Handy tables and charts.

[snock]

OK, thanks to Rich for creating and providing the following excel spreadsheets for general use.
He created this spreadsheet so that anyone can input the appropriate data to find out how many fills per scuba tank they'd get from their kit.

How many fills. (http://members.lycos.co.uk/snock/number-of-fills-v17.xls)

The second link gives the user the chance to see, with any given variation, how likely they are to exceed the 12ft lb legal limit.

Am I legal? (http://members.lycos.co.uk/snock/am-I-legal-v1_6.xls)

Pete.

Pellet list table 1. (http://www.airgunforum.net/articles/pelletweight.htm)
Pellet list table 2. (http://www.airguninfo.com/pellweights.htm)
Pellet list table 3. (http://airgungb.infinitehosting.net/pelletweight.html)

[bmhill]

how good is that?:D:D:D
cheers rich and snock

[snock]

Thanks.:)

Feel free to save them onto your PC.

[A16NS V]

Out of interest is there any way of adding guns to the drop down list? I assume they ar ein a look up table somewhere?

EDIT : I've just found them. :D Although I don't understand how the formulas work to insert an Ultra. It's resovoir is 50cc IIRC

[big gav]

I dont have xcel , any chance of posting it up in Word mate?

[snock]

Out of interest is there any way of adding guns to the drop down list? I assume they ar ein a look up table somewhere?

EDIT : I've just found them. :D Although I don't understand how the formulas work to insert an Ultra. It's resovoir is 50cc IIRC

The program was written some time back, so certain newer models won't be listed, I'm afraid.

I dont have xcel , any chance of posting it up in Word mate?

Sorry mate, not by me there isn't.
If you post what gun, hose, pellet, fill pressure etc., someone will input the date and give you a reply.

:)

[Pad. E]

Thanks for that link Pete. :)

I think I've done it right. I'm just not sure of the empty pressure on an AA S200. So I put 100 bar. Is that right?

Regards
Paddy. :)

[Crackerz]

Nice 1 Rich and Pete, I'll make good use of this thank you :)

[snock]

Thanks for that link Pete. :)

I think I've done it right. I'm just not sure of the empty pressure on an AA S200. So I put 100 bar. Is that right?

Regards
Paddy. :)

I'm not entirely certain, Paddy, but hopefully someone else more knowledgeable will tell you.

;)

[Rich]

If anyone has a rifle not on the dropdown list and they KNOW the reservoir capacity for it, post it on here and I'll add it when I get time.

Rich

[Pad. E]

I'm not entirely certain, Paddy, but hopefully someone else more knowledgeable will tell you.

;)

:)


Asking question again:

I think I've done it right. I'm just not sure of the empty pressure on an AA S200. So I put 100 bar. Is that right?


Regards
Paddy.

[Rich]

Pad, 100 bar is not a bad guess. Unregged rifles will be sliding down the power curve at this point. There is no absolute correct refill pressure, it's really when the shots start to drop more than you are prepared to tolerate.

You will get more total shots out of your dive cylinder if you fill when you have to, not keep topping up unnecessarily. Each fill loses the air in the hose and gauge. In the case of the S200 with its small cylinder, the void volume of the hose etc is quite a significant part of the whole. So this is important with S200s in particular.

[Pad. E]

Pad, 100 bar is not a bad guess. Unregged rifles will be sliding down the power curve at this point. There is no absolute correct refill pressure, it's really when the shots start to drop more than you are prepared to tolerate.

You will get more total shots out of your dive cylinder if you fill when you have to, not keep topping up unnecessarily. Each fill loses the air in the hose and gauge. In the case of the S200 with its small cylinder, the void volume of the hose etc is quite a significant part of the whole. So this is important with S200s in particular.


Thanks for the info.

What I generally do is by going on what I've heard & been told is; fill it up to 190Bar, fire between 40 -45 shots then refill.

