With high power motors, the flight controller can experience high frequency mechanical noise and leads to vibrations and oscillations in flight. Soft mounting is a way to isolate vibrations from getting to the gyro sensor on our flight controller.
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What is Soft Mounting
Soft mounting had been a hot topics in 2017 because vibration became a real problem due to more powerful mini quad motors, and faster PID algorithm and Gyro sampling rates.
You can soft mount the flight controller as well as the motors to reduce the amount of mechanical noise from motors getting to the FC/Gyro.
Benefits of Soft Mounting
You can probably get away from soft mounting and still fly fine, but if you ever experience issues such as oscillations and twitching, the first thing we recommend doing is always soft mounting your flight controller or/and your motors.
There are some other benefits of soft mounting FC and motors:
- Your quad flies smoother
- Allows higher PID tunes, and easier PID tuning
- Motors run cooler
- Reduces video noise (mechanical vibrations can be translated into electrical noise)
While soft mounting motors and FC helps some really noisy builds, it doesn’t cut off all vibration frequencies. Which means if your build isn’t noisy with the motors and propellers to begin with, you might not notice much of a difference.
For some gyros, I’ve found soft mounting is a requirement, otherwise those FC would be impossible to fly. Such as the ICM-20608 IMU, if you see this gyro being used on an FC, you must soft mount the board if you want good performance out of the quad.
FC Soft mounting
Here are some ideas to soft mount your FC:
- Anti-vibration M3 bobbins (Buy: Banggood | Amazon | GetFPV)
- 3D printed TPU mounts (following picture)
- O-ring (Buy: Banggood | Amazon | GetFPV)
- Grommets
- Foam tape
My current favourite option is the anti vibration bobbins. They are easy to get, affordable yet works exactly like nylon standoffs.
O-rings generally aren’t the best idea because they are too thin and often are made of harder material that doesn’t damp vibrations. Not to mention the screws are still passing vibration through to the flight controller.
Raceflight revolt FC has a good way of isolating vibration using grommets (RF call them “gummies”), but it only works if your board has over-size holes that fit these grommets. At the moment this only works exclusively for their own FC’s.
One of the oldest yet effective way is to use double sided foam tape. You could ignore the screws and standoffs, and just stick the FC on the frame. But then you won’t be able to stack anything above or under the FC like a PDB or 4in1 ESC.
Apart from soft mounting your FC, make sure there is no other things touching your FC that can transfer vibration from the quad, such as wires or zip ties.
Motor Soft mounting
The source of vibration is the motors because they are the only moving part in a mini quad. Therefore soft mounting could be very effective if you can stop the vibrations right at where they start and getting to the flight controller.
Damping effectiveness can be affected by the mass attached and dampener elasticity. FC’s are so light, the damping might not be enough. Damping at the motors might be a better option as they are heavier than an FC.
Update (21/05/2017): After soft mounting motors for a few days I found it too much of a hassle. You can’t tighten the motor screws so you have to check them every session or risk screws falling out during flights. Although it could be a more effective way of isolating vibrations than soft mounting FC, the result could varies a lot as you can’t control the tightness in the screws to be all the same in the 4 motors.
So i think soft mounting FC is more practical, and I might just do that and not soft mount my motors in the future unless they are really that bad and I have to.
There are many different materials you can use for soft mounting motors in a mini quad:
- Electrical tape (3 layers or more)
- TPU 3D printed motor mounts (Buy: Banggood | Amazon | GetFPV)
- Rubber sheet cut specifically for mini quads (such as these – Monkey & Gorilla-Rugz)
- 3M mounting tape (double sided)
- Silica Gel Pads (link to Product)
One thing to be aware of is you shouldn’t tighten the motor screws all the way, it will compress the the vibration dampening material and it will be less capable of absorbing the vibrations. Make sure to apply loctite on the screws as well as you are leaving the screws loose
Here is a good discussion too on our forum.
12 comments
I know this post is 3+yrs old, but it was so pretentious I had to reply…..
Well actually Paul, you super smart guy you, NOAD, Merriam Webster, OED, Dictionary.com, Random House and Wikipedia all have slightly different definitions, depending on if it’s a noun or a verb, but they all agree that unless writing a federal document, or something super formal, “dampen” can be used for either action. Merriam Webster and one other have Dampen as to deaden, or get rid of or lessen something physically, like sound waves or vibrations. Technical engineers, 20yrs ago, dampen was to wet damping was to reduce vibration, today most engineers use dampen for both. If you’re going to act like an elitist grammar nazi, at least complain about a word that is fragrantly misused.
our quads are completely submerged at all times in a medium: oxygen , co2, nitrogen, and many other various gases no matter what its “submerged” in if its connected tightly to something there will be as much vibration as the moving parts give off as vibrations through the frame so to damp or absorb those vibrations only prolong the life of whatever part needed to have less movement or vibration. With quads it should improve the gyro /fc performance and accuracy to a level which may be noticable or unoticeable depending on how well the particular human can perceive things or if he succumbs to the placebo affect which happens more than you might think but i guess the black box could prove them right or wrong… but if it’s faster in the races or you enjoy it more thats all that matters and if it can save you money in the long run of course.
i tried foam between the FC and the PDB below it, fully floating and only held down with a band like a hairband but stronger. Checked the gyro results in motors tab and went from numbers of 7 with rubber bobbins down to numbers of 4.
Improvement, yes, reliable, we will see.
So be careful with boards that connect to eachother such as the hobbywing xrotor AIO F4 with the 40 amp esc. I found that using the rubber bobbins between each board had too much play and was ripping out the connection point to the pdb/esc and damaging it beyond repair. After (2) being ruined I went to nylon standoffs with a rubber ring on both sides.
Hi Oscar,
This is the first reply I leave. I’m ready loads of your articles and am very impressed and happy about them, thank you :-)
I’m still quite new to quads and am still trying a lot of different things. What do you think about the combination of soft mounting your FC with the M3 bobbins you listed and the motors with o-rings? I agree that for something as lightweight as a FC, the o-rings are to hard. But for something as “heavy” and force loaded as the motors they might be great. I already tried silicon pads, but they usually don’t fit very nice and feel too soft almost. Silicon o-rings are a little harder but still very rigid. Any thoughts on this?
Thank you very much, I hope there is a lot more coming from you.
Best regards
Adrian
Hey Oscar, did you try to soft mount the motor with the M3 stand-off bobbins. Sadly I only have 4 of them lying around, but it fits really well. The screws must be shortened by a millimeter or two.
Motor damping is not as good as we think. We add a degree of movement. So for high frequencies oscillation is ok but for low frequencies, it could be amplify in fact.
Normally, you chose the damping system knowing the frequencies of oscillations. It more efficient, because every damping system need to be adjust.
Hi Oscar,
I attached a Piko FC on 30.5 mm mounting holes with zip ties for an obvious reason.
I wonder if it reduces vibrations… but that might interest you…
Nice article btw…
zip ties are probably too solid and doesn’t absorb much vibrations… also it’s hard to keep FC perfectly leveled i presume..
Please. To dampen something is to get it wet. To damp is to limit vibration. We don’t dampen our quads.
My dictionary tells me that they mean the same thing :)
but you are right, “damp” is a more common word to use for reducing vibration :)
You are both wrong. My experiments have shown that my quad has the least vibration when it is completely submerged.