Hacking the Crosman Vigilante
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Hacking the Crosman Vigilante
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Topic: Hacking the Crosman Vigilante (Read 45057 times - 7 votes)
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AmBraCol
Webservant
Expert
Posts: 1662
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Real Name: Paul
Re: Hacking the Crosman Vigilante
«
Reply #100 on:
April 22, 2017, 09:17:56 AM »
Looking forward to seeing it set up as a carbine.
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Risaralda, Pereira, ColOmbia
I'm a peaceful man and prefer the pursuit of peaceful sports. Those involving teams and balls of any sort tend to be deleterious to one's body and promote violence by both spectators and participants. The shooting sports, however, tend to promote self control and are peaceably participated in by those who know that their greatest challenge is their need to continually hone their own abilities.
George Schmermund
Sharp Shooter
Posts: 576
yes
Real Name: George
Re: Hacking the Crosman Vigilante
«
Reply #101 on:
April 24, 2017, 11:08:35 PM »
There has been a lot of discussion about "barrel harmonics" in some of the places that I've been reading lately. There is much conjecture, but very little in the way of testing and measurements so far. Maybe I'm spending time in the wrong places. At any rate, I've decided to put a few tests together and try to get some reasonable empirical information about the barrels I'm using. The tests are actually pretty straight forward, though not always simple.
My plan is to test the natural frequencies of the 10" barrels and then see what can be done to make sure that the vibration components that might interfere with a gun's accuracy can be brought under control. I've spent a lot of time with projects that involve sound and vibration which require interesting methods to evaluate various devices. Over the years these projects have required quite a bit of specialized hardware and methods to apply the instruments.
One of my pet instruments is a Bruel & kjaer Complex Modulus Apparatus. It's an old type 3930 and has been sitting on a bookshelf in my lair for quite a while. Some instruments are just to beautiful to hide in the attic or the garage's loft. I realize that it's all in the eyes of the beholder, but I have my weaknesses. Anyhow, I thought that some of you folks might be interested (amused?) in the next potential distraction that I'm probably going to get all caught up in now. This diversion will probably get me back to the acoustics tests that I want to do.
The photos show the 3930 with a 10" barrel mounted in the test position. I'll add more info as things progress.
«
Last Edit: April 24, 2017, 11:10:32 PM by George Schmermund
»
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Carlsbad, CA
One test is worth 10 expert opinions!
kj
Expert
Posts: 1415
yes
Real Name: kj
Re: Hacking the Crosman Vigilante
«
Reply #102 on:
April 25, 2017, 07:10:45 AM »
wow, you sure are putting in some work. on barrel harmonics. they affect longer skinnier barrels most. as the barrel gets shorter and/or thicker, it becomes less suscepible to the effects of harmonics. basically the barrel whips about and affecys where ot's actually pointing as the projectile leaves the barrel. sleeving and/or tensioning the barrel are common ways to lessen the harmonic effect. indexing barrels is an attempt to get the pellet to leave the barrel at the top or bottom, rather than off to a side. i'm not sure if this last bit is completely due to harmonics, perhaps the barrel crown or manufacture.
you'll probably find more about harmonics in relation to powder burners (pb).
peace
kj
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kjs custom gunstock carvings
gunstockcarvings.com
dv8eod
Expert
Posts: 1518
Re: Hacking the Crosman Vigilante
«
Reply #103 on:
April 28, 2017, 12:06:49 AM »
Some reading I thought you might enjoy, if it will post.
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AmBraCol
Webservant
Expert
Posts: 1662
yes
Real Name: Paul
Re: Hacking the Crosman Vigilante
«
Reply #104 on:
April 28, 2017, 09:40:45 AM »
Quote from: dv8eod on April 28, 2017, 12:06:49 AM
Some reading I thought you might enjoy, if it will post.
I'm getting the error message that its "not a real PDF" or "it may not be properly encoded".
