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 Posted: Wed Mar 24, 2010 12:22 am |
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| yourdaddyjoe |
| Supporting Member |
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| Joined: 26 May 2008 |
| Posts: 4027 |
| Location: Tatorville, USA |
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Thanks for interpreting Eric, Some day I might be so eloquent in my words...  Thank God for Spell Check  |
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| Posted: Wed Mar 24, 2010 12:37 am |
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| sniper |
| Silver Status Member |
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| Joined: 28 Nov 2008 |
| Posts: 3752 |
| Location: Star, Idaho |
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| yourdaddyjoe wrote: |
| Thanks for interpreting Eric, Some day I might be so eloquent in my words... Thank God for Spell Check |
there's a spell check on here? 
i guess i spell/type real good.  |
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_________________
I believe in gun control,
If there's a gun around I
want to be controlling it....... |
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| Posted: Wed Mar 24, 2010 12:44 am |
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| kanyon |
| Silver Status Member |
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| Joined: 09 Aug 2008 |
| Posts: 1582 |
| Location: New Zealand |
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All said and done..I do like the idea...
Very easy to make...But the valve dose need a better way
of holding it....I think what is needed is a step/shoulder
in the tube for the valve to back up on to..
New tube with a shoulder a slot & a few holes
not hard to make in the least...
A riser breech and the second section of the tank
thingy could be bigger in dia....
Was looking for a new 22xx project idea...  |
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| Posted: Wed Mar 24, 2010 12:13 pm |
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| Rodents' Rapture |
| Spammer |
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| Joined: 22 Mar 2010 |
| Posts: 17 |
| Location: Texas |
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| sniper wrote: |
nobody says you don't know. i'm not an engineer
but bob aka "professor" has more than proven his credentials here.
now, i say again... MAKE BOB A MODERATOR DAMNIT!!  |
He has my vote |
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| Posted: Wed Mar 24, 2010 12:36 pm |
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| rsterne |
| Moderator |
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| Joined: 15 Jan 2008 |
| Posts: 2998 |
| Location: Coalmont, BC |
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In all fairness, IF everything works the way it is supposed to, the product SHOULD be safe.... The high pressure tank has a narrow neck, and it is supposed to seal against the valve, hence the main tube is not supposed to be pressurized.... The problems I see are:
1. If you overtighten the tank threads, you are putting additional strain on that stupid little 6-40 screw Crosman uses to retain the valve.... Even it if was made of 80,000 psi material (questionable), with a 4:1 safety margin (normal) that screw is only good for 176 lbs. in shear.... Assuming the seal diameter where the neck of the tank meets the seal on the valve is 1/4" diameter, at 3000 psi, that is already 147 lbs.... Add to that the end force of tightening the threads (and yes, that is a VERY fine thread and can exert a lot of force with not much tension).... and you will quickly see the potential for a problem....
2. The poster states that there are "No Modifications Required" to the gun, and goes on to show that in the Installation Video.... Then he states in another post that the stock Crosman valve seal is only good for 1600 psi.... only half of what the tank is rated for.... Yes, he has a replacement seal available, and supplies it.... but installing that certainly doesn't qualify the gun as no modifications required.... You must pull the valve to install the seal....
3. If the valve seal fails, the main tube will become pressurized (up to 3000 psi).... True, there is no seal around the valve, but until the pressure bleeds off around the valve, there will be a HUGE end force on the valve.... 1325 lbs. at 3000 psi.... How do you think that little 6-40 screw will stand up to that load.... even if it's for a split second....
I have no doubt that the poster has spent a long time developing this product.... and that he thinks it is safe.... I am simply pointing out what COULD happen under various conditions.... He didn't like that and basically told me to mind my own business and either "buy the product or not".... He has since erased that post.... In addition, he didn't like my comments that he really had only a 6 shot string within the generally accepted tolerance of 10%, not the 12-15 shots he originally posted.... True, he posted a video of the actual shot string, and the numbers.... and I'm not implying in any way that he was attempting to decieve potential customers.... I was merely pointing out that if they are expecting a 10% velocity deviation, they will only get about 6 shots....
I made a suggestion that he could IMPROVE his shot string with a slightly weaker hammer hit, but he blew that away like I didn't know what I was talking about.... I wonder if he even realizes that unregulated PCPs should be designed so that the shot string is a bell-curve with the first and last shots about 90% of the peak velocity.... That is the way to get maximum efficiency with minimum deviation and the maximum number of shots.... His comment:
| Quote: |
| The first shot being a higher fps than the second is due mostly to me not backing off the adjuster throughout the string |
led me to believe he doesn't understand that.... I have never heard of someone "backing off the adjuster" during a shot string.... sounds totally impractical to me....
The original poster states that he is a retired aerospace engineer.... As such, he should be aware that people often exceed the design criteria when using a product.... especially when they are told to just screw in this tank, "no modifications required".... I personally don't care if he uses my suggestions or not.... I was merely making observations about what I considered to be possible safety concerns.... and how the product could be improved....
