robertj298 

I've seen some really nice looking book backpacks. That look like they could easily be converted to a rear rack bag and they are much cheaper than most bike bags' Here is an example of one

canklecat

Improvised bags are a PITA without the mounting hardware for racks. More trouble than it's worth. And potentially dangerous if a strap flops into the wheels. Been there, done that. Finally got proper bike panniers and handlebar bags.

thook

i say it's doable...or more so...with the right rack. my old jandd has more of a square'ish loading profile than say my old blackburn that has a more triangulated profile. however, i do agree...it is potentially dangerous. i've had straps come loose on a an actual pannier and get jammed in the wheel. i didn't wreck, but i did come to a fairly quick slow to halt. really messed up the pannier, and a real pita to get it unjammed during my ride. i think my partner gained an inch on his beard waiting

if you were set on doing it to save some coin, i could see it. but, you'd have to have your strapping modified to really grab the rack securely and well stitched to make it durable. that requires a legitimate machine/needle for the job. (hand stitching is not quite the same) and, by the time you've spent the money on doing that, you could more easily have found some second hand panniers

honestly, i've mulled it over several times to try your idea out with some backpacks i have. but, i realized the logistics to make it really work well wouldn't be worth the trouble. sometimes money is spent in the name of simplifying. just my opinion, though

Lascauxcaveman 

Works great on front. This bag moves from bike to bike as needed, take about 2 minutes to put on or take off:




The 'rack' that I made for it is just a strategically bent length of 1/4" aluminum round stock (shown with a 3/16" version of the same thing for a lighter bag:



Just hangs on the stem. The shoulder straps of the backpack get undone and you tie the upper part of them to the handlebars where the bars meet the stem and the lower parts tie together onto the head tube . Pretty simple and effective. It helps fit better if you ride larger size frames, like this one. After using it for awhile, I reinforced the bottom of the bag with a layer of stiff plastic (from a laundry detergent bucket lid) inside and a very thin 1/8" piece of plywood on the outside. This gave me a solid base to mount two P-clips to keep the bag centered on the rack tubing.

Lascauxcaveman 

On the back, I converted a case for a mini DVD player (anyone remember those, lol?) to hang from the back of the seat rails with nylon U clamps, as shown:



This pic shows, again, a thin piece of plywood reinforcement in the top of the bag to mount the screws in, with wing nuts to make for quick and easy removal:



And these are the nylon U clamps that hold it on the saddle rails:

thook

whoa! this is an approach that had not occurred to me! so cool!

i have an old gregory rock climbing pack with a compartment for a helmet, straps for roping, and water bottle pockets. i'd love to do this and be able to use my pack.

where'd you get the aluminum round stock? lowe's or similar? and, how'd you bend it without it snapping?

i'd guess you made atleast the hook for the quill by bending around the quill and bars. and, i suppose making the lower right angle bends just something of the desired shape? like what?

thook

gawd! why didn't i think of that?! i could see doing something like this nicely for a rectangular cooler bag for heat of the summer travels...or even winter to keep water from freezing!

Lascauxcaveman 

Yes, at Lowes or similar; I think most hardware stores stock this kind of thing.

Aluminum is easy to bend once, no problem. Try to bend it back the other direction, and that is when it snaps. But if you screw up, just go and buy another $5 section of round stock.

I make the initial bend on a section of broom stick clamped down in a vise. (Do this after you put on the protective sleve of vinyl tubing, if desired) Then I take the bent round stock to the actual handlebars of the bike I'm intending to use it on, and make the next bends in place. The last bends, where it's more or less 90 degrees to make the horizontal part the the bag sits on, is just clamp the stock in the vise.

Kovkov

I do that all the time. I take the backpack put it onto a the pletscher mod c rear rack and then use the straps to fix it on the seatpost.

Digger Goreman

Wife found an old East German backpack for next to nothing. Great on an explorer rack till one day (after many hours of riding) something caused it to rotate just enough to catch a buckle onto a spoke.... The perfect storm continued as I was on a sidewalk and going straight.... The skid marks are still there. Unfortunately my rack is not quite straight to this day....

What Canklecat said!

BFisher

Sure, a well-designed piece of bike luggage with the hardware to match is great.

But successful improvisation with cheap stuff can be very rewarding.

$5 eBay bag with a piece of chrome plated wire from an old shower caddie and a couple zip ties, voila!




Works great and the old Peugeot handles well with a front load.

SurferRosa

CliffordK

Lots of ingenious adaptations.

I've seen some camera bags that I thought would make good "trunk bags", with a little work.

It should be easy enough to convert a computer bag to snap on a rack, as long as one doesn't get too much heel overlap.

There are a few pack/pannier combos available, but still, more expensive than many packs.

I suppose one question is whether you need/want the pack straps. Take them off, and attaching the bag should be much easier.

Korina

If you can find a way to keep the straps folded to the front, maybe with a short strap with parachute buckles, something to make the back rigid, a couple of J hooks and a bungee cord.

Sentionc

And I personally haven’t been carrying different books with me for a long time, because I use them online. I even order tasks for the university at https://edubirdie.com/write-my-dissertation in order to save myself some time. I said write my dissertation, and I never had the opportunity to carry books with me, because my grades are now the highest

rseeker

You could try your local thrift / second-hand store, like Salvation Army if you have those. Around here they have tons of school backpacks, camera bags, gym bags, insulated cooler-bags, all for cheap.

wphamilton

I've used a book bag for a handlebar bag, no mounting hardware required if you rig it right.



You can also rig a book bag for the rear rack, like this
https://www.bikeforums.net/general-c...p-carrier.html

jetboy 

The best bags I have used for this are tool bags, from your local hardware store. they are stiff and don't have extra straps, and often have leather or metal tabs on them you can attach to. and you can get one for like $15.

thumpism 

What's wrong with buying an actual bike briefcase? I have them by Bushwhacker and another company.