Question about Belleville washers in regulators.

[happymecanic]

Can you measure the overall height of the washers you have?  I can't accurately find a washer arrangement without knowing that measurement. Also by 3000/850 do you mean a reg that adjusts from 850 to 3000 PSI or do you want it fixed at 850?

15 stacked spring washers like so:  )()()()()()()()  , measures 0.430''. This would give me about 0.020'' of preload.

3000 psi is the max fill pressure in my rifle's tank, 850-900 psi is the fixed, non-adjustable regulated pressure I'd like to get. This regulator is not originally meant to be adjustable. If that could be relatively easy to re-design the reg to be adjustable that would be nice, since I have to make a new body anyway. Thanks for the help Tom, very appreciated!

Surely we can come up with a better design than they have done.

What is the od and id of the small end of piston? It needs to be plugged with ball or wafer and then the shaft cross drilled.

Then the hp end of body needs to be designed to allow for existing oring seal to function on piston but only allow hp air to enter through the center of an adjustable plug.

I can draw this out but it might be a couple days.

Dave

Thanks a lot for the help Dave! You have the dimensions you need in my drawing, hope it's clear enough . Here's another pic of the internals if that can help:

[rsterne]

I have never built a "knife edge seat" style regulator that is fed from the side.... but if I was going to, I would make the diameter of the knife edge on the end of the piston the same diameter as the small end (shaft) of the piston, like the Lane Mk.9's.... That should eliminate and change in the output pressure as the tank pressure drops.... JMO....

Bob

[sb327]

I have done an initial mark up of your sketch to throw out some changes that need to be made to get this to a more conventional reg design.

Also, CS had a question that you need to answer.

Do you have the a lathe available for this?

Dave

[sb327]

Also, if Bob and CS could chime in on the proposed changes, it would be appreciated.

I’m sure I’ve probably missed something.

Thanks gents,
Dave

[rsterne]

Your changes would probably work, but I would recommend doing this....



Simply move the knife edge out to the full diameter by boring the taper out larger, and then adjust the seat in further.... This should eliminate any pressure change as the tank empties.... and no new parts required....

Bob

[sb327]

What does changing diameter of sealing surface change?

Dave

[rsterne]

The change in output pressure when you change input pressure is BECAUSE the sealing surface is smaller than the shaft of the piston, which is where it seals into the reg. body.... I explained that in Reply #4.... If the seat OD and the O-ring ID is the same (which it would be if there was no step in the end of the piston), then there would be nowhere on the end of the piston shaft for the HPA to push on when the reg. is seated.... Therefore, it wouldn't matter what the input pressure was, the setpoint would remain constant.... That is how the Lane Mk.9 regs. work....

Bob

[sb327]

I understand that dynamic. Do not refute it works. But it only has that dynamic AFTER the piston is seated. Not WHILE reg is cycling or in other words REGULATING.

Again, I’m not saying it doesn’t work, just haven’t messed with the Lane style.

And I definitely agree it would be an easier change than I laid out. Would definitely be worth trying before making a bunch of new parts.

Dave

[rsterne]

While there may be a TINY time lag during the cycling of the reg., once the seat is open the pressure between the end of the stem and the seat will be nearly the same as that inside the stem, and on the regulated side of the piston.... If you add up all the plus and minus forces, you will find that if that pressure is indeed equal, there would be no net force on the piston.... Regulators only open a very small distance, and the chamber in the regulator around the stem must fill through the small vent hole in the side of the regulator, and if the stem lifts more than a small distance, the primary pressure drop will be across the vent hole.... The area under the knife edge seat (for a 0.196" diameter) would equal the area of a 1/16" vent hole (0.003 sq.in.) when open only 0.005".... After that, there would be a greater pressure drop across the vent hole than across the regulator seat....

As I said previously, I have never had a Lane regulator, but they do work, quite well in fact, and that is the way they are built.... I would think there is probably a small difference in the output pressure as the tank pressure falls.... but in practice it does not appear to be any worse than a regulator such as a Ninja which fills through a tiny hole in the end.... For sure there is a difference in the force on the piston due to changing pressure in the tank with that design.... If the hole is 1mm (0.040"), the area is 0.00126 sq.in. and the force would be 3.8 lbs. at 3000 psi and only 1.1 lbs. at 850 psi.... That is a change of 2.7 lbs.... The effective piston area (big - small) on a Ninja is 0.1577 sq.in., so the closing force on the piston (that must be balanced by the Bellevilles) is (0.1577 x 850) = 134 lbs. at 850 psi.... That means a pressure swing of (2.7 / 134) = 2.0%, that you can do nothing about....

Bob

[sb327]

Thanks for that Bob. I was not taking into account the pressure drop at the side entrance.

Dave

[CableStop]

Wasn't he also experiencing o-ring extrusion because the regulator housing was too small?  You could try switching to more durable o-rings but that may just be a bandaid.  If you need to make a new housing anyway it opens up a lot more design options, I don't know if you could modify it to be adjustable using the stock Delrin piece.  I had been envisioning a design like Dave posted but Bob definitely has a good idea, especially if you were keeping the stock housing it would need much less fabrication. 