Bob |
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_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| | | | | | | | | The "PowerMax-HiPAC" in a small nutshell | | | | | |
| Posted: Wed Mar 24, 2010 3:18 pm |
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| Rodents' Rapture |
| Spammer |
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| Joined: 22 Mar 2010 |
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| Location: Texas |
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| The "PowerMax-HiPAC" is designed to turn a stock 2240 into a Co2N2HPA bulk feed or stand-alone system, without having to do any mods the gun. The pressure of the cylinder on the valve needs to be no more than it is when you tighten the cap down on a 12g pill. You've never used a wrench before and you don't use a wrench with the PowerMax. Overtighten it and you will only over-compress the red-rubber washer which will go out long before the screw breaks off. Pressurize it above 1600psi and the washer will blow out requiring a disassemble. If you want to continue to tighten it up you'll need a wrench. If you need a wrench it's a pretty damn good bet that you don't know what you're doing anyway. The stock washer blows out around 2000psi at which point the valve won't be holding anything anyway. If someone want to put a PM in their gun and tighten it up until the valve screw breaks, they probablly shouldn't be playing with airguns. No hand tools should ever be used. Just like screwing the cap down on a 12g pill. That's why I did the "Installation Guide" video. You probablly wouldn't want to use an impact wrench either. I have one valve that has a thicker/stronger screw. It required a little grinding on the frame behind the safety spring to fit the thicker crown but the valve with the factory screw holds in place with no problem, because the PM is only supposed to go in hand tight. The factory screw had shifted slightly like it was trying to shear off. It caused more damage to the backside of the screw hole where it was being pushed against. I used a wrench on it for that test. As long as the shearing force required to break the screw (and it is high) exceeds 100% compressability of the seal it ain't a problem. It'll be metal to metal at that point. You will have had to use a wrench to tighten it that tight. Finding the right rubber seal material was the key. It took almost 2 months of testing, testing and retesting, over 115 disassemblies of my gun and 15 types of rubber compounds to find the right seal material. If some one wants to shoot with a 3000psi HPA system it's going to require the seal (2 with every PM) but it won't require a wrench. Put common sense first and employ the same precautions you would if they were building a bulk-fill system. |
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| Posted: Wed Mar 24, 2010 3:24 pm |
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| rsterne |
| Moderator |
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| Joined: 15 Jan 2008 |
| Posts: 2998 |
| Location: Coalmont, BC |
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| Quote: |
| employ the same precautions you would if they were building a bulk-fill system. |
In other words, pin the valve.... standard procedure for bulk fill....
I'm done with this thread.... You obviously have no intention of taking constructive criticism, your product is perfect in every way.... I wish you luck with it and I hope your commercial liability insurance is paid up....
Bob |
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_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Wed Mar 24, 2010 3:27 pm |
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| yourdaddyjoe |
| Supporting Member |
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| Joined: 26 May 2008 |
| Posts: 4027 |
| Location: Tatorville, USA |
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| Oi... Pass me another beer... while I play with my SCUBA tank valve.... |
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| Posted: Wed Mar 24, 2010 6:49 pm |
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| Rodents' Rapture |
| Spammer |
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| Joined: 22 Mar 2010 |
| Posts: 17 |
| Location: Texas |
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| rsterne wrote: |
In all fairness, IF everything works the way it is supposed to, the product SHOULD be safe.... The high pressure tank has a narrow neck, and it is supposed to seal against the valve, hence the main tube is not supposed to be pressurized.... The problems I see are:
1. If you overtighten the tank threads, you are putting additional strain on that stupid little 6-40 screw Crosman uses to retain the valve.... Even it if was made of 80,000 psi material (questionable), with a 4:1 safety margin (normal) that screw is only good for 176 lbs. in shear.... Assuming the seal diameter where the neck of the tank meets the seal on the valve is 1/4" diameter, at 3000 psi, that is already 147 lbs.... Add to that the end force of tightening the threads (and yes, that is a VERY fine thread and can exert a lot of force with not much tension).... and you will quickly see the potential for a problem....
2. The poster states that there are "No Modifications Required" to the gun, and goes on to show that in the Installation Video.... Then he states in another post that the stock Crosman valve seal is only good for 1600 psi.... only half of what the tank is rated for.... Yes, he has a replacement seal available, and supplies it.... but installing that certainly doesn't qualify the gun as no modifications required.... You must pull the valve to install the seal....
3. If the valve seal fails, the main tube will become pressurized (up to 3000 psi).... True, there is no seal around the valve, but until the pressure bleeds off around the valve, there will be a HUGE end force on the valve.... 1325 lbs. at 3000 psi.... How do you think that little 6-40 screw will stand up to that load.... even if it's for a split second....
