Looking for large, strong (and inexpensive?) daypack

Howdy,

I use a bicycle for transport, and need a heavy-duty daypack for carrying
groceries. A 30-pound load is typical and the larger the better, of course.
I'm hoping to find something around 3000 cu in.

I don't need any sort of hydration deal or 17 gadget pockets or three internal
dividers or even strings and loops to hang things off of. Just a BIG daypack,
with shoulder straps that won't kill me over a three-mile ride.

I'm poor (hence the bike...can't afford a car) so I need something reasonably
priced, but I DO need quality; a pack that will last for many years of daily
use and weekly torture coming back from the grocery. (After over twenty years
of reliable service, my Army rucksack is finally disintegrating...sniff.)

Thanks for any recommendations. :)

I just bought a Jansport Big Bear Internal frame pack.

It's actually pretty nice for medium duty work.

(I consider 30lbs medium duty)

Has a capacity of 5000 C.I., weighs about 3.5 lbs.

I paid $59 at Campmor, but I believe REI has 'em for $49

Having commuted to school and work on bike until I retired a few years ago, plus toured in Europe and the US, my opinion and experience is that backpacks on bike are a pain. You might consider getting a good, solid rack and panniers or one of the folding baskets that go on rear racks. Rear racks work better than front racks. Loads on racks, especially when mounted low on the sides in panniers or the side baskets, require a lot less effort and are a lot better balanced. You can find such things in good bike shops, or contact Hostelling International (used to be called American Youth Hostels in the US - search the net for their current website).

Like you, most of my grocery shopping is on bike. I used to use a bike trailer to carry the groceries, but we sold that when Young Son started riding his own bike (it was a Cannondale trailer - often wish I still had it, since it is much the easier way to carry loads).

If you really insist on a backpack, Cascade Designs Seal Line division has a line of waterproof commuting packs. I tested one a couple years ago. It worked very well, except for being a backpack instead of a rack-mounted setup. http://www.seallinegear.com/urban.asp?Action=UrbanBackpack&Category=Urban
They are a bit more expensive, but quite rugged, and they are waterproof, so you get rain and snow protection much better than regular packs. I also have a Eureka waterproof pack, but I think it is available only in Europe (I got mine from Sierra Trading Post). Like the Seal Line Urban Pack, it is a plastic coated, heavy duty pack, but with the usual array of pockets that most backpacking packs come with these days.

If you still want a backpack rather than Bill's pannier suggestion, you may try another army surplus backpack. Plenty are available in surplus stores or on line or on ebay.