I recently acquired a beater bike that I really enjoy riding around town. I added a small basket to the front, but I wanted something to hold a patch kit and and few odds and ends. I also constantly find myself without a light for this bike sine it's usually attached to my less crappy bike. Obviously I could just buy a dedicated light for this bike, but I liked the idea of incorporating a light into my saddle bag, so that's what I did. It took two half days to make, but that's because I was figuring stuff out along the way.

This bag can also be attached to your handlebars, or you can add a strap to make it a purse or small messenger bag.

In the future I hope to do a better job of housing the electronics. I'd also like to add some sensors so they can double as turn and brake signals. But for now, let's begin!

Step 1: Materials and Tools

So you can get by with only minimal tools for this saddle bag, but obviously your cuts will be much cleaner if you have some specialty tools.

Tools you need

Knife of some kind (I love Olfa's utility knife)
Awl (cheap but decent scratch awl from Tandy)
Hole punch (this set is super cheap and they're not bad once you sharpen them)
Saddle needles (a bit pricey but these saddle needles have a rounded tip that keeps you from puncturing your thread.)
Snap setter (this set of snaps comes with the setting tool.)

Tools that make it easier

Rotary punch (lots of sizes, easy to use. Don't go too cheap of the handles will bend. This one works well.)
Rotary cutter (Fiskars makes a good but affordable rotary cutter. Olfa's is nice, too. 45mm and up is best.)
Strap cutter (super handy for cutting straps, especially long ones. This one is made in the USA.)
Half round punch (good for cutting the ends of straps. I have one that's about 1.25")
Pointed strap end punch (mine's from CS Osbourne and is 1" I think. This one is 1.5". Good for finishing the ends of straps, especially one that will run through something, like a belt.)
Oblong punch (I have a 3/4" punch since most of the straps I make are 3/4". Plus I assume I could always punch twice to get anything wider.)
Buttonhole punch (a 4 mm punch is supposedly for 7mm button studs, but I found this too tight, especially for the thick leather I use. I have better luck with a 5 mm punch.)
Chisel punch (I have a 2 prong and a 4 prong, but this set looks nice enough. Probably best to sharpen on some fine grit sandpaper before using.)
Leather edge stitching groover (this one is a bit cheap but works ok.)
Soldering iron (being able to adjust the temp is great.)
Wire strippers (I have these.)

Materials

For the bag

Leather (I like veg tan leather best. Looks great, doesn't use a lot of chemicals, and wears well. This bag is made from 8-9 oz leather. I think you could get by using 6-7 oz if you wanted.)
Waxed thread (waxed linen works great, but use whatever you like.)
Snaps - I used three (like I said above, this set of snaps comes with the setting tool.)
Chicago screws or rivets - I used three (normally I use copper rivets, but I wanted to make it easier for the people that want to make it, so Chicago screws it is! 1/4" was slightly too long for my leather, but it still works.)
Button studs, 7mm if you're using a 4-5mm punch - I used two but you'll need four if you want to add the optional shoulder strap (these cost an arm and a leg from Tandy so look elsewhere like here and here.)
Cereal box (works great for making a pattern. I made one you can print out and glue on. Just make sure your scale is correct.)

For the electronics

Copper wire (anything works but I used this doorbell wire.)
LEDs - I used 6 red ones (actually, I only had two red LEDs. The other four were RGB LEDs and I just connected to the red)
Resistors for the LEDs (after I did my math I decided to use 60 ohm resistors. I think you typically use 100 ohm resistors with LEDs. This party pack should work out nicely for you.)
AA battery pack (pretty pricey if you just buy the one, but if you have time to kill you can get it cheaper.)
Solder (lead free is nice but use what you have.)

Step 2: Making the Pattern

I actually made the pattern before I created the CAD file. I find it easiest to trace directly to the leather when I have a thick pattern, hence the cereal box. Any thick paper will due. Probably the easier thing to do is print all four pages of the pattern, glue them to the cereal box (you'll have to cut it open and lay it flat), then cut that out to trace.

Step 3: Cutting the Body

Since I use a scratch awl to trace my pattern, I'm always worried I'm going to scratch the leather in the wrong spot. Sometimes I trace on the backside, but it gets hard to see. If you're going to use a pen, definitely trace on the backside. If you have a scratch awl, it's best to use the outside of the leather. If you cover your leather with your pattern, there's a next to zero chance you'll scratch where you don't want to scratch. I lay something heavy on my pattern so it doesn't move. Then I line everything up and trace away. Use your awl to mark the holes that you'll punch later.

