Hello
We are designing a portable vibraphone in a case. It requires a small, compact and very quiet motor. The motor turns 1/4" aluminum rods approximately 2.78 feet in length known as pulsators with butterflies (flaps) that open and close air space over a resonators (for vibrato effect).
See link of pulsators/butterflies for vibrato effect
youtu.be/M6CgYgu1fgU
The weight of both pulsators with butterflies and pulleys total less than 32 oz. The rotation we would like is 25-100RPM load but can have a higher RPM.
Specs:
compact
square if available
bottom mount
25-100 RPM
variable speed
We could also consider a step motor so move back and forth in rotation.
Attached is a photo of the pulsators and butterflies.
Let me know if you need more understand the project.
Best,
Shannon
Hi,
How are you planning to control the motor (switches, potentiometer, etc…) ? Choosing the motor will depend on the driver (if you already have one).
After choosing the appropriate motor, you will also need a coupler to link the rod to the motor’s output shaft.
Geared Motors : robotshop.com/en/gear-motors.html
Steppers : robotshop.com/en/stepper-motors.html
Motor Couplers : robotshop.com/en/hubs-couplers.html
Regards,
Hi Brahim
We would control the motor speed via a potentiometer and toggle switch. We do not have a driver yet. We’re looking for the smallest, most compact items. Do you have a motor you feel would suit this need?
Shannon
Do you need a motor that can do continuous rotation like a DC Motor, Stepper or Continuous Rotation Servo ?
If not, you could use a regular RC servo (easier to control than steppers and DC motors) that can rotate the torque generated by the pulsators with butterflies and pulleys.
This torque value can be approximated at the center of gravity of the 1/4" aluminium rod, which would be equal to about 0.908Kg (32Oz) * 84.8cm (2.78’) / 2 = 38.5Kg-cm
Therefore, you would need a servomotor that can rotate 38.5Kg-cm torque at 25-100RPM.
Then, you can directly control it with this Mini Servo / ESC Tester or this Manual Servo Controller MX-04.
However, if you are designing for positioning precision control, you are probably better with steppers (one which can rotate the torque calculated above) but controlling the stepper with a potentiometer will be more complicated than controlling an RC servo.
You would need a stepper driver with a microcontroller board and a potentiometer as an analog input. You can use for example an Arduino Board like the Arduino Uno R3 USB Microcontroller.
You can find an Arduino example code of controlling a stepper with a potentiometer here.
The third solution : in case continuous rotation is needed, speed is important and precision is not an issue, you can use a DC Geared Motor with this DC Speed Controller for Actuators.
Mechanically, you would need a coupler/hub that will link the actuator’s output shaft to the aluminium rod. This is chosen depending on the shaft output size and type of the motor you will be using in your project.
HI Brahim
Thank you for your thorough explanation.
Ideally we’d like to use a motor to give us this result (see link) – if you jump to 9 minutes you’ll see how the pulsator stops with the butterfly open and it moves back and forth (different degrees of rotation for varied depth of vibrato).
youtube.com/watch?v=ZoHjNOulCkg
If this proves too costly, we’d opt for a continuous rotation but with the ability to change speed from 45-100 + RPM.
Based on the above information, which motor and accessories would you recommend for each scenario?
Shannon
Here is a nice example that shows a homemade programmable vibraphone motor system similar to the one you are planning to build :
youtube.com/watch?v=Xpzj7BlVu9I
And here is his explanation : buildavibe.blogspot.com/
buildavibe.blogspot.com/2017/09/ … motor.html
He used a 146RPM 12V DC Geared Motor with built-in encoder. Here is a similar example : 12V, 118RPM 958.2oz-in HD Premium Planetary Gearmotor w/ Encoder
He also built a a box around the motor and covered it with foam to reduce the sound and vibration :
buildavibe.blogspot.com/2017/11/ … onics.html
Hi Brahim
Yes I am aware of that homemade instrument. We have a much more refined and sophisticated design, CAD drawings and many of the parts already machined. We’re in the prototype phase.
I simply referenced the youtube video so you could see the type of motor we are considering to answer your question, “Do you need a motor that can do continuous rotation like a DC Motor, Stepper or Continuous Rotation Servo?”
So, based on that link I provided, what motor would you recommend in order to perform in a similar fashion that is quiet, compact and what components would you recommend with the particular recommendation?
Shannon
