Do it yourself crashbar bags from Rothco shoulder bags

RCinNC

Well-Known Member
Joined
Aug 30, 2014
Messages
2,816
Location
North Carolina
I always carry two sets of raingear on the bike (I often ride two-up). Since my bike is my main vehicle, I like to keep the panniers empty for things like grocery shopping, so I’ve gotten in the habit of carrying the rain gear in crash bar bags. For the past ten years and over 100,000 miles I’ve been using a couple of repurposed military gas mask carriers, but they were due for an upgrade. The old ones look like this:



The bags have to be big enough for the raingear, but no larger, as I didn’t want a couple of backpacks hanging off the crash bars. Eventually I settled on these:



They’re Rothco canvas shoulder bags, approximately 10” x 9” x 4” and very close to the same dimensions as the old bags. They’re the perfect size for a set of rolled up raingear. I would have preferred Cordura over canvas, but none of the Cordura ones I found were satisfactory as far as size and shape.

I removed the front pockets, canvas shoulder straps, and canvas webbing flap straps from the bags.

I made a template of the rear of the bag out of foam core board, and placed it against the crash bars on both sides of the bike, so I could determine where the attachment straps would need to be.

Once I figured out where the attachment straps would go, I created the pattern for the various pieces of the bags on a graphics design program called Inkscape. Inkscape is far superior to my old way of designing things, where I used graph paper and a lot of redrawing and erasing. In a limited way it allows me to build the project on the computer before any actual construction starts. One great feature is that it allows me to easily check the clearances between parts of the project, and to ensure that any holes that need to be drilled will line up with other holes.



This is a screenshot of what the design looks like on Inkscape. The individual parts of the plan can easily be converted paper templates that can be attached to the raw materials of the project and used for cutting and drilling guides.

I decided to create an internal frame for the bags, to distribute the load in the bags more efficiently. The frame also keeps the rear of the bag rigid, which makes it easier to load and unload when it’s attached to the crashbars. The internal frame for this project is simply a piece of 3/32” ABS sheet plastic, slightly smaller than the height and width of the bag. I bought the two sheets of 3/32” x 8” x 12” ABS from ebay for $12.66.

I glued a paper template of the frame to the ABS sheet using a glue stick and cut it out. The frame was then covered with a piece of black cloth that I had left over from a long-ago project. The cloth was attached to the ABS sheet with 3M Super 77 spray adhesive; it’s definitely not coming off.



This photo shows the actual template for the internal frame that was created from the Inkscape program, glued to the ABS sheet. The template is removed from the part once everything is cut out and drilled; soaking it in hot water melts the glue from the glue stick, and the templates come off easily. All of the holes that were eventually used to sew the attachment straps to the bag were drilled out using my benchtop drill press.



Here’s the front of the internal frame, with the fabric attached.

The hardest part of a project like this is the sewing. I don’t have a sewing machine. Sewing through multiple layers of ABS plastic, webbing, fabric and leather can be tough or impossible, even with a sewing machine, and the kind of machine that can reliably sew through heavy duty materials can be pretty expensive. To get around this problem when I’m sewing things like polypropylene webbing, I take a heavy duty hand sewing needle and attach it to the shaft of my soldering iron with a few twists of wire. Once the iron gets hot, you can easily melt tiny holes through the webbing with the needle. It makes the sewing part much easier. The positions of all the sewing holes were laid out in the Inkscape program in advance. I made templates for the pieces from the Inkscape program and attached them to the webbing, and then burned all the holes in all the pieces at once. The hot needle burns easily right through the paper and the webbing. Do it someplace that has good ventilation though; polypro webbing stinks when it burns. Templates were made for the leather reinforcing pieces also, and the sewing holes for the leather pieces were drilled with the drill press.

For outdoor projects, I always use polypropylene webbing rather than nylon. Nylon webbing can stretch when it gets wet, something you don’t want when the function of the webbing is to hold something tight.



This is the rear of the left bar bag, showing all the straps that attach it to the crash bars. The extra velcro patches adjacent to the straps are to secure whatever excess strap material is left over after the straps are tightened (the straps have to be long enough to easily get a grip on them when you’re cinching the bags down). In addition, the extra velcro makes for a more secure attachment, since it increased the surface area that the straps are attached to..

