Why do people adjust velocity through their lpr?

[m20power]

This weekend I was reffing and I saw a kid with a brand new timmy. Hes been playing a few months and had started out with an a-5 but his parents have cash so he upgraded.
We were at the chrono and he adjusted the velocity by changing the lpr preassure. I asked him why he was doing that and he said that its what people at the shop told him to do.

To me it makes more sense to adjust the gun through the reg. It seems like if you messed up your reg preassure and started fooling with the lpr you could overpreassuise the selenoid and blow it. Also if your reg slips you may end up adjusting your lpr too low and it would give you inconsistant shots.

Am I way off base?

Thanks for any comments.
No thanks for any flaming for my lack of spelling.

[Eatem Alive]

i think he probably misunderstood the guy at the store. i never adjusted my velocity with the lpr.

[vonort]

According to the Freestyles manual thats the way they tell you to adjust it also.

[Evil Bob]

If you're using a preset HPA system, the LPR is the place you need to look at for changing velocity. Lazy airsmiths wont even bother asking what kind of HPA system you're using, they'll just tell you to play with the LPR.

There are three ways to control velocity on a poppet valve itself:

1) change the PSI going into the valve (either LPR or HPA reg)
2) change the spring on the hammer hitting the valve (stronger spring ='s longer open time)
3) change the weight on the hammer.

Beyond the poppet valve, there are a few more ways:

1) change the air passage size (vm68 used a hex screw in the bolt face)
2) change the effective barrel length
3) change the barrel diameter

By far the easiest of all the above is to adjust the external air source instead of messing around with the mechanical aspects of the marker.

-Evil Bob

[Python14]

Adjusting the LPR does the same thing that adjusting the Velocity adjuster on a cocker or spyder. It increases or decreases the pressure with which the hammer strikes the valve pin.

I usually sweet spot the LPR, then adjust with the HPR.

[magman007]

python does it the correct way. the lpr should baisically be set it and forget it. Most lpr's are self compensating anyways.

depending on what style timmy he has, he should set the pressure at 75(new) and i believe 90(old) and leave it there

[Steelrat]

On some guns you have to adjust the lpr to change velocity, like the cyborg.

[pbjosh]

I usually sweet spot the LPR, then adjust with the HPR.

Doncha mean "sweet spot the HPR then adjust the LPR"

But what you are saying is right on. To many people are told to adjust the LPR to some set pressure (90psi), then adjust the HPR to match. But since your operating a poppet valve, the valves' sweet spot is the important factor. This will allow the gun to fire at the highest velocity with the smallest amount of hammer input.

So you could run the ram at a lower pressure and still get the same velocity. A lower operating pressure for the ram means a smoother cycling gun and less pressure on the ball also.

Josh

[O_o]

According to the Freestyles manual thats the way they tell you to adjust it also.

No, the LPR has very little effect on the FPS on the freestyle. You change your LPR when changing to HPR to balance out the regs for the best settings. So when you turn your HPR up for more FPS, you should also turn up the LPR accordingly.



For timmies, I set my LPR to where it doesn't cause any FSDO or shootdown and chrono with my HPR from there. Same goes with similar guns like bushies, cyborgs, vikings, etc.

[kurama]

I usually make smaller velocity changes on the LPR like if I want to go down about 10fps. Otherwise, I do it on the tank or HPR.

[tony3]

You are correct he is doing it completely wrong. Adjust your lpr to 60-85 psi, which is what the guage on your VA reads, then adjust your velocity through the hpr.

[Blazestorm]

Freestyles should be turned up till it leaks then back off. Adjust HPR for velocity.

All cockers/timmies etc. have the regs sweet-spotted and the springs or LPR adjusted to the pressure to get your velocity.

Or if you want to reduce kick you can also increase the dwell + lower the LPR more. (Timmies + Ego's)

[pbjosh]

Blazey!

Total thread steal here but-

Hows it going? We have a pump only day coming up Sunday at Westside! You wanna come out for it?

email me-


Back to the thread-

ALL poppet guns (not spoolers, like the FS) will have a sweetspot. That is figured out by setting the Supply Air (HPR) to the point the valve will release the largest amount of energy with the smallest effort. The LPR just sets the strength of the ram's cycle. If you bump it up, you get more velocity, just like you did on your old Spyder (I know you had one.)

To optimize ANY poppet valved gun, you need to sweetspot the HPR. Then do the balance with the LPR. It might not be the way you were told to do it, but it is the best way to do it.

Josh

[Blazestorm]

Westside? Pump Only?

What are you talking aboot!?

:)

BTW I was taught this awesome knowledge by Josh, I never really thought about it until he brought it up, all guns really should be done that way.

[CoolHand]

Adjusting the LPR does the same thing that adjusting the Velocity adjuster on a cocker or spyder. It increases or decreases the pressure with which the hammer strikes the valve pin.

I usually sweet spot the LPR, then adjust with the HPR.

I don't know what kind of 'cocker you own, but all of them I have ever seen or heard about use springs to drive the hammer.

All the LPR on a 'cocker does, is control the force applied to the bolt, not the hammer. You want just enough umpfff to compress the main spring, and not much more, to keep the possibility of chopping down.

And whoever said that all poppet type markers have a sweetspot is right. BUT, the sweetspot is not always the best place to run the marker. It is the most efficient place to run it, but if you have ever sweetspotted an LPR equipped Imp, you will see that by the time you get to the sweetspot, you are having to hit the valve so hard, that the marker kicks like a mule.

This is most likely why BL says to set the LPR at Xpsi, and then run the HPR up to velocity. They have found that their recommended set points give the best compromise between shots per fill, kick, and shootdown.