Chain management
Chains can be a challenge. I found that there are two basic sizes of chains: a wider chain that is used on single speed bikes like the BMX. These are too wide to go through derailleurs properly, so I had to use the thinner chains, which was ok, because the trusty boneyard had plenty (or, $9.00 at Walmart). The bike was wide so I had to piece together longer chains--easy with a chain tool after a little practice. Early on, I decided that the pedalers would not have the option of changing gears--a shift cabling nightmare, and the possibility of rambunctious folks getting out of hand (o:
However the crossed chains were more tricky.
However the crossed chains were more tricky.
Straight chain guide
Left is what I ended up using for the straight chains with little problem.
I was initially pretty successful using standard derailleurs from my bike parts boneyard for the chains that weren't crossed. Since the bike frame gets wider toward the rear, adjustments were slightly different as I worked back. One derailleur per (uncrossed) chain seemed to work, keeping the chain from "spontaneously" shifting gears while pedaling. They have adjustment screws on them so I could line them up properly.
Twisted chain guide version 1
This what seemed to work with the longer twisted chains toward the rear. That bracket is made from a stud plate from Home Depot, just hammered over the rail to shape it, with a piece 3/8' of threadstock (Home Depot folks call it "all thread") through it, and double-nutted.
The ultimate chain guide solution
My friends at Atomic Zombie came through for me again. I saw that some used these belt idler pulleys from garden tractors on their recumbant bikes. Brad himself answered back to me, suggesting that I lose the derailleurs altogether, as they won't last, and go with these. He's right; I've had one come apart. So I installed pulleys on the two front twisted chains. If I did it again I might have used these exclusively. I still used part of a derailleur as a guide (see photo) as it seemed to really allow the chain to pass itself more smoothly on the shorter front chains that were crossed (the rear ones didn't seem to have that problem). As I mentioned, my hand is in a cast right now, so the rest will stay on for now(o: The bike has probably 30 miles on it so far, and everything seems stable.
So then, what speed?
Where to set the chains? When we went out on the maiden voyage, I had set the chains about in the middle of the range (I don"t remember exactly; my calcs are on that bad yellow copy on the design page). Riders said it was too hard to pedal on the inclines. So, for the next run (it actually took about three trials before success; the first time we didn't hardly make it out of the yard before an unrelated breakdown(o:) I then set all the chains to their easiest position. Now top speed is, maybe 2-3 miles an hour. Nobody seems to care; two girls came up to me and told me how much fun it is to ride because it is so easy to pedal. It's effortless. As few as two of us can pedal it around without much effort (with a third steering). I guess it's the journey, not the destination. It easily kept up in the Las Vegas Halloween parade.