First off excuse the ignorance, but I got think about applying the same knowledge and approach in shortening the on/off pin some do with there pneumag. I think the only topic of shortening the RT on/off pin from the standard .750 down to ~.730 for a more reactive valve with trigger pull have all been associated with a xvalve or RTpro valve. For those knowledgable and familiar with the subject, why haven't I heard anyone approaching this with a minimag/classic valve's on/off assembly? Can you shorten the pin length, by gradually filing it down, on a classic valve or minimag valve's on/off pin? Is it possible to use the RT on/off pin as some do in the minimag/classic valve and shorten that assemblies pin, therefore finding a sweet spot with a increased reactive trigger? Again, I'm sorry if this is a dumb question. However, I thought I would ask where I know someone would know the answer, and/or know how to explain if I was lost understanding a simple concept.
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I don't know about the technical aspects of this question, but I will say that I picked up an emag RT on/off with a .712 pin and dropped it in a classic valve... didn't fire.Originally posted by barkingspider View Post
Then I bumped up to a .750 and have had excellent satisfaction. I haven't tried filing it down at all though. If I had a spare rod, I might try it and let you know how it went! -
Your question is a good one.
Reactivity is a function of several factors, one of the most important of which (and arguably THE most important) is force differential between the top and bottom of the pin.
The classic valve is a (quasi) pre-regged valve, so the pressure acting on the pin top is the valve's operating pressure of ~ 450-470 psi (in case of L10 bolt).
In the classic valve, this amounts to about 5 lbs top force. The pin is single diameter, so pull force is relatively high. Good luck with reactivity there.
The RT-style valves, on the other hand, are post-regged, so pressure acting on the pin top is whatever the tank is outputting that day. If it is 850 psi you now have about 9.6 lbs acting on the top.
To add to the mix, the pin in the RT has two diameters which create an additional force differential, so that pull force is roughly half that of the single diameter classic on/off.
When the valve recharges, you have a lot of force (close to 10 lbs) acting to push the pin down, and the trigger forward. That, coupled with a lighter trigger pull introduces a meaningful differential, which translates to speed. The greater this differential, the more likely you are to hit a sweet spot and have the RT effect, and the higher the cyclic rate will be. Increasing input pressure increases your effective rt bandwidth AND rt cyclic rate. Shortening the pin increases the rt bandwidth.
Pin length is part of what effectively times the valve (though most people don't think of a mag valve being timed). Effective pin length is inversely proportional to rt bandwidth. Too much effective pin length and the sweet spot will be impossible to find (and may not even exist) and you will move toward starvation. Too little length and the sweet spot will be impossible to avoid and you will move toward runaway.
Shortening the pin decreases the time between sealing off the dump chamber and releasing the sear, which decreases the travel necessary to get things going again, and thus increases the likelihood of finding the 'sweet spot'.
Again, there are several factors at work here, all balanced, all working together, to make the rt effect a reality.
To your purpose, the classic valve recharges more slowly and with less force, making it impossible to recharge as quickly, and nigh impossible to cycle in any remotely 'reactive' way.
The good news, however, is that you can get an RT on/off, slap it in and cut your trigger pull in half.
Get a shorter pin (Tuna sells all manner of lengths) and you can increase responsiveness to a pretty decent degree.
In super ultra rare extreme cases, at least according to legend, if you are impossibly lucky and sacrifice just the right maiden in just the right volcano, you can get a slight bit of reactivity out of the classic in this manner.
But don't count on it.
Even the RT-style valves usually need some help to get trigger bounce.
Classic valves need radical invasive miraculous intervention.
It isn't that people haven't tried to improve the classic valve (they have); it's just that you are fighting an uphill battle, when you could simply get an RT-style valve that was built (whether deliberately or incidentally) to run that way.
Hope that helps.Comment
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i've tested this, but only with .750, .745 and .740 pins. it will not affect "reactivity"; the classic valves just don't do that. i'll have to look for my data, but i seem to recall it not really making much of a difference. up to a point i'm sure it will cease to operate. the main thing is the lighter trigger pull.Comment
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add to all of that^^^...
