|Oct 02, 2012, 10:36 AM|
AP/AV Basics #4. It is time for Desert and we are serving Jello.(vibration issues)
It seems like I've been answering lot of question about Jello lately, so, I want to put some basic primer on vibration control today. There is NO EXCUSE to have jello or vibration in your AP/AV multicopter and if you have it, you need to kill it and it all starts at the Source.
PROPS: Lousy balancing of props are the biggest cause of Jello. Cure starts with high quality props and good balance job. here is a good video on prop balancing: I know some prop makers say their props are prebalanced. well, may be good enough for Nitro plane, but not good enough for AP/AV.
In general, larger the prop, more critical it is to balance the prop in both blade, tracking and hub. I've found that sub 10" props are much easier as hub balance gets less critical, but most AP/AV setup requires larger prop. Even Graupner props will need some work in balancing, but usually less so. Why lot of graupners gets used in AP. APC props are notorious for poor hub balance and requires lot of work to get them to perform well. Even my favorite zingers requires balancing (but easier since I can sand down the wood ) Invest in good balancer and learn to balance your props. I've been selling lot of zingers for multicopter AP use, as they do really well in wind flying. not the most efficient, but very stable. I would avoid cheaper nylon props. In general, EPP props are lousy for AP/AV. heck, I don't even recommend APC props as their SF perform poorly in wind even when balanced well and their EP props seems to perform poorly due to stability issues. The most commonly used props for AP/AV are: 1) Graupners, 2) Xoar/zingers woodies, 3) APC props and 4) gemfan carbon filled. issue with graupners are cost and availability. same with xoar.
Motor: GOOD QUALITY MOTOR will not cause vibration. if you have motor vibration, you need to replace them. sunnysky, tigermotor, avrotos are all good quality motor with good balance. Dynamic balancing of motor IMHO is waste of time for AP/AV. I've rarely got good result from it. NO FREE LUNCH here. and frankly spending 200 bucks on set of motor is cheap investment.
Frame: GOOD RIGID Frame and NO POOL NOODLE on Landing gear. this will allow what small vibration that remain to be high frequency and easy to isolate. Pool noodle on landing gear really can cause issues. avoid it if at all possible. you can build cheap RIGID frame or buy one. lot of frame makers out there.
ONCE you have done these 3, the next step is isolation. IF YOU DO NOT HAVE good handle on above 3 itmes, YOU WILL NOT GET GOOD RESULT Unless you literally hang the camera off the frame, which is an option, but not recommended.
ISOLATION SYSTEM: you still need good isolation system. lot of way to do this. our favorite is EARSC isolator and Silicon Grommette. Silicone grommette is really good for high frequency vibration. EAR isolations are good, but bit fragile for heavier load. (and need lot of them) In some cases, you may need dual layer, depending on camera. Camera like HV9X and RX100 has OIS that is more sensitive to vibration. good damping system is mandatory for these cameras. I do carry both isolators in stock. you can roll your own. Jesolin has whole list of possible materials in the mega index.
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