The Steve Howard frame I’m currently working on weighs under 2 lbs (around 1.8lbs). It is made out of 3 chunks of aluminum and a piece fo tubing. It rocks.
The Hunter style frames look cool and are really strong. I have plans to build one out of titanium, but replace the 1/2" tubing with 5/8 or 3/4". More on that a bit later in the post.
Steve Howard made a design of bearing holders that could potentially be made into a quick release bearing holder. It has a piece of aluminum that basically wraps around 3/4 of the bearing, with the fork leg making the final 1/4 of the bearing. The piece of aluminum overlaps the fork leg, where it could be skewered by a quick release clamp.
Titanium is an okay material for frame construction. It has an 8% failure rating (or something like that), so if it breaks it won’t become a spear, instead it will bend. It’s 2x as strong as steel with half the weight. The only problem is that it’s very difficult to machine and also rather hard to weld correctly. Also, it flexes a lot, so larger diameters of tubing than steel are neccessary. That’s why my titanium Hunter design has larger diameter tubing for the fork legs.
Carbonfiber is cool because it’s stiff, light, and strong, but I don’t think it’s durable to be a very good freeride muni frame. Maybe for XC style with a 700c, but a hard crash on one’s muni could possibly crack the CF as could a hard crash during a sidehop.
Aluminum is about 1/3 the strength of steel with 1/3 the weight. That means that with larger diameter thin walled tubing, aluminum frames can be lgihter than steel ones. Steve Howard frames are also lighter than most steel frames, too. Aluminum frames must be made stiff, because if there is any major repetitive flex in the tubing the metal will fatigue and fail. This means the both with bike and unicycle frames, the aluminum must be VERY stiff. Some people like this, and like the weight savings, but I’ve heard of people who absolutely hate their Wilders.
Steel is a very good material because it is extremely resistent to fatigue, so you can crash on it, bend afork leg, and simply bend it back. Mike Middleton Crashed his Hunter, anf bent the fork legs out of alignment. He simply bent them back and it’s just as good as before. You couldn’t dfo this with aluminum or carbonfiber. Steel is also extremely strong and readily machined and welded. Not to mention it’s dirt cheap compared to almost everything else.
As for frame shape and design, I personally think that Hunter, Vortexes, and KH muni frames look the best. I don’t like the look of the Wilder, and some don’t like how it rides . Others love both it’s looks and it’s feel. Ovalized tubing or rectangular tubing is pretty much a must unless you do a Hunter design, which in effect is a giant tapered oval. KH frames use ovalized steel tubing. From the perspective of someone who uses their muni for trials while on the trail, I think that a low-profile crown is a must. The Hunters and KHs and Wilders and DM Vortexes have this, but not much else. The numbus crown sucks because it bashes your knees and catches your shorts.
As for that titanium HUnter I have plans for, I’m basically going to eventually make a Hunter frame out of titanium, but I plan to have 5/8" tubing instead of 1/2" in the legs. It’ll have a 28.2mm seatpost ID, and be somewhere around 2 lbs in weight. I plan to skirt the process of machining the titanium somewhat by making the brake bosses out of aluminum which I clamp to the fork legs and also making the bearing holders a-la Steve Howard so that I keep the machining of the titanium to a minimum. Here’s a link to a thread that talkd a bit more in detail about the thoughts behind the design, including some info on the materials: http://www.unicyclist.com/forums/showthread.php?s=&postid=218151#post218151