I got my 12 lt bottle filled earlier today, so now I can use this as a base & compare. Which means I should get about 1800 shots :cool:, not bad when it cost me £2.75 to fill the bottle. :D

Regards
Paddy. :)

[chrissy]

I think it must be down to individual guns and filling systems. I charge my S200 to 180 bar "indicated" on my Hills pump, any more is wasted effort. I then fire a magazine through it and then have 5 magazines more worth of air with very little variation. The pump then seems to kick in again at about 100 bar (so I assume that's where it got to) Mine is .22 and I use AA field running to approx 11.5 ft/lb. This gun seems to hate heavier pellets so I'm hopeful that I'll stay on the right side of the law! I can't say I'm over confident about my pressures but don't seem to be able to push it over the limit.

Cheers Chris.

[chrissy]

I think it must be down to individual guns and filling systems. I charge my S200 to 180 bar "indicated" on my Hills pump, any more is wasted effort. I then fire a magazine through it and then have 5 magazines more worth of air with very little variation. The pump then seems to kick in again at about 100 bar (so I assume that's where it got to) Mine is .22 and I use AA field running to approx 11.5 ft/lb. This gun seems to hate heavier pellets so I'm hopeful that I'll stay on the right side of the law! I can't say I'm over confident about my pressures but don't seem to be able to push it over the limit.

Cheers Chris.

[Top*Shot]

Im not easily impressed normally but I have to admit it, im impressed with the technological knowlege, mathmatical ability, programming skills and general level of intelligence demonstrated by some on this forum.
With a bit of encouragement and if pointed in the right direction I believe that they could actually make something of themselves and be successful in life.:D:D:D:p

No Seriously. These are useful tools. Thanks guys.

[Andy Bee]

Am I legal? (http://members.lycos.co.uk/snock/am-I-legal-v1_6.xls)

Thanks,
Excellent spreadsheet. I added another tab to build a database for my rifle. I'm shooting a Co2 rifle (first time with Co2). The spreadsheet has been invaluable to track performance vs the pressure changes as I use the gas, or prove/ disprove what I've read about Co2.

I've got the fps/ ft/lbs/ joules (energy) logged for different pellet gr weight. Next job for me is to make something to measure the pellet energy at the poi 20yd - 40yd.

Now my of knowledge of physics ends and my experimental mind starts starts. 1 lb weight / 12 inch pendulum, a pencil to describe an arc.........

[deadeye dick]

Is there some place to put in the calibre of the pellet

[Andy Bee]

Is there some place to put in the calibre of the pellet

The pellet weight and the fps are the variables. The calibre isn't necessary. The calc. between the grain and the speed gives you the info regardless of calibre. Its good for .177, .22 and others. Same maths.

[deadeye dick]

The pellet weight and the fps are the variables. The calibre isn't necessary. The calc. between the grain and the speed gives you the info regardless of calibre. Its good for .177, .22 and others. Same maths.

Cheers for clearing that up

[Harry's Lad]

He created this spreadsheet so that anyone can input the appropriate data to find out how many fills per scuba tank they'd get from their kit.

How many fills. (http://members.lycos.co.uk/snock/number-of-fills-for-bbsv15.xls)


That’s a reasonable first guess but a little naïve. ;) It assumes that air is infinitely compressible and behaves as an Ideal Gas . Unfortunately, that is not the case. Consequently, the model will slightly underestimate the number of fills if the bottle pressure is less than ~232 Bar and progressively overestimate if it is greater.

e.g.,

‘Calibrating’ the spreadsheet with bottle volume=6 Litre, Bottle Pressure=232 Bar, Rifle Fill Pressure = 200 Bar, Rifle Bottle Volume=200 cc (AA S410 Standard), ‘Empty’ Pressure = 120 Bar and ‘Standard’ hose type (10 cc) gives an estimated 10 fills. Changing the only Bottle Pressure to 300 Bar suggests 33 Fills.

Entering the same data into FillCalc (http://www.chairgun.com/download/FillCalc_Setup.exe) (which has the Van de Waal corrections applied) yields 10 fills and 24 Fills @ 232 Bar and 300 Bar respectively.

I guess that most folk use 232 Bar bottles anyway (so the increasing discrepancy above 232 Bar is fairly academic) but please be aware that, if you’re considering a 300 Bar set-up, you’ll get considerably fewer fills than this spreadsheet suggests.

