diameter of on/off pin in the ULT on/off.......

[the electrician]

does anybody with a ULT have a set of calipers?
somebody? anybody? that could measure the diameter of the head and the skinny side of the on/off pin in a ULT on/off?

I would really apprectiate it if anybody could take the time and measure it for me and post or PM me.

thank you very much.

[redlaser666]

Here you go,
Head of pin: .0720"
Skinny side: .0325"
Pin support: .1250"
Shims: .0050"

Hope that helps!

[the electrician]

holy crap thank you redlaser666!

wow. that is small.

as a matter of fact the head is the same dia. that was the dia of the skinny part of the RT on/off.

so, let's say it works good on 800 psi?
so that's only 3.25 lbs of force for the top part of the pin, and only .66 lbs for the skinny part. that is enough to return the trigger? doesn't seem like enough.

no wonder they say it is not meant for a standard mag.
the skinny part would only produce .37 lbs of force and only 1.83 lbs on the top with an operating pressure of 450 psi.

so why was I having problems with the RT on/off in a standard valve? it was producing 4.83 lbs of force on the top and more importantly 1.83 lbs on the skinny side.

perhaps I should replace the worn sear and try it again.
and I really should try and get an accurate operating pressure reading.

I should, theoretically, be able to take an RT on/off and modify it to make a type of ULT on/off for the standard valve. nothing too fancy, but a lighter trigger that will not lose recharge rate, and will return properly so as not to cause excessive sear or bolt wear.

to the lab!

thanks again redlaser!

[redlaser666]

No problem, Im glad I could help!

[the electrician]

a new sear helped the problem of the modified rt on/off not returning properly.

the other thing I noticed was if you shim the on/off too much, making the pin just seal, that this let's air through too soon and causes the bolt to not want to reset properly. at that point I backed off about .010" and it started working proerly again.
also, the quad seal o-ring seems to help with recharge, keeps it from chuffing or having drop-off shots.

makes me want to try and make a pin with a .116" top and a .053" to .043" skinny side.

.043" dia. at 450 psi will produce the same .66 lbs of force that 800 psi did with the ULT's .0325 dia.
that might be too reactive...

[BlackVCG]

You need to run your math again for the bottom area of the pin. It's not just the small diameter converted to an area and then multiplied by the pressure.

It's the difference of the two areas that gives you the "pressure area" where the pressure in the chambers acts upon. Basically draw two circles - one inside the other and then you want to find the area around the smaller circle and inside the large circle.

[the electrician]

well for a standard valve, when the pin is down, letting air through, the air is able to be around both sides of the large part of the pin right? doesn't this in effect "cancel out" that part of the pin as far as down force created by the pin?

or are you talking about the RT/X type valve body?

[athomas]

I think it works for both AIR valve and retro valve. When the pin is in "limbo", the force on the top and bottom of the larger section should cancel each other out leaving only the force pushing out on the small area (lower section) of the pin.

But, maybe I'm missing something too.

[the electrician]

well that's what I'm saying about the standard valve.
you say "limbo" but basically when the pin is pushed down all the way, (using an RT on/off in the standard valve) air is on the top and bottom of the large part of the pin.
this leaves nothing but the force of the small part of the pin.

well I measured my operating psi, its more like 500, not 450 or 400. this is with the lvl 10. I know it's using a bit more air with the lvl 10 than with the standard valve.

so what I'm guessin here is mostly just calculations:
I noticed I've been able to reduce the input psi into my sear actuator down to 50 psi when using a slightly modified RT on/off in the standard valve. it's a .375 bore actuator, so it's power factor is .11, 50 psi generates 5.5 lbs of force. the actuator is pushing on the sear right where the trigger rod and clevis was attached.

now 1lb of this force is directly accounted for by a return spring. that leaves 4.5 lbs to pull the trigger.
the bottom of the on/off pin (the skinny part) is .072" and is acted upon by 500 psi(not 450). this creates about 2 lbs of force. that leaves 2.5 lbs of force... to pull the sear off the bolt? that's just a guesstimation.

black VCG- please explain further the problem with my calculations, because I'm not gettin' it.

another question- what exactly is it about the ULT that doesn't get along with the standard valve? does it have problems returning the sear properly? or is it more of a recharge problem? the lower psi going through a smaller orfice.?

your help is greatly appreciated.

