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HAM Sniper
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EVOL Evol .30 5000 psi Burst Disk Thread Pitch?
- Thread starter Ezana4CE
- Start date
- Latest activity Latest activity:
- Replies 75
- Views 9K
- Original poster
- #62
@Airgun-hobbyist I have not been able to get it to hold air. I haven’t done anything else to it since my last post in this thread. The next step will likely be to make a Delrin disc. That’s been the consensus among knowledgeable and experienced airgunners and airgunsmiths whose opinions that I value. I have to make time to do it once I get some Delrin. Thanks again for your timely input. It is very much appreciated. And thanks for following up with me on this.
- Original poster
- #63
Last edited:
To update the thread, I ordered some Delrin rods and I'll try making Delrin discs to remedy this issue once they arrive and I make time to do so. I opted to go this route because I have been curious about making small things like this for myself. If I can't successfully make what I need, I've had an offer from a generous member to send me a disc or something to seal this area. I may take them up on it if I need to and if the offer still stands.
I might of missed it...
Some compressors pulsate at the output more than others. This causes a vibration in the air column, which can vibrate the burst disc. This eventually causes the disc to fail. Fact is, some types of valves do the same thing. It is always best to carry spares in your range kit.
Some compressors pulsate at the output more than others. This causes a vibration in the air column, which can vibrate the burst disc. This eventually causes the disc to fail. Fact is, some types of valves do the same thing. It is always best to carry spares in your range kit.
any luck as of yet?
Hateful McNasty
Grand HAMster
Yup, I got that too. Thing is the longer I let them sit it's become a long sit now .. lol. As long as I got things to shoot and shoot so well that procrastinating sets firmly.
- Original poster
- #68
Last edited:
Update time:
So I took the advice of @Hateful McNasty and @Airgun-hobbyist (post #s 54 & 56) and used the plastic cap of a gallon milk jug (I didn’t photograph it before I cut it up). I cleaned it with soap and water, let it dry, then cleaned it with isopropyl alcohol and cotton swabs and let it dry. Next I used wire cutters to cut through the threads in three places. This made it easier to cut away the threaded sides of the cap leaving the flat top. Taking it in hand, I cut as close to small circles as I could with a pair of sharp scissors and measured them against the bottom of the burst disc.
I selected the best looking makeshift washer on the lower right in the photo below.
Before the circles got too small I punched holes in them with a leather punch as advised by a friend then I measured the alignment against of hole in the piece of the milk jug with the hole in the burst disk. A little Krytox on the flat surface surrounding the hole ensures that the makeshift plastic washer stays put during installation.
Next I screwed in the burst disk and tightened it with a socket. Then I cocked the cocking lever and aired up my Evol from a SCBA tank. It’s been holding air since. Without the makeshift washer it would start dumping air around 1000-1500 psi when I attempted to fill the reservoir. I’ll see how it holds over night.
I was unable to use the Delrin rods because I was told I would need a lathe to machine Delrin disks from a solid Delrin rod.
So I took the advice of @Hateful McNasty and @Airgun-hobbyist (post #s 54 & 56) and used the plastic cap of a gallon milk jug (I didn’t photograph it before I cut it up). I cleaned it with soap and water, let it dry, then cleaned it with isopropyl alcohol and cotton swabs and let it dry. Next I used wire cutters to cut through the threads in three places. This made it easier to cut away the threaded sides of the cap leaving the flat top. Taking it in hand, I cut as close to small circles as I could with a pair of sharp scissors and measured them against the bottom of the burst disc.
I selected the best looking makeshift washer on the lower right in the photo below.
Before the circles got too small I punched holes in them with a leather punch as advised by a friend then I measured the alignment against of hole in the piece of the milk jug with the hole in the burst disk. A little Krytox on the flat surface surrounding the hole ensures that the makeshift plastic washer stays put during installation.
Next I screwed in the burst disk and tightened it with a socket. Then I cocked the cocking lever and aired up my Evol from a SCBA tank. It’s been holding air since. Without the makeshift washer it would start dumping air around 1000-1500 psi when I attempted to fill the reservoir. I’ll see how it holds over night.
I was unable to use the Delrin rods because I was told I would need a lathe to machine Delrin disks from a solid Delrin rod.
