As a commuter, I was looking for an everyday solution to attach a backpack to the rack of my P Line Electric, and that’s how I came across the "Saddle Pipe Hack." For this project, I bought a PVC pipe with a 2 cm diameter at the hardware store and cut it to a length of 22 cm. I wrapped it in black electrical tape and used the tape to secure end caps (which were actually intended for chair legs) to each side. I then attached the prepared pipe under the saddle using black zip ties. It can stay there permanently and doesn't interfere with folding or riding.
To transport the backpack, I can now place it upright on the luggage rack and hang the shoulder straps over the pipe. My backpack has a chest strap, which I also wrap once around the seatpost. Then, I use a tension strap to secure the backpack to the end of the rack. My strap features a net, which provides extra grip and keeps the backpack stable in this position even on cobblestones. To prevent any loose straps from dangling into the spokes, I’ve found it helpful to keep a rain cover over the backpack.
So, when I leave home, I place the backpack on the rack, lift the shoulder straps over the pipe, and fasten the chest strap and the bungee cord. When I get on the subway, I only have to release the bungee cord and chest strap before I can put the backpack on and fold the bike. It’s quite fast and has proven very effective for my commute so far. Since I secure the backpack to the rear end of the rack with the tension strap, I haven't had any issues with heel strike yet. I’ve attached a few pictures for illustration.
by frau_raula