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.

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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.

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.

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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).

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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:

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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.

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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.

Big And Cheap: DIY Cargo Bike Bags

There is another post that shows later improvements to these bags.  Here is another one that covers a hole I left in this article below.
Great Big Bags 2.0 uses a better attachment method.

I have a Mongoose Envoy that I turned into a project bike.  I essentially took a very inexpensive bike with low end components (but a fantastic frame, with a good fork and wheels) and rebuilt it into a high power, heavy duty cargo bike with better components than I’d get if I paid for one from a major manufacturer.

The Envoy comes with two almost-38L-each panniers (24″ long x 16″ tall x 6″ deep).  Thats one hell of a lot for a bag on a normal bike.  But on a mid tail cargo bike frame, they’re smaller than what they could be.

The stock bags look skinny, and are no thicker than a normal pannier.  But I’ve had them loaded with a complete Costco grocery run where the bike ended up well past its 140-lb rated cargo capacity.  Using an elastic bungee net to make sure everything stayed tight to the bike, all I had to do was lumber home without killing myself.

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Figure 1.  A light shopping run – not using front bags.  The bags we’ll make here are about the same size as the ones shown, but more than double the width.  Note the cargo net used here as insurance that those bags stay put.

So… the bags work great and are essentially free.  But I’d like something that better suits the capacity that the mid-tail cargo frame can handle.

I managed to score a brand new set of Surly Dummy bags for a great price.  I found they were great bikepacking bags not suited to bulk grocery hauling.  Whats needed is a giant hole you can dump stuff into and zip closed.

It looked to me like the Yuba Go-Getter bag ($300 plus shipping for the pair) was the closest fit to this idea, and to my frame (It is meant to fit their popular Yuba Mundo cargo mid tail)  I contacted Yuba about the exact size of the bags, and that they would be going on a non-Yuba bike.  They promptly got back to me with this:

  • Length – 29″ / 74 cm
  • Depth – 10″ / 25cm
  • Height – 17″ / 43cm
  • Volume comes to about 84 quarts or 79.5 liters.
  • It is important to note that we designed the Go-Getter to be specifically compatible with our Yuba Mundos and we cannot guarantee its compatibility with non-Yuba bikes.
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Figure 2: A single Yuba Go-Getter bag mounted on a Yuba Mundo cargo bike.

Thats pretty awesome in terms of capacity.  However, those dimensions are just enough to worry me on my bike.  The Envoy’s bags are 24″ long.  29″ might end up pushing into my heel clearance.  The height of 17″ is for sure an issue.  Envoy bags are 16″ tall, and its already a problem that those bags essentially sit directly on the lower rack.  While the bike frame is rated for 90 lbs, the lower rack is only rated for 20 per side, or 40 lbs total.  Now, they can handle much more than that in real life, and I have reinforced the lower rack’s attachment to the frame (Supplementing the factory’s four connections with an additional six that are each stronger than the simple factory bolt), but still a bag that basically sits its weight on that lower rack is not ideal.

What would be better would be a bag that is a little shorter, that bows downward under load, putting strain primarily on its hanging hooks, so only partial weight is borne by the lower rack.  Add in a couple straps to help take the load off those 4 hooks and its better still.

I think my solution accomplishes that.  Bear in mind everything I did here was done specific to this bike.  You can take these ideas and make adjustments so this basic concept fits to yours.

The Budget

Lets call the number I am trying to beat the cost of the Yuba Go-Getter bags, which were my benchmark for capacity:  $300.  So I wanted this project to come in as far under this number as possible and still get a quality bag.  As you can see from the build sheet below, I came in well under the commercial product’s price point.

Build Sheet ($111.50, or $55.75 each)

Rothco Parachute Bag (2)             Amazon   45.98
3"x30"velcro cinch straps (8)        Amazon   21.54
C.S. Osborne #6 13/16" grommets (8)  Amazon   11.36
Stainless 0.3"/0.78" S hooks (8)     Amazon    2.67 
Therm-a-Rest Classic Foam Pad        Amazon   29.95

The Bags

I want something more durable than the fabled, dirt cheap Ikea bag.  But really those bags got dropped as candidates because the zippered version is so short at 11″ that it would be putting the load unnecessarily high.  Also its 28″ length is again just enough to worry me.  And how sturdy is it?  The zipper in particular?

I had a candidate already in my hands in the form of a Rothco Parachute Bag.  These are simple, cheap $23 bags made of reasonably thick canvas and strong, smooth zippers with a snapped storm flap.  Dimensions are 24″ long (identical to the Mongoose stock size), 15″ tall (1″ shorter than stock, so addresses my height/weight concerns) and 13″ deep.  Work out those measurements to cubic inches (4680) and convert to liters and you have a 76.7L pannier bag.

