FX Barrel liners with and without external o-rings
- Thread starter Drumsnguns
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I would like to chime in with my archery experience, may sound unrelated, but I am an engineer as well and I am willing to call in more opinions with statics+stress engineers as well.
The arrow is a tube, same as the barrel...the material is different but we talking about a tube that suffers accuracy from hard to avoid frequency's.
The arrow you apply a "force" at the end (like hitting a tube end with a hammer) nd flexes a certain amount...same as the barrel (or inside liner if you wish) but you hit the pellet with a hammer, transfers the stress through friction to the tube (plus the internal pressure) and that tube will flex...it will flex between two points these are called "node points". So the "node point" will stay zero and everything in between and outside will "vibrate" with a certain frequency. Now I am trying to use a simplified language everybody shall understand.
(If you brake a time into micro-seconds and you will see the flexing is an amplitude and the two ends flexing more likely in an opposite direction from the centre...and a flex have a frequency and slowly slowing down...not going into details how much is a "flex" amount that comes from a material properties , these can be calculated.)
Very roughly from an ordinary guy's view...between a 1/3rd and 1/4th of a total length from each end is a node point (and remember every tube have it no matter of a length). That point is "moving" zero so doesn't make a sense to put an oring there because that point is not moving anyway. Both ends are hard connected to other parts, these transfers a "vibration" to the body. Only the center portion in between "node points" of the tube you need to dampen down, where you will put the orings, let say 20mm/1 inch from the nod point each side -> inward towards center and one in a middle. Don't use hard material but the oring rubber compound is just perfect. Hot climate= southern folks can use NBR90, and four season folks can stay with NBR70.
Sorry, I wanted to make it pimplier but I am an engineer not a teacher I am not trained to transfer a best knowledge, also have a bit of problem with a language, but hoping you got some picture.
The arrow is a tube, same as the barrel...the material is different but we talking about a tube that suffers accuracy from hard to avoid frequency's.
The arrow you apply a "force" at the end (like hitting a tube end with a hammer) nd flexes a certain amount...same as the barrel (or inside liner if you wish) but you hit the pellet with a hammer, transfers the stress through friction to the tube (plus the internal pressure) and that tube will flex...it will flex between two points these are called "node points". So the "node point" will stay zero and everything in between and outside will "vibrate" with a certain frequency. Now I am trying to use a simplified language everybody shall understand.
(If you brake a time into micro-seconds and you will see the flexing is an amplitude and the two ends flexing more likely in an opposite direction from the centre...and a flex have a frequency and slowly slowing down...not going into details how much is a "flex" amount that comes from a material properties , these can be calculated.)
Very roughly from an ordinary guy's view...between a 1/3rd and 1/4th of a total length from each end is a node point (and remember every tube have it no matter of a length). That point is "moving" zero so doesn't make a sense to put an oring there because that point is not moving anyway. Both ends are hard connected to other parts, these transfers a "vibration" to the body. Only the center portion in between "node points" of the tube you need to dampen down, where you will put the orings, let say 20mm/1 inch from the nod point each side -> inward towards center and one in a middle. Don't use hard material but the oring rubber compound is just perfect. Hot climate= southern folks can use NBR90, and four season folks can stay with NBR70.
Sorry, I wanted to make it pimplier but I am an engineer not a teacher I am not trained to transfer a best knowledge, also have a bit of problem with a language, but hoping you got some picture.
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Thanks, bigHUN,
Very insightful information. Ordered some o-rings and when they arrive I going to start experimenting with placement. Might have to get some 90’s cause I’m south but for now I’ll mess with 70’s.
Very insightful information. Ordered some o-rings and when they arrive I going to start experimenting with placement. Might have to get some 90’s cause I’m south but for now I’ll mess with 70’s.
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Ernest,
Your tip (video) was very helpful. I took the liner out and did the 4 rings in center with teflon tape. I took it a step further and put two rings each a few inches from the center just inside the perceived nodal points. Maybe over kill but the liner went from "Meh" to Stellar. It's still windy and I'm low on air but I did a quick harmonic tune and I'm shooting 0.903" groups at 103 m (113 y), with 38.5 gn NSA at about 910-915 fps. Sub MOA
Not enough air to do some real tuning but I think this is good enough for now. I set up some clay targets which I'll post on the Slugs and Projectiles page. I hit each target on the first shot with a cross wind. That's good enough.
Thanks again for all the help!
KP
Your tip (video) was very helpful. I took the liner out and did the 4 rings in center with teflon tape. I took it a step further and put two rings each a few inches from the center just inside the perceived nodal points. Maybe over kill but the liner went from "Meh" to Stellar. It's still windy and I'm low on air but I did a quick harmonic tune and I'm shooting 0.903" groups at 103 m (113 y), with 38.5 gn NSA at about 910-915 fps. Sub MOA
Not enough air to do some real tuning but I think this is good enough for now. I set up some clay targets which I'll post on the Slugs and Projectiles page. I hit each target on the first shot with a cross wind. That's good enough.
Thanks again for all the help!
KP
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Update:
Nothing is working for me. I'm in touch w FX Cust. Service. I removed the slug liner and put in the pellet liner. I reset the reg back down to low 100's and I can't get a good group at 27 m where I zero. At this setting I'm getting an average velocity of 875 with an ES of 8 with JSB MKII 34 gn. There's something going on that I can't figure out. Maybe the scope? It's a new Athlon Midas Tac, so wouldn't think, but not impossible. Oh well, I have my Gen 1 Impact with 600 mm pellet liner A that shoots around 0.3" groups at 60 m. Here's a target that I shot last night. Note, I started shooting and tuning at 100 Bar and it started looking good but as I continued on the row at the top...it fell apart. Scratching my head. There is a pattern to the groups, though.
.
875 fps; ES-8, HSTA-21.70 (57 mm spring); Valve 8,90 mm....all shot at 27.5 m
Waiting to hear back from FX
Nothing is working for me. I'm in touch w FX Cust. Service. I removed the slug liner and put in the pellet liner. I reset the reg back down to low 100's and I can't get a good group at 27 m where I zero. At this setting I'm getting an average velocity of 875 with an ES of 8 with JSB MKII 34 gn. There's something going on that I can't figure out. Maybe the scope? It's a new Athlon Midas Tac, so wouldn't think, but not impossible. Oh well, I have my Gen 1 Impact with 600 mm pellet liner A that shoots around 0.3" groups at 60 m. Here's a target that I shot last night. Note, I started shooting and tuning at 100 Bar and it started looking good but as I continued on the row at the top...it fell apart. Scratching my head. There is a pattern to the groups, though.
.
Waiting to hear back from FX
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