Need help finding a utility bike...

[Nightspore]

Hi, everyone. I'm new here and new to cycling. Currently, though, I don't have a bicycle, and that's my biggest problem. I don't know where to go or what to buy. Hopefully, that's where you come in. I need someone to steer me in the right direction.
Where I live and work, a lot of the roads are in poor condition. There are gargantuan potholes, cracks and speed bumps everywhere. Beside that, I spend a lot of time on dirt and gravel roads, and it's not uncommon that I need to travel through nearby forests. So, I need something that can stand up to adverse terrain. And I'm definitely not in this for recreational purposes, not that cycling isn't fun regardless. I'll need to be able to carry heavy loads without the use of a trailer. Another important thing is that I won't be using this on every odd weekend. The last thing I need is to get something designed to be ridden on an infrequent basis. I'll be riding on most days for long periods of time.
Of course, what's more important to me than anything else to me is simplicity. I need something I can maintain and make basic repairs on by myself. So, I'd prefer something with only a single speed, no extra gears or shifters and no fancy suspension system. I know this will make for a significantly less comfortable ride, but I'm more than willing to make that sacrifice. Self sufficiency and rugged simplicity are more important to me than comfort.
So, any suggestions? Will I have to order most of the parts individually and assemble my own custom bike? If so, what parts am I looking for and where do I get them? If that's not necessary, is there someplace I can go to order a full assembled bike that already suits my purpose?

[vik]

http://www.yubaride.com/Images/mundo_bike_6speed.jpg

The Yuba Mundo (http://www.yubaride.com/) sounds like what you are after. Comes as a complete bike 1 or 6 speeds. Keep in mind a heavily loaded single speed bike is only going to work if you are riding in a dead flat area. Trying to get 200lbs of cargo uphill in a gear suitable for flatland travel will be murder and if you gear it for the hills your top speed on the flats will be way too slow.

http://www.xtracycle.com/images/big_dummy.jpg

You can get a number of complete bikes from Xtracycle (http://www.xtracycle.com/complete-subs-c-5.html) that will meet your needs - except you will be trading a bit more complexity for better gearing/performance. Keeping in mind mountain bike drivetrains are design for hard use and should be just fine with minimal maintenance.

[Torrilin]

How heavy is heavy? A regular length bike can handle quite a lot of cargo if the load is balanced well. It's not unheard of for touring bikes to carry more than 70 lbs. A bike that isn't designed around cargo will usually max out somewhere in the 40-50lbs range.

The real problem with a regular length bike is it doesn't handle bulky cargo well. Building materials and the like are *right* out. An Extracycle or other long-bike design will handle some kinds of bulky cargo. If you're getting into real weight (say, over 200 lbs), there probably aren't any bikes that will do the job alone. And really, at that kind of weight, most trailers won't do the job and I'm not sure off road is the brightest idea either.

For normal off road use (no jumping tree trunks etc), any reasonably sturdy bike should do the job. A rigid bike will handle a lot more in the way of potholes, speed bumps and tree roots than you might expect :). As long as it's on gravel roads, fire trails etc, you'll probably be ok. If you anticipate things like riding down stairs or jumping downed trees, a bike is probably not the way you want to haul cargo.

Often on flat ground, I need to gear down just to get the bike moving with a heavy load. If you haven't done a lot of loaded biking, you may be overestimating the repair problems of a geared bike and underestimating how hard it is to move stuff around on a bike. I can count on one hand the number of problems I've had with my drivetrain over the last year, and there's no way I can count how many times I needed a lower or higher gear than my normal cruising speed. (sum total of drivetrain problems: chain dropped twice. first time, I couldn't fix it myself and took it to the LBS for a quick lesson. second time, I fixed it myself and continued on my merry way.)