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Old 05-24-2010, 07:05 PM   #1 (permalink)
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Spring length question

I was trying to tune my 98 pump a while ago... I want to FVA all the way out(with it in it directs airflow back out the valve. I don't want that) but the velocity was ~350. So I cut the spring. I cut 2 coils, put it back together, rechronoed, and repeated. I ended up cutting somewhere between 14-20 coils before I stopped, and I still didn't get a lower velocity at all.

So there's my first question: that isn't normal is it? The spring had something like 60 coils to begin with. I'd think that by cutting 1/3 of the coils it wouldn't be as strong.

Here's my second question. I ended up cutting so much that the spring wasn't putting tension on the hammer with it all the way forward. I stretched it out a bit, but it ended up shrinking back down a bit. Will that affect performance with it being shorter? And would stretching it affect its strength?
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Old 05-24-2010, 07:28 PM   #2 (permalink)
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It's too late to do this, since you've already cut the length BUT...

Springs have a specific minimum length, when they are completely compressed and a specific maximum length when they are expressed.

Those values allow a spring to fit between the hammer and bolt when compressed and fill the available gap between when expressed.

The strength of the spring between those two values is comprised of how many coils it has and how hard it resists being coiled.

You can shorten the number of coils by cutting it, but not increase it.

The other option is to change the springs resistance, which is done with heat. Annealing (slow cooling) will soften the spring, Hardening (fast cooling) will strengthen it.


Quote:
I was trying to tune my 98 pump a while ago... I want to FVA all the way out(with it in it directs airflow back out the valve. I don't want that) but the velocity was ~350.
A Tippmann?
I should read this stuff before typing tech advice.
Of course it directs airflow back, it's a pneumatic reostat. It regulates velocity by wasting the excess.
Don't cut springs, use the velocity adjuster the way it was meant to function even if you don't "want" it that way. That's how it works.
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Old 05-24-2010, 07:36 PM   #3 (permalink)
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I can use it how its supposed to but I'll get better effeciency if I pull it out all the way.
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Old 05-25-2010, 04:03 PM   #4 (permalink)
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Quote:
Originally Posted by magmoormaster View Post
So there's my first question: that isn't normal is it? The spring had something like 60 coils to begin with. I'd think that by cutting 1/3 of the coils it wouldn't be as strong.

Will that affect performance with it being shorter? And would stretching it affect its strength?
Still looking for answers to these questions.
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Old 05-26-2010, 03:29 PM   #5 (permalink)
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Why not get a Tippmann 98 spring kit and use a lighter, but equivalent length, drive spring?
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Old 05-26-2010, 03:35 PM   #6 (permalink)
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Put a reg on it and turn down the pressure?
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Old 05-26-2010, 04:07 PM   #7 (permalink)
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Quote:
Originally Posted by idkfa View Post
Why not get a Tippmann 98 spring kit and use a lighter, but equivalent length, drive spring?
This is what I will likely end up doing, but it still doesn't answer the questions...
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Old 05-26-2010, 07:39 PM   #8 (permalink)
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1 spring kit
2 rva
3 reg

in that order

when you cut coils off a spring you actually increase the spring rate, ie making the spring stiffer.
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Old 05-27-2010, 02:36 AM   #9 (permalink)
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Have an RVA. Don't have a reg. Don't plan on it either. Its consistant already(+/-5 with budget paint).
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Old 05-28-2010, 10:54 AM   #10 (permalink)
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Ah. Get a stiffer valve spring or an LP tank then. Likely your gun was set up to run ~350-400 psi and running it at 850 psi is giving you too much pressure.


Edit: Sorry, blanked on the fact that you're running a Tippmann 98 and not a 98 Sniper. Valve spring advice stands though.
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