[athomas]

I used a retro on/off in an AIR valve quite successfully. That was before the level 10. It does lighten the pull a bit.

If the on/off top of the ULT is as small as redlaser666 says it is, then there could definately be recharge issues. The standard on/off has a larger opening and can only recharge the valve at a rate around 12 - 16 cps.

The area of the on/off top dictates the starting pressure to push down the pin but the area around the pin probably affects the flow as well. The standard pin is about .1" in diameter (based on 4lbs of force at ~400psi without actually measuring). That translates into a circumference of .314". This is the edge that opens to allow air flow. On the ULT the circumference is only .226", which is a 29% reduction in opening. Based on that, the ULT would probably experience some recharge issues.

electrician, if you are designing an on/off pin for the standard mag, make the bottom the same as the ULT but make the top larger to allow more flow.

A ram, eh? Maybe you are getting sticktion (FSDO syndrom) caused by the o-rings sticking to the walls of the ram and/or cylinder. This could cause the need for more pressure.

[the electrician]

so you've been using an RT on/off in a standard valve?
because that's what I'm doing now. definitely not for the purpose of reactivity, just for the dual diameter pin and the fact that the top of it is the same .116" to .117" as the standard valve pin is. these numbers are actual measured numbers. the standard on/off is .116" diameter and the RT on/off pin top is also the same size.
I measured my operating psi and it is actually 500 psi.

A standard valve with a lvl 10(yes that makes a difference) can cycle up to 18 bps with a modified on/off asembly and an input psi of 800. I think I can squeeze 20 bps out of it with a bit more tuning. it can already do 20 bps with a standard bolt and the modified on/off, but it will chop paint fairly easily.

you can't really make the bottom the same as the ult because at first the RT(or X) valve is getting 800+ psi through the on/off until the reg shuts off the flow. so if the ULT is .0325" on the bottom part, then to create the same force at 500 psi, a .042" bottom dia is needed for the pin. not that much larger. I would leave the top the same as it is in the standard valve and the regular RT on/off (.116").

I've been using the same QUAD o-ring that the e-mag uses and I've noticed that it helps with recharg rate.
your only pushing the pin in enough to use one of the inner seals inside the o-ring. this means when the pin is coming down, it opens to a large area of flow faster than it would when using a normal o-ring. that's what put me up to 18 bps from 16.

I modify the RT on/off by boring the top of it out to the same dia as the standard on/off valve body, .150" and I take the four holes around the outer top piece , up close to the edge of the brass, letting the air get through sooner. I also use an exremely friction o-ring in the middle of the on/off. I shaved the pin down to .720 and shimmed the on/off .040". this is with the quad o-ring. this combination recharges in about 25 msec. much faster than the 33 msec it was with the unmodified standard valve.

ram? I built an e-mag that uses an lpr to send lower psi air to a mini solenoid 3-way in the grip that is mounted to a valve actuator( kinda like a ram) that has been modified for this purpose. here's the thread:

http://www.automags.org/forums/showthread.php?s=&threadid=125891

no there's no stiction problem and no FSDO at all. I was able to lower the actuator operating psi from 80 to 50 psi because I started using the RT on/off.

by the way thanks for the reply, I've been wanting to discuss this before I procede further.

[BlackVCG]

From what I see, you took the area of the thin shaft of the on/off pin and made that your pressure area. This is incorrect because pressure never acts upon that surface. It acts upon the area of the bottom of the head of the pin.

To get that area you need to take the area of the head minus the area of the thin shaft area. That will give you the area you have static pressure acting on.

To get the overall force you have pushing down on the pin, it's the force on the top of the pin minus the force that acts on the bottom of the pin. It's called your resultant force.

This acts the same way in every Mag valve where you are using a stepped on/off pin.

Simply put, the ULT does not work well in the AIR valve because of the pressure with which the valve recharges the on/off.

