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melon farmer
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567 Posts
Discussion Starter · #1 ·
For those of you who have taken apart their DHX Airs and are aware of the twin sleeve design of this shock... read on. If not, it is worth looking at this excellent post on the Turner forum about chaging the stock air sleeve on the DHX to an RP3 air sleeve:
http://forums.mtbr.com/showthread.php?t=182747

In short, the DHX Air has two air sleeves connected by a tiny hole at the top (body end) of the inner sleeve. See pics in thread above.

Given the location of the hole (about 1" from the top of the main chamber), I've been thinking that what happens is the main air chamber has the volume of the two sleeves combined until the shaft reaches the very last 1/2" or so of stroke, by which time the hole has been passed by the seal at the end of the shock shaft, and the main chamber volume is then reduced to just the inner of the two air sleeves. This would produce a shock that is linear for the most part of the stroke (because of the large volume of the two air sleeves combined, but ramps up at the end due to the decrease in volume when the second (outer) air can is effectively cut off from the first...

So... what I was planning on doing was blocking the hole with silastic or something removable (guess it make take a decent dab of silicone and very clean surfaces), and then drilling a similar sized hole further down the inside of the inner air sleeve. This way the shock will still have small bump sensitivity, but will ramp up nicely (like and RP3), when this hole is bypassed by the lower air seal on the shock shaft..

What do people think of this idea? The only issues I can think of are maybe altering the structural integrity of the inner air sleeve with the second hole, and maybe the problem of cleaning up the inner surface of the new, lower air hole so that it doesnt damage the lower air seal..

Before I do this possibly foolish mod, I'm keen to hear other people's opinions.. is my theory about the two chambers flawed? If the lower seal never passes this hole, then the whole idea may be stoopid..

thanks and apologies for the long winded post.

Attached photo is from MK_'s post. Hope this is OK with you MK_..
 

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I would think the pressure generated under compression would push that mentioned material right out. I have heard of JB weld and solder used for other sealing applications but I think the pressure would still be too high. A shot from a tig welder would probably deform the aluminum sleeve ???.
 

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melon farmer
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567 Posts
Discussion Starter · #3 ·
Silastic = silicone sealant

Sorry should have mentioned this in first post. Yeah, I'm a bit uncertain about what to use to block the hole that could be removed easily if needed..

thanks for the feedback.
 

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No, that's not phonetic
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14,313 Posts
Don't do it. You're shock will get "stuck down" every single time the piston head passes your custom hole.

The RP3 uses a self-setting negative air chamber. Near full extension air is allowed to escape around the piston via a dimple in the air sleeve. Stuck down shocks become stuck because air escapes around the piston seals at a point in travel other than down at the dimple. Under normal operations, I don't think the piston ever passes the stock upper hole that allows air to move into the large outer volume sleeve. If you moved the hole down, pressurized air could escape from the outer air sleeve down under the piston head into the negative chamber, and your shock would not be able to extend fully again: it would be stuck down.
 

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melon farmer
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567 Posts
Discussion Starter · #5 ·
Ahhh damn it! Foiled again.

Thanks for the info Tscheezy. I'm guessing the DHX Air and RP3 work the same with respect to the self setting negative spring?

Back to the RP3 air can idea for me, then.
 
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