Great, Kid. Don't Get Cocky!

The front wheels are finally on the bus! We can't propel ourselves forward yet, but the Falcon is finally off the floor and on all of her tires. 

Figuring out how mount the front wheels took a while, but once we did, it then took another while to modify the standard bicycle wheel hubs to attach the non-standard CV axles. We bought new hubs to facilitate adding brake discs and keep the required measurements the same for both wheels (they originally had a front and a wider rear hub). We had to make sleeves for aligning the hubs to the axles and stainless steel bolts to secure them.

 

I tried to create a super-tight fit between the sleeves and the CV axles by reducing the inside diameter of the sleeves by .02 inches. Usually, the interference is more like .002, so getting these on cold (at room temperature) would be impossible. The plan was to heat the aluminum spacers to expand them and drop them onto the CV axles. Then they would tighten around the axles as they cooled. 

This did not work.

I heated the first spacer so much that it melted. I did not melt the second one, but it went on so cockeyed that I had to cut the sleeve off. 

I had to make new sleeves and since we had to make new ones anyway, I changed the inside diameter to be .006" smaller than the CV axle. I remade the parts on the Tormach (I love the Tormach). 

The inside of the sleeves were now large enough that I did not need to heat them at all. I was able to press them on using the machine shop's 20-ton press. The last step was to add holes to the entire hub assembly for clevis pins. 

The pins lock the hubs to the CV axles and prevent the stainless steel bolts from backing out. We don't want the front wheels falling off the Falcon, now do we? 

Drilling through the hardened steel of the CV axles and stainless steel bolts proved to be very difficult. After destroying an end mill and 3 drill bits, I managed to drill the holes we needed to move forward.

Once we were finally done modifying the hubs, it was time to rebuild the front wheels. I already rebuilt the rear wheel and that experience definitely helped with the front wheels. There are more spokes on the front wheels than the rear, so the spoke lacing pattern is slightly different. But lacing the rear wheel taught me that I need to take a lot of pictures of the wheel before I take the spokes off. Using those reference images, it didn't take too long to put the wheels back together.

We still had to true the rims up but since they have to spin freely, so we couldn't just mount them on the CV axle. Fortunately, I saved the bearings, cups, and axle bolts that came with the hubs. I put them back on the hubs and reattached the original axle bolts, essentially turning them back into bicycle wheels. 

Then I was able to use the truing stand at Lowell Makes to align the wheels.

Mounting the wheels on the Falcon was the last step. Lining up the holes and installing the clevis pins took some effort (and a hammer), but it was easy in comparison to some of the other issues we've dealt with. 

Now, we just need to add the whole pedal mechanism to power this beast.

The Canopy

We've made progress on the canopy frame since we made the 80" ring. This frame isn't supporting any significant weight, so I actually TIG welded the frame together! 

Some segments are better than others, but the main frame is together. 

Now we're working on making the cage that supports the foam panels that will give the Falcon its look. 

We started printing the scaled up sections of the falcon. We're using these drawings to lay out the cage and will also use them as patterns for cutting out the foam pieces.

Cross-section pieces for the mandibles

Minion Tie Fighters

Minions are our crew of bike riders that follow the sculpture during the race. We are decorating the handlebars of their bikes to look like Tie fighters. Hopefully, it'll look like a bunch of fighters chasing the Falcon.

We consulted with the captain of Lowell Makes' Cosplay shop, Castro. He's got a lot of experience making movie/toon props and costumes out of all sorts of material. 

He gave us a tutorial on how to build the fighters. Andee has been busy building the prototype out of 1/2 inch thick foam.

The race is in 17 days (!) and there's still a lot to do, but we are marching ever forward.

Rudy August 31, 2023

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They Told Me They Fixed It...It's Not My Fault.

The Hyperdrive is finally assembled! Appropriately named, this is the central drive for the Falcon. Our pedals drive freewheels that are connected to the input shaft of the Hyperdrive. The two pulleys on the input shaft run the road/mud gears. Although they both sit on the same shaft, only one pulley is secured to it at a time. 

A long belt connects the front and rear pulleys together. This allows us to drive all of the wheels. The front and rear pulleys are sized so the large rear wheel spins at the same relative rate as the smaller front wheels. This is the road gear. The inside pulley connects the pedals directly to the road gear.

When I first tried assembling the Hyperdrive two weeks ago, I discovered the long belt was too long. And the next shorter available belt was way, way too short. The easiest way forward was to somehow increase the length of the path the belt takes around the pulleys. To take up that extra slack, I added another idler pulley. Luckily, I found a spot on the frame where I could attach a post for the new pulley.

I only needed one part to fix this, but it took almost two weeks to get it. After I drilled a hole and mounted the new pulley, I snaked the long belt around and tightened up the tension. 

The road gear seems to work well. Nice.

The race's mud obstacle is a big worry. Many a sculpture has gotten hopelessly stuck in the mud. Every race veteran cautions us that the key is getting the gear ratio as low as possible between the pedals and wheels. On a typical mountain bike, you get a 1:3 reduction which is not enough to move through mud.

When our mud gear is engaged, the input shaft will drive a series of belts and pulleys that gives us a 1:16 reduction! This slows down the wheels' RPMs 16x, but also multiplies the turning force at the wheels by 16. If everything works as intended, the Falcon will very, very slowly, crawl through the mud. Glorious.

After mounting many, many pulleys, I installed all the short belts for the mud gear. 

The mud gear also seems to work well, but of course there's a caveat. The road and mud gears converge at the front pulley. 

They share the shaft that drives the front wheels. 

