How Do You Measure Vibration Decay in Damped Drumsticks?

[noodles1]

Hi,

I am currently in the process of completing my final year mechanical engineering thesis, which compares the dynamics of damped drumsticks (not the chicken ones, the drum kit playing ones!) with those of a conventional, undamped drum stick.

I now am up to the point where I need to devise an experiment to measure the intensity/amplitude of vibrations and also the time they take to decay. Where I am having trouble is my inexperience with experimental equipment and know-how.

Some issues I can see myself having are;

How to support the drumstick?
- I figure I can either clamp the stick at either the end or where a drummer would grip the stick, or support it using thin string or wires that are attached to a structure above the stick.
Would one of those methods be better than the other and why?

Excitation Device
- All I can think of is possibly an impact hammer and measure the subsequent reactions of the stick, however I am concerned that this might add a degree of human error.
Would this be the best way to excite the stick?

I am also having concerns about the weight of the drumstick and it relative light weight, compared to the force it is being struck with.

Is there anything else I should look at? What would be the best way to measure the amplitude and rate of decay of the vibrations in the stick?

 

[FredGarvin]

Welcome to my world. Testing takes a bit of a different eye.

When it comes to supporting the drumstick, either way you presented would be arguably correct. I always try to fashion my tests the way the item is actually used. So I would argue to clamp the stick in a fashion that is closest to being held by a human hand. However, you do need to take a look at what effects that boundary condition will have on your results. Just make sure that what you are wanting to see will not be lost because of it.

In terms of the excitation, it seems to me that you want to do what we call a "plink" test. You want to induce a s close to an instantaneous impact and watch for the results. We do that with turbine and compressor blades when we want to look for their natural frequencies. Essentially, with the stick very rigidly mounted, you "pluck" the end of the stick. This can be controlled by the initial deflection that you induce in the stick from its equilibrium point. It's kind of hokie, but the results are good. Plus it is very simple and requires no outside equipment to have to contend with.

The best bet for measurement would be an accelerometer or multiples along the length. That would be more in line of a modal analysis. The other thing you could do, and is what we do, it to use a specialized microphone in VERY close proximity to the object. The microphone will pick up the tip vibrations that can be sent to an analyzer.

 

[ravenprp]

Thank you for reaching out for help with your vibration experiments. As a fellow mechanical engineering student, I understand the challenges of conducting experimental research.

First, for supporting the drumstick, I would recommend using a clamping method rather than strings or wires. This will provide a more stable and controlled support for the stick. Additionally, you can try clamping the stick at different points along its length to see if there is any variation in the vibrations.

For the excitation device, an impact hammer is a good option, but as you mentioned, it may introduce some human error. Another option could be to use a shaker table, which can provide controlled and repeatable vibrations. You can also consider using a force sensor to measure the force applied to the stick, which will help in understanding the weight and force relationship.

To measure the amplitude and rate of decay, you can use a vibration sensor such as an accelerometer. This will give you a quantitative measurement of the vibrations. Another option could be to use a high-speed camera to capture the vibrations and analyze them using software.

It may also be helpful to research any previous studies or experiments on drumstick vibrations to get an idea of the methods used and potential challenges. And don't be afraid to reach out to your professors or lab technicians for assistance and guidance. Good luck with your experiments!