[the electrician]

thanks for the reply balck vcg. much appreciated.

so you're saying that the resultant force will be different than the numbers I came up with for the small part of the pin? you say the pressure never acts upon this surface, but this is my thinking: the pressure on the top of the pin, is partly cancelled out by the same air pressure that is on the bottom side of the head of the pin. this leaves nothing but the surface area of the small part of the pin.

your suggested calculation

surface area of the head: .01075" (.117" dia used)

surface area of small part: .00407" (.072" dia used)

surface area of bottom of head: .00668"


force created at 500 psi:

head: 5.375 lbs

bottom of head: 3.340 lbs

resultant force: 2.035 lbs



my way of calculating

suface area of small part of pin: .00407" (.072" dia used)

force created at 500 psi:

small part of pin: 2.035 lbs

you can see why I use this method. it is a bit quicker.

I know that the psi is not actually "pushing" on the small part of the pin. but that's how much of the surface area of the head that is left after the cancellation of force occurs due to the same air psi being on the bottom side of the head.

so maybe this is all just a misunderstanding of what I understand about what's going on with the pin.

after the gun has fired and you let off the trigger, the pin goes down, and let's air through, de-pressurizing the passage between the reg and the pin. this opens the reg valve pin, letting whatever the input psi is, through to fill the dump chamber, and the little surface area of the on/off area. once the operating pressure is reached, the reg closes.

so in a classis valve, the the input psi has to go through the reg, and past the pin to get to the dump chamber and fill it.

in the RT,input psi goes through a passage up to the on/off pin, then is able to fill the chamber and the reg at the same time. when the operating psi(set by the reg) is reached, the reg pin closes off the passage to the on/off pin. this is why it recharges faster. is that correct?

to me it seems, that if you want the classic valve to recharge faster, you need to be able to 1)increase the input psi a bit, and 2)decrease the operating pressure a bit. not sure how to do the second one, but the first one, I'd say I'm going to give the classic valve 1000 psi instead of 800 psi and record the results. see if it increases the recharge rate.

so in the RT, when you go to pull the trigger. the "resultant force" is actually generated by the operating psi, not the input psi. only the initial down force on the pin is at input psi.

[BlackVCG]

Ahh... I see what you're doing. I just looked at your numbers wrong. My misunderstanding.

The ULT won't behave any different in a classic valve based on input pressure, because it gets regulated as it goes to the on/off. The whole design of the RT valve was to get rid of that and dump straight input pressure into the chamber.

[the electrician]

so were on the same page about the forces of the pin.
sometimes I don't explain myself very well.

I started thinking about the input psi and the operating psi, the speed at which the gun recharges, has a bit to do with the velocity of the air going through the gun to fill the chamber. higher pressure air has a higher velocity, for a given orfice size, to a certain extent. when I first researched solenoid valve designs, I noticed that the valves flow rate (scfm or whatever measurement you like)was higher when the input psi was higher.
because the reg is first inline with the classic valve, I know the flow will be getting reduced in velocity, faster than it does in an RT. but I think higher input psi can make a difference in recharge rate.

I have a tank that outputs 1000 psi fairly consistent. I'm going to see if it makes a difference in the recharge rate of the classic valve. it will be tested by recording the minimum needed msecs of time for full recharge at a 800 psi and 1000 psi.

the regular ULT will probably never work properly in a classic valve, they're just not designed to work together.

but what about the same type of set-up, only keep the top part of the pin a .116 diameter,reduce the bottom part of the pin to .0325 just like the ULT pin, use a standard RT on/off, modified to use the ULT pin support and modify the top to work in a classic valve. perhaps shorten the pin(like close to what was done in the e-mag) to .720" and use a quad o-ring to help with flow. of course use the shims to get it just right.

I think it's worth a try for all the classic valve users.
people who are just plain not going to spend the money on an X-valve. most of these type of people who own classic mags are quality, honorable players. they want to perhaps get back in the game, and a simple inexpensive drop in mod that would make the gun a bit easier to shoot, would spark interest and we would see more mags at the local feild. not electric spyder/clones.