The SeatPack
We travel a lot with our kids. Every trip seems to require at least
one layover in a large airport, requiring us to lug three kids, 1-3 car seats,
a diaper bag, and a few other carry-on bags from one gate to another.
Whew! that's a lot to carry.
So I decided to convert the carseats into "back-packs", so that I could
carry the seats hands-free. I often stuff some of the smaller carry-on
bags, coats, sweaters, etc, into one of the seats. It's so much more
comfortable than lugging them around in my arms!

One drawback is that you have to be really careful when you turn around,
lest you bop somebody on the head with the carseat.

I ordered a simple set of back-pack straps from Campmor.
I spent about $30 per seat and got some nice straps, but you could probably
find nearly the same thing at any outdoor gear store, or probably places
like KMart, probably for less money. You don't need anything fancy:
just a pair
of straps, four sets of clevis
pins with split rings, and probably a few washers. (The pins
and rings attach the pack straps to the seat.) I was lucky to find
holes in the seats in just the right places; I needed to add a few washers
to strengthen the connection. I suppose it wouldn't hurt to drill
a hole, if necessary, but I can imagine a seat manufacturer claiming that
voided the warranty.
The straps don't interfere with the seat's usage in the car, so I leave
the straps on all the time, ready to go.

Disclaimer
I would never use this rig to carry my kid on my back. The parts
of the seat to which I attach were not designed for that sort of stress,
so the pins might pull right through. Also, as you can see in the
middle photo, the system depends on the shear stress of the ring, unlike
in most back-pack systems that depend on the shear stress of the pin.
So I'd be afraid of the pin pulling through the plastic hole on the seat,
or the ring shearing through, if there were a lot of weight. If I'm
just carrying a diaper bag, and it fails, so what... but if I'm carrying
a kid, and it fails, I'm in big trouble.
I doubt it would be good for long distances, unless you added some padding
along the back.
It's not really a back-pack in the sense that I can carry big loads.
I guess it's a car seat you can carry on your back.
David Kotz
June 2000