Introduction: Toy Mack AC Bulldog Truck -- Part 6 -- Additional Details

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About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first to…

The first Instructable in this series can be found here. This is the sixth in the series and deals with miscellaneous additional details that enhance the realism of the truck replica. The introductory photo (opening screen) shows my grandson playing with the finished truck.

The photo shows what is a heavy casting at the very front of the truck. The engine crank protrudes from below the large arc shown (broken by the crank) in red. I used 1/8 x 3/4 inch bar. I marked the correct arc and removed most of the waste steel with a cutting wheel. Then I used a grinder to remove the rest and to get the curve right. I welded this piece to the front of the truck frame, but from behind the piece so the welds do not show.

Then I made two short pieces with a smaller arc (also shown in red on this one from the right side of the truck). The front piece and the side piece join between the two yellow lines. The side pieces are also welded from behind to keep the welds from showing.

Smooth any sharp edges with a Dremel and a grindstone or a hand file. Round the corner a fair amount.

Step 1: The Company Emblem

For a time Mack trucks were part of International Motors. The emblem on the front of the truck may look like a signal from Batman, but is really an "I" superimposed over an "M." The two are inside a circle.

I thought for a long time about how I might make this emblem, or a likeness of it. I drew the "I" and the "M" portion on a piece of 0.030 inch steel sheet I have used extensively in this project. I did my best to remove as much waste as I could with a cutting disc on a Dremel tool. Then I used mini-files to add precision.

See the second photo. I made a ring by wrapping steel rod around a water pipe approximately the right diameter and welded the rod ends together. I worked at grinding the weld area smooth and at getting my ring as precisely round as possible.

I welded the very ends of the "I" and the "M" to the front of the engine cowl. I used as little welding as absolutely possible. I did not want to risk an adhesive. I am hoping this truck lasts long enough that my grandson can give it to his grandson, and adhesive may not be up to that job. I ground away a little of the weld to make it less visible.

See the second photo. I welded the ring around the "I" and the "M" in three places. I ground away some of the weld to make it less noticeable. (At the end of the project, I smeared Bondo (auto body putty) around the ring and shaped it. Then I painted the emblem a contrasting color. See the third photo. You can see how the emblem looks on the finished truck. (On the actual Mack AC trucks the emblem is not raised, but it is on an air intake for the motor. The actual trucks also have louvres in the sides of the engine hood, but I decided those would be too difficult to replicate and omitted them.)

Step 2: Floor Pan and Seat

I used a paper pattern to determine the size and shape of the floor pan. The pan rests on the frame members, extends outward to the cab frame on both sides, bends downward and then out to attach to the inner side of the running boards. The first photo shows the paper pattern I used. Notice the crease marks. The floor pan welds to the inside edge of the running boards with small tack welds. I did not weld it to the rear face of the radiator. I did smear some Bondo on that joint to avoid any slight opening along the joint.

See the second photo. I sized the seat by "eyeballing" it in relation to the rest of the cab, including the position of the rear window and the steering wheel. I cut a piece of 0.030 inch steel to fit between the frame members of the cab. I marked lines across it with a square to indicate roughly where the bends should be. I clamped the sheet steel in a vise with a 3/8 inch rod. Bending around the rod gave me the nice curves in the seat profile. I left the sheet metal a little long at the top and bottom, in case my bends were high or low on the steel. Then I trimmed the ends so the seat fit properly in the cab.

The seat is tack welded at both sides of the bottom corners to the floor pan. The tack welds were made from behind the seat. No further welds were made at this point.

I fitted, marked, and cut covers for the open ends of the seat. These were welded to the cab frame, the bend in sides of the floor pan, and to the edges of the seat. In preparation I used masking tape to pull and hold the top of the seat tightly against the back of the cab. I ground the welds as smooth as I dared without weakening the welds. The welds would be covered with Bondo later and sanded for smoothness.