Logged
Risaralda, Pereira, ColOmbia
I'm a peaceful man and prefer the pursuit of peaceful sports. Those involving teams and balls of any sort tend to be deleterious to one's body and promote violence by both spectators and participants. The shooting sports, however, tend to promote self control and are peaceably participated in by those who know that their greatest challenge is their need to continually hone their own abilities.
dv8eod
Expert
Posts: 1518
Re: Hacking the Crosman Vigilante
«
Reply #105 on:
April 29, 2017, 05:22:33 PM »
Sorry guys, when I try to attach it from the computer, it says that the file is too large. If it can be downloaded, try renaming it by removing "%20" and replacing it with a single space. Can't guarantee that it will work.
If you really want a copy, PM me your email address.
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George Schmermund
Sharp Shooter
Posts: 576
yes
Real Name: George
Re: Hacking the Crosman Vigilante
«
Reply #106 on:
April 30, 2017, 07:06:55 PM »
Doing some vibration measurements on the 10" barrels that I'm using has been very instructive. Since the Complex Modulus Apparatus (CMA) is a good experimental representation of a clamped end barrel with no intermediary supports it can be studied as a clamped end, single tine, tuning fork. This model offers an easy way to get into the physics of barrel harmonics. I have to start somewhere.
The measurements so far show that the natural frequency of each of the 4 sample barrels is 107 HZ +/- ~1HZ @ ~70º F. The 2nd harmonic is more than 6 times higher in frequency and of very low amplitude and can be ignored for the time being. This is still a proof of concept experiment, so I'm trying to make things easy. As an aside, if I put my ear close to the end of the barrel when it's being driven the tone can be heard, though I don't see any movement without using magnification.
The CMA can now be mounted sideways and a fixture arranged to allow barrels of different lengths to be measured by actually firing the gun at a target. Barrel rings and different damping materials can then be experimented with. The CMA's non-contact measurements will simplify many of the calculations needed to evaluate the data.
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Carlsbad, CA
One test is worth 10 expert opinions!
George Schmermund
Sharp Shooter
Posts: 576
yes
Real Name: George
Re: Hacking the Crosman Vigilante
«
Reply #107 on:
May 06, 2017, 04:42:28 PM »
The Vigilante carbine is making good progress. Right now I'm fitting a Crosman stock to the pistol by doing some milling and carving. It's crude in the present form, but it snaps into place nicely and with some more work I'll be able to bolt it into place solidly. The stock will probably be modified to allow just one of the side grips to be removed in order to allow access to the powerlet without having to remove the whole stock. The grip can then be snapped back into place.
I've already put many clips through the new pistol arrangement and the overall improvement in feel and accuracy is remarkable. The black box that is shown in the photo is a lithium ion battery pack that will be used to power the heaters on the powerlet. It fits nicely into the stock cutout. I've got a thermistor temperature controller on order that will also fit into the stock next to the battery pack. The controller will allow setting and maintaining the powerlet temperature within 1º F or better.
I'm finally able to hit what I'm aiming at without relying on a bench vise! The next step is to lengthen the barrel to somewhere between 16" and 20". This should make the gun quieter and produce higher muzzle energy.
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Carlsbad, CA
One test is worth 10 expert opinions!
Rob M
GTA Senior Contributor
Posts: 6304
Re: Hacking the Crosman Vigilante
«
Reply #108 on:
May 06, 2017, 06:32:44 PM »
looks incredible./ I cannot wait to see some groups.. the muzzle velocity should skyrocket near 16 inches of barrel.I modded a crosman 1088 with a 9 inch barrel many years ago using a 1077 barrel section.. I doubled the FPE and went from 380fps to 525 .