ATB
Dave

[snock]

Naturally you're going to suggest Chairgun is more accurate, Dave (;)), but as I'm not so inclined to trawl through volumes of physics books to discover which table is more accurate, I'll let the creator of the table speak for it.


:)

[Harry's Lad]

Naturally you're going to suggest Chairgun is more accurate, Dave (;)),

Sorry, I tried not to make it read like that. An earlier version of FillCalc used the same model as the spreadsheet and – although I was vaguely aware of air’s compressibility issues – I didn’t consider them particularly relevant (but then thermodynamics was never really my thing :o ). However, as demonstrated, the differences above ~240 Bar are too big to be ignored. ….

. . . but as I'm not so inclined to trawl through volumes of physics books to discover which table is more accurate, I'll let the creator of the table speak for it.
:)

No need for any books (or trawling through same), just Google ‘Van der Waal’, it’s there for all to see. Consider the post as a simple warning that the number of fills from 300 Bar may be found to be misleadingly high. :rolleyes:
Having said all that, the Van der Waal model is a pig to work with (assuming the linear relationship is much simpler) and the differences are pretty much irrelevant under the magical ~232 Bar level. :)

HTH
Dave

[Edit] By the way, did you ever wonder why 232 Bar is/was a popular working pressure for a pressure vessel? Why 232 Bar; why not 225 Bar or even 250 Bar? It turns out that 232 Bar is the pressure (for air) where the Ideal Gas approximation holds true. At pressures below that you get slightly more than you expected; at over 232 Bar you progressively get a lot less; the compressibility ensures that the Law of Diminishing Returns takes hold with a vengeance.

[Rich]

Being the original author, let me say that I am and was at the time aware that the maths were simplified and ignored the Van Der Waal issue, rather like the earlier versions of Chairgun and other ballistic software had simplified approaches to residual energy and trajectory.

Number of Fills was released at a time when money was being raised by members of this forum to support breast cancer charities, and the spreadsheet was given away on the basis that recipients who found it useful would make an appropriate donation. I have the papers on file somewhere, as I dare say the posts and threads from that era have long gone. We made about £170 for breast cancer charity on the first evening; I recall sending about 75 emails with a copy of the spreadsheet attached, before I went to bed at 2am.

There seems to be little point in re-releasing number-of-fills as pretty well everyone these days will choose a 300 bar bottle over a 232 so long as they can get it refilled relatively easily. The cost of getting to the filling shop is for many the largest single factor, so it makes sense to buy the biggest and highest pressure bottle you can manhandle.

If I were to update it, I would not bother with a true Van Der Waal correction, but simply use the present elementary maths substituting an arbitrary value of something like 285 bar whenever the user thought they were selecting 300 bar. That would give a closer approximation. In any event the accuracy is affected by whatever allowance is made for dead volume in the hose and gauge, and experience has shown me that some decant sets are far more wasteful than others.

The other factor to consider is that number-of-fills has a look-up table with the reservoir capacities for several popular rifles (and that's out of date now too.) Readers may think that getting the reservoir capacity from the manufacturer only requires a phone call. In practice one firm steadfastly refused to let me have the information declaring it was a trade secret. I ask you, how can it be a trade secret of any worth when firms such as Theoben specify the size of the buddy bottle?

The example of the S410 with 200cc is actually incorrect as later information has shown this reservoir to be 216cc. The carbine and export models have also been amended.

If I could move to the am-I-legal spreadsheet, I do commend this to all members especially in the light of current issues regarding rifles approaching the legal limit. This time the maths part does not rely on any science or engineering, it's purely a matter of statistics, more specially probability.

An over-the-counter chronograph will have an accuracy of something like plus or minus 1 percent of reading. The owner will not know whether his chrono reads high, low, or spot on. The chrono used by the Home Office testing station will be a precision piece of kit and will have a calibration certificate, with a tolerance of something like 0.4% of reading.

It would be possible for your domestic chrono to be at one end of its limit and the testing station chrono to be at the other end of its limit, a variation of 1.4%. Remember that the chrono measures velocity, but it is muzzle energy that is specified by law. As there is a square function from velocity to energy, 1.4% variation in velocity equals 1.96% variation in power.

