GEN 1 Quick question factory fox shocks

[Nesc204]

Not real sure, I haven't seen anything about it either, I'm no engineer but in my head as the shock goes through it's travel (compressing), the IFP is compressing the nitrogen so it would read a higher pressure at part/full travel...

That's why I'm asking. I'm assuming it's a separate reservoir, if so then it wouldn't matter, unlike the struts I service on Aircraft, for example I'll service a NLG strut at 245 psi at full extension on a Large Cabin Gulfstream but with weight on wheels its in the THOUSANDS. But just want to be 100 percent sure

 

[BenBB]

Makes sense! Given that, it should be the same for these, whether it's the fronts with the Internal Floating Piston or the rear with the external reservoir, the nitrogen charge is separated from the shock fluid by the floating piston and gets compressed as shock fluid flows into the oil side of the chamber as the shock compresses; might not be quadruple digits but I do think it will be higher (possibly exponentially) as more weight is on it. Gas can compress, fluid can't...

 

[Bert Bogden]

PV = NRT when there is a change in the shock position (weight on it) the volume goes down, therefore the pressure goes up.

 

[Gumby]

PV = NRT when there is a change in the shock position (weight on it) the volume goes down, therefore the pressure goes up.

Nope this is wrong!!! the shock will read the same pressure if the truck is on the ground or the shock is on the bench.
The fluid moves the nitro piston when the rod moves. If it is static the pressure is the same as if it was on the bench. The rod must move the fluid witch moves the nitrogen.

 

[BenBB]

Nope this is wrong!!! the shock will read the same pressure if the truck is on the ground or the shock is on the bench.
The fluid moves the nitro piston when the rod moves. If it is static the pressure is the same as if it was on the bench. The rod must move the fluid witch moves the nitrogen.

But...when the fluid flows into the reservoir that the floating piston lives (as the shock compresses the piston displaces fluid somewhere), wouldn't the volume of the nitrogen get smaller, increasing pressure? Maybe I'm envisioning it wrong, from what I remember from high school physics, pressure is inversely related to volume (thanks Google for verifying Boyle's Law heh).

 

[Gumby]

But...when the fluid flows into the reservoir that the floating piston lives (as the shock compresses the piston displaces fluid somewhere), wouldn't the volume of the nitrogen get smaller, increasing pressure? Maybe I'm envisioning it wrong, from what I remember from high school physics, pressure is inversely related to volume (thanks Google for verifying Boyle's Law heh).

Hard for a dumb A$$ like me to explain the shock rod moves through fluid with passes when it finds its home on the truck( truck on the ground) the 200 psi of the gas moved the fluid through the passes and is now setting at 200 psi only when the rod moves from this point will the pressure change. Make sense

 

[BenBB]

Hmm knucklehead here also haha! So it would make sense if the back side of the shock piston is also shock fluid, so fluid passes through from one side to the other as the shock goes through it's travel. But then the only time the IFP moves is if fluid is lost? And the nitrogen charge is there to force the fluid back through the piston to the extended side?

 

[Gumby]

The shock rod travels in a sleeve that has holes in it. there is a cap on the bottom of the sleeve the oil has to pass through holes in the sleeve to the shock body to move the IFP. All I can say is the the shock on the truck setting on the ground is the same pressure as if you filled it on the bench. FOR SURE I just checked Bozz and Mwaite09 the other day. filled to 200 a year ago and sitting on the ground have 200 in them. I understand how it works. (mostly) but lack of brain power... can't explain it. @Jhollowell might he is definitely smarter than me.

 

[Jhollowell]

A test is worth 1000 expert opinions. If the shock is built correct, there should be only fluid on one side of the IFP and only nitro on the other side. If the shock compresses at all the IFP should move and decrease the volume of the chamber, increasing the pressure. With the shocks installed on the truck and the truck sitting on the ground, all the shocks should be compressed slightly. But if Gumby charged shocks and checked them after intstall i would stand corrected. The only thing i would question, is that he checked it a year later so there is a chance some of the nitro leaked out over that time, but having exactly the same psi is quite the coincidence. I don't know all that well but one thing i found was after i charged a shock to 200psi, i left it on a cart in the sun, went to the auto parts store and checked it again and since it heated up the pressure was much more. I don't remember the actual number but it was higher than the original 200psi i started with.

 

[Gumby]

A test is worth 1000 expert opinions. If the shock is built correct, there should be only fluid on one side of the IFP and only nitro on the other side. If the shock compresses at all the IFP should move and decrease the volume of the chamber, increasing the pressure. With the shocks installed on the truck and the truck sitting on the ground, all the shocks should be compressed slightly. But if Gumby charged shocks and checked them after intstall i would stand corrected. The only thing i would question, is that he checked it a year later so there is a chance some of the nitro leaked out over that time, but having exactly the same psi is quite the coincidence. I don't know all that well but one thing i found was after i charged a shock to 200psi, i left it on a cart in the sun, went to the auto parts store and checked it again and since it heated up the pressure was much more. I don't remember the actual number but it was higher than the original 200psi i started with.

I agree with this ^^^^^ when the truck is sat on the ground the oil is aloud to flow around the sleeve and come back to the 200 psi you originally started with. The truck hits a bump in the road. there isn't enough time for the fluid to move through the small holes so the IPF moves and the pressure goes up. The pressure only increases when the shock collapses and the oil can't move through the holes fast enough. The spring returns the shock to its resting position.
The oil flows to a resting position because it is being pushed by the 200 psi on the other side of the IPF.
This is the best I can do at an explanation.