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Participant

Join Date: Nov 2016
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# Shock Absorbers - Calculation Of the Amount of Gas

11/04/2016 12:24 PM

Hello,
I would like to ask if somebody knows how to calculate the necessary amount of nitrogen which must fill the damper to give specified force?

I will be very gratefull for any help or suggestions

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Join Date: Mar 2007
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#1

### Re: Shock absorbers- calculation of the maount of gas

11/04/2016 12:29 PM
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Guru

Join Date: May 2007
Location: Annapolis, Maryland
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#2

### Re: Shock absorbers- calculation of the maount of gas

11/04/2016 12:59 PM

Is the nitrogen there primarily to provide spring force or is it to help prevent foaming of the oil with a bellows/bladder? Seems like the Fox Twin Clicker damper with remote reservoir on my (old) motorcycle was pressurized to 300 psi (2.1 MPa) but the pressure was only to prevent oil foaming. It still had a very strong coil spring.

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#3

### Re: Shock absorbers- calculation of the maount of gas

11/04/2016 1:39 PM

Shock absorbers or nitrogen lift cylinders?

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Join Date: Nov 2016
Posts: 2
#5

### Re: Shock absorbers- calculation of the maount of gas

11/05/2016 4:00 AM

Shock absorber.

It has a chamber filled with gas (monotube shock absorber)

https://www.tein.co.jp/e/special/ni_toryu/img/img_tigai.gif

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Join Date: May 2009
Location: Richland, WA, USA
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#4

### Re: Shock absorbers- calculation of the maount of gas

11/04/2016 2:39 PM

1. Determine the required force.
2. Divide by piston area to get required pressure, barg being the most convenient unit.
3. Determined volume of nitrogen behind the piston when at the desired position.
4. Multiply that volume by the normal density of nitrogen at STP and then by the barg from step 2. This gives the mass of nitrogen needed.
5. You may also need to correct for temperature, especially if the device cycles a lot.

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#6

### Re: Shock absorbers- calculation of the maount of gas

11/05/2016 2:20 PM

Yes. The equipment manufacturer can give this information over the telephone. It may also be found in the manufacturer's technical sales information.

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