Dynamic balancing with a scope and small speaker 

I’m a vibration analyst by trade and your method is spot on! The only additional thing we do with the “test” weight information is build a vector diagram on a polar plot to determine where the optimal final weight should be located. Then there is some math to determine the weight amount but that’s just some simple cross multiplication. Doing this all with a speaker and o’scope is just downright genius.

Really interesting to see a speaker used that way. All you need is a sufficiently capable rotary encoder for position tracking and you've nearly caught up to industrial impeller balancing systems.

This is a pretty clever method! Thanks for sharing with us.

Mind blown. It would never occur to me that there was an issue, let alone following such a logical approach to fixing it.

With two speakers configured orthogonally and two channels on an oscilloscope, Lissajous curve could be displayed. You could directly find the vibration vector. If you further know the phase of the motor, you could even calculate and display the exact angle at which you should add or remove weight.

I confused dynamic with active. I thought you were going to feed back the vibration into the weighted voice coil to damp them that way (with destructive interference). Your way makes way more sense. Particularly for the heavy cutter. Looking forward to the conclusion!

I love the low cost approach to everything you share. It is so refreshing in a world of "Look at all this cool stuff I got for free to show you, please go buy it".

Wow Matthias! You never cease to amaze me! The way you combine intuitive understanding with real-world electronic know-how is clever and clear. When I was a kid and built slot-car motors, (circa 1964) I just chucked the armature into a drill, spun it, and lightly touched it with a magic marker. Then wherever the marks were thickest, I drilled a small hole in the armature; Reversed the armature, and did the same thing from the other side. That was as close to dynamic balancing as a cash-strapped kid could get, But it worked.! Of course I didn't have access to these electronic measuring devices then, so that method was a tedious iterative process. Even now, I would have never thought of using a speaker to generate a readable pulse into an oscilloscope. Brilliant idea!

That impresses me the most in your videos is the didacts you have. Even when I know nothing about what you are experimenting with I'm always able to understand the concept. You would be a perfect college professor, for sure!

Absolutely the best video i have seen in the past thousands

Wow, get this circulating around the shade tree, DIY engine builder community for balancing crankshafts. Very impressed by your ingenuity. Thanks for posting!

If you have a small mirror and a laser pointer laying around, you could probably do this completely analog. Put a piece of paper on a wall far away to mark out the sweep of the laser. The added benefit is electrical noise would have no effect.

I never knew how balancing could be done before this. Fascinating video.

Wow, I'm blown away by the analysis and the use of the speaker is ingenious. Thank you for the video.

This is quality content. I like it a lot. Balancing fans and rotating things with a cheap diy friendly way and increasing their lifespan, lowering the noise and vibration is a really good thing. The earlier video you had with balancing a fan really helped me right after i bought a box fan (brand new) it wash shaking violently and dancing over the floor, but after a few minutws balancing it it became very silent and no noticeable vibration

You could possibly get similar results using a 'vibration meter' app on your phone (for those of us without an oscilloscope). I dynamically balanced the drive pulley on my metal lathe by taping an old phone to the headstock and measuring the vibrations.

Man! That was a super cool video! I am astonished by your method, as always. I dream of being "your kind of smart" but the truth is, I'm a little lazy about trying to be. However! You explain the details so perfectly that I sit here and think to myself "That makes total sense. Of Course that's how that works!". I truly do understand and follow your explanations. I just, would never have gotten there myself. "That" is what perplexes me sometimes. That's the fun in it all... Right?! I have thoroughly enjoyed every one of your experiments over the years. The mice experiments were lots of fun! I appreciate your dedication to not only the true and sometimes brutally honest results but also to the storytelling arc. Thank you.

My God, dude. Your methods are simply inspired! What an awesome approach. I've yet to see a video from you where I did not learn something. Bloody brilliant.

This is fascinating. Definitely beyond the scope of any of my projects but it's interesting to read all the comments from all these knowledgeable viewers.

