How I Design a Custom Tank Mounting Tab in Fusion 360

A repeatable way to make a one-off bracket fit perfect the first time — using a photo, one known hole, and a little CAD.

Mounting a gas tank on a custom chopper always comes down to the little stuff — the tabs. You can't buy a bracket that lands exactly where your tank sits on your frame, so you've got to make one. Here's the exact process I use to design a custom tank mounting tab in Fusion 360, from snapping a phone pic all the way to a part I can hold up against the bike and check.

The whole trick to this method is using something on the bike you already know the size of as a reference. Get that right and everything you draw comes out to real-world scale. For me that's almost always a bolt hole. Let me walk you through it.

01. Snap a photo and drop it into Fusion

First thing I do is take a clean, straight-on picture of the area I'm building the tab for. Try to shoot it square — get the camera as perpendicular to the mounting area as you can so the photo isn't distorted. The flatter your angle, the more accurate everything downstream is going to be.

Then I bring that photo into Fusion 360 as a canvas (Insert → Canvas). Now I've got the real bike sitting right there in my sketch environment to trace over.

02. Set your reference datum — the known hole

This is the most important step, so don't skip it. A photo on its own has no scale — Fusion has no idea if that tank is six inches or six feet. So I give it something it can trust.

My datum is the mounting hole. I know it's a 5/16" hole, so I draw a 5/16" circle right on top of it in the photo. Then I scale the canvas image up or down until the hole in the picture lines up perfectly with my 5/16" circle. The second those two match, the entire photo is now to scale — every line I draw from here on out is a real measurement.

03. Design the tab around the tank

Now the fun part. With the image scaled, I sketch the tab right over the photo, following the curvature of the tank so the top edge hugs it where I want them to meet. I start from that reference hole and build the shape out to the contour of the tank and down to the frame.

Once the outer profile's locked in, I clean it up and add a lightening hole in the middle — knocks out some weight and honestly just looks better than a solid blob of steel. This is where you make it yours.

Time to mock it up — two ways to do it

Once the design's done, I want to hold it up to the bike before I ever cut steel. There are two ways I go about this, depending on what you've got in the shop.

Method A
Extrude it and send it to the 3D printer

My go-to is to extrude the sketch to whatever thickness I want the finished tab — say 3/16" or 1/4" — and now I've got a solid 3D model of the part.

Send that to the 3D printer and a little while later you've got a physical part in your hand. It's not the final steel piece, but it's a perfect mock-up to check fit and proportions.

Then I bolt it right up to the bike. This is the payoff — if the photo was square and the reference hole was right, the tab drops in and meets the tank exactly where it should. If something's a hair off, I tweak the model and reprint. Way cheaper to find out now than after you've cut and welded.

Method B
No 3D printer? Print it 1:1 and cut it out

Don't have a printer? No problem — you can still mock this up with nothing but paper and scissors. Take your tab and create a drawing in Fusion 360, and here's the key: set the scale to 1:1. That makes the printout the exact real-world size of your part.

Print it out on regular paper. Because it's 1:1, what comes out of the printer is dead-on the size of the tab.

Cut the shape out with a pair of scissors. Now you've got a paper template of your tab.

Hold that paper template up to the bike and check it against the tank, just like you would the printed part. You can mark it up, trim it, hold it at different spots — it's a quick, dirt-cheap way to confirm the shape before you commit to steel.