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 added skid pads to the raft to protect it from scraping along the pavement.

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. 



I managed to find weld-on adapters online and welded them to custom-length shafts to make the extenders.


The original front drive sprocket on the Hyperdrive was smaller than the rear sprocket. The ratio of the sprockets was the same as the ratio of the wheels. That way, when the sprockets turn, the different-sized wheels would roll the same distance over the same amount of time. This meant that the front wheels needed to spin faster because they were smaller than the larger rear wheel. 

With the wheels now all the same diameter, we swapped out the front drive sprocket to be the same size as the rear. Of course, this changed the length of chain needed to complete that loop. We ultimately had to insert another sprocket into the rerouted loop to keep the chain tight.

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.






Rudy October 09, 2024
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Two successful road tests. Two successful water tests. But we had a problem.  The wheels needed to be lowered 12 inches but we couldn't do that with the current suspension system. The top of the raft that we selected for flotation clears the axle of a 26 inch wheel. Switching from 20 to 26 inch wheels would allow us to mount the raft completely under the truss frame,  keeping all the machinery out of the water. 

Can I get a lift?

I had just got this bucket together and now I had to make major changes. It took two weeks to come up with a game plan. We were running short on time so reusing most of the existing work at the front end was our first requirement. I first tried to design something closer to a traditional vehicle suspension. 

The idea was that we would be able to adjust the ride height during the race. With the start of the race looming, I realized that the idea was too complex to accomplish in the time we had left. We decided instead to keep the suspension static, but relocate the axle and differential below the truss frame.  We designed the idea around a steel box beam that would support the main truss. We also added ledges just below the axle for the pontoons, but also for more structural support.

Using the 26 inch wheels also required us to widen the wheelbase by 12 inches. The larger wheels interfered with pedaling while turning, so they had to be moved out for clearance. We decided to make it out of steel, because it's faster (and easier) to weld--but it's sooo heavy. Some quick stress analysis confirmed the basics of the idea. 


We got to work fabricating. Caroline and I welded all the U-shaped legs onto the the box beam. Then we welded together the lower knuckle support brackets and pontoon ledges. 

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I used the original knuckles to position all the pieces for welding. 


After painting it, I mount new front end.

Wheels on the Falcon go round and round

Switching to new wheels also required modifying new bicycle hubs. Clevis pin holes had to be precisely placed to work with the existing CV axles. However, we discovered that they were too thin to completely hollow out. Instead, we only hollowed out one side then turned down the mounting bolts to fit the hub's existing diameter. It required some creative holding to lock it down, but it worked great.


I handed off the hubs to Steve who then rebuilt the 26 inch front wheels in Lowell Makes' Bike Shop.


While Steve worked on those, I rerouted and reattached the chain from the Hyperdrive to the differential. 


Once Steve was done with the wheels, I mounted them onto the Falcon!


Now we just have to reattach the steering linkages to the front wheels. To upgrade the front end, we had and take the wheel from the rear end, because of course! This sounds worse than it is, since we were already rebuilding the rear end

This task is not as involved as the front end, but there is still work to do back there. Time marches on.

Rudy September 17, 2024
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While I'm nose down redesigning the front end because of reasons, Andee and Kreg have been spearheading the canopy upgrades. First, I had to cut the the support tubes in half, to lengthen the entire canopy by 14 inches. I also added some structural improvements to stop the mandibles, cockpit, and escape pods from slouching . 


Andee and Kreg then trimmed out all the unfinished areas of the canopy.

Then Andee, Castro, and Dusty painted the upgrades.

We are also working on adding main engine lights.



Race day is fast approaching. There is still much to do. We are making progress, but Time is a harsh mistress.





Rudy September 15, 2024
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During our successful road test, we not only pedaled up and down the street, but we also rode up the hill on the side of our house!


As exciting as that was, there's no time for laurel resting. We immediately turned our attention to the water.

99 problems and flotation IS one 

The race has a water obstacle. We have to roll into the water and climb a steep beach to get out. All of that and staying above the water require flotation. Last year, we used foam to float the Falcon (theoretically; we didn't actually make it to the water). I didn't like how much the foam obscured the guts of the sculpture. 


The mechanics are just as much art as the aesthetics. The veteran builders typically use inflatable pontoons; we decided to follow their lead. Andee sourced a very large inflatable raft with a 660lb weight capacity. It's longer than the truss and not too wide.  I thought it would work but to test it, we would have to ruin it as a raft. 

The idea was that the front of the raft would support the heaviest part of the Falcon while the side pontoons would support the pilots. To make it more stable, we would spread the back of the pontoons out to create a 'V' shape. To do that meant cutting out the back and most of the bottom of the raft. At least this would also remove some dead weight.


The test was straightforward. Inflate the raft with the Falcon on top, then climb on and see how far we sink. 


Everything went well. Because the raft was longer than the Falcon's frame, we were able to add supports at the middle and rear of the raft. This made it very stable, front to back. It easily handled the Falcon's weight, barely submerging into the water. 


We didn't spread out the pontoons for this test, so it was unstable laterally. We are confident that spreading out the back of the side pontoons will solve that issue. However, there was another issue that now needed addressing.

The raft sits under the main truss frame and is very tall. Because of the way the wheels are attached, they do not touch the ground when the raft is inflated. This is a problem because we have to roll into and pedal out of the water during the race. To solve it, we must lower the wheels 10-12 inches. And that requires upgrades (read redesign) to the front suspension. No pressure.
Rudy August 20, 2024
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Steering has been a moving target (🥁). I had some early success with the control arms attached the the front wheel, but the human controls proved to be challenging. 