This looks like a job for a piezo transducer! Also thanks for the demo. I am about to buy one of those blowers and this will help a lot if it's unbalanced.

Very cool. You never cease to impress, Matthias.

Very impressed with everything you do. Thanks for sharing.

Fascinating approach to dynamic balancing! Cant wait to see the Shelix cutter head balancing :-)

I'm very excited to see the process done with your planer!

I proposed a system like this for using a speaker and diaphragm weight to dynamically balance motors about 20 years back on the electronics forums. The one thing you missed which would have been an improvment would be to place the whole assembly on an elastic suspension, which could have been as simple as a springy foam block. Your setup was damping the vibration into the table which reduced the measurement amplitude and accuracy. Very cool project! 👍

I could watch this a billion times and still have no idea how you did that.

Thank you very much for this very interesting video on DIY balancing.

Matthias blows my mind every time I watch one of his videos.

*checks notes* Dynamic Systems Laboratory, Junior year! Super clever implementation of the 'accelerometer!' love your videos, WoodGear.

I have some 3D-printed flywheels on small RC brushless motors that I need to balance, and this method looks like it would be ideal and uses stuff I already have on hand. Thanks for the tip!

Fantastic idea without expensive equipment, love it!

Nice and simple approach to solving this complex problem. I like how you use a speaker instead of a fancy pant accelerometer.

On the driven end of the rotor I believe you were seeing a central frequency of 60hz and sidebands each side, offset by 10hz. I suspect it was caused by geometrical angular/offset misalignment between the motor and fan rotors if they are rigidly coupled together. Very smart use of the speaker to measure the waveform!

That is a pretty cool idea. I really appreciate your sharing that.

Have you thought about marking a zero position with reflective tape and use an optical pick up to mark the zero position on your oscilloscope? That would make finding the “location” of the imbalance easier than trial and error.

Wow!! I never would have thought to check the balance of these things. Makes perfect sense though! I love these videos! 👏👏

Now THAT is really neat. Thanks for sharing.

That's just brilliant diy!

Very clever! I imagine that squirrel cage fans are pretty tolerant of imbalances given that they all collect dust, and any dust buildup will likely throw off even the most carefully balanced fan. However, a balanced fan will give off less fan noise and that's always a blessing. Good show on the use of low cost test gear to analyze a problem!

A guy at work once had a fan very similar to that where a blade had busted off and was no where to be found. He was trying very hard to fabricated a thin blade to replace it when I suggested we just count how many blades there were and snap one off from the opposite side. We counted and it was all good and snapped the opposing right off and it ran sweet.

Amazing! Anyday I will try to use this method!

Fine work by you and exposition for us.

This is pure gold!

This is excellent to see, really cool!

A simple practical demonstration like this is great for a lay person like myself

You are a genius gentleman!

Oh my, that’s smart! Thanks for sharing!

Super fantastic! Thank You!

That's a brilliant idea , seat of your pants engineering . Food for thought , thanks for posting the vid.

That's an awesome method!

I'm excited for the followup!

Clever guy, another great video

Thank you for this idea.

in the 1980s the company I worked for looked at analysing vibration from the heavy industrial machinery it made in an attempt to give the operator maintenance information much earlier than his ears could detect. It actually worked quite well but few end users would pay a worthwhile price for it.

Very interesting topic and clever idea of using a speaker. Nerdy stuff as usual ;)

Can't wait for part 2!!

Really cool and interesting video!

WOW!!! Way cool. Get HOT on balancing that shaper/planer! Im very interested! Looks like a very cool project!

my father has a balancing machine for big rollers and ducts. Althought its a little bit more sophisticated with a control computer etc., it messures the vibration on both sides of the tube (its laying there on bearings) and always knows at what position the duct is with the help of a light sensor and a glued on tag, after you run it it tells you the spots that need weight automatically.

That's a pertty interesting idea to use a speaker as an accelerometer. Ive seen them used as microphones, but never for low frequency. It's not a calibrated measurement, but for some quantitative analysis it's more than good enough.