The maths part looks not only at the rifle's velocity but the consistency of that velocity. It is the case that a rifle that is inconsistent is more likely to throw a rogue high value at some time. That is why the spreadsheet can give you the surprising and maybe unwelcome answer that ten or even twenty shots close to the limit (but all under it) bring a risk of failing a Home Office test if the rifle is inconsistent. When it says, there is a 3 percent risk of failing a test, think of it this way. You and 32 friends line up to have your rifles tested, all supremely confident that your trials at home have kept you under the limit, albeit close to it. One of you will be disappointed to learn that you are in possession of a section 1 firearm, without a licence.

Rich

[Harry's Lad]

Being the original author, let me say that I am and was at the time aware that the maths were simplified and ignored the Van Der Waal issue, rather like the earlier versions of Chairgun and other ballistic software had simplified approaches to residual energy and trajectory.

The first ChairGun version, as it evolved through several iterations, was an adequate model of airgun ballistics as used in the context of airgun usage at that particular time. ChairGun2 evolved from a different ballistic model that more accurately met different (and more challenging) criteria – mostly driven by the requirement of long-range shooting in Oz and the USA. In both cases, the software operated accurately within its stated restraints.
That’s the difference; your spreadsheet is capable of giving results that, because of the known and ignored oversimplification, are erroneous. I was simply pointing out that, given the deficiencies of the simple model used, the 232 Bar + results may be seriously in error.

There seems to be little point in re-releasing number-of-fills as pretty well everyone these days will choose a 300 bar bottle over a 232 so long as they can get it refilled relatively easily. The cost of getting to the filling shop is for many the largest single factor, so it makes sense to buy the biggest and highest pressure bottle you can manhandle.

Perhaps that’s a good reason for re-doing/releasing the spreadsheet since it is the > 232 Bar predictions that are in error. The conjecture was, on acquiring a 300 Bar bottle on the basis or your spreadsheet, that the punter could be very disappointed in the number of fills realised.

If I were to update it, I would not bother with a true Van Der Waal correction, but simply use the present elementary maths substituting an arbitrary value of something like 285 bar whenever the user thought they were selecting 300 bar. That would give a closer approximation.

You could do that . . . or you could do it properly :) although writing an accurate working algorithm in VBA could be quite challenging.

In any event the accuracy is affected by whatever allowance is made for dead volume in the hose and gauge, and experience has shown me that some decant sets are far more wasteful than others. The other factor to consider is that number-of-fills has a look-up table with the reservoir capacities for several popular rifles (and that's out of date now too.) Readers may think that getting the reservoir capacity from the manufacturer only requires a phone call. In practice one firm steadfastly refused to let me have the information declaring it was a trade secret. I ask you, how can it be a trade secret of any worth when firms such as Theoben specify the size of the buddy bottle? The example of the S410 with 200cc is actually incorrect as later information has shown this reservoir to be 216cc. The carbine and export models have also been amended.

True. But then, we can only use the data that we’re sure of. Otherwise it’s just GIGO again.

ATB
Dave

[Rich]

I really can't get into a protracted dialogue over this I'm afraid.

I've never had anyone complain that they have been hoodwinked or duped or misled into buying the wrong bottle. Quite the reverse; many have written to say how close the predictions are to their own experiences. I know that is only their perception and that it almost certainly differs from actuality, but for many folk their perception is 90% of reality.

Writing code to fit the Van Der Waal correction when only two points on the curve have any relevance, i.e., 232 and 300 bar (as bottles aren't rated as far as I know to any intermediate values) would be a waste of time and I don't rise to such challenges any more.

ATB

[Harry's Lad]

I really can't get into a protracted dialogue over this I'm afraid.

I've never had anyone complain that they have been hoodwinked or duped or misled into buying the wrong bottle. Quite the reverse; many have written to say how close the predictions are to their own experiences. I know that is only their perception and that it almost certainly differs from actuality, but for many folk their perception is 90% of reality.

Writing code to fit the Van Der Waal correction when only two points on the curve have any relevance, i.e., 232 and 300 bar (as bottles aren't rated as far as I know to any intermediate values) would be a waste of time and I don't rise to such challenges any more.

