Fabricated Tailgate

[Mdevill]

Hello Everyone,

I found my M37 in a barn in South Louisiana in 2012. My son and I started the restoration in 2015 and got it on the road in June, 2020, one month before he left for Ft. Leonard Wood for BCT and MP AIT. During that span of time our restoration received significant support from historical data found on this site. Thanks to all for that. Our truck came to us with no tailgate and, after no luck finding a decent unit for sale, I decided to try to fabricate one. My goal was to build one as close to factory as possible using “standard” fab processes. Building a stamp and pressing a tailgate was not a viable option. A fellow forum member, M-37Bruce, follows my son’s Instagram and was nice enough to comment on the end result there and on this site. I figured that it may benefit the group if I were to post pics and build data here. Maybe it could help others or generate more marketable fabrication options.

Other than support from this form, I owe lots of people for lots of fabrication favors granted to me in this fabrication. I designed the tailgate in SolidWorks and created the overall design that makes the fabrication possible but I don’t weld and do not have direct access to industrial brakes, sheers, etc.

I have attached a pic of the finished unit but when I have access to my PC, I’ll post some build pics and data tomorrow and this weekend.

[John Mc]

Nicely done!

Looking forward to seeing more.

[Cal_Gary]

Indeed, that looks fantastic!
Gary

[Mdevill]

I met a guy who is fairly local with a tailgate who was nice enough to allow me to take measurements. With my tape measure, calipers, and laptop in hand, I created a solid model of his tailgate with as much accuracy as I thought I needed. Later, I would find myself taking more measurements and scaling my model against Internet pics to make sure I didn't make mistakes.

Verified Tailgate.JPG (43.57 KiB) Viewed 2700 times

From that file, I created a second solid model eliminating features which required special tooling or other fabrication challenges such as the top rail and lower radius hinge section.

Derived Tailgate.JPG (50.31 KiB) Viewed 2700 times

For the top rail of the tailgate, I developed a solution that caps the main body of the tailgate and plug-welds to it on the top flange and the lower flange. My cousin happens to work at a sheet metal fabrication shop and built two of them. I used one for the front bed wall I also fabricated and the other for the tailgate. It is the red portion in the pic.

top rail.JPG (24 KiB) Viewed 2700 times

More to Come...

[Mdevill]

For the radius section at the bottom of the tailgate, I didn't want to tool up with some sort of press brake die so, instead of bending sheet metal, I modeled a section based on round tubing. I have a second cousin who works at a local machine shop who machined a solid steel rod with 1.32-inch diameter to a shape as shown in the pic. It includes flats on the "top" and "bottom" to eventually receive the sheet metal, turned down end sections to fit plastic bushings he also made that would then fit the hinges on the truck for a tight, solid feel when lowering the tailgate, and a relief in the middle for the support bracket. The file indicates a pipe but he used material he had which happened to be solid.

Hinge Section.JPG (35.26 KiB) Viewed 2700 times

The next pic is one of a 3D printed test piece I did which shows the machined part along with what will eventually be the sheet metal parts. The intention is to bevel, weld, then blend the top/bottom points for a seamless, factory looking piece.

3d hinge.JPG (19.87 KiB) Viewed 2700 times

At this point, I was decently confident I could make the tailgate but needed a way to stamp the main section of the unit. I chose to use 12 gauge steel, if I recall correctly, which I think is thicker than factory so the thickness and the press needed to stamp a blank was out of the question. After months of evaluating various options in SolidWorks and contemplating the chances of success on the first try on all of the options, I decided on the pattern shown below. I was fortunate enough to have a great friend with an industrial size (maybe 50-ton, I don't recall) press-brake and an offset die. He formed the piece shown in the pic and provided the sheet of Corten steel.

Blank.JPG (69.42 KiB) Viewed 2700 times

I created three stamped sections and would eventually cut off the largest one and use it later. The reason for adding it into the blank now was so that I would be able to use the bends later when I started fabrication. More on that later. At this point, I am ready to start lots of cutting and fitting.

More to come later.

[Turbothis]

12ga is hefty stuff

[greeno]

Could you share the model?