On a single slow pull, a shorter classic on/off pin should break with the same feel as a longer one. The main difference will be felt when rapid firing. With a shorter pin, your finger won't have to pull as far against the on/off, or let off as far for a recharge which would help with chuffing. It's still easier to trim an RT on/off where you want it, with a lighter take-up.Comment
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Thank you all! I think I'm a little clearer on the concept, and appreciate you all for sharing your wisdom.Comment
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I thought I remembered reading at some point someone (Tuna maybe?) mentioning the ideal length pin for an RT on/off in a classic valve, and I thought it was shorter than .750, I'm guessing to both reduce short stroking and shoot down when rapid firing on a classic with this setup. Anyone remember what that magic length is?Comment
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.750 allows for manufacturing tolerances and some overlap in the function of the on/off against the release of the sear. "Finger tight" on the field strip screw easily varies that height 0.010 from person to person. If you are consistent in your assembly, you can shorten up any one setup right up to the edge of operation. That puts extra wear on the tip of the sear and the edge of the bolt. If you consider those parts consumable, the wear is not so bad. However, you will have a hard time ever wearing out a sear and bolt on a classic that are maintained with a good spring and a .750 pin.Originally posted by Chrome View PostComment
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Does anyone know the ideal length for a Classic RT valve to increase the Sweet Spot? I have a .750 pin in there now and there is almost no sweet spot at all even with 1050psi input pressure. Trigger seems to be the correct distance from the rod when aired up, but no luck with the RT sweet spot. (LVL 7 bolt, stock trigger/frame)Comment
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Go down to .740 but not too much more or you risk wearing out your bolt and sear. The shorter the pin from stock, the more you risk.Originally posted by BassdudeBTB View PostComment
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Just curious because I have been tempted to replace my stock L7 on/off pins with RT pins to "improve" trigger pull on my Classic valves - will replacing the pins with same length RT on/off pins cause any difference in bolt/sear wear?
What is the standard factory length on the Classic on/off pins?Comment
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Standard size is .750. You can't just change the pins. You must change the whole on/off.Comment
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what frame are you using? if it's a benchmark frame, it'll be much harder to sweet-spot. also, reactivity depends on the friction in your on/off o-rings, in addition to input pressure and pin length. the looser the fit, the easier it is to get it to bounce. up to a point of course, beyond which it will leak.Originally posted by BassdudeBTB View Post
on a tangent, have you tried just walking the trigger instead of getting it to bounce? i have an rt classic with a benchmark frame that doesn't bounce at all at 975 psi, but i can walk it like an electro lol.
you can use an rt on/off in a classic valve; as posted in this thread it will give you a lighter trigger pull.Originally posted by JKR View PostComment
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Thanks Tunaman. I thought to myself how can I achieve this effect without grinding the pin down... (Since I don't have another at the moment)
So I experimented a bit and made 0.004" & 0.009" shims with a leather hole puncher from thin plastic laminator sheets and put them in my on/off and BAM! Off it went. It was hard not to shoot full auto.
From 0" to 0.015" is the full range I found for the trigger to work. (full auto to not shooting at all.)
With just the 0.004" plastic shim it has a large sweetspot and can easily rattle off bursts of 2 to sometimes even 8 rounds! I have to practice with it a bit. But I played a few games with it last Sunday without any shims and left my on/off a quarter turn loose and it shot well. It seems shimming the on/off is the way to go for now since it is easily reversible.
I must note that over-shimming won't allow the valve to slide back onto the body.
Cyco-Dude - I have a stock frame & trigger. I'm not sure how to change the friction of my on/off o-rings predictably besides maybe different lubricants... I keep my mag well lubed
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well, it's usually a bit stiff with new o-rings, and just gets better over time as they wear in. some o-rings are tighter than others though, and you can test the fit by simply pressing the o-ring onto the fat end of the on/off pin.Originally posted by BassdudeBTB View PostI have a stock frame & trigger. I'm not sure how to change the friction of my on/off o-rings predictably besides maybe different lubricants... I keep my mag well lubedComment
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