I had to take off work a little early today. I had a wheel to pick up, a unicycle to put back together, and a test ride to take. There is a description of the uni.5 SH 29er in this thread and a description of the first test ride in this thread in which the soft, 1018 steel axle twisted.
There is a photo gallery of the new unicycle here, where nothing has changed except the cranks and axle.
The new axle is machined from 17-4PH stainless steel recommended to me by Steve Howard, the artist who also designed and built the gorgeous frame. The alloy was easy to machine, left a nice finish, welded easily to the 1018 mild steel planet cage, and was a snap to harden by heating the welded assembly to 900F for an hour and allowing to air cool overnight. Amy Drummond, the ever persuasive master salesman at unicycle.com (and master mechanic and rider to boot, I might add … I have photos to prove it) convinced me to buy a pair of Dotek aluminum alloy cranks because they have VERY low “Q” and they are available in 140mm (5.5") length. I bought some steel Schwinn 140mm cranks also. She was right, the Doteks are perfect for the application and lower “Q” than the Schwinns.
I chose the 140mm cranks so that they would be smoother (shorter) to pedal and to start in the right range for mechanical advantage. In 43.5" mode the 140mm cranks provide substantially LESS mechanical advantage than the standard 150mm (6") cranks on a 36" wheel (Coker). The payoff is that the bigger wheel means more speed and the shorter cranks mean more stability at high cadence. In 29" mode, the 140mm cranks offer substantially MORE mechanical advantage than the stock Coker setup. So, with the movement of a single bolt and spacer (25 seconds on my workbench, 30 seconds in the field) I have either a respectable hill climber or a screaming roadster.
I put everything together and (being accustomed to geared uni’s) freemounted on the ninth try. Ha ha ha … I did it on the first try but it was tough. The light, aluminum 700c wheel and the relatively thin and lightweight Nanoraptor tire makes for much less rest angular momentum than a big, heavy, honkin’ Coker wheel and tire. When you put your foot down it goes and is already ahead of you. Starting was jerky to say the least. I rode about a mile and returned to my workbench to tighten the cranks and get a backpack full of tools and spares. Then I took off for a 5 mile ride before it got dark. The rolling mount on a geared unicycle began to come back.
There are a couple of VERY steep hills in my neighborhood, 15% grade or more, but very short. On the ride out I took these in 43.5" mode going up with some difficulty, mostly because of the unreal responsiveness of the wheel. Down the steep hills the unicycle practically launched me off of the saddle. On the flats it was frighteningly easy to get going faster than on a Coker and I was still finding the touchiness and sensitivity to be a little unnerving so I sat up straight and took it kind of slow, just under my runout speed supposedly. I was able to relax after about a mile and began to notice that riding this unicycle was much closer to riding a bicycle than any other one-wheeler I had been on. I was close to the ground and going REALLY fast without spinning my brains out and I was on a big wheel that gave me a smooth ride. The fat Nanoraptor at 65 psig had low rolling resistance and still soaked up the bumps.
After a couple of miles I got off, had a drink of water, checked the cranks, and shifted to 29" mode. In less than a minute I was back on a normal unicycle again. It was easy, although now strange, to mount. I could idle the 29er and ride it backwards easily. I rode it for about a half mile, the 29er supposedly being a respectable commuter in its own right, and it actually got boring; I was used to the high Mach numbers now. So I switched back to 43.5" mode in about 30 seconds and decided to save the 29" action for the hills on the way back in. The feel for the geared uni began to return more and more and the backlash, less noticeable than on the original 24" after its tour, began to fade away into the background. The inertia of the Coker that has to be overcome in turns was not there at all.
When I got to the hills I shifted back to 29" mode. I mounted going uphill with no problem and grabbed the SH, or Kinport, handle on the seat to start cranking up the hill. And then I thought, hey, why am I doing this? I let go of the handle and cruised up the hill like it wasn’t even there. Then I rode down the other side easily and fully under control. This is really transportation. It’s fast where it’s flat and can be shifted for long climbs or descents. It weighs nothing, the frame is something like 850 grams and the total is 15 pounds, about half a Coker.
I remember getting my Coker. It was so weird and such a gas to ride. Suddenly I could ride a unicycle faster than I could probably run. It was also fun to design and build this hub and put it on a 24" wheel so it could be compared to the 36" wheel on the Coker. But I really wanted to build a unicycle with a bigger effective wheel than the Coker or there was no point. Making it shiftable was just a bonus. Without any exaggeration, this is the most incredible unicycle I have ever ridden.