An “M” Bag for a Brompton

The “M” is for “modded”, because this bag was made to fit my cut-down S frame.  This is the latest bag I’ve made in my never-ending search for the perfect bag for every conceivable cycling purpose.  (Everybody needs a hobby, right?)

This front bag is made to match Basil’s underseat bag, which accompanies us at all times.

The goal here was was to make a small bag I could use for all-day trips when I’d need to pack a little more stuff than I can get into the underseat bag alone.  But I also wanted a bag into which I could toss my tablet if I wanted to do nothing more than go and sit in a coffee shop and surf.

Inside, there’s a padded pocket for exactly that purpose:

The red ribbon goes under the tablet so that I can pull on the nylon triangle and lift the tablet out of the sleeve easily.  (I love being able to add the features I want to the bags I make!)

The long green flap below folds over the open tablet sleeve.  (It’s lifted out of the way in the picture above.)  I took the front flap off for this shot, so that the tablet sleeve cover would show up better.

I wanted pockets on the inside, but didn’t want to make them myself, so I used commercial mesh pockets I’d picked up at a back-to-school sale.

They worked perfectly.  I added zipper pulls cannibalized from an old bag, since the metal ones on the pockets are a little too small for convenient use inside a bag.

I added a D ring on the upper left for keys and such. (The bag is inside-out here.)

There’s a different sort of mesh bag to the left.  It’s for a water bottle.  I made the sleeve with a deep open hem at the top, so that I can slip a bit of plastic mesh screen next to the mesh, into the pocked made by the hem.

The mesh supports the sleeve, and makes it easy to pop a bottle in or out, without subjecting it to drag against the mesh fabric. Here’s the view from the top:

If I don’t want to carry a water bottle inside the bag, I can remove the mesh, in which case the netting collapses and is easily pressed against the side, leaving that much more room in the bag, as you can see below.

The screen is sufficiently small and light that it can tuck anywhere in the bag for future use.

There are exterior pockets on either side of the M bag.  These lie flat when the bag is fully open.  This photo shows the side of the bag before I added magnets.  (More about those further down.)

Hidden inside are clips for a shoulder strap:

The clips are off-center because the bag, when worn, is weighted slightly toward the frame. Putting the strap closer to the frame makes the bag easier and more comfortable to wear.

Hiding the clips not only makes the bag look more streamlined, but also helps keep the strap from flopping wildly when it’s attached.

I wanted to be able to use this bag infrequently as a wide-open rectangle, but wanted it to have a slimmer profile most of the time.

I sewed magnets to the each side of the bag so that it could be quickly switched from one configuration to the other.  When the magnets are flipped together, the bag is more compact.

I like the way the side pockets open a bit when the bag is folded, allowing ready access to their interior (these will be used for snacks, as a rule, so it might be nice to be able to reach inside easily.  When riding in some areas, one pocket will also hold an easily-grabbed small canister of Halt!, which I devoutly hope I never have to use).

The bag is closed with a single large buckle, hidden beneath the flap.  Taking a cue from the authentic Brompton S bag, I made the flap removable.

The flap is in both of Basil’s colors, and matches his underseat bag, but the bag itself is just green, with black binding.  The removable flap means that I can change the look whenever I feel like it, simply by sewing a new flap.  (Heh, heh . . . why, yes, I do have something particular in mind!)

Here’s the back of the bag, showing the modified S frame, and where the flap attaches to the bag with hook-and-loop fasteners.

(The flap’s not set perfectly over the fastener on the right, so you can see the soft loop fastener just below the strapping. I should check these things before snapping the pictures!)

The bag is lined with ripstop nylon, and all interior edges finished with twill binding.  Plastic mesh provides stiffening for the bag; it’s sandwiched between the main fabric and the lining.  The tablet sleeve is additionally padded with a sheet of closed cell foam cribbed from packaging that either came with my tablet, or with one of its covers.

I’m excited about the potential daily utility of this new bit of luggage, and eager to try it out.  By the time this post appears on the blog, I will already have done so, but as I’m writing this, I still haven’t even seen the bag on Basil!

(Edit: Yep, my posts are out of order, and, though I hadn’t seen the M bag on Basil when I wrote this, I have now, and so has everyone who saw Errandonneuring On a Brompton, Part 2. some days I just can’t keep up with myself.)

12 replies on “An “M” Bag for a Brompton”

All I can say is WOW

man I would luv to be able to design and make a bag for “The Legend”

Ill be jut as happy to be able to make some “extensions” for my O Bag :/

That is one nice little bag. If you ever decide to pursue making these as a business, I would but a black one without hesitation. I’ve been looking for a small bag for my Brompton, and the Mini-O bag is the right size but the colours are horrible. Yours looks as good, with some really nifty design features. Well done!

Thanks, Drdul! I’m probably never going to make these commercially, but I wish someone would offer something similar. The Mini-O is probably great for some, but I’m disappointed in it for several reasons, including those colors which just won’t work for my B at all. (Couldn’t they have at least done a solid black???)

Please, please, please go into production. If you saw my effort of attaching a small bag to a fabricated adapter for the luggage block, you’d probably take pity on me & ship me one of yours? (wouldn’t you?)
BTW, there are 2 new Mini-O bag colours “available” – solid black & green/black. I’ve lost interest however, because I tried my iPad in a Mini-O & it didn’t fit very well (& I couldn’t justify buying a Mini iPad to go with a Mini-O bag?)

I’m more tempted than you might guess, Ian. Unfortunately, I’m just barely dog-paddling my way through the commitments I already have in life. Making my bags commercially would be a second career that I just can’t see right now.

You’ve got me thinking, though. I’m going to see if I can find a small bag that could fit on the S frame and see if I can write a practical tutorial on how to make that work. This might not happen fast, though . . .

Thanks for the tip about the Mini O. Just saw the black one on the Brilliant Bikes site — that should be a good seller for them. They’re great bags, but I have my own reservations about them, which include the rigid sloping shape of the sides and bottom. My “iPad” is a Galaxy II, and it’s not a good fit, either, if I remember correctly. Love that waterproofing, though, which Ortlieb do so well.

This is amazing… I wish I had your talents and skills :) I do recognize some of the internal mesh zippered compartments from a set of mesh gear bags I found a Staples? I use the orange one as a bag for my tools that I tuck into my T bag.

You got some mad skills!


Yep, it’s Staples, Andrew. Actually saw the same set at Office Max today, although for 50% more. It was great being able use the ready-made pockets for the shortcut, and they are holding up nicely.

Funny, I use one of the orange ones in my B’s underseat bag for tools, too. Brompton minds think alike, clearly! (Waiting on the toolkit, which is due in Brompton Time 201? . . .)

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