I made what’s basically a modified MOLLE style attachment system for the bags. Heavy duty 1” polypro webbing is sewn to the bags, with gaps so that the attachment straps can be passed underneath the webbing (kind of like a belt through a belt loop). This makes it very easy to replace the straps if they get worn out or damaged, and it doesn’t involve any sewing in order to replace the strap.



This shows two of the straps in the closed position, the way they’d look when wrapped around the crash bar.



This shows the same two straps in the open position. You can see how the straps weave under the 1” heavyweight polypro webbing. The straps go through those rectangular rings and then double back on themselves for a very secure fit.



This is what I used to make the attachment straps:



This shows the frame installed in the bag. All of the polypropylene webbing and velcro is sewn through the webbing and velcro, through the canvas bag, and then through the pre-drilled holes in the frame using a hand needle and thread. The frame is also sewn around its perimeter to the bag through pre-drilled holes in the frame.





These photos show the leather reinforcing patches inside the bag. Cinching down the straps on the bag can put a lot of stress on the material over time, as can the load inside the bags bouncing around over bad roads. To help reinforce these points on the bag, I sewed small squares of leather to the interior of the bag at the points where the polypro straps attach. The straps are sewn through the canvas and then through pre-drilled holes in the leather pieces.



I added a strap to the side flaps of the bag, just to keep everything secure inside. The strap is ½” lightweight polypro webbing with a quick release buckle.



Here’s the front of the bag. The front straps are ¾” lightweight polypro webbing with quick release buckles.



Here is the right side bag, attached to the crash bars.



Here’s the left side bag.



From the front.





Here are closer shots of how the straps attach to the crash bars.

I think they turned out well. I hope they have the longevity of the old ones.
 

Cyclops66

Active Member
Joined
Jul 4, 2022
Messages
131
Location
Bear, Delaware
Man that is a great idea. Even the needle soldering iron tip is a useful tip to prevent the blood I usually put in my projects like RCinNC.... lol It will convert blood to blisters in my case,
 

RCinNC

Well-Known Member
Joined
Aug 30, 2014
Messages
2,816
Location
North Carolina
That trick does work pretty well, Cyclops; I wish I'd thought of it years ago on some of the projects where I was jamming a needle through multiple layers of webbing using a pair of pliers. I used the technique a couple days ago for a different project, and this time I didn't even use a needle; I just sharpened the tip of an unbent heavy duty paperclip with a file and wire wrapped that to the soldering iron. I couldn't push too hard or else the paper clip would bend, but you don't really need to push hard; the hot paperclip does all the work.

One thing is that I think the heat takes the temper out of the needle, so it seems like it bends a lot easier if you try and use it later to sew by hand. If you decide to use the technique, I'd dedicate one of your needles to use as a heated needle and don't use it later for hand sewing.
 

RCinNC

Well-Known Member
Joined
Aug 30, 2014
Messages
2,816
Location
North Carolina
Heavy duty upholstery thread. I'm not sure of the exact brand I used on this project; it's on an unmarked spool that I got quite some time ago. The brand I recently bought to replenish my thread supply was made by Coats and Clark.
 

RCinNC

Well-Known Member
Joined
Aug 30, 2014
Messages
2,816
Location
North Carolina
Oh, and I didn't cover this in the original post because it was a later addition to the bags. The handle on the bag was made by sandwiching a 3/16" OD piece of vinyl tubing in between two strips of 3/4" webbing and then sewing the edges of the webbing together. It makes a nice stiff handle that holds its shape and doesn't flap around in the wind.
 

Wenisgoodenuf

Well-Known Member
Joined
Jun 26, 2022
Messages
634
Location
Winnipeg
I picked up a cheap cobbler manual sewing machine off Amazon. Planned to make a knife roll for my son but turns out it has been incredibly useful especially in instances like yours. Made straps to mount Wolfman bags to the crash bars and tool rolls, and replaced zippers on two pairs of shoes. Highly recommended
 
Top