It turns out that we need that common shaft to be able to drive all the wheels in the mud. But when we're on the road, it adds a lot of extra resistance. 

Right now, the easiest solution I can think of is to only install the last belt of the mud gear when we are driving through mud. I also wanted to use the mud gear to help the Falcon get out of the water, but I think we'll need a better solution to do that.

Rudy August 24, 2023

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She Still Has a Few Surprises Left in Her, Sweetheart.

We're firing on all cylinders now. I mean, I'm desperately trying to keep all the spinning plates in the air. Race day is one month away and there's still a lot to do. We've made more progress on the front wheels, seating, pedals, and we've started the "canopy."

Front Wheels 

I finally finished the last two pieces that secure the front fat tires to the CV axles: the outside bolts that screw directly into the CV axle. It was my reacquaintance with the lathe. It was not rudimentary.

The first one took a while and had a lot of chatter. It's not supposed to chatter. After our machine shop captain pointed out all the dumb things I was doing (my words, not his), the second one took half the time and hardly made any noise. The highlight of the job was drilling and tapping an M16 hole in the stainless steel bar. I had to walk through 6 different progressively wider bits to get up to the 14.5mm diameter pilot hole. I also used the lathe to tap the hole.

 The CV axle threads onto the bolt nice and easy, like I planned it. 😎 

I then had to mill flats into the hub bolts so a wrench could be used to tighten them down. It took a couple of tries. During my first attempt, I did not set up the part very well and burned out my end mill before I realized. That's when the tool gets so hot that it melts the material instead of cutting it.

Turns out I was spinning the end mill too slowly, milling in the X direction instead of Y, and taking too shallow a cut per pass. Our machine shop captain informed me that a shallow depth-of-cut concentrates too much heat on the corner of the tool, quickly destroying its sharp edges. So that's how it happened. It makes sense when someone with a ton of experience says it. 😅

SO, spin twice as fast, use more of the side and less of the bottom of the tool, and work in the Y direction. I also centered the part in the vice and used the mister to spray coolant on the end mill while it cut. The new parameters did the trick!

The inside surface of the hubs I purchased had a small lip on the outside edge of the tubes. They need to be smooth all the way through so the hubs stay in full contact with the axle spacers and bolts. Otherwise, the wheels would probably wobble.  I used a Dremel tool to grind the lips down flush. All the parts now slide snugly into the hubs. 

The last manufacturing step is to assemble the hubs and axles then drill holes for clevis pins it's just the "simple" task of rebuilding the front wheels. I did this for the first time ever with the back wheel. Hopefully, that experience will make these next two wheels a little easier.

Seating

I worked on the structure that supports the seats. Two thick aluminum tubes are attached across the main truss. They are notched and bolted in place. Steel angles are bolted to these tubes to support the seats.

We are using the seats from last year's sculpture, Big Fish. Other than some bicycle hardware and loose PVC, these were the only things to survive deconstruction..

However, to use the seats they have to be modified. They need to be freestanding and slide on the steel angles so pilots can adjust their position relative to the pedals. The seats need to be on rails

I cut and shaped rails from the same electrical conduit that we originally used to make the seats (more deconstructed material from Big Fish) and notched them so they fit snugly up against the existing seat frame. 

I was having trouble lining the tubes up to drill the notches until I made a jig using the steel angles. I just screwed the angles down to a couple of scrap pieces of plywood. Keeping all the pieces aligned was much easier with a jig.

Once everything was notched and dry-fit, I then carefully welded the new tubes to the existing seat frames (without melting any of the seat material!).

Now the seats are freestanding and they're adjustable.

Pedals

The sculpture still needs pedals to make it kinetic. We were originally going to make custom frames, but time marches on. After a couple of visits to The Bike Connector's junk pile, we were able to find two aluminum bike frames that were destined for the scrap heap. 

I did some work figuring out how the frames should be oriented and how they will attach to the Falcon.

The bike frames will tilt back like they are "popping wheelies." The pedals are placed so the pilots can use them recumbently. The freewheels will end up under the seats and roughly line up with the input shaft of the Hyperdrive. The seat post is a great spot to mount the steering wheel!

Canopy

We've been talking about the kinetic part for so long, you might think that we forgot about the sculpture part. The canopy will give the Falcon its look.

We started with the giant loop that makes up the Falcon's saucer. I turned to Jen, one of the members at Lowell Makes, who makes lyras out of steel tubing. She graciously spent the better part of a day teaching me how to bend tubes.  I learned a lot from her, enough that I think maybe I could do it alone. Haha.

We used a tube bender with a motorized attachment to shape the large outer circle of the canopy from super-thin aluminum tubing. 

It took three 8-foot tubes to make the 80" ring. 😎

I made custom collars to join all the seams. This should make it a little easier to weld.

Next, we will attach all the straight pieces: the mandible tubes and the support structure for when it's attached to the base. 

To get the canopy to look like the Falcon, we plan to build a thin cage on the canopy frame and lay out "cosplay" foam sheets over it. We'll layer the foam to build out the surface features. The more accurate we are to the scaled up features, the better the canopy will look. But we don't have time for too much experimentation.

I came up with an idea to hopefully lay everything out to scale without too much work. I purchased a model for 3D printing the Falcon. It's actually a bunch of models that you can print out and assemble a 16-inch scale model in plastic. I imported all the pieces into Fusion360 and scaled everything up to the size that we will need for our sculpture. 

Then I created full-scale drawings of each section and its features. Here's one for the half of the drive section in the rear (in purple)

We'll print them out on large sheets of paper and use them as patterns to trace onto the foam sheets. It's going to loook awesome!🤞

Rudy August 16, 2023

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