Dangerous Information On Charging Shocks with air. - Page 2 - Ducati.ms - The Ultimate Ducati Forum
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post #11 of 21 (permalink) Old Jun 14th, 2018, 4:24 am
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I'm no engineer, although I did once build half a Thunderbird 2 out of Lego.
Which half?

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post #12 of 21 (permalink) Old Jun 14th, 2018, 4:48 am
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I'm guessing that the compression explosion issue does not apply to air assist forks simply because the fork seals would give out long before the pressure required for combustion is reached. With the smaller volume, sealed canister reservoir of a rear shock, much higher pressure is easily reached.
However, I'm no engineer, although I did once build half a Thunderbird 2 out of Lego.
No explosions because there’s just nowhere near the amount of compression to heat the air fuel/oil mix that is highly unlikely to exist in a fork tube. And on top of that the ratio of air fuel/oil has to be correct and the fuel/oil atomised to a small enough partical to begin burning.
Thunderbird 2 was my fave as well. Sadly my model burnt to a crisp when I tried (in vain) to attach a couple of sky rockets to see if it would fly.
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post #13 of 21 (permalink) Old Jun 14th, 2018, 8:05 am
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Whew ! What a relief. The thought of rear shock shrapnel piercing my privates was keeping me awake at night.
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post #14 of 21 (permalink) Old Jun 14th, 2018, 8:35 am
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Which half?
The other one.

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post #15 of 21 (permalink) Old Jun 14th, 2018, 8:48 am
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Whew ! What a relief. The thought of rear shock shrapnel piercing my privates was keeping me awake at night.
you worry to much
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post #16 of 21 (permalink) Old Sep 17th, 2018, 10:24 pm
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Not my first choice, but air has been used as a backup by others from what I've read. The guys on the DRZ forum are reporting using oxygen for their frequent valving/shim changes. I have not heard about any explosions with motorcycle shock bladders.

Is not air already 78% Nitrogen and 21% oxygen? Makes sense that performance wise, it will do backup but not ideal.

Also, if you squeeze air into a tighter space, the number of oxygen molecules remains the same so the concentration is same relative to the other elements in the confined bladder. I don't think this would increase the risk of explosion either.

I'm curious about the temperature of the shock oil under working load. I would think it would need to vaporize to become explosive.

If the bladder leaks, nitrogen or air, then you will have air bubbles in your shock oil. Now, that would be dangerous while riding?
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post #17 of 21 (permalink) Old Sep 22nd, 2018, 2:09 am
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I'm one of the guys that frequently use air in my shock after making a reshim. If succesfull I take the shock to the shop and replace the air (from a mountainbike shock pump) with nitrogen. After three times inflating/deflating I hope most of the the moisture is out.....

Since my shock is mounted between the exhausts it will heat up anyways. Last weekend I charged the shock with air up to 145 psi and after a test drive (while stinking hot) it reached close to 200 psi.

While this is a huge pressure increase, it's not in a dangerous territory.

Anyways, for long term usage I would suggest just using nitrogen, but no immediate dangers exists from using air.

Michel

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post #18 of 21 (permalink) Old Jun 12th, 2019, 3:59 pm
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Hi,
Just had the ohlins rear shock absorber oil seal fail on my 750s. Am more than happy to strip and replace but need to know if the gas can be left in the reservior while the unit is apart with no oil in it. Will the bladder fail, and if it does can it be replaced? Am struggling to find a definitive answer. If the shock might be irrepairably damaged i will have to go for a service repair but £120 seems steep for what appears to be a straight forward strip down and seal replace.
Should I risk it??
Dave
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post #19 of 21 (permalink) Old Jun 12th, 2019, 7:55 pm
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No, the gas needs to be bled out before you take the shock apart.
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post #20 of 21 (permalink) Old Jun 12th, 2019, 10:26 pm
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Call me whatever you wish to, but I'm not keen on using an accelerant in a pressure vessel on my motorcycle. Oxygen is an accelerant. A very efficient one at that.

Nitrogen is inert. It can be used to extinguish a fire, that is how efficient it is. Oxygen is a highly active accelerant ... it is used to excite a fire. Which is why it is used with acetylene because O2 increases the BTU ("heat") of the fire by leaps and bounds.

If you biff, and the fuel in your fuel system ignites while your bike is on it's side burning away on the street, when that reservoir with high pressure O2 ruptures there's going to be some serious fireworks. If you're unconscious and first responders approach the bike without being provided with that crucial bit of information (pressurized O2 in a sealed vessel) and the reservoir ruptures ... which is not uncommon .. you may have someone's death on your conscience for the rest of your life ... "Maybe not today, maybe not tomorrow, but soon, and forever".

I clearly remember my mother often telling me when I was young ... "if everyone were jumping off of a cliff, would you as well?". I say that in response to the idea that ~big shot teams use O2 to pressurize their suspension systems, so I'm going to use it too~

I mean, y'all do what you want.

I'm not tellin', I'm just sayin'.


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