Hateful McNasty
Grand HAMster
Well also now your making one up if that goofs you can try a different material/ plastics or something you can grab up around the house and try again .
With that one above I got my
Good luck
- Original poster
- #70
Last edited:
It held pressure overnight. I lost about 200-300 psi due to the filling of the reservoir from the initial fill from zero. It was very warm from the initial fill from empty. However, I think this repair will work. For how long? That remains to be seen, but I’m really thankful for the suggestions. I probably looked like a jerk when a buddy offered to send me a Delrin washer, but I told him that I need to be able to make repairs like this on my own. I haven’t had a whole lot of extra time lately and hadn’t been too motivated to address this burst disk issue, but I managed to get it done with help from the HAM community. I’ll post about any changes if any occur.
Manometer after sitting overnight
Manometer after sitting overnight
- Original poster
- #71
And less than a year later I’m back at square one. I pulled the rifle out to shoot it a little this evening and it had very little, if any, air in the reservoir. I cocked, connected the fill fitting, and began to air it back up. All was well until about the 1500 psi mark, then I began hearing air escaping. At first I thought it might be from the manometer gauge. Nope, it’s the burst disc again. I can feel it with my finger and when I touch the burst disc it impedes the flow of air and sounds different. I think I shot the gun briefly once or twice since i tried the milk jug washer idea. I think I’m ready to get rid of this Evol.
I recently had a problem with an air hose fitting leaking, and I used the thick(3mm) derlin washers that they give with compressors and the small filters. I had to tighten that fitting so much that I thought something was going to break, I really did. Even worse than that, I replaced the airguage on my TalonP and I had to tighten that a full turn past what I believed was safe, to get it to finally stop leaking. Niether items now leak, but man, I couldn't believe how much tightening it took. Easy for me to say, I know, but maybe you need to tighten it more than you think. If you send it to a tuner, or back to AOA, they are just going to put on another burst disc plug, spray on leak detector, and tighten until it stops leaking. With that said, maybe you should just ship it to them to do, and if they screw it up, they will have to fix it. Don't get rid of your gun because of one little part, that isn't even made by AAA. Any other airgun you buy could use the same part and start leaking too, except they won't be made as well as the Evol.
- Original poster
- #73
@Pumacarl I’ve owned and shot enough airguns to have determined which guns fit me. I don’t like working on guns, but I’ve learned to work on several. This is one I’m not going through that with. It’s simply not for me. I never shot it much and have been pretty open about my experiences with it. It’s not trashed and I’m not going to trash it. I’d rather it go to someone who will use and enjoy it. It’s not the gun that’s soured in me, but my experience with it.
I can understand that. It took me a while to actually like using .30 caliber for varmints because of the bafflingly bad performance that I got compared to all the great performance that I have always gotten from .25 caliber. I still like .25 the most, but for porcupines up a tree, or plinking long range, the .30 works and can be great fun. I would part with it quickly though if Tom ever made a lightweight unchoked shrouded barrel 18" twist, in .25.
First impressions, or bad history, are really hard, if not impossible, to get over sometimes.
Airgun-hobbyist
HAM Sniper
As disgruntled as you might be with the failed burst disks and micro leaks, please try one more tactic that we have not done... that's lubing the disk and threads, so it does not seat dry and moves to seal easier. I know they say silicone grease is not a lubricant, but I have found that it does help make sealing disks and o-rings much easier.
American Air Arms
HAM Marksman
General information, most burst disk leaks are due to overtightening. The burst disk is a multi layer/part piece that can leak between the layers when overtightened. Once they leak between the part there is no fixing, the disk must be replaced.
In this case, from the pictures, the bottom of the bore where the burst disk seals looks pretty rough and needs to be resurfaced.
I suggest you send this gun in for repair we can resurface the sealing face in the receiver and replace the burst disk.
Alternatively, we can send you a new burst disk with a copper sealing washer which will conform to both sealing surfaces.
In this case, from the pictures, the bottom of the bore where the burst disk seals looks pretty rough and needs to be resurfaced.
I suggest you send this gun in for repair we can resurface the sealing face in the receiver and replace the burst disk.
Alternatively, we can send you a new burst disk with a copper sealing washer which will conform to both sealing surfaces.
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