ATB

Absolutely fair enough. :)

I made the comment in the first place because I could only imagine that you were unaware of the considerable error - at 300 Bar - caused by your oversimplification. It now seems that you were well aware of the errors but did it anyway. :eek:
Personally, I wouldn’t do that but each to his own.

Only your 300 Bar point is affected – the 232 Bar point would be near enough – as explained above.

ATB
Dave

[snock]

Is it possible that by attempting to belittle someone else's work, Dave, that you feel you're in some way trying to bolster Chairgun as the prime source of ballistic data for airguns? I'm afraid that's how it's looking, to me, anyway.:)

Chairgun isn't particularly accurate either. Sorry to drop that on you, but Chairgun 1.8 said that I will need 68 clicks on my big nikko if I shoot AA fields at 55 yards, zeroed as I am at 23 yards wilth all other parameters as built.

Chairgun 2.? says - for EXACTLY the same physical parameters - I need 58 clicks. Practice tells me I need 56 clicks.

At the end of the day, does it really matter about a few clicks or a few fills? No, it doesn't.;)

The two can live along side each other in perfect harmony without picking holes in someone else's work.

This thread's sole aim was to provide FREE tables and charts to guide those folk who like that sort of thing.


Atb,


Chairgun can be downloaded here. (www.chairgun.com)

[Harry's Lad]

Is it possible that by attempting to belittle someone else's work, Dave, that you feel you're in some way trying to bolster Chairgun as the prime source of ballistic data for airguns? I'm afraid that's how it's looking, to me, anyway.:)

I’m not trying (or have tried) to belittle anyone or anything – simply pointing out that an error exists. I sited FillCalc (not ChairGun) as a source of comparison (although the same FillCalc algorithm does exist ChairGun2/3). You were the first to mention ChairGun in your post #24. I’m left wondering why you would accuse me of ‘in some way trying to bolster Chairgun as the prime source of ballistic data for airguns’ when it was you who introduced the topic in the first place . . . :confused:

Chairgun isn't particularly accurate either. Sorry to drop that on you, but Chairgun 1.8 said that I will need 68 clicks on my big nikko if I shoot AA fields at 55 yards, zeroed as I am at 23 yards wilth all other parameters as built.
Chairgun 2.? says - for EXACTLY the same physical parameters - I need 58 clicks. Practice tells me I need 56 clicks.

As mentioned above (my answer in #25 to Rich’s specific reference in #24) ChairGun has evolved, and continues to evolve, subject to specific and changing criteria. ChairGun1 had problems (and errors) in certain areas (although these were resolved by the last – V1.99 – iteration). Changing requirements lead to the adoption of a better mathematical model that had benefits in all areas and ChairGun2 was born.
Two clicks at 55 Yards is something around ¼ MoA; pretty good when ChairGun2’s specified accuracy is +/- ½ MoA. Did you actually measure the BC or assume a nominal value? :confused:

At the end of the day, does it really matter about a few clicks or a few fills? No, it doesn't.;)

Quite true. However, does 1/8” Inch of error in 55 Yards really relate to 33 to 24 fills difference (37.5% error)? The former is almost negligible, the latter monumental. :eek:

The two can live along side each other in perfect harmony without picking holes in someone else's work.

Again, I’m not ‘picking holes’ or ‘belittling’ anything or anyone – simply pointing out that an error (a correctable error at that) exists. The more serious point is that Rich (not Rob, sorry), having admitted prior knowledge of the essential Van der Waal correction, failed (for whatever reason) to make said correction and released the flawed spreadsheet anyway. If you’re not bothered by that then perhaps you don’t understand the problem or my concerns.
It may have been done quickly … it may have been for a good and worthy cause … but, when all is said and done, it’s just plain wrong. :(

This thread's sole aim was to provide FREE tables and charts to guide those folk who like that sort of thing.

FillCalc is free too. :)

ATB
Dave

[Rich]

The 232 bar point would indeed be near enough, an error of about 3 percent I think.

The error at 300 bar is still only around 8 percent. As I said, it hasn't led to complaints from users - only yours, Dave.:)

Compressibility is actually also temperature dependent so unless yet another input parameter is called for, it's going to have to be an approximation.

