backbone was made by cutting many slots into the metal and then using a die grinder the “tabs” were cut off.  What tabs were left were then gripped with a pair of pliers and bent back and forth until they broke off.  The edge was then filed smooth and the edges around the whole piece gone over with the flap wheel to dress it.

I measured 3/4 of an inch for the depth of my plywood and an 1/8th of an inch on the ends for the end pieces (photo). 

I then clamped the piece in place (photo).

Here you can see the side piece welded in place (photo).  Here is the end piece clamped and ready for welding.  I run a weld bead down the outside corner.  Once it is welded, I go back and clean up the weld with the flap wheel in the angle grinder.

The Devil Is In The Details 

I don’t do rivets.  Having said that, many people do and there is nothing wrong with that.  I use some simple methods for my details and I tack weld them in place.  While they may seem unusual at first, an award won at the Train Mountain 2003 Triennial for “Best Diesel Locomotive and Consist” says that they are at least believable. 

For my stirrups I use a 1/8” x 1/2” x 8” piece of stock.  The marks are laid out at 1.5”, 1.5”, 2”, 1.5”, and 1.5” respectively.  What you see is a 2” step, a 1.5” vertical and a 1.5” twist on each end.  I make four stirrups, one for each corner.

Start by placing your piece in a vise and using a square to square it up to the vise head.  Then using a hammer, bend the metal over for the verticals at the marks (photo). 

Next clamp one of the verticals in the vise at your mark.  “Choke down” on the piece about 3/8” with a pair of pliers and push away from you ninety degrees.  Turn the piece around in the vise with the other vertical being clamped.  Again come down 3/8” with your pliers, this time pulling the pliers towards you ninety degrees.  This will cause your twists to rotate in opposite directions to each other.  Weld these to the inside of the side pieces at each end of the car (photo)

For stake pockets 1” channel can be used.  Layout a series of marks evenly spaced down the sides of your car for stake pockets.  Be sure to leave room at each end for the grab irons.  Apply a weld bead on each side of the stake pocket for a secure hold.

 For grab irons I use 1/8” brazing rod.  Center punch your locations.  Using a #53 drill bit drill the holes and then insert the grab iron.  In this picture you can also see the stake pocket and the stirrup in place (photo). 

Point the welding gun at the center of the rod sticking through the side and tap the trigger.  The resulting button weld will hold the grab irons in place very securely (photo). 

This sample sheet shows some variations that are possible.  The two on the right have been button welded as above.  The two on the left have had the ends hammered flat on the anvil of my vise and the holes drilled out.  They are then riveted in place (photo). 

The brake wheel plate is a 2” x 3” piece of steel that the sides were also made from.  It is shown here with Precision Steel Car’s brake wheel housing from their kit.  Decide where you want to place the plate and clamp it to the end piece.  Tack weld it in place.  If need be, square it to the car.  If you want a walkway under your brake wheel you can use the expanded metal that you see behind the plate in the picture.  Weld two small angle brackets below the plate and tack a piece of expanded metal to them.

What if you are building a car that has ribs?  We can handle that.  I use 1/2” square tubing that is plug welded from the inside.

Here is a rib clamped to a sample sheet (photo).  I drill 3/8” holes in a row where the rib will go.  Make sure the rib is lined up over the holes (photo).

To plug weld the ribs, start your weld up on the side of the hole.  When you can see the edge of the hole drop your weld down into it and follow the edge around the circle.  When all your plug welds are done, grind them flat with your flap wheel.  If you end up with divots in your weld, run a bead over them and grind the area flat again.  This will give you a surface that will require little to no prep work for paint.

To show the strength of the weld I beat on the bottom rib with a hammer.  You can see the sheet metal beginning to fold before the weld would break (photo).

Here you can see the ribs on a gondola.  The ribs have been plug welded and the sides are clamped in place to be welded. 

If you have small detail pieces, purchase a tube of Loctite 330. It is a two part adhesive that once set creates an extremely strong bond.  You will probably destroy your part if you try to remove it. 

All that is left for you to do is cut the plywood floor, paint the car, and apply any decals that you want.  In a very short time and with basic tools you have created your own car.