B-29 Superfortress (Part 2)

This is the second part of my series on my B-29 model.

I decided to back-track a bit and re-do part of the fuselage to better balance the model, and to further strengthen the wings, and to try to attach an electric motor to the shaft that drives the propellers.

As I build each of my models, I am constantly evaluating and changing my plans. I might tweak something here, another thing there. Sometimes, it means re-doing large portions of a model over and over again until I get it just right.

Unfortunately, I soon had to give up my goal of motorizing the propellers because I could not get the correct gear ratio to drive the shaft, and I couldn't fit the battery pack and motor inside the fuselage without it drastically unbalancing the model. Also, I had anticipated motorizing the propellers from the start, so I had built the wings around the shaft. This actually prevented me from modifying the shaft further in order to accommodate the motor, without completely tearing apart the wings. So, I decided to let it be, and chalked it up to a lack of foresight on my part.

I also added more weight to the front by re-building the engines. I made them as strong and as heavy as I could, while also taking another opportunity to further strengthen the wings, as having heavier engines caused the wings to start to sag too low.

I now had about 75% of the model complete. As I was still figuring out the details of the landing gear, I took a few minutes to have a little fun with this project (as if I wasn't already having fun at this point, right?).

I cleared all the loose pieces off my work table and laid down a mock-up of an airstrip - with a full flight crew and ground team to go along with it. The crew was kind enough to allow me to snap a few photos as they went about their business.

Here's a sneak peak at the finished product - I put a temporary roof on the fuselage just for the photo op:

After completing the fuselage and the wings, I now had to return to the issue of the landing gear. Again, I still wanted to make them retractable and that proved to be the most difficult requirement. I also had to work around the existing wing structure and wheel bays so I didn't have a lot of wiggle room. And, of course, I had to make them strong enough to hold the weight of the model, so it could roll freely on the table. Here's what I had to work with:

I had to get down under the model to work on it at this point, because I couldn't flip it on its back:

After trying a lot of different methods, I finally came up with a mechanism that worked perfectly. It was strong, streamlined...

 ...and easily retractable:

I added a piece that allowed the landing gear to snap into place when retracted and when lowered. When lowered, the springs were totally compressed due to the weight of the model, and when retracted, the spring was expanded, so I had to place the wheels just right in order to accommodate both positions.

I finally mastering the landing gear. Now I had to find a way to make the propellers work. It just wouldn't be the same without them, and it would add a lot to the model. I didn't want to settle for a half-working model. So, I decided to tackle the propellers again.

Once again, I removed much of the fuselage and tried to take a new approach to inserting the motor and battery pack. After a lot of tinkering and thinking (like I did with the landing gear) I finally came up with a way to make it work - and I was able to include a switch to easily turn it on and off.  Here is a video of it in the early stages of testing:

Once all of this was done, I was then free to add details and make any modifications I wanted. For example, I took off the roof of the front of the model to build out the navigator's seat, just behind the cockpit.

I'll keep you posted with more pictures of the aircraft and it's crew in Part 3.

B-29 Superfortress (Part 1)

I was inspired to begin this project after visiting a museum in Washington, DC that housed a B-29 Superfortress. Not just any B-29 - it was the Enola Gay - the most famous (or infamous) B-29 in history. And I saw it up close and personal!

I immediately began to determine the scale of the model I wanted to build. I researched schematics of B-29s and found the dimensions and specifications. I wanted it to be roughly to scale to a LEGO person, so it would have to be about 140 units wide and 100 units long - about 4 ft x 3 ft. As with most scale models, the size is not the hard part - I can always buy more pieces! The major challenges I faced were with the landing gear, the propellers, the wings, and the cockpit.

My biggest challenge was the landing gear. I wanted to make them retractable, yet be strong enough to hold the weight of the model. Of course, at this point, I had no idea how heavy it would actually be - I could only estimate. Half way through the project, I discovered that my estimations were off when the landing gear buckled, so I had to completely remove them. I decided to leave them off until I knew the full weight of the model. I created some temporary supports in place of them while I continued building it. Below is an early prototype or mock-up of the right-hand side landing gear.

I had to overcome all of these challenges while still creating a frame, wings, and a fuselage that were strong enough to hold their own weight. I sketched a few drawings (below) of what the interior framework of the wings and fuselage would look like to ensure it was strong and that the wings could accommodate the wheel bays behind the #2 and #3 engines. The "skin" would then fit around the frame to give it shape while also adding to its strength. 

 

Next, I had to capture the B-29's iconic tubular fuselage and rounded cockpit. This was difficult as most traditional LEGOs are not rounded but have sharp angles. I needed to be extra creative. I eventually came up with a design that utilized hinges to make the rounded shape for the cockpit, while also serving as the web-like panels in the windshield. I also had to purchase more pieces to create the smooth, curved edges for the fuselage and the engines.

In the photo above, I've just finished the frame and most of the "skin" is already in place around the wings. Below, the fuselage is mostly complete. 

Even though the proportions were all accurate, the model was back heavy so it leaned back, as shown below (you can also see the temporary supports in place of the landing gear). A real B-29 is better balanced towards the front, mainly due to the weight of the engines. I had to add more weight to the front of the model to balance it.

My next challenge was to make the propellers rotate in unison. (First, as a side note, I had to do a bit of research on this as to whether all four propellers on a real B-29 rotated in the same direction. In some twin-engine planes, the props will rotate counter to each other to prevent torque steer which is present in single-engine aircraft. I eventually discovered that all four of a B-29 engines rotate the same direction.) I placed a rod through the wings that connected to gears that drove the propellers. I also geared it so that turning the nob slightly would rotate the propellers quickly, giving it the "flying in mid-air" effect. 

Stay tuned for Part 2! I'll have more photos of the completed model.