[Rich]

And it's Rich, by the way, not Rob.

[Harry's Lad]

The 232 bar point would indeed be near enough, an error of about 3 percent I think.
The error at 300 bar is still only around 8 percent.

Sorry Rich, but I don’t know where these percentages came from (or to what they refer). As I mentioned before, thermodynamics isn’t really my thing but, ‘Standard’ air behaves as the Ideal Gas that your model assumes at around 232 Bar. Above or below that pivotal pressure a mass-to-pressure error exists - below 232 Bar, the vessel’s pressure drop is slightly less than the Ideal Gas assumption anticipates; at higher pressures then the pressure drop is progressively much greater than your assumption would anticipate. Unfortunately, in the real world, the greater-than-anticipated pressure-drop means that at every iteration (fill) the pressure discrepancy increases and so, by cascading that error, there are considerably fewer fills to be had.

As I said, it hasn't led to complaints from users - only yours, Dave.:)

I haven’t complained. Far be it for me to complain. I’m just flagging an error.

Compressibility is actually also temperature dependent so unless yet another input parameter is called for, it's going to have to be an approximation.

Indeed it does but the temperature range we’re considering is comparatively small. Any temperature variation would apply equally to both models anyway.

And it's Rich, by the way, not Rob.

Noted and corrected. Sorry about that. :o

ATB
Dave

[Rich]

Perry's Chemical Engineers' Handbook. I can't give you a page reference, I no longer have a copy. It was a useful document when I was in industry.

Compressibility varies by around 5 percent between 250K and 300K, say one percent per 10K variation. 232 bar at factor 1.0 is true at 250K, maybe 3 percent adrift at "room" temperature. That is why I estimated a 3 percent error at the "base" point.

[RobF]

It's academic when you don't know the length of line used to fill the cylinder. We also don't shoot at a fixed temp... i think last year I covered 35 degrees.

I don't think anyone is going to get upset about the fill count not meeting x person's predictions... the benefits of 300 are that if your shooting at 200 bar you can hold a lot more air in the same volume for a longer amount of fills.

Reminds me... I need to get my 3L filled... i've forgotten how many fills it's done... but it's down to 185 and i'm scrounging air. Even though I shoot almost every weekend, and regularly each week, I can't for the life of me remember how many fills I get out of my 4 pcps... all with different sized cylinders.

Rob, not Rich :D

[tomosmond]

will they open with open office. Im downlading it at the moment and just wanted to know.:)

[Rich]

Tom, yes, I just tried it and it seems to work OK

Number of fills does not contain any macros.

[Rich]

Am I Legal also seems to work fine.

I haven't checked them side by side with Excel but no error messages came up.

Am I Legal also has no macros, the maths is done with Excel built-in functions.

[tomosmond]

thanks snock and rich:)

[El Tel]

As you shoot an EV2 I am surprised it is not in the list.

[Rich]

At the moment I'm waiting for some more details to come in from one or two manufacturers and when I have it I will be releasing a version with more current rifles in the list. The EV2 will be included.

For the moment, anyone with an EV2 can "pretend" it is a S400 classic for this purpose as they share the same reservoir tube. :)

[carld41]

Brilliant Thread Rich, Lot of work for something that's FREE.
I for one applaud you
All the best
Carl

[BSAlightning_XL]

OK, thanks to Rich for creating and providing the following excel spreadsheets for general use.
He created this spreadsheet so that anyone can input the appropriate data to find out how many fills per scuba tank they'd get from their kit.

How many fills. (http://members.lycos.co.uk/snock/number-of-fills-v17.xls)

The second link gives the user the chance to see, with any given variation, how likely they are to exceed the 12ft lb legal limit.

Am I legal? (http://members.lycos.co.uk/snock/am-I-legal-v1_6.xls)

Pete.

Pellet list table 1. (http://www.airgunforum.net/articles/pelletweight.htm)
Pellet list table 2. (http://www.airguninfo.com/pellweights.htm)
Pellet list table 3. (http://airgungb.infinitehosting.net/pelletweight.html)

V.handy...thanks very much :D

[pcken]

|Thank you for the very useful charts I've printed them off to take to the club.

ken