Handlebars had seemed to be the simplest solution for turning the Falcon. My knees would clear the handlebars while pedaling and the brake and shifters would have a natural mounting location. However, the range of motion of the steering arm, at greater than ±90°, was too large to use handlebars. They didn't run into my knees, but they did poke me in the ribs. This was not a workable solution.

Handlebars were actually my second idea. I went back to the original idea of using a steering wheel. I had previously bought a go-cart racing wheel last year that had a very flight-oriented look and also had a spot for mounting a handbrake. It would easily handle the range of motion, but this scheme needed a new place to mount the gear shifters. Since I already had to make an adapter to attach the steering wheel to the steering column, why not also use that to also mount shifters? 

I designed a simple adapter with a hole pattern for the steering wheel on one end and a square hole to lock onto the steering column at the other end. Most of the inside was removed to reduce weight. I carved a "saddle" into the neck of the adapter to match the profile of the original handlebar neck. 

I then mounted the handlebars on the adapter and the shifters onto the handlebars. This placed the shifters close to my fingers  (similar to car paddle shifters).

Using a steering wheel also required re-routing and re-supporting the steering column. Originally, it ran underneath the bike frame and connected directly to the steering arm. To get the steering wheel better aligned, I had to go up and over the bike frame. I secured the steering column using two haim joints. Haim joints are eye bolts with self-aligning eyes. They are mounted to the bike frame on threaded rods so the steering wheel location can be adjusted when needed.


The front wheels turn by tugging on a long arm attached to the left wheel, called a Pitman arm. It's attached to a steering arm that pushes or pulls on the Pitman arm when it turns.


Having the steering arm swing under the pedals was problematic. A mating bolt stuck out too much and intermittently impeded the pedals. This would definitely be a problem in the race, so I rotated the steering arm 180 degrees to avoid pedal interference altogether. But this created a different problem. 

Turning in the right direction

Rotating the steering arm 180 degrees caused the tires to be out of phase with the steering wheel. Steering left now turned the tires to the right! And steering right turned them left. 🤦🏽‍♂️ I tried for many days to find an in-phase spot for the steering arm, but the new location was the only way to get the full turning radius of the tires. I finally came around to it. I needed gears. 

Instead of attaching the steering column directly to the steering arm, I would connect them using gears. The steering column would turn a gear that drove the mating gear attached to the steering arm. It sounds complicated but a picture is easier to understand.

The gears needed to sit parallel to each other at a specific distance. This required yet another mounting plate and a new steering arm. I designed the mounting plate in Fusion 360, wrote the machining program to make it, and carved the part out on Lowell Makes' Tormach CNC mill.




I made the three pieces that make up the new steering arm, mostly on the lathe and mill but also with a drill and hole saw. Then I welded those pieces together.

After installing the steering upgrades, I discovered another wobble that I did not anticipate. Instead of turning the tires, the steering column dances like a tree in strong wind. We need all the turning energy to get all the way to the tires.

I figured out that problem. There is a long shaft on either side of the universal joints. The top one is secured at two locations, but the bottom one is only secured at one. I needed to also hold the shaft higher up, but there was no easy place to mount this new support.

I decided to create a tall bracket to hold the shaft in place and secure it with the same bolts holding the gear platform in place. The bracket was made up of three pieces, welded together.

I used the existing plate and gears to align the support bracket, then finished welding it together.

Once I finished the tall bracket, I installed it on the Falcon. I think my designs are looking a lot more Star Wars!

Shifting into gear

The last thing we needed for the Falcon to move was to wire the derailleur shifter and attach the bike chain. I mounted the shifter and ran the cable to the derailleur under the seat.


The bike cassette is mounted slightly forward from the usual location. My first attempt at support brackets worked for a while, but aligning the brackets to each other was very difficult and eventually jammed up the axle. 

I realized I only needed to support one side of the cassette because the other side was already supported by the Hyperdrive frame. By using only one support, we avoided the alignment issues. I quickly designed a new plate that better clamped to the bike frame and produced it in record time.


Once the freewheel was re-secured, I wired up the front derailleur for a full transmission test.


I mounted the chain and checked the system.

The next road test

We were finally ready for the next road test. I checked the brakes one more time. I checked the transmission one more time. Finally, I checked the steering one more time. *#$^&*!$. The steering had failed again. What I thought was a loose set screw was actually a broken universal joint. The last universal joint in my possession. smh. The pins holding the joint together snapped off. There seems to be a lot of torque between the tires and the steering wheel.🤔


I really wanted to get to the next road test, already, so I fabricated a longer steering column to bypass the broken joint. It's not how I want it for race day, but it was good enough for a test.


Now. NOW, we were ready for the next road test.


All in all, it was a good test. The Hyperdrive upgrades are great! There was zero deflection of the drive axles. The chain between the freewheels and the Hyperdrive did skip a bit while coasting downhill. We'll need to take a look at that. 

The driver's side transmission works great! I was able to shift through the main range of speeds in both the front and rear derailleurs without the chain breaking or falling off. 

Steering...passed. I was able to turn the steering wheel, but it required A LOT of effort when the Falcon was standing still or moving slowly. We need to work out some kind of steering assist. I also think the breaking of the universal joint will not be a rare occurrence. We'll also need to beef up the steering in general.

All that being said, we cannot deny that the first transport is away!







Rudy July 30, 2024
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