Mejzlik, a leading company in the field of drone technology, recognized the need for folding propellers that are safe, reliable, and efficient. Last year, the Mejzlik team was working on these challenges to come up with the first version of the multicopter folding propellers (MC folding 1.0), based on the successful design of Mejzlik's fixed multicopter propellers.
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Safety and reliability were the main design goals, as mission failures due to inappropriate design or engineering on the folding propellers available on the market were quite common. One of the most crucial parts of a folding propeller is the hub-blade connection, which is typically ensured by threaded bolts that are prone to fatigue disorders. To tackle this issue, Mejzlik's team implemented a customized shoulder bolt made from high-grade steel (12.9). This bolt ensures enough strength and precise positioning of the top/bottom hub parts and the blade. Additionally, the shoulder bolt is mechanically pressed into the upper part of the hub to eliminate the risk of bolt loosening in case of hard flight conditions or nut loss. As the top part is connected directly to the bottom part and the motor, the whole assembly is very robust and compact.
Extensive testing was performed to verify the initial calculation and safety of the design, including a centrifugal load test according to EASA CS-P 350. The performance of the folding propellers was also tested against other folding propellers available on the market.
Mejzlik's folding propellers come with specific hub sizes to minimize the weight of the propeller assembly and fit the most common motors on the market. The hub design also protects the blades from hitting each other in the folded position. Currently, there are various sizes available, including 14x4.5, 18x6, 20x6.7, 22x7.4, 28x9.4, 30x10, and 32x10.6 (all in two-bladed versions). All these propellers can be assembled in both configurations (tractor/pusher) and are therefore also suitable for coaxial.
I found these new DAL Folding Props to be very interesting so I bought a few sets to try. What are the advantages of foldable props, and are they just gonna be another waste of money/time? Let's find out in this review!
Actually, folding props are nothing new, they have been used in RC planes and DJI drones for years. People had tried to make these work for FPV drones in the past with little success as they just didn't perform as well as normal props. Well, this time I think they finally found the 'secret sauce' ' these DAL Fold props are totally legit!
They perform so well, I am actually considering replacing all my 5' quads with these props now. For other props I like see my recommendations.
F5 (5.1×4.75×3):
At the moment they only do 5', I hope they will introduce other sizes in the future.
The folding prop came unassembled, but it's pretty easy to put them together.
First, sort the blades into two piles ' CW (clockwise) and CCW (counter clockwise).
Take the centre hub and insert the individual blades. Be careful NOT to insert the wrong blade, you should only use CW or CCW blades in the same prop.
In the following picture, the bottom side of the blade is facing up.
Then secure the blades in place with the top plate. It's a press fit, no screws or bolts needed, quick and easy!
Prop size is 5.1-inch, with a pitch of 4.75-inch, and 5mm shaft hole (diameter). Learn about prop specs here.
The blades can rotate freely and they can be folded up to save space.
The total weight of the DAL Fold F5 Prop is only 4.3g! With all those plastic pieces I am quite surprised at the light weight.
Here is a comparison to my favourite HQ props from , the HQ 5.1×4.1×3.
The DAL folding prop is actually lighter than the HQ 5.1! I think that's due to less 'meaty' blades and mostly hollow hub in the DAL.
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Both props are made of very strong poly-carbonate material, but the HQ 5.1 is stiffer because of the thicker blade.
Note that the hub of the DAL is thicker at 8mm, while normal props like the HQ 5.1 is only 7mm. So to install the DAL foldable props with standard lock nut, your motor shaft should be 14mm or longer.
The DAL foldable props also support motors with POPO technology.
It's great for transportation as the props can fold up and they are less likely to get bent. When they are all folded up, the form factor is almost like having no props at all.
And the weight is surprisingly low given all the plastic in the hub. This will really improve handling, smoothness and responsiveness.
Although the blades have less 'meat', it doesn't seem to affect durability as much as I expected. It uses the same flexible polycarbonate that we see on other DAL props, and it's very durable. In fact, since the blades can fold, it makes it even more so upon impact! Probably cause slightly less damage too when it hits someone?
It's possible to change blades too I guess, so you just have to replace the broken ones, it potentially saves money in the long run (Greenpeace approves!). But the hub is really hard to take apart without breaking it. Maybe that's something they can improve on in the future.
As the blades can fold, it's less likely to get caught on branches/gate, and also it's more likely to get your quad out of a tree if it does get stuck, because the props are flexible!
And I can confirm that turtle mode works with these props. And if the props are obstructed, it's now less likely to burn your motor/ESC as the props can now fold.
When tightening the props, It doesn't cut your fingers anymore!
I can easily grab 8 of these props in one hand :) I think the design makes shipping much easier, and less likely to get damaged during transport.
The hub is 1mm taller than traditional props, your motor shaft should be at least 14mm long if used with standard prop nuts. I wish they could make the hub 1mm lower.
They are harder to manufacture due to the tight tolerance between the blades and hub. And all the blades have to be close to identical in order to achieve perfect balance. If there is an issue with balance, these props would become almost useless as it's impossible to manually balance them due to the flexible blades.
Finally, folding props are double edge sword, they don't protect your motors in a crash like normal props do.
I can't think of anything negative when it comes to performance!
DAL got off to a really good start with these foldable props! I am well impressed!
If they keep the price competitive to traditional props, I can see these to eventually replace traditional props and become the standard for FPV drones. While there are so many advantages, but with the same performance (if not better performance), what's there not to like about these folding props?
Manufacturers and resellers can also benefit from this fold-ability as the package size becomes smaller, and they don't get damaged as easily during shipping.
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