Hello guys, We noticed a serious problem with stock Cinestar 8 frames when 550mm booms are used. 550mm booms are needed if you want to throw in 16" or 17" props on a flat octo setup. Even longer booms should be used for 18" props on a flat octo setup. When 550mm or bigger booms are used, the arms start to vibrate since only the small portion of the boom is secured by the center plate. The overcome this problem, we created a small boom plate which is installed on every boom and connected to each other with a 18cm long boom. This increases the stiffness of the frame very much. This also aligns all the booms at the same level. Boom alignment becomes a problem when longer booms are used. The prototypes are cnc'd with 4mm aluminium but 3 mm thickness provides more than enough stiffness to the frame. To make Cinestar 8 a real heavy lifter, this mod helps a lot. Also changing the plastic clamps to aluminium ones is another must. In the picture, I just installed three parts. I'll send the full pictures when I have enough small booms
What is the total additional weight? It is a problem for me too since I am throughing 18" props on 700mm booms but it might be self defeating with the shorter flight times.
I always preface comments such as these with “I’m not an engineer”, so take this with a grain of salt... I am not certain that your technique will be as efficient as you hope. The reason is that there is no physical connection between your additional structural components and the central hub. Plus, there is opportunity for torsion between odd pairs of arms, as there’s nothing other than the tension of the clamps to hold the arms steady. If you could make your connectors into a ’T’ and have the descending arm of the ’T’ connect to the center hub, then I think you’d be accomplishing your intended task. But like others, I’m sure we look forward to your results.
It adds around 550gr to the weight. If you compare the stock CineStar 8 weight to the recent heavy lift frames, CineStar 8 is considerably lighter (1.3 kg). For instances, look at Gryphton frames, it's 1.8kg. I finished the assembly minutes ago and on the bench it looks like it helped quite much. Now the booms are not vibrating and the frame is much rigid. I'll look into the ways making it lighter, but for the time being I feel safer with this mod. IMO, the other way to make the Cinestar 8 more rigid without adding too much weight would be to make the center plates 2-3cm wider in diameter and adding a 3rd arm holding clamps. Will post some nicer pictures later.
I didnt have this problem when I ran 550 mm booms. I think it could have more to do with the motor you are using as some older design motors create a lot of vibrations with the type of bearings they use. My old QC 3220 motors had a lot of vibration on the main frame and the Tiger U5's are extremely smooth.
Hi, I have been experiencing the same problem recently and thought about bracing the booms as the length could well cause resonance (I guess this is what has prompted the goose-neck design of the Alta). Are your boom plates available commercially, I really would like to get more ROI before I switch to the Alta. Many thanks.
I found that by replacing the top and bottom plate with a stiffer material, in my case G10, I was able to completely elimate the flex and vibration from the frame. I am using 16" props and 550mm booms without issues at all. Likely my fix and yours weight about the same. the other fix I have seen is to replace the center plates with larger ones that allow for 3 clamps per boom.
this is what I did to strengthen my frame, ran a tube all the way through the centerplate and had some custom carbon cut https://instagram.com/p/oz0xpbPOkQ/?taken-by=jamescolephoto This setup is so bomber now, we can put 16lbs under it with our Movi M10 and its sooo strong. Rated for 25lbs payload
Simon, I ended up using double center plates and a thicker carbon boom (25x21mm instead of 25x23mm). James's solution is way lighter and it definitely works good
why not just have shorter booms and use the new 15.5 inch 3 blade KDE props instead of 17 or 18 props 2 blade props?