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More mythbuster nonsense

S

spidey07

No Lifer
Trying to bust the myth that you can destroy a car with sound...

These yahoos mount a crankshaft to the drive shaft of an oldsmobile. This provides the linear motion for a large 4 foot or so subwoofer.

What's problem?

I'm just thinking....20 hz wave = sub has to move up and down 20 times a SECOND. That means the drive shafe is 1200 RPM.

Doesn't that seem a litte fast for a drive shaft? maybe I'm off here, but I wouldn't think the differential would reduce the gearing that much.
 
In a vehicle without overdrive, the driveshaft turns the same speed as the engine in high gear. So 1200 RPM is no where near unheard of...that's just off idle
 
Originally posted by: spidey07
Trying to bust the myth that you can destroy a car with sound...

These yahoos mount a crankshaft to the drive shaft of an oldsmobile. This provides the linear motion for a large 4 foot or so subwoofer.

What's problem?

I'm just thinking....20 hz wave = sub has to move up and down 20 times a SECOND. That means the drive shafe is 1200 RPM.

Doesn't that seem a litte fast for a drive shaft? maybe I'm off here, but I wouldn't think the differential would reduce the gearing that much.
Click to expand...

Stop, hold on to your horses! What's the problem? It's no longer a subwoofer but a machine to generate noise. If you want to see how much NOISE it takes to blow apart a car, it's much easier to use C4. :laugh:

Not to mention 95% of the systems out there generate mostly noise but that's besides the point. 😛
 
Actually what they should do since they're attaching things to the driveshaft is build the reciprocating machine with its flexible attachment in the middle of the driver seat for excitement. :evil:

:laugh:
 
Originally posted by: PottedMeat
wasn't that some 80's Mercedes diesel?

and the guy said 160 something dB at 16Hz so 16*60 = 960RPM?
Click to expand...

That's what I was thinking. Guess I forgot about the ring and pinion gear in the diff. I don't know how much that reduces it. Interesting point about the drive shaft rotating as much as the motor. I guess it's not unheard of to have a final drive ratio of 1.00? It just seems like a tire rotating 20 times a second is awfully fast...some smart guy can figure out how fast that is.

oh well, neat episode anyway.

And to MS Dawn - some sort of solenoid driven sub should certainly be able to achieve high SPL. But I guess a regular sub is just one big solenoid anyway.

There's some wacky designs out there. I'm espeically fond of martin logans approach (in their statement line)
 
Originally posted by: spidey07
Originally posted by: PottedMeat
wasn't that some 80's Mercedes diesel?

and the guy said 160 something dB at 16Hz so 16*60 = 960RPM?
Click to expand...

That's what I was thinking. Guess I forgot about the ring and pinion gear in the diff. I don't know how much that reduces it. Interesting point about the drive shaft rotating as much as the motor. I guess it's not unheard of to have a final drive ratio of 1.00? It just seems like a tire rotating 20 times a second is awfully fast...some smart guy can figure out how fast that is.
Click to expand...

The transmission will have a 1:1 ratio (or close to it, usually 4th gear), but the diff also reduces the speed of the wheels, so the driveshaft will be spinning 3-4 times as fast as the wheels. Depending on what kind of diff you have...high-ratio for acceleration, low-ratio for fuel economy.
 
Who gives a crap? It's good TV, they blow stuff up and they have a hot redhead named Kari. What else do you want?
 
Originally posted by: MS Dawn
Originally posted by: spidey07
Trying to bust the myth that you can destroy a car with sound...

These yahoos mount a crankshaft to the drive shaft of an oldsmobile. This provides the linear motion for a large 4 foot or so subwoofer.

What's problem?

I'm just thinking....20 hz wave = sub has to move up and down 20 times a SECOND. That means the drive shafe is 1200 RPM.

Doesn't that seem a litte fast for a drive shaft? maybe I'm off here, but I wouldn't think the differential would reduce the gearing that much.
Click to expand...

Stop, hold on to your horses! What's the problem? It's no longer a subwoofer but a machine to generate noise. If you want to see how much NOISE it takes to blow apart a car, it's much easier to use C4. :laugh:

Not to mention 95% of the systems out there generate mostly noise but that's besides the point. 😛
Click to expand...

Take a garden flower pot, fill it with some thermite.
Place on the roof if said car just above the gas tank.
Fill the gas take up with of course gas.
Light thermite via long fuse.
Run

Watch nice explosion. 😀

 
Originally posted by: spidey07
oh well, neat episode anyway.

And to MS Dawn - some sort of solenoid driven sub should certainly be able to achieve high SPL. But I guess a regular sub is just one big solenoid anyway.

There's some wacky designs out there. I'm espeically fond of martin logans approach (in their statement line)
Click to expand...

Yes but there's a difference between creating an accurate representation of the air movement of the electrical (sinus) input. Few designs are truly faithful, and many are horribly wrong. Then again few hear accurate bass and believe if they can "feel the notes" their subwoofer is good.

 
Originally posted by: jagec
The transmission will have a 1:1 ratio (or close to it, usually 4th gear), but the diff also reduces the speed of the wheels, so the driveshaft will be spinning 3-4 times as fast as the wheels. Depending on what kind of diff you have...high-ratio for acceleration, low-ratio for fuel economy.
Click to expand...

Thanks for the explanation. So motor turns at 4000 rpm, tranny outputs 4000 RPM, then the small pinion gear turns the large ring gear? at 3-4 times reduction in the diff we have 1000 or less RPM at the wheel?

So 20 Hz = 1200 RPM, easy done at the drive shaft at idle. But to make this work we'd probably want more rpm and more torque and hence would use a lower tranny gear, but hit the torque curve of the motor.

mmm, mixing subs and cars. me likey.

Who's got an old car we can play with?
 
Originally posted by: spidey07

Thanks for the explanation. So motor turns at 4000 rpm, tranny outputs 4000 RPM, then the small pinion gear turns the large ring gear? at 3-4 times reduction in the diff we have 1000 or less RPM at the wheel?

So 20 Hz = 1200 RPM, easy done at the drive shaft at idle. But to make this work we'd probably want more rpm and more torque and hence would use a lower tranny gear, but hit the torque curve of the motor.

mmm, mixing subs and cars. me likey.

Who's got an old car we can play with?
Click to expand...

Again for what purpose? This is not a subwoofer but an apparatus for generating noise. A loudspeaker has a role to reproduce sound from an electrical signal which was once a sound previously recorded.

This "sub" in essence is a device on its own for making a sound but cannot reproduce a recording in airspace. There are many, many devices out for production that will do this powered a variety of ways. One uses propane and can create a low frequency vibrating effect that can break windows out of buildings for *miles* if the operator chooses to build it large enough and is crazy enough. :evil:

 
MS Dawn,

Guess you've never been to a machine gun shoot. We blow it up because it's there. Doesn't matter how or why. Because it's there and we can come up with ingenious methods to destroy it.
 
Originally posted by: spidey07
MS Dawn,

Guess you've never been to a machine gun shoot. We blow it up because it's there. Doesn't matter how or why. Because it's there and we can come up with ingenious methods to destroy it.
Click to expand...

No but I bet I can come up with some pretty creative ways to destroy just about anything in sight on land. 😉

 
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