Is Ultralight 5 inch the new FPV drone hotness in 2021?
Last edited Feb 1, 2021
If you don't already know, we are one of the first designers to work on sub-250g micro long range 4 inch design, check out our design blog post of the AirBlade Transformer Mini 4 inch here.
In this blog post, we want to talk about our journey toward the AirBlade Transformer 5, specifically the design and thinking process behind this setup.
The early success of the AirBlade Transformer Mini 4 inch setup had us thinking, why not 5 inch? So we started brainstorming the next product to add to our AirBlade Transformer line up in June of 2020 (yes, our development process actually takes a long time).
We almost had all the right ingredients for this setup:
- The 26x26 AIO FCs were getting better and better with more UART ports, more features.
- We can definitely design a 5 inch frame.
- The Li-Ion batteries we were testing are able to handle bigger setups
- The only missing piece here is the motor, hence that's where we started
What is the right motor?
As with almost everything in this hobby, there's no one right answer, which is the beauty and also a curse in and of itself. We started out testing the AirBlade 1606 motors which is a great motors for builds ranging from 3 inch all the way to 5 inch. However, we discovered that it is best suited for 3 and 4 inch. During our tests, we felt that there was still a lot of top-end performance to be achieved with bigger motors, hence our quest to make that new motor.
What we wanted out of the new motor size is a blend of both efficiency as well as performance. What we've learned from the launch of our AirBlade Transformer Mini 4 inch is that while it is impressive to be able to build a FPV drone capable of flying for 20 minutes, most people get bored after 10 minutes or so. And therefore, in our quest, we didn't set out to make the most efficient motor. We wanted a motor that will work with mid-range builds, but also a good candidate for freestyle and even racing.
What we learned from the past with 1806 motors is that they are really powerful, but at the cost of efficiency. At around the time when we were prototyping, there were a few 2004 motors hitting the market. We felt that 2004 size can be an efficient motor, but we wanted a little bit more power and control out of our new motor, and given the weight constraints, we decided to make a 1905. 1905 motors have larger stator volume size than 2004 and hence providing more torque and control, which makes it suitable even for racing FPV drones.
We originally started with 1600kV, 2100kV and 2600kv but early tests indicated that 1600kV was leaving out some top-end performance while 2600kv was more inefficient than what we would have liked. As such, the production models are now 1800kV 2100kV and 2400kV.
Some other considerations we kept in mind when designing is motor were durability, weight, smoothness/performance and compatibility. We decided to use slightly larger bearings, 3x8x4 to ensure the smoothness of the motor. We opted to use 3mm internal shaft and 1.5mm external stub shaft to increase the overall durability of the motor.
If you're interested in this motor, you can now Check out the new AirBlade Superman 1905 here.
What about frame choices?
There were already a few ultralight 5 inch racing frames on the market by the time we started experimenting with this setup, however the choices for freestyle/mid-range/long range frames are still lacking. Hence we decided to focus on that market. The good thing is our AirBlade Transformer line was already well loved by customers and it's a really good platform to expand, so we decided to modify that design for 5 inch. It is our general design philosophy to build on existing platform instead of reinventing the wheel.
There were a few challenges we had to work through:
- We want to keep this build sub-250g which means the frame has to stay as light as possible
- Since this is a 5 inch frame with bigger motor than the Transformer Mini 4 inch, it is better to go with removable arms instead of unibody design. It is also better to go with 3mm arms for more durability.
- Since we are already using thicker arms, and removable arms require additional hardware on the frame, it is imperative that we design the arm locking mechanism as simple and hardware-light as possible.
- We need to retain most of the existing design features so it is somewhat backward compatible with the AirBlade Transformer Mini 4 inch
With this in mind, we were able to keep the top plate and side plate (camera plate) the same, that means it is fully compatible with the existing Transformer Mini 4 inch. However, to keep this as light as possible, we decided that the arm mounting mechanism has to be as simple as possible, and hence we opted for a 2 point mount system, with the second point being shared between all 4 arms. This means there is only a need for 5 screws instead of 8 screws.
Because the second mounting hole is shared between all 4 arms, it is impossible to have just the arms attached nakedly to the base plate securely. We had to add the brace plate to keep all the arms in place. The base plate has to be as lightweight as possible while still doing the job it is intended to fulfill. Furthermore, we also opted for pressnuts instead of locknuts to reduce the weight even further, while also maintaining a cool aesthetic for the frame.
One added bonus to this design is that the arms can be cut along the weave for extra durability, unlike the unibody Transformer Mini 4.
Overall, the entire frame came out at 46g including hardware, a mere 13g increase over the 4 inch design.
The AirBlade Transformer 5 is being tested right now. Check back to this blog post regularly to get more updates on our prototyping and testing progress.
Don't forget to subscribe to our newsletter to get notified when this frame is released.