Building A DIY Custom Bicycle Rack From Scraps

Making A Customized Bicycle Rack On The Cheap

Ever since I’ve had a… let’s call it a “longstanding personal dispute” with a certain member of my family, I’ve been using my bicycle for all my transportation needs. One of the major things I rely on my bicycle to do is carry cargo. Groceries don’t walk, and no store in my area delivers. Other things- library books, clothing, reclaimed junk- they don’t tend to have legs either. Last time I checked the bus service does not accept bulk materials.

Now I already have a rack that does that job just fine. Were that all I needed, I wouldn’t bother building a new one. My problem is that I’m also trying to add a motor to this bicycle. I already have a battery, motor, controls, and even the transmission ready to go. Despite my best efforts though, I cannot fit this stuff to the existing rack. Not even for a temporary test. That rack had to go sooner or later.

I have plans beyond just a rack, which is why I’m not so willing to just buy one that works. Plans are in the works for more effective cargo mounts. If I can find the parts, I’d also like to experiment with a longtail conversion. All of that hinges on a rack that suits my unique needs. Possibly literally for that longtail conversion.

As it turns out building a sturdy bicycle rack is actually really easy! You don’t need anything more than basic hand tools and some scrap metal. I don’t regret buying that rack, but if I knew how easy it was back then I never would have bothered.

Custom Bicycle Rack Design

My primary design constraint, as well as the entire reason I’m bothering to do this, is that I have to mount this sheet metal enclosure to my bicycle:

If that PCB looks familiar, there’s a reason for that. Stuck in development hell for literally years, I may finally be able to use it!

Currently I have a rack that works fine for everything else. Attempts to combine the two were resounding failures. The rack was cheap, so I don’t feel too bad for replacing it. Perhaps I can use it somewhere else (front rack?).

Cheap, dependable, and incredibly useful. You will be reborn cargo rack, just as soon as I figure out something to use you for. That basket on the other hand is basically done.

Were it not for the little curved bit on the front and back, I could have just slapped my enclosure on top and called it done. Why did I not buy a flat-top rack to begin with? I can’t remember but I assume it had something to do with being a cheap ass broke bitch. Besides, it never was a problem before now.

My solution to this predicament is to make my own rack, loosely based on my current one, that can carry this enclosure and cargo on top. I have extensive plans for improving the cargo capacity that will be much easier to integrate into a custom rack too.

Material Considerations

At first I had a fairly complex design using hand-bent 1/2″ aluminum tubing. One tube would would make the bulk of the structure, bending through elegant curves to both support the load and connect to the mounting points. Unfortunately I have no experience in this kind of tube bending. I don’t have enough budget to learn the hard way either. I hesitated over getting the tubing for months. That turned out to be a good thing.

While doing various measurements I realized I can just use straight lengths of angle stock throughout. No need for tubing at all! My scrap pile has plenty of aluminum angle stock I have no other use for.

Once these bars were the guides on a (failed) CNC machine. Until now they’ve just kind of been “hanging around”.

There are a few issues with this design, but I consider them solvable. Notably the front support bars have to be made of something else. Not a big problem; these bars are loaded primarily in tension. Thinner stock will work just fine there.

Calculations show that 3/4″x3/4″x1/8″ aluminum angle stock is plenty strong. Too strong perhaps. 1/16″ thick angle stock would be just fine too. 1/2″ flanges would also work. In all of these cases one strut can support the maximum allowable load (at least 55pounds/25Kg) on their own with significant safety factor.

As for how the pieces are connected, I used standard M5x0.8 bolts. Bolts are easy to work with, easy to get, and reasonably strong. They won’t be as rigid as other joinery but I can work with that. I have a tap set, so I can just thread the parts. Nuts can be used with a bit of care- remember that a bicycle rack will be subject to severe vibration!

Bicycle Rack Schematics

I didn’t have too much of a plan for the new rack. Still don’t. I drew these plans after building the rack. Sometimes you can’t really build something “on paper” before building them for real. Happens all the time.