[happymecanic]

Wasn't he also experiencing o-ring extrusion because the regulator housing was too small?  You could try switching to more durable o-rings but that may just be a bandaid.  If you need to make a new housing anyway it opens up a lot more design options, I don't know if you could modify it to be adjustable using the stock Delrin piece.  I had been envisioning a design like Dave posted but Bob definitely has a good idea, especially if you were keeping the stock housing it would need much less fabrication.

I actually enjoy machining airgun parts, it's half of the fun! I also find Bob's idea the easiest to start with, should come up with a prototype spool and reg body real soon. I have some free time ahead this week-end, and some 304 SS available. Let the chips fly!

[PikeP]

Hmm, not sure why they put a step into the piston as stated by others...remove the step in your next iteration without question...as that just causes variation on the high pressure side during pressure swings as already noted by others.

If they did that by design, I can only imagine where else they burgered things up. Sheesh.

[happymecanic]

I have done an initial mark up of your sketch to throw out some changes that need to be made to get this to a more conventional reg design.

Also, CS had a question that you need to answer.

Do you have the a lathe available for this?

Dave

I may have missed that question???

Yes I do! It's a King Industrial KC1022-ML (Canadian model), a clone of the Grizzly G0602.

I'm finishing my coffee and I'll start the spool.

Good day all

Francois

[sb327]

Great!

You can make ANY type of reg you want.

Odd coincidence, the first reg I designed and made was for a Listone Victor. They had a large check valve where the reg should be.

Dave

[happymecanic]

Hmm, not sure why they put a step into the piston as stated by others...remove the step in your next iteration without question...as that just causes variation on the high pressure side during pressure swings as already noted by others.

If they did that by design, I can only imagine where else they burgered things up. Sheesh.

LOL! You don't wanna know .

I already have quite a few hours of repair work in that rifle, but so far it's worth it as it doesn't cost me much money to improve it, and it gives good results. I also like to see it as a learning platform in PCPs for me, as it was my very first PCP airgun.

Cheers!

[CableStop]

I think Dave might have meant me asking about overall height, I just divided the total height of the stack by 15 given that they were all evenly arranged in your answer. That got me 0.0286" which when you subtract the 0.0197" thickness leaves 0.009" of deflection per washer.  Using that info it seems like your washers should take 112 lb of force to deflect completely.  The actual arrangement depends on how much space you end up with in your final design and how much travel you want in the adjuster.  I'm not sure that you can effectively get a full swing from 850 to 3000 in one regulator, 850-1700 is probably more reasonable, again it depends on how much adjustment travel you want/have.  Also I don't think I'd preload the washers in an unpressurized state just for ease of assembly.  Hope you have fun with it, I can hardly keep one working gun in my collection because I'm always taking them apart and "improving" them.

[happymecanic]

So I just finished the new spool, it's dimensionally identical to the original one. Only differences are it's made of 304 SS and the seat tip no longer has a step, based on the suggestions made by Bob Sterne.

The edge is about 0.005'' wide, and rounded and polished. I made the Oring groove with radiused corners insead of square, had good results in the past with this design. The through-hole is 1.5 mm ID like the original, took about 15 min to drill that small size hole . I used a Dremel 37.5° (included angle) HSS cone bit to cut the inlet cone. I was even able to make these tiny M3-0.5 threads for the puller I use to extract the reg from the tube, not easy to thread that smal in SS . I polished the stem, where it rides in the Oring, with up to #1000 grit wet/dry sandpaper, then finished with #0000 steel wool. Surface finish is very nice, the Oring shouldn't have difficulties sealing on that. I made the stem of the spool 0.010'' longer and shaved 0.010'' off the face of the delrin screw to a new smooth finish. So far, so good .

The next frontier, the regulator body .

[CableStop]

Very nice work, SS is a pain in the butt.

[happymecanic]

I think Dave might have meant me asking about overall height, I just divided the total height of the stack by 15 given that they were all evenly arranged in your answer. That got me 0.0286" which when you subtract the 0.0197" thickness leaves 0.009" of deflection per washer.  Using that info it seems like your washers should take 112 lb of force to deflect completely.  The actual arrangement depends on how much space you end up with in your final design and how much travel you want in the adjuster.  I'm not sure that you can effectively get a full swing from 850 to 3000 in one regulator, 850-1700 is probably more reasonable, again it depends on how much adjustment travel you want/have.  Also I don't think I'd preload the washers in an unpressurized state just for ease of assembly.  Hope you have fun with it, I can hardly keep one working gun in my collection because I'm always taking them apart and "improving" them.

As designed, the total spool travel is 0.063'' with the lock ring installed, let's say 0.065'' to allow for a little ''crush'' of the delrin seat. That is 48% of total possible deflection of 0.135'' (15 x 0.009''). If I'd remove one washer, I'd have no preload and 0.126'' of possible total deflection. 0.063'' of travel equals to exactly 50% of that. If I refer to the Spaenaur spec sheet, that would mean 54 lb of force @ 50% of deflection, correct? Bob calculated that @ 850 psi, there would be 113 lb of force on the spool head, couter-balancing the spring washers force. As I'm seeing it, I could make a threaded adjustable delrin seat, similar in function to what Dave kindly posted, and have enough adjustment range to find the ''sweet spot''. Does my reasonning seems logical?

Very nice work, SS is a pain in the butt.

And thank you!