Excellent! Thanks for sharing man!

With this technique, you have to make sure the resonant frequency of the speaker is not the same as the DUT. Otherwise the vibrations will look a lot stronger than really is.

Brilliant. Thank you.

I don’t always get what you’re actually doing but it always looks so cool

You made an electronic stethoscope to diagnose an illness with that fan :-) nice work.

Brilliant, Matthias! 😃 Looking forward to see the process on the jointer! Stay safe there with your family! 🖖😊

I tried with a piezo speaker and some weight glued to it. Worked great also for high frequency vibrations.

This should be on your main channel. Clever idea.

Fascinating stuff.

Clever boots. I look forward to the joiner balancing video.

Clever, thank you.

That's cool, would like to see further improvements on this concept.

Very very cool way!

Very interesting! I'm thinking of combining this to Denis' approach (channel "the GADGETS playlist") to dynamic balancing, ie, using a microphone (or speaker) to listen to the vibrations and reference it using a photocell to figure out where the weight should go - and perhaps combine it with the Y approach, ie, instead of adding weight at position 0, add it (for instance) at positions -3 and +3. Denis uses an accelerometer to measure the vibrations, not sure which option would be more accurate.

30 years ago we use to characterize disk drive motor samples with a similar set up sensitive and expensive B&K gear. Today, you can pull the 9 axis of freedom board off your drone and couple that with your favorite eval board (pi, arduino, stm32) and throw together a pretty darn good sensor system. Couple that with all the free firmware that deals with static and dynamic behavior and you will know more about anything you want to measure. The vibrations in the handle of your weed eater, lawn mower, shovel, hammer or vibrations in the motors... you could spend your whole summer on this..

Very informative video 👌👌

That is so cool!

Promising hypothesis !

i might actually use this method. ive made fans and fast rotation devices before and many times simple field balancing techniques will not suffice. it also shows the thousands of uses for signal analyzation of electro-mechanical components using an oscilloscope.

That was intense

Super idea !!

Very good 👍

Beautiful and insightful work, congratulations! The 69-ish Hz you described at timestamp 5:08 is possibly due to the aliasing between the 60Hz network frequency and the 50-ish Hz of the rotational speed. The aliasing or beating frequency generates a pair of side bands (+10 and -10 Hz) The 10Hz can be also observed at the 10Hz region of the spectra and as a sideband of every 60Hz harmonics. If the system responds well to higher frequencies, you may also find a series of 100-110-120-130 -140Hz and so on.

Okay this is actually awesome. I've actually "Saved" this video... which I never do. 😂

Creative thinking.

I would love to see your take on the DML speakers. Thanks for this, quite interesting.

Mind blown. How do I always end up learning something in every one of your videos?

With the addition of either an optical sensor tach, on the scope, the phase of the vibration relative to the shaft position, can be used to find the offset and amplitude of the balance for accurately finding the weight and position for the correction. This is how a tire shop wheel balancer works.

cant wait to see you balance moore stuff

Awe....This was one giant tease! 🙂

Like others have said, quite clever using a weighted speaker as a contact mic, but I was expecting something like noise-cancelling headphone technology, where a vibrating mass cancels out the vibration of the tool in real-time 😄

Imterestimg video. In the past I've wondered if there's some way to balance a ceiling fan besides by trial and error. I have to believe this approach could be adapted for that.

Very neat.

Clever! 😎

Thank you so much for this. So well explained and demonstrated. The only thing I'd like more information on is the weights added to the speaker. How much? The purpose? Etc.

thanks for explaining what dynamic balancing entails. Now i'm curious: it's possible that dynamic balancing can throw off static balancing? Also: i read on their brochures how some bandsaw manufacturers balance their wheels both statically and dynamically; would it be worthwile trying that on one of your bandsaws?

So cool

Too cool to be true!

Good video I did this users ago on a paper shredder

Great!