Once I traced and cut everything, I used an edging tool to cut a groove to make it easier to punch. This tool makes it easier to keep your holes in a straight line, even if you're using a prong punch. It also helps your thread to lay flat. If you use a prong punch, you don't need to use the pattern to mark your holes. Keep in mind that, a, you can't use a four prong punch on a curved surface, and b, the spacing between holes on the curved bit needs to be slightly less than the straight section to accommodate the inside vs the outside of the curve.

Step 4: Cutting the Straps

For this project, the strap cutter isn't necessary since the straps are so short. However, if you needed something longer than, say, 18", the straps cutter really does come in handy. I used some pieces I had previously cut to 3/4" and then cut those down to size. The end punches works great because all it takes is a whack with a wooden mallet and you have a nice, clean end. You could always just cut straight lines with your knife, or try and cut the curves freehand as well. I find it best to score the leather first, and then makes 4-5 passes, cutting it bit by bit. If you try and saw with the blade you end up getting a jagged edge that's obviously been cut by hand.

Step 5: Punching the Holes

When cutting the holes in the strap, I used my rotary punch for the holes that will accept the Chicago screws and the snaps. I used my 5mm buttonhole punch for the holes that will accept the button studs. You can always just punch and then cut a slit with a knife. The third image shows a side by side comparison of one strap that used a buttonhole punch and end strap punch. The other just used a normal punch with a knife to make the slit, as well as cutting the end at an angle with the knife.

I used the 3/4" oblong punch on the main body of the bag to punch holes for the straps. You can always punch two holes that are spaced correctly and then connect them by making slits with the knife. It works well enough, but you can definitely tell the difference. The last image shows the two methods side by side.

Step 6: Adding Snaps

Admittedly I added most of my snaps after I sewed the bag together, but that was because I got too excited and forgot. The only permanent snaps on the bag body are the two at the bottom front that act as a switch, and the one on the flap to secure everything. For the switch, use a knife or wire strippers to expose about an inch of wire. Then wrap it around your base and attach it to the tool like you normally would. Since you're doing things in the correct order, you'll be able to attach all of the other electronic bits before you sew everything.

Even though I had a battery pack with a switch, I wanted to have an external switch on the outside that was hidden. I decided to use a leather strap with metal snaps to complete the circuit. Since you cut two similar looking pieces, be sure it's the right one. It's the 5 1/4" one. When you attach your snaps, make sure the wire is on the backside so it stays hidden.

Step 7: The Electronics

I did the math to find the correct resistors, but I think a 100 ohm resistor is usually what you use on LEDs. The math came out to 60 ohms and I used a 62 ohm resistor for each LED.

I also found it easier to use a piece of cardboard as a jig of sorts. It keeps the spacing of the LEDs in the right spot and makes it easier to keep everything in it's place. Just make sure you give yourself enough length in your wire for everything to fit without stretching too much.

The trickiest part was soldering the inside wires, the ones that are connected to the snaps on the inside. In the future I definitely want to revisit this design and make it cleaner and easier.

Step 8: Stitching the Bag

Just in case you don't know how to thread your needles, hopefully you can follow along with the images. The picture shows me cutting my thread about 4 times longer than the stitch i'm going to do, but that turned out to be barely enough, so I say go ahead and cut it 5 times longer. Then put a needle on both ends because we're going to be doing a saddle stitch. Line up one of the side panels with the main piece. I usually go through the first hole twice to give it some added strength but i don't think it's necessary. I'm not going to explain a saddle stitch here, so hopefully you already know what that is or can watch one of the many tutorials on it.

Occasionally you might find that you can't easily push your needle through. That's a good time to use the awl to help line up and enlarge your hole. This is especially true when you get to the curved section of the bag It's very tedious and slow going, but it's nice to see the bag take shape.

Once you're at the end, you can go back through your last hole to double up the thread, and then put the needles through through the third to the last hole and pull them out on the inside of the bag. That why you can tie your knot and cut and tuck it so it doesn't show on the outside.

What's that? Your fingers hurt? Well now you're backs gonna hurt... just kidding. But actually it might because now you have to do the other side.

Step 9: Finishing Up

If you haven't already, now you can add your straps using the Chicago screws. For the straps that will attach to your saddle/seat, you can attach those in one of two ways. You can attach it so the button stud is on the inside and your straps are mostly hidden. This makes it harder to attach and detach, which might be a good thing if you want to leave this on your bike. You can also attach the button stud on the outside so you can easily take the bag on and off. This leaves a bit of strap dangling, which isn't really a big deal. Just aesthetics.

Step 10: Optional Shoulder Strap

If you want this saddle bag to double as a small messenger bag or purse, you can add removable straps to the sides. There are lots of ways to do this, but I opted to use button studs.