DESIGN SOLUTIONS
Landing Gear Design – Success in first Flight!
Company: Zeva Aero – eVTOL Aircraft
Tacoma, WA
Project: Zero Emissions Electric Vertical Aircraft
Problem: Existing landing gear was big and bulky which served well for early testing, but needed design modifications for in the field flight.
Request: Work with the Zeva Team to lighten and update the Zero’s landing gear for in-flight tests and create a sleek looking design that was also extremely durable
Close up view of landing gear, January 2022 flight test
The First Iteration of the Landing Gear was large, durable “training wheels” which had stood the test of time with some crazy test landings over the past 10 months. The arms were cedar 4×4’s with heavy duty 10” diameter inflatable caster wheels. The cedar 4×4’s socket into an aluminum structure that connects to the frame ribs of the Zero. Cracks were detected a couple months ago in the aluminum sockets so they were take in to get re-welded.
With advances in the controlling of the flight of the Zero, the team was anxious to get the vehicle outside flying, without the overhead safety lines.
To have the best chance of success, the vehicle needs to be as light as possible, and to be honest the “training wheels” were looking bulky, and not very “aerospace”.
Early designs served well for testing purposes
As most projects start, this one also started with a flurry of brainstorming. Helicopter-like skids were considered, but were complex to manufacture, and required bolt-on wheels for transportation. Inspired by light aircraft landing gear we went down a path where a pair of 8” inflatable wheels would be suspended on a straight rectangular bar “axle” directly under the vehicle.
The axle was designed to flex to absorb the impact. That was pretty elegant, so now stabilizing the vehicle was necessary. The thought was lightweight arms similar to the training wheels would work. Being cost sensitive Steve Tibbits ( Team Zeva ) suggested we purchase some used pole vaulting poles off ebay and use those. They looked OK so we ordered two of them. We tested the flex as shown below, and Chris T designed the blocks, and we 3d printed them, to restrain them on the axle. We still wanted casters, but lighter weight, so we found some heavy duty office chair caster wheels that were rated at 600 pounds – perfect. We figured since the poles were flexy, it would be wise to angle the pole ends with the casters downward below the floor level, so when to vehicle landed the poles would be preloaded a couple inches and give the Zero more stability. Unfortunately on the first test the pole flex was high, and the plastic connecting parts were also weak and flexing. The result was the vehicle tipped forward and broke the pole vaulting pole section, and the plastic connector pieces.
Landing Gear Testing
Strength testing the pole
Pole Assembly
Testing the pole vaulting section
The result was the vehicle tipped forward and broke the pole vaulting pole section, and the plastic connector pieces
pole failure during testing
At this point the decision was the made that the design was too weak and flexy and rather than beef everything up, we wanted to try another solution. This solution was to replace the pole sections with 2- 96” long sections of 1.5” square aluminum extrusion. The team scrambled to get it all assembled. There definitely was concern that the square aluminum tubing would bend at the junction of the axle, so the engineers devised a series of stress reduction plates similar to leaf springs to place on top of the square tubing, which really looked like it would do the job. It was now time to mount some slightly larger casters on the ends of the tubing. Larger casters were suggested because the outdoor field conditions in a parture were going to be rough.
When the system was tested it looked good. The casters hit before the inflatable wheels in the center, and the Zero did still tilt a bit, but also felt secure. It was determined that the tilt was the result of the axle not being directly under the center of gravity of the vehicle, so that was adjusted the Zero was now standing tall and felt stable.
It was only 2 days before the flight test and everything looks good as far as the new landing gear. We had lightened it up significantly and honestly it looked pretty good. It was then that we discovered that the new landing gear was too wide to fit on the trailer used to transport the vehicle. Bummer. The solution was to trim off 20 inches of the overall arm length, and we got to work doing that. It looked good, but now when we tested, the shorter arms resulted in stiffer arms, and now the entire weight was on the casters, and the inflatable wheels were sitting .75” off the ground!
Some more quick thinking resulted in spacers (Blue box in photo) that would lower the inflatable wheel 1”, which seemed like it would work fine. It did, and then the day before testing, we tightened all the bolts, put on a coat of black spray paint, and I must say it looked good and was ready for field testing.
What’s next? While this gear worked well, the arms are not very sturdy in the direction perpendicular to the axle. They do not stay parallel. One solution is to tie the arms together with cross bracing, though this will come at the expense of aerodynamic drag. Another is to make an indexing web where the arms cross the axle. As of today the solution is not defined.
We also need to be thinking about the production vehicle. For that there will need to be aerodynamic improvements and/or consideration of retractable landing gear. I let you know where we end up
For more information on this project, vist Zevaaero.com
Watch the flight test highlights HERE.
PRESS ARTICLES HERE:
• Yahoo Finance: “Zeva Sucessfully completes Historic First Flight Test“;
• Geek Wire: “Zeva puts its ZERO ‘flying saucer’ eVTOL through first free-flying test in a pasture south of Seattle“
• Daily Mail: “Travel like a superhero! Bizarre zero emission electric craft that will allow its ‘Superman-like’ pilot to whizz through the air at 160mph completes its first untethered flight test“
Brainstorming solutions for next landing gear iteration.
This is the FUTURE… pretty exciting to be on the cutting edge.
Team Zeva feeling the STOKE!! after four successful flight tests in January, 2022.
If you want to “join the team”, you can learn about investment options HERE.
