With the front end rebuilt, we turned to the rear of the sculpture. We had to use the rear wheel at the front, so the back was now wheeless!
That was actually according to plan, but it was late in the game. Our hill test had revealed that the single rear wheel of the Falcon could experience large lateral forces if the sculpture titled sideways. This was a sure way to "taco" the rear wheel.
We determined that using two wheels at the back would significantly reduce that possibility. Although that would technically make the Falcon a four wheeled vehicle, we would keep the wheels close to the frame so that it would still look like a reverse tricycle.
Rebuilding the rear end was easier than the front-end reconstruction, but the wheel hubs we used to build the new rear wheels were different than the front wheel hubs from last year. We originally thought we could use a single bar that supported both ends of each hub. However, the interior of the hubs are tapered. Hollowing them out would've severely weakened them. Instead of using one solid tube across the hub, we created steel inserts that slipped on from either end of the hub.
The inserts were designed to be held in place by the same pins that secure the hubs to the shaft. Since the the hubs tapered before the inserts reached the pin holes, I added that same ~5 degree taper to the inserts 😎.
Water propulsion
Doubling the rear wheels and moving them to the outside of the frame opened up a spot in the back to mount a paddle wheel. We talked through several ideas. We could mount two thin 26 inch bike frames and attach paddles between them. We could also rig up a kind of snow/mud chain to an inflated wheel and attach fins to that. But both those options seemed like they would take too much time to implement—time we didn't have.
Then, Andee came up with a great idea that reused stuff we already had. We would take the now available 20 inch rim and bolt last year's fins onto the end. Adding the fins made the overall diameter 24 inches--well within the 26 diameter of the road wheels.
While I made the inserts, Kreg and Andee assembled the paddle wheel.
Putting it all (back) together
We dry-fit the road wheels and inserts on the shaft, then marked and drilled holes for clevis pins. We also marked and drilled the pin holes for the paddle wheel in the center. Then, we located the drive sprocket on the shaft and cut a keyway there to lock the shaft to the sprocket.
All the pieces of this puzzle were finally ready. With one day until race day, I assembled the new rear end.
Once the base was rolling again, it was a mad dash to complete the rest of the punch list. We had to reconnect the wheels to the Hyperdrive (the sculpture's main drivetrain), rebuild the steering mechanism, rerun the brake lines, make the flotation support mounts, add lights and sound, and, of course pack up the Falcon and load out for the race. There was a lot of smaller things to do, but we still had most of the day left and we had help.
Kevin created a bluetooth sound box!
The combination of 4 switches allowed us to select 16 different tracks from an SD card and played it over a Bluetooth speaker. Kevin, Greg and Andee also added lights to engine area of the Falcon.
Steve worked on the brakes, pedals, and derailleurs.
Andee also attached the rear wheel chain.
We had already reconnected the differential at the front, but because of the new, wider wheelbase, we had to create and install extension bars to bridge the gaps.
The last thing we needed to do was drill attachment holes in the poles that connected the main truss to the side pontoons of the raft. This was key to us not sliding off of the raft when we hit the water obstacle.
The sun was already up. It took ALL night, but we actually completed everything we needed to get to the race! We really tried to avoid staying up all night. We're too old to run races on zero sleep. But it was what it was.
We loaded the Falcon onto a rental truck and drove to the start line. It was time to see the Falcon in action.