[Mdevill]

I don't mind sharing some of the models I created but not sure of the best way to transfer them.

With the round bar (lower hinge) and the upper cap already made, I got the sheet metal back from my friend with the brake. The upper section, which I intended to cut off, is too wide but would work for my intentions. The pics show the sheet after I got it back then with the top cap mocked up on it after I cut off the upper section. The pics also have marks I made in areas I intend to cut.

[Mdevill]

About a year earlier, I had asked my cousin who works at a machine shop to make me a die that I had modeled in SolidWorks. He was nice enough to make it and, after a few adjustments, it seemed like a viable solution for pressing the corners.

Test Corner Blank.jpg (126.61 KiB) Viewed 2607 times

This is a first pass at a test blank.

Blank on DIe.jpg (91.33 KiB) Viewed 2607 times

Ready for press

Die Test.jpg (84.87 KiB) Viewed 2607 times

First test worked but not perfect dimensions. The die needs adjustment.

[Mdevill]

After adjusting the dimensions of the die, I created a new test piece to verify the height of the stamp to ensure that it was equal to the height of the step-die press brake bends in the main body of the tailgate. I also 3D printed some test corners to be used for fitment tests to come later.

The successful test makes two 90-degree corners.

Corner Blank.jpg (90.65 KiB) Viewed 2606 times

I started removing sections of the blank that need to remain flat.

blank with cut-outs.jpg (123.09 KiB) Viewed 2606 times

I cut pieces out of the upper section I had removed earlier. I flipped these pieces and trimmed them to fit into the cut-outs in the blank so I could have them welded in later. For fitment testing, I used the 3D printed corners.

Testing Corners.jpg (116.03 KiB) Viewed 2606 times

[Mdevill]

Hours and hours of cutting, trimming, and testing...

Corner Testing 1.jpg (75.45 KiB) Viewed 2605 times

Corner Testing 2.jpg (109.49 KiB) Viewed 2605 times

Corner Testing 3.jpg (106.44 KiB) Viewed 2605 times

[Mdevill]

After more hours of making corner blanks, cutting them out, trimming them to fit, and making more flat sections, I got my brother, a professional tig welder to weld the corners onto the small sections so that I could blend them all before he would weld them onto the tailgate blank.

Corner Testing 4.jpg (92.78 KiB) Viewed 2603 times

Mocked corners.jpg (105.06 KiB) Viewed 2603 times

mocked blank.jpg (108.81 KiB) Viewed 2603 times

[RCrombie]

Wow.
That is a lot of work! I’m amazed at the finished result. Good job.

[Mdevill]

Thank you!!

After my brother finished welding the corners onto each insert, I buffed the welds and continue to fit each piece into its place. My original intention was to use the upper section I had cut off previously, to fit perfectly into the cut-outs between the bottom stampings but either I calculated the wrong width in the SolidWorks files or we just messed up in the bending process. Either way, the width was too much which caused me to cut then weld them back together.

In this pic, you can see that the inserts are welded in but not to the edge. I left that unwelded so that we could bend in a later step. I was advised to avoid trying to bend perpendicular to a weld.

welded pieces.jpg (107.06 KiB) Viewed 2589 times

After blending all the welds, I am fairly happy with the resulting blank. Of course it will need body work but it is shaping up to be a decent result. After checking and double checking measurements, I got the sides and the lower flange bent which created more structural strength.

Bent Edges.jpg (123.33 KiB) Viewed 2589 times

Next, I tested the fit on the truck. In this pic, you can see the top cap placed on the blank and the lower flange mentioned above clamped to the bottom flat milled on the solid rod. As for the flat milled on the top of the hinge rod, I had a section of Unistrut which had a tight bend and would work perfectly for this piece. In this pic, the galvanized (silver) colored piece clamped to the hinge bar is the piece of Unistrut. I could have had one fabricated but I had the Unistrut and it worked perfectly so I used it. You can also see that I left the sides long for now so that my brother could use them as leverage in the welding process if required.

Test fit.jpg (102.43 KiB) Viewed 2589 times

[Cal_Gary]

Impressive!
Gary