«
Last Edit: May 06, 2017, 06:34:46 PM by Rob M
»
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Louisiana
George Schmermund
Sharp Shooter
Posts: 576
yes
Real Name: George
Re: Hacking the Crosman Vigilante
«
Reply #109 on:
May 08, 2017, 10:31:41 PM »
The stock for the Vigilante carbine is moving right along. I was wondering how to deal with the awkward installing and uninstalling of the stock to change the powerlet. I finally decided to do some more milling and carving to make an opening for the powerlet to just drop in through one of the grips. It's still a crude affair, but the scheme works well. The stock can now be installed somewhat permanently with some recessed machine screws. I'll make a cover for the powerlet slot and secure it with a couple of small NIB magnets that will stick to the powerlet cylinder.
I had almost given up hope of ever being to shoot an airgun accurately, but this carbine design has turned the Vigilante into something special. It's like someone else is shooting the gun for me. If the new longer barrel project makes this gun even better I'll probably soil my pants!
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Carlsbad, CA
One test is worth 10 expert opinions!
George Schmermund
Sharp Shooter
Posts: 576
yes
Real Name: George
Re: Hacking the Crosman Vigilante
«
Reply #110 on:
May 13, 2017, 10:48:17 PM »
There was a mention in the early days of this project that the powerlets could be heated in order to maintain a constant pressure in the power plant by controlling the temperature. Someone requested "now to find a way to make it portable". Well, here we are with the way!
The photo shows the Lithium-ion battery pack and the temperature controller as they will be installed in the stock. I'll make a mounting plate for these devices and do the simple wiring needed to power the heaters. This has turned out to be much easier than what I thought would be necessary when the original heaters were installed into the pistol frame and powered using a bench power supply.
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Carlsbad, CA
One test is worth 10 expert opinions!
AmBraCol
Webservant
Expert
Posts: 1662
yes
Real Name: Paul
Re: Hacking the Crosman Vigilante
«
Reply #111 on:
May 13, 2017, 11:48:55 PM »
And suddenly, firing a CO2 gun in the fall and winter becomes doable!
Looking forward to seeing how this progresses.
Logged
Risaralda, Pereira, ColOmbia
I'm a peaceful man and prefer the pursuit of peaceful sports. Those involving teams and balls of any sort tend to be deleterious to one's body and promote violence by both spectators and participants. The shooting sports, however, tend to promote self control and are peaceably participated in by those who know that their greatest challenge is their need to continually hone their own abilities.
Rob M
GTA Senior Contributor
Posts: 6304
Re: Hacking the Crosman Vigilante
«
Reply #112 on:
May 14, 2017, 01:00:29 AM »
very cool..what wattage are the heateers
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Louisiana
George Schmermund
Sharp Shooter
Posts: 576
yes
Real Name: George
Re: Hacking the Crosman Vigilante
«
Reply #113 on:
May 15, 2017, 03:20:05 PM »
The heaters that I'm using are rated for 28 volts. I use 2 of them and can run them in series or parallel using just 12 volts. This will produce either 5.5 or 11 watts for heating. The powerlet's steel case will act as a thermal flywheel for rapid firing. When I finish installing this heating arrangement I'll be able to plot out the powerlet's temperature vs number of shots vs time. This should be interesting.
Logged
Carlsbad, CA
One test is worth 10 expert opinions!
George Schmermund
Sharp Shooter
Posts: 576
yes
Real Name: George
Re: Hacking the Crosman Vigilante
«
Reply #114 on:
May 21, 2017, 04:43:54 PM »
The powerlet heating system is working out well for keeping the CO2 pressure reasonably constant, but there is a practical ( and sensible) limit to how much heat should be applied. Once the powerplant is up to temperature at any given setting, it is the liquid phase of the propellant that is maintaining the pressure in the system. When the gun is fired the gas expands into the barrel and begins to rapidly cool itself and the barrel.
Since the barrel is already at a lower temperature than the heated powerlet, typically, it's a downhill temperature drop from there on. Now, if the barrel was heated to a higher temperature than the powerlet there could be some extra gain in pellet velocity. The heating could be substantially greater than that applied to the powerlet because the barrel is not under pressure except for the few milliseconds that the valve is open and the pellet remains in the barrel.
