Need nitrogen schrader valves on fox bumps extended. Bad idea?

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Feb 7, 2017
6
0
0
#13
I'll look at the other brand for ideas, thanks. I am afraid we are already invested in these Fox bumps though. A hard line could be routed, but not as easily.The thread inside the top of the can I've been told by someone who is guessing, is 5/16 x 1/32. It is an oddball thread. Neither of my local hydraulic hose shops could measure it. If I did this, I'd have to either thread on an extension line to the schrader permanently ( said extension line and fitting is only good to 300psi. Or, I could drill and tap said hole to something common that would accept a 3000psi braided brake line. Seems like a no brainer, but I'm not getting the impression it's a good idea. I wish I could upload a picture, I've tried several different file sizes and dimensions of a jpeg and it always gives me the "not valid file type" error.Thanks for the point about volume differences!
 
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84projectford

Senior Member
Sep 8, 2010
524
56
28
Phoenix Az
#15
Without the secondary cap in place you do risk blowing the needle out like i did. However i doubt it would be an issue for this guys use. When i blew mine out i had over 300psi in the bumps
maybe its the pressure your running but i see no reason a cap will stop that. the cap doesnt put any pressure on the valve core its self, all it does is keep stuff out of the schrader so you dont push crap into the bump or resi when you fill them. it adds no support to that pin or valve.
 

Scott F

.........................
Jan 3, 2005
1,914
7
38
Tucson (was Anaheim)
#16
I just called FOX and they confirmed that the thread is 5/16-32 ORB. The OR is O-Ring and I think the B is Block.

1/8 NPT takes a .339" #R drill bit. You should be able to drill and tap the existing hole if there is enough material around the hole.
 
Feb 7, 2017
6
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#17
Scott thanks for that very helpful info. I googled and there is a 5/16x32 ORB (which means o ring boss) to npt adapters that could easily have hydro lines made from. At the other end I'd just go in reverse and have the original schrader on the end, all using the smallest ID line so as not to add too much additional volume. So the question remains, will this bump actually spike a pressure sufficient to burst a 3000 psi steel braided hydraulic line? I'm not sure there is going to be an answer to that question with out experimenting. If anyone has heard of someone doing this, please send them over to comment!
 

Motiracer38

Super Senior Member
Feb 14, 2006
3,396
27
48
Santa Clarita
#19
It could reach an infinite pressure, that's called hydrolocking and usually it just rips the bump apart. On my 4in stroke bumps I fill to the top and pull 10cc out when it's collapsed all the way. Mine are an old design with a mix of parts in them so the standard 175cc fill doesn't work so well. Boyles Law says that P1*V1=P2*V2. P1 is typically 200psi, V2 is the 10cc that I take out when fully collapsed, V1 would be the displaced volume of a 1.25 rod stroked 4in, converted to metric to make it easy which , plus the 10cc I leave out at the end which equals 79.2cc. Plug them into the equation, solcve for P2, ignore any influence from thermal expansion and assume your oil has no air emulsified into it, my bumps only reach 1784 PSI.

Solving again for only taking out 5cc of oil, the result is 3568cc which is where you would get a bit nervous using 3kpsi working hose.

Math, good for something.
 

84prerunner

2:AM Fabrication
Feb 7, 2008
21,418
32
48
Covina CA
#20
It could reach an infinite pressure, that's called hydrolocking and usually it just rips the bump apart. On my 4in stroke bumps I fill to the top and pull 10cc out when it's collapsed all the way. Mine are an old design with a mix of parts in them so the standard 175cc fill doesn't work so well. Boyles Law says that P1*V1=P2*V2. P1 is typically 200psi, V2 is the 10cc that I take out when fully collapsed, V1 would be the displaced volume of a 1.25 rod stroked 4in, converted to metric to make it easy which , plus the 10cc I leave out at the end which equals 79.2cc. Plug them into the equation, solcve for P2, ignore any influence from thermal expansion and assume your oil has no air emulsified into it, my bumps only reach 1784 PSI. Solving again for only taking out 5cc of oil, the result is 3568cc which is where you would get a bit nervous using 3kpsi working hose. Math, good for something.
That is highly inaccurate for this application, however that does five a baseline. That is only considering the nitrogen pressure and excluding the force created by the shims/valving.
 

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