What metals can create a low frequency resonance for Harley exhaust pipes?

[gr91325]

Hi, I wonder if anyone can help me with a personal research project. Besides being an educator I am also a motorcycle aficionado. I enjoy the deep rumble of a Harley Davidson motor. I own three Sportsters. My goal is to give my "small" Harley's the deep rumble of their bigger siblings. To this end I am searching for a metal or metal alloy which produces a low frequency resonance when placed inside the unbaffled exhaust pipes of my Harley. I have created a horizontal V, or wedge design, which when placed with the vertex facing the exhaust headwind will reverberate as the exhaust gases pass over it, kind of the way a flag will flap in the wind. My goal is to find a metal with high vibration yet a low frequency resonance that will create a loud yet low rumble within my pipes. I've considered brass, steel, and copper but I'm wondering if there are others I could try. Thanks for your help!

 

[Drakkith]

Can you not simply buy another muffler that would accomplish this?

 

[AlephZero]

Your idea isn't going to work. What you need to do is change the shape of the silencer to get a lower pitched resonance.

Basically, you need to make a bigger volume, and/or a smaller exit hole. Google "helmholtz resonator" for the theory. However doing that could mess up the engine performance significantly.

Finding somebody who sells modified exhaust systems would be the easiest way.

 

[gr91325]

"Can you not simply buy another muffler that would accomplish this?"

No. The obvious purpose of mufflers is to muffle sound. That's why many motorcyclists who want louder sound, replace the mufflers with "Drag pipes" which are basically hollow cylinders made of 1/16th to 1/8th inch thick steel. They are much louder.

"Your idea isn't going to work. What you need to do is change the shape of the silencer to get a lower pitched resonance."

Actually it already works as many motorcyclists and their neighbors can attest. My goal is to find a deeper "rumble".

"Basically, you need to make a bigger volume, and/or a smaller exit hole...

Placing an obstruction in the way of the outflowing gases creates a affect similar to a smaller exit hole as it changes the velocity of the gases as they exit.

"However doing that could mess up the engine performance significantly."

Actually, increasing the volume of gases exiting, increases performance as it reduces backpressure on the piston recoil. However, some back pressure is neccesary in order to sustain low-end torque.

"Fnding somebody who sells modified exhaust systems would be the easiest way. "

The point of my project gentlemen is not to "find somebody" and do it the "easiest way". It is to do it myself and create something better than what is offered out there now.

Thank you for your time and contributions. However I was looking for advice and ideas on metal resonance from an expert, such as a metallurgist. Any ideas where I can find one?

 

[AlephZero]

The point of my project gentlemen is not to "find somebody" and do it the "easiest way". It is to do it myself and create something better than what is offered out there now.

Thank you for your time and contributions. However I was looking for advice and ideas on metal resonance from an expert, such as a metallurgist. Any ideas where I can find one?

You could try the Materials and Chemical Engineering subforum. Send one of the mentors a PM if you want to move this thread to there.

Reading your comments, I'm inclined to agree with you that you aren't going to get much help (that you will accept) from people who know about sound and vibration.

 

[Drakkith]

No. The obvious purpose of mufflers is to muffle sound. That's why many motorcyclists who want louder sound, replace the mufflers with "Drag pipes" which are basically hollow cylinders made of 1/16th to 1/8th inch thick steel. They are much louder.

Exhaust, mufflers, same thing to me lol. I know they are different, I'm just not familiar enough with vehicles to always use the right word.

 

[gr91325]

Thanks anyway Drakkith, I appreciate the effort. I've submitted my question to a metallurgy website and am awaiting a response. Take care.