Since I already had one of these bags in my closet, I was able to toss in some full size pillows (it ate 3 of them and still wasn’t quite full) and sized it to the bike.  Looked like a perfect fit.  So I bought two more for testing.

Attachment

After a fair bit of fussing around, trying to figure out exactly how I wanted to attach the bags to the bike (it actually took a few weeks), I settled on primary support being grommet holes in the bags, which will connect to simple S hooks mounted to the frame.  These will be further supported by straps.

I used the C.S. Osborne #6 grommet, which has a 13/16″ hole.  Why this brand and size?  Well, there are drapery grommets, shower curtain grommets and outdoor tarp grommets.  The grommets for curtains are nowhere near strong enough to work on a tarp… or a pannier.  I knew from experience the Osborne grommets are solid and will distribute the forces involved as well as possible.

I chose a 13/16″ size because… I had the grommets and the grommet tool already.

20170218_143537Sidebar:  The #6 grommet size is the smallest size commonly available that will let you fit an XT90 connector thru the hole.  Thats why I have the grommets and tools in my garage – from building battery bags for my custom ebikes.  I grommet the pass-thru holes in the bags.  And since I have been using them for years, I know they hold up.  The bag on the right was made in early 2017 and is still in use today.  This $12 Amazon bag with reinforced holes is way cheaper than a custom ebike bag.

  • You can see in the first pic below, three of the four grommets’ upper edges match the seam of the bag, while the forward-most grommet is lower.  Oops.  My second bag had them all even and all in the lower orientation.  Despite the different mounting, you can’t tell the difference in how they sit on the bike.
  • The single brass grommet was deliberate as I wanted a quick visual cue to help me orient the bag.  Brass = rear for both bags.

Straps

Not wanting to rely totally on the hooks, there are two dedicated three-inch velcro cinch straps.  These are actually made up of two 30-inch straps combined to make one longer strap.  I had to do this as there does not appear to be a 3″ wide velcro cinch strap in a 60″+ size on the market.  If you wanted to save some money and use a narrower strap, 2″ cinch straps are widely available.  In fact, the pics below show an early test fitment where I was using 2″ x 72″ straps, which worked OK but were so long they were a bit unwieldy.  Shorter straps were more convenient and the wider 3″ version provided more support.

The right way to use the straps:  Loop over the rack at top, and the very bottom, directly underneath.  But do NOT loop under the lower rack and then go up over the bag.  Instead, from the bottom of the bike frame, loop the strap directly under the bag and then back up to the top.  The top loop over the rack helps support the bag’s weight.  The bottom loop onto the lower portion of the frame (or rack depending on your bike) helps hold the bag close to the frame so it won’t flop around.  And the remainder of the strap, directly up against the bag and not under the lower rack, holds up the bottom of the bag, preventing – along with the padding – the bag from sagging.

Hooks

These are pretty straightforward.  I wanted an S hook with beveled edges that allows quick attach/detach, but at the same time is shaped in such a way that the bag will not easily come undone from it as I bounce from pothole to pothole.  I searched for months for such a hook for a cargo net and fell into the ones I am specifying in the build sheet.  Originally meant for my cargo net, they are also perfect for this project as well.  I have the painted black versions but I am spec’ing the unpainted stainless versions.  For your own personal bike, you may need something different.  Follow the link above and note the seller offers three sizes.

More Options

  • Most of the reason I used pre-made cinch straps rather than buying webbing and fastex-style buckles is that hook/loop strapping is much easier to adjust.  This makes it easy to cinch up the straps when the bags are empty, and fold the bags up quite nicely.  There is even a deep, wide pocket formed by this process that is a decent candidate for stuffing in whatever fits.
  • During testing of the bag when fully loaded, I ran a 15″ x 30″ cargo net from my top rack, over the bag and underneath to the bottom rack.  It provided great support to keep the bag from sagging, and held it firmly, close to the frame.  For really heavy loads this looks like a smart thing to have available; especially since it can lay flat in the bottom of the bag and take up no extra space.
  • I have a 24″ x 36″ cargo net (see it in action in Figure 1 above) that I can use to stretch over my entire cargo area.  Up over a side bag, the loaded upper deck and back down over the other side.  For big, heavy loads, a net like this can put a gentle, compressing and enveloping grip over the entire load in the rear.

Where Do You Go From Here?

Unless you have a Mongoose Envoy then your bags will need to be tailored to whatever your bike fittings are.  Expect to put the grommets in different places.  Maybe use a different size of S hook.  Don’t expect my project to work perfectly for your bike although the parts I am using should be mighty close to universal once you space things out per your bike’s needs.

In the photo above: I had so much room in the new bags after loading up my shopping cart, I never even used the 36″ x 12″ duffel that sits atop my 40″ rear deck.  There is almost 154 liters of pannier space in those bags, and after dumping that whole shopping cart into them (the front bags helped too)… they still aren’t full!