I frequently commute with a backpack on my '90s steel race bike, and encounter the usual issues of sweaty back and tired shoulders. The riding position is also not perfect for carrying a backpack on my back.
I don't want to switch to another bike, so I want to add a front rack to this one. However, I am afraid the fork would snap, as the bike was never designed for a rack, but to be as lightweight as possible. The tubing is Tange cro-moly (some promo material I found on the internet calls it "Tange Champion").
There are no mount points of course, so I am considering a rack that mounts at the brake hole on the top, and to the wheel axle on the bottom.
Is this idea fairly safe? If so, how much weight would be OK to add to the fork (combined rack + backpack)? My backpack is usually ~3kg, and racks themselves weigh from ~300g (narrow racks with thin tubes) to ~1.5kg (porteur-style racks). I am fairly lightweight myself, ~65kg.