Simplified plans for the bicycle rack showing critical dimensions.

Pretty much every bicycle rack I’ve seen uses a similar inverted kingpost design. A few use just one strut in back, but that will not be rigid enough when bolted joints are used.

All the initial measurements were taken from my existing rack, substituting my enclosure on top. By their nature they are highly dependent on on the bicycle. I’d suggest making a mockup out of cardboard before trying the same with metal. Not all of the angles are simple, and it becomes difficult to tell at a glance how much material you need to bridge the gap. A temporary mockup will give you the answer faster and more reliably than trying to calculate it.


This is a project where I don’t have a lot of other interesting things to say. Instead of boring, dry, unnecessary narration I’ll just show some photographs of the assembly process with terse captions.

Two lengths of angle stock connect to the bottom of the sheet metal casing. These are just about the same width as my rear fork. That’s good because I installed them long before I actually got real-life measurements to compare against!

Here’s the main support post. I had to re-drill the holes on one piece but otherwise it worked first time.

I calculated the length of the rear support using basic trigonometry. Real measurements matched up remarkably well. That never seems to happen to me!

The support bars are tightly fitted, so they need some relief cuts to make room. Rear supports are rounded on both ends while the tops of all the supports are cut down a little bit to make room for the sheet metal cover.

Those front support straps are an example of something that’s difficult to measure. Cardboard mock-ups are invaluable for parts like this.

I was a little worried I’d have to buy some new material to build the front supports. Scrounging my scrap pile turned up an old roof rake that had exactly the right kind of stuff. Hole locations were taken from that previously mentioned cardboard strip. That strip helped a lot!

Fully assembled and ready to roll! There are still a few remaining issues, but I can work on them later.

For the most part everything went smoothly. I did not need to get more material, my machining was acceptably accurate, and my plans did not need significant revision. The only tools I needed were a drill, a hacksaw, and a file. Aluminum is pretty easy to work by hand, so power tools are optional.

Were it not for the documentation I had to do along the way, this project would only take a couple of hours. Maybe even less. You can literally build a rack the same day you need it.

Finishing Up

Given how fast and easy building your own bike rack is, I’d strongly suggest giving it a go. I only needed the most basic of tools. All my material was recycled from other things. The only thing I had to buy was a new set of M5x0.8 bicycle bolts which are technically optional- only the frame mounts need M5x0.8 bolts, and they usually have some already installed. Work amounted to a single lazy afternoon using basic tools. If you ever find yourself suddenly needing a bicycle rack, this is a totally viable on-the-spot solution.

Obviously I had a casing I wanted to build into the rack. That dictated most of my design choices. However if you simply replace the casing in my design with a few stretcher bars and a top deck it becomes a generic cargo rack. Dimensions can be changed to suit- part of the beauty of this design is that you can easily change it if you want something else. Since I bolted everything together that can be done after the fact should I ever desire it.

Angle stock is a reasonable choice of material, but I feel tubing would still be better. Tubing is a little easier to cut to length since you can just use a pipe cutter. There won’t be nearly as many clearance issues because you can just flatten the tube ends. On the plus side, angle stock is easier to modify with extra mounting holes.

The only remaining issue is a lack of lateral rigidity. I’m putting this down as a consequence of the thin sheet metal making up the bottom of the case. It’s handling pretty much all the side to side load. In the event that becomes a problem I’ll add some stiffeners. I expect the motor mount will help this situation.

While functionally complete, you won’t be seeing me ride around town with this new rack quite yet. I have a few more things to add to make it a proper replacement for my current rack. Being able to fully disassemble it greatly eases adding mounting holes for my cargo bags!

In the meantime, I’ve got the motor system to work on. Part of the reason I’m building this rack now is so I can test the motor under real conditions. Expect more in a week or two.

Have a question? Comment? Insight? Post below!

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