Cheap DIY Cargo Bags: Update

Recently I posted up about how I made some Big And Cheap DIY Cargo Bike Bags. Since I made that post, I have made a couple of improvements worth mentioning (including learning to lock my front wheel… look closely at that pic above… doh!).

The Straps

While I discussed them in my original post, my use of 3″ wide straps hadn’t actually happened at that time. The straps were in transit. They have since arrived and been installed. I do prefer the wider size, and the shorter length of just under 60″ (I’m using two 30″ straps connected together). You can see them in use in the picture above.

It is worth noting the clumsiness I experienced with the longer 2″ x 72″ straps went away with a couple of days’ use. I simply got used to them, so as I mentioned in my original post, there is nothing wrong with 2″ straps. 1-piece, 2″ x 60″ straps should work just fine, will cost a bit less and be a hair less complicated. Although they will give a little less support.

The Hooks

Discussing the improvement to the hooks is a bit more involved.

Lets backtrack a step: Originally when planning this project I ordered some AN970 Large Area Washers from Pegasus Auto Racing Supplies. I intended to use them in conjunction with the M5 mid-frame braze-on bosses on the Mongoose Envoy to permanently anchor the bags to the side of the bike. Later on as the project matured I decided to just use the straps and not bolt the bags to the bike. So I never utilized these washers.

I bought the 1/4″ size which have an outside diameter of 1.125″ (28.6mm). Inside diameter is suitable for an M6 bolt, and usable with an M5. Washer thickness is 1.6mm so these are very beefy. Additionally they are made with Grade 8 heat treated steel. These washers are VERY strong. I have used the 1/2″ size, unsupported except for a nut, to secure end link bushings on a track (race) car and they held firm without bending in that very extreme job. If you toss your bike out of an airplane, these washers will probably be the only thing not bent on impact.

So… I have a bunch of unused washers. So what? Well, as you can see from the original build, the S hooks fit inside of a fairly large 13/16″ hole. The hook has plenty of lip to hang on thru bumps and bonks while going down the road, but it still moves and there is a little rattling. I hate rattling. When I build a bike it doesn’t rattle. I don’t care how big of a cliff you ride off of. No rattles. So… I took steps. Afterwards, the bags remain easy to remove from the bike. You just do it differently.

img_20191201_082723 — Fig. 1: Here’s everything we need to get the first part of the job done (stabilize the connection of the hook to the bag)

Step 1: Attach the big washer

These washers are big. 1 1/8″ wide in fact (essentially the same size as a headset stem cap). They are so wide they cannot fit inside of the narrow end of the ‘S’ hook unless we spread it a bit. So lets do that.

Take your pliers and spread the small end of the ‘S’ just barely enough so the washer will fit inside of it. Fit the washer in and then again being very careful not to over-crimp the ‘S’, take it back to being the same shape (parallel) it was originally.

Fig. 2: Original is on the left. You don’t need to do much for the washer to fit.

Fig. 3: This washer has been fitted. The ‘S’ has not yet been carefully crimped back to being parallel in its original position.

When you are done, you can stop here and fit the resulting product onto your bag grommet to see what you have accomplished. You will fix the hook by putting the big end thru from the inside of the bag. It will look like the picture below. At this point the connection is much more solid and when on the bike very unlikely to come undone unless you want it to.

img_20191201_083417 — Fig. 4: If you over-crimp the hook it will be too tight and will no longer fit. If you leave it spread out, it will rattle and move around. Just put it back the way it was before you put the washer in and everything will be fine.

So, we could stop here, but if you recall, I said no rattling. So lets take this another step to further solidify the hook into the hole and, as a bonus, make it silent.

Step 2: Add mastic tape to washer

Everyone knows duct tape is a gift from the Gods. A million uses. For bicycles and particularly ebikes, 3M Moisture Sealing Tape, Type 2228, is even more useful. This stuff is available at your local hardware store for about $10 a roll for the 1″ wide stuff. Its magic comes from the fact it is 65 mils thick (five or six times thicker than what you think tape thickness should be) and is a soft, adhesive rubber that can be stretched, bent, squished and molded as you see fit. And when it sticks to itself it literally welds together.

For this job, for each hook I snipped three snips of tape, each about 5mm in length. I didn’t actually measure – no need to be so precise. I just eyeballed it. Two of the snips went to the inside side of the washer, pushed inward to hold the hook in place and more or less fully face the washer with thick, soft rubber tape (3 guesses on how that affects rattling).

img_20191201_083921 — Fig. 5: Do a better job than I did here and cut yourself a little more tape so it goes edge to edge on the washer.

Step 3: Add tape to hook

With the above complete, plant the hook in the grommet hole – now you have to do it from the inside of the bag – and use the third snip to wrap around the hook, so the tape is between the hook and the grommet face. Like so, below. This will be a snug fit, but the tape’s tendency to weld to itself makes this job certain despite the fumblefingering that will ensue during job completion. When done, you have this:

img_20191201_085540 — Fig. 6: The 3rd strip of tape silences the hook rattling against the grommet.

Repeat the process with all four hooks. Here’s a peek inside the bag. Notice the washers completely cover the grommet hole.

img_20191201_090027 — Fig. 7: View from inside. Pretty sturdy connection compared to poking a hole in fabric with a hook.

The hooks worked fine as conceived in the original build. But these are now a more secure, stable mount. For long term use this is a better way to do the job, and the cost to do it is about 80 cents.

FYI its fine if you don’t use these Grade 8 uber steel washers… look for something similar at your hardware store, probably a 1/4″ zinc fender washer. Cheaper, too.

Upgrade The Hooks

This is not such a big deal but it works just a little better. All of the pics above use the black steel hooks that presently retail for $8.99. These hooks are powder coated so the black is on there pretty good, But its not going to be perfect, and rubbing paint (bike frame) on powder coat (hook) means you get some rubbing off on both the frame and the hook. Plus that powder coat isn’t as smooth as polished steel. These hooks come in a polished steel option for an additional $1 for the 30-hook pack. I got a pack of these and they seem to fit more smoothly against my frame (where the hook is exactly the size of the frame rails, so fitment is always rubbing-tight).

There is a slight cosmetic difference as they are slightly visible now whereas the black ones were not. I’ll leave it to you do decide if you care.

These hooks, in the best tradition of Chinese marketing, are described as “premium metal steel” so we’ll have to see whether either behaves differently. I am using polished on one side and powder coated on the other. Time will tell if either will rust.

Author: m@Robertson

I'm responsible for the day-to-day operations at my place of business: Leland-West Insurance Brokers, Inc. We do classic and exotic car insurance all across these United States. I'm also an avid auto enthusiast, a born again cyclist (i.e. an ebiker) and participate in medium and long range CMP and NRA sanctioned rifle competitions. View all posts by m@Robertson