Swiss Cheese & General Piston Weight Reduction

[jagillham]

Re: Swiss Cheese & General Piston Weight Reduction

What's the right answer then

I know Db is "logarithmic" - so isn't as simple as 1 is half the noise of 2.

[Spooros]

Re: Swiss Cheese & General Piston Weight Reduction

I may have to hang my head in shame



1*10-12 W/m2

[jagillham]

Re: Swiss Cheese & General Piston Weight Reduction

That's all well and good... but what is the answer to:

How much quieter is 94Db against 98Db. In terms of say percentage?

[SAS Scott]

Re: Swiss Cheese & General Piston Weight Reduction

98 db thats very loud 0.0

[Spooros]

Re: Swiss Cheese & General Piston Weight Reduction

In comparison terms it goes from a train to a lawnmower

[ElCarl]

Re: Swiss Cheese & General Piston Weight Reduction

That's all well and good... but what is the answer to:

How much quieter is 94Db against 98Db. In terms of say percentage?

I think 1 Bel is 10x volume. So 10Db is 10x, not 1Db.

[jagillham]

Re: Swiss Cheese & General Piston Weight Reduction

So what we saying here..... 98Db is roughly 3x louder than 94Db??

[North West Outpost]

Re: Swiss Cheese & General Piston Weight Reduction

Isn't it -3db half as loud?

At 98db that is above the first stage action, so you should think about ear protection. The meter should be 1m away from the source for the readings.

[jagillham]

Re: Swiss Cheese & General Piston Weight Reduction

For those who seem to be saying the reading is not right....

Environmental Noise

Weakest sound heard 0dB
Whisper Quiet Library 30dB
Normal conversation (3-5') 60-70dB
Telephone dial tone 80dB
City Traffic (inside car) 85dB
Train whistle at 500', Truck Traffic 90dB
Subway train at 200' 95dB
Power mower at 3' 107dB
Snowmobile, Motorcycle 100dB
Power saw at 3' 110dB
Sandblasting, Loud Rock Concert 115dB


Seems about right to me!

Full article here anyway....

I read a lot of this lately, some call it a myth.
So i just test some things:

a) Alupiston & head: 38g
b) JG stockpiston & head: 21g (-17g)
c) JG stockpiston swiss cheesed (SC) & head: 17g (-21g)
d) JG stockpiston swiss cheesed (SC) & head without bearing: 12g (-26g)

Testsystem:
- JG GB from AUG A3
- CA motor
- 400 fps
- white stock JG piston, think its made of PC or nylonfibre or something else...
- JG pistonhead with bearing
- JG MOSFET (1404) with DEANS and awg 14 cables
- 9,6V 1500 mAh NiMh battery, 2/3A cells

ROF:
Measured with audacity
a) 17 RPS
b) 19 RPS
c) 19 RPS (! see fps! )
d) 20 RPS (! see fps! )
Here a pic of this test: 1x track b) and 2x from a), 1 second is marked:


FPS:
Chrony Xcortech X3200
a) 2nd ROF-test, forgot fps
b) 1st ROF-test, 400 fps
c) 4th ROF-test, 380 fps (i dont know where the missing 20 fps are)
d) 3rd ROF-test, 360 fps (bearing has 5.7mm, so less compression of the spring)

Loudness:
measured with a decible meter, 50cm from the front of the GB, 20cm to the side (but doesn't matter much):
a) 98 dB
b) 95 dB
c) sry, forgot
d) 94 dB
dont forget that decibel is a logarithmic unit. 10 dB would be twice as loud for your subjective feeling.

My conclusion so far:
Less piston & pistonhead weight will give you more ROF and reduces noise.
Here in this test: minus 45 % weight => 12 % more ROF

The swiss-cheesing test fail because of the unknown dropped fps. Have to test this again.