As just me mentioned, there is the $1,600 Sportsrig (originally marketed as Howling Dog many moons ago) which was designed for carrying lightweight sports equipment weighing up to 250lbs -- or 450lbs with the heavy-duty shocks. We have friends who purchased these and they look slick and work well. The only real downside was/is the cost. Well, there are also some hidden costs. Unless you already own a collection of sports rack (aka, Yakima, Thule, Saris, etc) bike mounts that you'd normally use on your roof-mounted sport rack, you'll likely need to add the cost of those to your total cost for setting up a SportsRig trailer.... and they're not cheap. Again, the SportsRig is exactly what it's advertised to be: a trailer-mounted sports rack system. So, for a triplet, unless you're good with an arc welder or welding torch, you'll likely find yourself shopping for a non-rotating Atoc triplet mount: again, not an inexpensive proposition. The latter might suggest that a roof-mounted system (towers & crossbars) would be far more cost effective than the trailer since both would require a triplet mount.
The Haul-Master line of trailers sold by Harbor Freight constitute the lions share of trailers that I've seen aside from the Howling Dog models. These cost between $180 - $300 and are comparable to the $1,300 SportsRig model in terms of what you get. So long as you don't go nuts with plywood decking and the like, the weight of these things is usually under 200lbs vs. 150-200 lbs for the SportsRig. The biggest knock on the utility trailers -- aside from the lack of the cool looks of the SportsRig -- is their leaf-spring suspensions which are designed to handle up to ~1,000lb payloads. To be fair, there are two answers to the "jolt" and "vibration" issue. The first is, you can get 12" wheels and run the tires at their minimum psi ratings since you're only carrying less than 10% of the trailer's designed load capacity which will go a long way towards softening up the ride. The second is, the jolts unloaded bikes take on the back of a trailer are no where as severe as the ones they must deal with when they're being ridden on the same roads with one, two or in your case up to three riders. So, while it's nice to coddle our bikes during transit, there are few things short of being run into an overhang or falling off the mounting system at highway speeds that will put a greater strain on the bike than what they are designed to deal with in normal use. As for mounting hardware, you can pretty much get buy using a $25 bolt-on fork mount -- perhaps with a riser block -- mounted on a 2x4x10 trimming to the correct length for your rear wheel. You can simply strap the rear tire to the 2x4 using any one of a variety of different methods.
Now, my one word of caution with trailers and tandems is to hang a red flag and/or an 2"x2" red clearance light on the rear wheel with a velcro strap. In most cases, the rear wheel of your very narrow tandem will invariably be sticking out well past the back-end of the trailer and the trailer's tail lights are usually several feet ahead of the back wheel. Given the nearly invisible rear profile of a bicycle, you'll want to make sure a motorist sees your outsize load so as not to "bump up" against the rear wheel. This recommendation is based on having followed one of our friends hauling their tandem on a Howling Dog trailer. I'd liken it to trailing a sailboat with a kick-up rudder installed: the motorists will see the trailer's lights and the back of the boat, but that rudder is nearly invisible... until you hit it.
Last edited by TandemGeek; 08-18-07 at 06:48 AM.