Paging the baffleisti

What makes a quiet baffle? I have a set of straight thru pipes where
the baffle (about 4 inches long) has a set of punched holes with the
metal dimples facing the inside of the baffle - however there is still
a straight run down the centre of the baffle.
Is this enough to cause the exhaust gases to bounce around and lose
energy?
I have a notion that if the exhaust gas were prevented from going
straight down the centre and thus being forced through the punched
holes before exiting it would be quieter , or would that simply
strangle the exhaust?

Steve

 

That would be an "anechoic chamber", IIRC.

Lose /some/ energy, yes.

Yes, and probably.

 

I'd /love/ to hear a Bofors gun at high rpm.

 

<quiet mode>???<\qm>

 

It doesn't work like that: the noise does not come from the exhaust
gas proper but from the pulsing as the cylinder exhausts at each
cycle. A silencer works by setting up multiple reflections so that the
sound (the pulses) partially cancels. You can build a silencer just by
having an expansion followed by a contraction in the pipe. The baffles
and such inside help by dissipating sound as it travels up and down
the silencer. If you stop the gas flowing down the centre, you will
probably lose performance, because the gas can't get out, and have no
effect on the noise.

 

Theres me 1st problem - there isnt a silencer.....

<snip>
That'll do me - i'll give blanking off the inner end a go and see what
happens.
Looking at the 'DB Killers' pics on ebay seemed to show that they were
all open at the inner end....

Cheers

Steve

 

<Googles and rewrites sentence>

.... but when running at tick-over renders an exhaust note a tiny bit
like one would imagine a 20mm Bofors gun would sound running at four
times design speed>

Happy now?

--

+-------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 |
+-------------------------------------------------------------+

 

In communiqué <>,

I wouldn't be in a hurry to do anything not easily reversible if I were
you. You could really **** up your carburation. As Mr Carley says, a lot
depends on reflection and wave formation. Even with an open 'inner' end
there will be some effect with just a smaller diameter baffle tube.

Do you mean literally straight through *pipes* or "straight through",
i.e. absorption type cans?

--

+-------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 |
+-------------------------------------------------------------+

 

Oh, I knew what you meant. I just liked the idea of a high-rpm Bofors gun.

 

Ditto.
My favorite is the Vulcan 20mm gatling gun, there's no mistaking it's
sound.

 

These are straight through pipes - its a Hardly Ableson you see.
Twont be irreversible but i'll see how it much its going to annoy the
neighbours first then decide what to do....

Steve

 

In fact, not knowing that much about the mechanism of a Bofors, I think
there is almost certainly a fundamental error in my logic in respect of
firing frequency, given that it is a gun and not a four stroke single
engine.
--

+-------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 |
+-------------------------------------------------------------+

 

I'm thinking more of continuous rapid traverse and banging out as many
rounds as you can in whatever direction the gun happens to be pointing at
the time.

 

Sort of a laying waste to everything around you just because type of
thing? I'm in.

 

Fire as your guns bear!

 

In the US Army, this is called 'recon by fire'.

 

Praise the lord and pass the ammunition.

 

YM "surrounded".