I have no doubt that the poster has spent a long time developing this product.... and that he thinks it is safe.... I am simply pointing out what COULD happen under various conditions.... He didn't like that and basically told me to mind my own business and either "buy the product or not".... He has since erased that post.... In addition, he didn't like my comments that he really had only a 6 shot string within the generally accepted tolerance of 10%, not the 12-15 shots he originally posted.... True, he posted a video of the actual shot string, and the numbers.... and I'm not implying in any way that he was attempting to decieve potential customers.... I was merely pointing out that if they are expecting a 10% velocity deviation, they will only get about 6 shots....
I made a suggestion that he could IMPROVE his shot string with a slightly weaker hammer hit, but he blew that away like I didn't know what I was talking about.... I wonder if he even realizes that unregulated PCPs should be designed so that the shot string is a bell-curve with the first and last shots about 90% of the peak velocity.... That is the way to get maximum efficiency with minimum deviation and the maximum number of shots.... His comment:
| Quote: |
| The first shot being a higher fps than the second is due mostly to me not backing off the adjuster throughout the string |
led me to believe he doesn't understand that.... I have never heard of someone "backing off the adjuster" during a shot string.... sounds totally impractical to me....
The original poster states that he is a retired aerospace engineer.... As such, he should be aware that people often exceed the design criteria when using a product.... especially when they are told to just screw in this tank, "no modifications required".... I personally don't care if he uses my suggestions or not.... I was merely making observations about what I considered to be possible safety concerns.... and how the product could be improved....
Bob |
(1) What a genius, Bob. You will tighten the PM to 176 ft/lbs pressure. Wouldn't you need a wrench for that, Bob? Do you use a wrench to tighten the CO2 pill in, Bob? DON'T USE A WRENCH, Bob. This one is reeeal stupid but you went there. What does the PM's psi ability have to do with the ability of a gun, Bob. You think it's a requirement to fill to 3000psi, Bob. It does work at lower pressures you know. Just like CO2, Bob. Don't exceed you presonal psi, Bob
(2) Actually the factory seal is good to 2000psi, Bob. 1600psi gives a 20% safety factor which may keep some one from having to take their gun apart to replace it, Bob.
(3) The seal didn't fail when tested at 4600psi for 24hrs, Bob. There you went assuming you knew something about what I have already done, Bob. No number 4 so i'll put one there for him.
(4) I erased that post because everyone thought I was rude and to that I apolpgized to you. However, since you want to bring it up, and to the attention of all, for whatever reason let's go there. You didn't know what you were talking about and I did my best to keep from telling you where and how deep to stick your suggestion. Let me see if I can finds Ricks' email. BRB. Here it is.
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Just a quick update... I just warmed up some CO2 and crosman premier pellets (14.3 grn) started at 438 FPS but quickly dropped below 400 and then bottomed out at 315ish at 50 some odd shots... I filled up the HiPAC and started again.. consistently 450ish for the majority of the shots, in cold weather, no matter how fast I shot.. certainly better than CO2.. It takes about 30 pumps to go from zero to 1600 +/- PSI with my Discovery pump.. For folks that want to shoot their CO2 guns in cold weather this is going to be a God Send.. guns like the 1077 and the QB78 will have even more functionality.. I've notified (i removed the name of the company because it's none of Bobs' business) about your product.. I'll let you know what they say..
Cheers.
Rick
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This is so simple, Bob. I explained the physics of this to 3rd graders once before and i'll do it one more time since you missed that class, Bob. I can't make it any simpler than this...Shot pressure will drop sharply if the volume of air expelled per shot is equal to a large percentage of the available air in the tank. Forget psi for a second and look at it like this, Bob. If 128oz (gallon volume) of air is compressed into an 8oz volume (cup), and 8oz of air is expelled each time you shoot; you can expect to get 16 shots but will find a big drop in fps after every shot due to less air volume in same space. Still with me, Bob? Now let's say you expell 2oz of air every time you shoot. Expelling only 2oz of volume per shot the drop will be quite a lot less. That is, in simple to understand numbers, Bob, 128 shots with at least the first 1/3 of the total shots using only 43oz air. That leaves 85oz of air still compressed into 8oz. but lower psi due to volume. Pretend you knew that already, Bob.
Anyway, since I have you to thank for bringing me to this mental place please let me finish.
(5) I blew you off because I knew you didn't know jack-sh!t about what you were saying in reference to the PowerMax. My 12 yr old son knows that a weaker hammer spring works at lower psi, Bob. Use a weaker spring with that amount of internal valve pressure and it will laugh at you just like we are right now, Bob. Really, I showed that statement to my son and he laughed.
And there you go again, Bob. You're mentioning something else that you've never heard of people doing. It shouldn't be done because Bob has never done it and don't know it's benefits from a rats a$$.
Don't be an assumer, Bob. Something has Bob feeling that I need Bob to point out what Bob considered design problems. He's never seen anybody do it and it's not practicle.
Thank you Bob, and remamber. Don't use wrenches |
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| Posted: Wed Mar 24, 2010 6:59 pm |
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| broommaster2000 |
| Moderator |
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| Joined: 10 Mar 2007 |
| Posts: 5714 |
| Location: City of Groningen, Groningen, The Netherlands |
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| Going south quickly. Locking this for now. |
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