Step 3: Headlights

The headlights are something that is not really necessary, but is one of those little details that make the truck stand out. I wanted them to be rugged and stand up to all manner of abuse.

The headlights are mounted to the truck on 1/8 inch rod bent in the shape of an "L." I drilled through the 1/8 inch bar that replicates the sides of the heavy casting shown in the Introduction to this Instructable.

But, first, I drilled a 1/8 inch hole deep into a 3/8 inch rod that will be the body of the headlight. That 1/8 inch hole is centered about 3/16 inch from the end of the rod. Then I turned the end of the 3/8 inch rod in my hand to grind the bullet point shape of a headlight onto the end of the rod.

I ground a slot in the back of the headlight. See the first photo. I inserted the 1/8 inch rod into the hole. I welded the 3/8 inch rod to the 1/8 inch rod. Then I ground the weld to fit the contour of the rest of the headlight.

See the second photo. I cut the shaped headlight section from the rest of the 3/8 inch rod. I did a little final grinding to shape the headlight.

At this point I bent the "L" into the 1/8 inch rod. I did have some trouble with the headlight "rolling" so it no longer pointed forward. It may be better to bend the 1/8 inch rod first and adjust for alignment of the headlight during welding.

Cut the bent 1/8 inch rod, insert it into the frame hole and tack weld it to keep it in position.

Step 4: Toolbox

Some AC Bulldog trucks are shown with one or two toolboxes on the rear of the running boards. I chose to add one toolbox. It is made from 3/4 inch square tubing with a flat piece of steel welded to each end of the square tubing. I welded the toolbox to the running board as best I could and smoothed the welds with grinding and Bondo.

Step 5: Body Putty and Primer

Originally I had hoped to make such smooth welds that no body putty would be necessary. That may be possible with a good MIG welder using shielding gas, but I have a flux core welder and welding thin materials is more difficult than with a MIG. I filed and I ground welds, and I smoothed further with Bondo. The first photo shows the cab primed. I wanted to see how it looks with primer after looking at weld burns and pits for so long. I also planned to use a pressure washer to clean up some of the welding flux, and I wanted paint on as much as possible before blasting the bottom of the truck with water at high pressure. This was to reduce any rusting.

Step 6: Tires

The original trucks from the early years had hard rubber tires. I wanted to create that illusion. I also wanted to provide a soft contact surface to protect wood floors and furniture from unnecessary scratches.

I decided to use a bicycle inner tube sliced crossways to make bands that can be stretched over the wheels. My wheels are about 1.90 inches in diameter. I found a tube in that size range.

I discovered the best way to make tires for my wheels is to cut bands a bit wider than the wheels. I turned the bands so the inside of the tube is out. The inside is smoother and free of moulding seam marks. I stretched the bands a little and pulled them onto the wheels. Remove tucks. Align the outer edge of the rubber and the wheel rim. Hold the rubber firmly on the wheel so it does not creep. Trim the inside edge with a sharp scissors.

Step 7: Painting

After I cleaned and sanded the metal, I sprayed with primer from an aerosol can. I sprayed a little, starting before the spray came onto the metal and continuing just a little as the spray passed from the metal. Too much paint at one time causes runs that will be visible later.

I used Q-tip cotton swabs as an applicator to accent the company emblem and the steering wheel in black. Doing this makes the truck more interesting and makes it stand out. I masked around the steering wheel to keep paint from going where I did not want it.

I sprayed white paint onto a Q-tip and daubed at the face of the headlights. Too much paint softens the red basecoat and the headlights are pink.

Painting the emblem black was easy because it is raised. I simply needed to keep a steady hand and a light paint load on the Q-tip.

The very last thing was to add self-stick vinyl letters to the side of the dump box. As I mentioned earlier, I wanted to put the name of my grandson, Joshua, where a company name might normally go. I used the point of a pocket knife to hold and position the letters before the first edges touched the smooth painted surface.

I am excited to give this toy truck to my grandson when his birthday comes in less than two months. I hope he will be able to give it to a grandson of his own one day.