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Old 08-09-2014, 04:38 PM #1
Pakistani
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What does spring tension and dwell effect?

Hey guys, quick question-
the whole inline poppet/automag style platform is new for me despite having years of experience teching guns. My question is, what exactly do the different spring lengths(boss bolt) and dwell settings effect on the axe?

For example, on a DM, higher dwell = lower LPR and smoother shot overall.
on an Axe, it doesn't quite seem to behave the same way. Does running a longer spring ultimately make the gun softer on paint? is that the only purpose?
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Old 08-09-2014, 07:39 PM #2
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irony can explain all of this better than I can, but Axes are pressure-controlled poppets (more specifically, decreasing-force poppets), not inline poppets (Bob Long Victory) and not Automags (spool valve).

A longer bolt spring provides more rearward force on the bolt, which opposes the operating pressure pushing the bolt forward. So yes, a stiffer spring should make the gun softer on paint.

Dwell on a DM shouldn't affect LPR pressure directly. A high dwell would allow the bolt to sit in the forward position longer, so it would more completely vent the HP air behind it. Then you could adjust the LPR down a little.

High dwell on an Axe can help to lower its OP a little bit too, but overdwelling can also make the gun louder. A better way to lower OP is to increase the poppet lift (unscrewing the back cap).
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Old 08-09-2014, 07:52 PM #3
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Quote:
Originally Posted by tyronejk View Post
irony can explain all of this better than I can, but Axes are pressure-controlled poppets (more specifically, decreasing-force poppets), not inline poppets (Bob Long Victory) and not Automags (spool valve).

A longer bolt spring provides more rearward force on the bolt, which opposes the operating pressure pushing the bolt forward. So yes, a stiffer spring should make the gun softer on paint.

Dwell on a DM shouldn't affect LPR pressure directly. A high dwell would allow the bolt to sit in the forward position longer, so it would more completely vent the HP air behind it. Then you could adjust the LPR down a little.

High dwell on an Axe can help to lower its OP a little bit too, but overdwelling can also make the gun louder. A better way to lower OP is to increase the poppet lift (unscrewing the back cap).
that was what i was saying when i mentioned DM's. running your dwell higher will allow you to lower LPR a little bit and get the same FPS.
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Old 08-09-2014, 08:21 PM #4
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Quote:
Originally Posted by Pakistani View Post
that was what i was saying when i mentioned DM's. running your dwell higher will allow you to lower LPR a little bit and get the same FPS.
Yeah, but from your post, other readers might try bumping up their dwell and immediately lowering their LPR. I pointed it out for future reference and clarity.
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Old 08-11-2014, 09:46 PM #5
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Longer springs return the bolt quicker and more reliable in a tight setup. Normally for every size spring you go up you increase the dwell .5ms
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Old 08-12-2014, 11:01 AM #6
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Quote:
Originally Posted by Pakistani View Post
Hey guys, quick question-
the whole inline poppet/automag style platform is new for me despite having years of experience teching guns. My question is, what exactly do the different spring lengths(boss bolt) and dwell settings effect on the axe?

For example, on a DM, higher dwell = lower LPR and smoother shot overall.
on an Axe, it doesn't quite seem to behave the same way. Does running a longer spring ultimately make the gun softer on paint? is that the only purpose?
I tried to give an overview of the operations in this thread: [url]http://www.pbnation.com/showthread.php?t=4051197[/ur]

One of the links I provided in the dwell section of that thread is this explanation from Simon: http://www.pbnation.com/showthread.php?t=2520431


Running a longer spring is just adding more preload. Without knowing the exact spring rate it's kind of hard to say exactly how much the force curve is modified, but suffice to say that longer springs usually result in a lower bolt SPEED. The weird part is that the dwell on axes directly affects the poppet actuation. (An interesting tidbit is that the check valve is extremely critical for the bolt return. If it weren't for that, the bolt would be prone to oscillation at the end of the stroke in overdwelled applications.)

I'll try to simplify it a little... on spools, the valve is coupled directly to the bolt position. Many use a secondary valve as a stop-loss for efficiency. On the axe, the bolt and valve are connected via the solenoid. The timing of the poppet gains some forgiveness with the back pressure dump down the bolt guide, which helps open the poppet. Using a shorter spring, your are advancing the timing of the bolt and poppet. The problem is that the poppet bleed ratio is fixed and if you don't get the dwell perfect, then you'll see very erratic velocity (I believe it's poppet oscillations or incomplete actuation). You can compensate by reducing the friction of the poppet (polish, xring and slick lube). The problem I have with this is that as the day goes on it tends to be finicky.

Using a stock or medium spring helps embed some forgiveness in the timing. Lighter bolts tend to have a higher bolt speed (according to Simon's research). Part of the reason Ryan/ Lurker (and I) started working on a poppet was to be more responsive to advanced timing. We found that the overall timing envelope of the axe is pretty dang small. His bolt has an undercut which advances the timing further than most, so the bolt speed is pretty important. That's why Lurker bolts need to be run with the stock spring and some amount of friction. Basically, you slow the bolt back down to the tuning window and it works well.


Sorry, I kinda jumped around a bit but the dynamic is pretty complicated. Also, I'd consider the automag a spool most akin to the etha and crossover.
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