Using a second temperature controller and heater for the barrel would be easy. There is enough room for another controller board in the stock. The question now is how much heat can be transferred to the CO2 in the short time short time that its in the barrel. Any thoughts out there?
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Carlsbad, CA
One test is worth 10 expert opinions!
Rob M
GTA Senior Contributor
Posts: 6304
Re: Hacking the Crosman Vigilante
«
Reply #115 on:
May 21, 2017, 04:50:59 PM »
the barrel is quite vaguely connected to the valve and co2 cart, id guess bringing the valve up to temp would be more beneficial..
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Louisiana
George Schmermund
Sharp Shooter
Posts: 576
yes
Real Name: George
Re: Hacking the Crosman Vigilante
«
Reply #116 on:
May 21, 2017, 05:16:43 PM »
Actually, the barrel being thermally isolated from the pistol's frame is a good thing. The plastic barrel housing itself is a poor heat conductor and has some heat tolerance (to be determined). The barrel is therefor a good place to do the heating. If the valve was to be heated it would be a large heat sink because it is mounted directly against the metal frame. This would mean that the whole frame would attempt to come to some thermal equilibrium with the valve. That would be a very inefficient use of the battery and ultimately make the frame too hot to hold comfortably without gloves.
Logged
Carlsbad, CA
One test is worth 10 expert opinions!
George Schmermund
Sharp Shooter
Posts: 576
yes
Real Name: George
Re: Hacking the Crosman Vigilante
«
Reply #117 on:
May 21, 2017, 09:54:11 PM »
Doing some preliminary testing for the barrel heating experiments It was instructive to measure the muzzle velocity of some pellets while the gun was back in the vise. With the powerlet temperature at ~ 80º F the first few shots were all well in excess of 600 fps. This was with the new 18" barrel. Within the same clip the velocity began to slowly drop to below 600 fps even with the powerlet temp being maintained. I found this to be a curious situation and waited a short time between shots to see if the velocity would come back up. It slowly crept back up a ways, but not to the initial numbers even thought the powerlet temp stayed the same. I then probed the inside of the barrel with a TC gauge and found that the temperature was several degrees lower than the room temperature. This must mean something!
This is only a simple observation and nothing quantitative, but I thought I'd offer it up for further speculation.
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Carlsbad, CA
One test is worth 10 expert opinions!
Rob M
GTA Senior Contributor
Posts: 6304
Re: Hacking the Crosman Vigilante
«
Reply #118 on:
May 21, 2017, 10:16:16 PM »
very interesting , and the velocity is impressive.. thats higher than the average for a 1077 out of the box.. So, i guess these numbers will be a good baseline for comparison to the heated barrel
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Louisiana
dv8eod
Expert
Posts: 1518
Re: Hacking the Crosman Vigilante
«
Reply #119 on:
May 22, 2017, 01:13:44 AM »
Will you try heating the whole barrel or just a portion of it? It seems to me that the amount of heat needed to counteract the cooling effect from the gas would need to be quite high. Then there is the possibility of warping the barrel around the transfer port. You are rapidly chilling a hot piece of metal. It could lead to a split chamber, an oversize or undersized chamber, or a set bend or bulge. I'm not saying the effects would be immediate, but they are possible with chances getting better over time.
Then again, it's such a small metered amount of gas that is being used, there might not be any effect at all.
Something that might be going on; by heating the cartridge, you are increasing the amount of gas (from pressure) moving through the valve reducing the amount of liquid left in the cartridge. It might explain why it didn't recover to the previous speeds even after the break. The temperature in the barrel is interesting to say the least. I just can't imagine it being so cold as to hold the gas back from rapidly expanding.
As an aside, do you have a method to determine how many CCs are released each time the valve is opened? Something to compare shot to shot?
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Hacking the Crosman Vigilante