I’ve been thinking about designs for small paniers to carry tools, spare tube and patch kit and my bike lock. I was getting my dog ready for a hike and was putting a backpack on him and the light bulb went on: dog packs are just small saddlebags with a panel at the top just about the same width as the deck on a bicycle rear rack. I tried it on my bike for size and sure enough, it was like a custom made item.
I knew that I would run across another dog pack at a thrift store sooner or later, and I got one yesterday for just $4. It is an Outward Hound brand pack and this one has a separating pack and harness with hook and loop strips so you can leave the harness on the dog and remove the pack while resting. So all I had to do was to take the harness off and slap a section double stick hood and loop material on the top deck of my rack.
The pack bags are about 12″ long, “6 and 3” deep. That comes to about 3.5 liters each and probably a bit more as the sides bow when loaded. For the record, pack volumes are officially measured with regulation sized plastic spheres (ASTM F2153, using what are basically .75″/20mm ping-pong balls) just because of the difficulties of measuring the volume of a odd-shaped fabric bag. I think the packs is a size medium and weighs 8.5oz without the harness.
I like it! Totally dirtbag “applied junque” technology and cheap. There is a buckle at the front edge that originally tied the harness and pack bag together, keeping it fomr peeling off the hood and loop strips. I salvaged the harness side of the buckle and that can be zip-tied to the front frame loop on the bike rack for the same purpose. That will keep it on, yet allow me to peel it all off for storage or theft prevention. The test will be how the hook and loop tape weathers. If that fails, I can still use bungee cord and attach the pack bag using the d-rings on the top. I have the option of adding a bungee cord array through those d-rings to stash a jacket or other gear. If you find the extra large size dog pack, it will have storage volume rivaling touring panniers. The larger size might need bungee cords and hooks to keep them stable on the bumps.