Can you make a DC motor run more quietly?

[Doris]

Hi everyone,

I'm using a 6 volt DC motor with a built in gearbox to drive an automata I'm working on and the motor seems to be so noisy! I've tried opening up the gearbox and spreading the grease around, boxing the motor in and even running the motor at 3 volts and still this loud drone is very audible!

Does anyone have any suggestions or experiences on sound proofing a noisy motor that I could perhaps try.

Thank you

 

[Spectric]

It sounds like a cheap motor, you could box it in using PIR insulation but really the motor needs some airflow and with airflow comes the noise. What is an automata ?

 

[bourbon]

It sounds like a cheap motor, you could box it in using PIR insulation but really the motor needs some airflow and with airflow comes the noise. What is an automata ?

 

[eribaMotters]

if you put it in a box it will make more noise. You need to sit the motor on something comparatively heavy to absorb the noise.

Colin

 

[Henniep]

if you put it in a box it will make more noise. You need to sit the motor on something comparatively heavy to absorb the noise.

Colin

....or, try mounting it on a rubber mat. The drone might be going through whatever it's mounted on?

 

[Mike Fletcher]

Or, use a stepper / sychro motor.

 

[Jamesc]

It is unusual for the motor to be too noisy, it is usually the gears and you have tried the ony practical solution with the grease.
I would suggest looking at a different motor, perhaps with a better build quality. A google for 'silent DC geared motor' brings up a lot of options.

 

[ChaiLatte]

What speed is the output? How long does it run for at one 'showing'?

A geared DC motor will run very fast on the input side before it goes through the gearbox to produce the slow output speed (and multiplied torque).

A more powerful, higher voltage, slower running, direct drive motor might be an option.

A belt drive would be quieter than a gear drive.

Add some audio to the user experience and it will drown out the motor.

 

[Doris]

It is unusual for the motor to be too noisy, it is usually the gears and you have tried the ony practical solution with the grease.
I would suggest looking at a different motor, perhaps with a better build quality. A google for 'silent DC geared motor' brings up a lot of options.

I did take the gearbox apart yesterday and run the motor without the gearbox on and it is a noisy motor. This was a cheap motor from china as the speed I need to run this automata at 18 RPM. Trying to find one in this country I wasn't able to find anything. This was baterry powered as well but am now considering a 12 v mains powered version if such as thing exists running at around that speed.

 

[Doris]

What speed is the output? How long does it run for at one 'showing'?

A geared DC motor will run very fast on the input side before it goes through the gearbox to produce the slow output speed (and multiplied torque).

A more powerful, higher voltage, slower running, direct drive motor might be an option.

A belt drive would be quieter than a gear drive.

Add some audio to the user experience and it will drown out the motor.

These are some good suggestions! I'm not sure what you mean by "showing"? I hadn't thought of a belt drive at all. The motor needs to run at around 18rpm.

I did pick up this high torque motor as I thought it needs to be able to rotate a millers falls drill, so the motor is attached to the drill chuck and rotates the handwheel. I do have a mini motor that runs more quitely but I'm not sure if it has enough guts to drive the drill if you see what I mean.

 

[throbscottle]

There are slow AC motors. It's called a synchronous motor. Used for rotating the table in a microwave, running the timer in an older type washing machine, things like that. They are locked to the mains frequency so as accurate as that is (+/- 5% I think). I have a few but probably not the speed you want. You would only need simple gearing with one of these and they are quiet - can hardly hear them. In DC motors, the main categories are 3 pole and 5 pole. 3 pole ones are cheap, fast, noisy and powerful. 5 pole ones are quieter, slower, less powerful but can be controlled down to a slower speed . They are favoured by model rail enthusiasts so you may have some luck in that area. So called "precision" DC motors are also quieter. You commonly find them in printers.
Your best bet is a synchronous motor. If you must stick with the DC route, use a speed controller to run it more slowly, use the highest voltage motor you can, and make your own gearbox. A worm drive will give the greatest reduction to noise ratio I would think.
I have a lot of motors I don't need, (dismantled from things) so if it's economical to get one to you (I am near the centre of England), you are welcome to a few of those!

 

[ChaiLatte]

I'm not sure what you mean by "showing"?

I guess the machine does not run 24 hours a day, 7 days a week nor do people look at it for this same time. Is the time it does not run or it is not being viewed enough to charge up a 12v battery with an external charger?

 

[throbscottle]

It also occurs to me that you can vary the speed of a synchronous motor (or any induction motor for that matter) by adjusting the frequency of it's supply. You would need a split DC supply, square wave generator and half bridge to do this. You can get low voltage versions of these motors so 12v is feasible, either for a variable frequency or just a transformer connected to the mains.

 

[Sideways]

Some dc motors are quieter than others.
I can't recommend anything specific as I don't use them, just have encountered a few over the years and noticed this variance.
Slowing it down typically would reduce noise so dropping the voltage was a very sensible thing to try.
My first thought was about the gearbox. Worm drive on the motor shaft and a large primary gear will give a big speed reduction and increase of torque which you probably (?) need. Worm drives are also quiet so this could reduce gearbox noise it that is part of the problem.
Designs like this (random google search)
https://www.amazon.co.uk/Sourcingmap-20kg-cm-Reversible-Turbine-Electric/dp/B071YT58QS

Other than that, I would guess that better quality motors might be better made and therefore quieter.

Brushless motors should be quieter as they don't have a commutator and brushes, but they need an electronic controller so more cost and complexity. Brushless make maximum power by spinning fast so you'd still need to sort out a gearbox, but then DC motors are a high speed thing too.

Stepper motors provide high torque at low speeds with no need for a gearbox and you can get simple driver modules on ebay, but they have a distinctive sound as the motor steps through typically 180 positions per revolution / 54 per second at 18 rpm.