19 replies to this topic

[Samurai kidd]

First off, thanks to MIG for his spring-tightening method. Without it, this would not be possible. Also, thanks to Poptachi and his YT channel; I was watching it when I got the idea.

To begin, you need this stuff:
PETG
1/2” Brass
17/32” brass (optional)
Lighter or hairdryer



Nest the 1/2” brass in the PETG. Use the 17/32” brass if you want to keep part of the PETG at it's original dimensions.



Heat a section of the PETG with the lighter. This works best if you rotate the tubing quickly and keep the section between 1-2 inches.



Pull (yes, pull) the two ends of the PETG apart. This stretches the tubing and shapes the ID to fit the OD of the 1/2” brass, giving the PETG a similar ID to 17/32” brass. The 17/32” brass keeps that section of the tubing at a 17/32 ID, or normal ID.

Move along, and do the same to the rest of the tubing.



This is really easy to do, and has a great fit for darts. Unlike the spring method, the ID is a lot more constant so the dart seal should be a bit better.







Q/C/F?

[DartSlinger]

The PETG looks very wrinkled. Is it still straight?

[Crusher9051]

Is there any noticeable difference like range, and/or accuracy?

[Draconis]

'DartSlinger', on 18 Feb 2013 - 10:29 PM, said:

The PETG looks very wrinkled. Is it still straight?

No, it is not. I was attempting to use a similar method when attempting to create my own sleeves for the rockets. No matter how slow and even I heated the plastic (I was using PETE pop bottles), they would come out all mottled and distorted when they shrank. This seems to be partially due to the water which is trapped in the polymer matrix (PETx polymers are hygroscopic, and thus absorb a small amount of water), because it does not heat at the same rate and then wants to evaporate out, which in turn cools that area slightly. This is a problem for reuse, but not really during the original manufacturing process because the new, hot plastic bottle blanks have not had time to absorb any water yet.

All that said, you are better off using a different material and shoving it inside the PETG.

[burning-ice]

'Draconis', on 18 Feb 2013 - 11:14 PM, said:

No, it is not. I was attempting to use a similar method when attempting to create my own sleeves for the rockets. No matter how slow and even I heated the plastic (I was using PETE pop bottles), they would come out all mottled and distorted when they shrank. This seems to be partially due to the water which is trapped in the polymer matrix (PETx polymers are hygroscopic, and thus absorb a small amount of water), because it does not heat at the same rate and then wants to evaporate out, which in turn cools that area slightly. This is a problem for reuse, but not really during the original manufacturing process because the new, hot plastic bottle blanks have not had time to absorb any water yet.

All that said, you are better off using a different material and shoving it inside the PETG.

Adding to that, I know that when people go to mold polycarbonate and other plastics, they bake them at somewhere around 120 degrees celsius to remove most water. Not sure if this link is approved but, Heat-treating Polycarbonate. This is an option but is not practical unless you can find a spare oven.

[Draconis]

'burning-ice', on 18 Feb 2013 - 11:49 PM, said:

Adding to that, I know that when people go to mold polycarbonate and other plastics, they bake them at somewhere around 120 degrees celsius to remove most water. Not sure if this link is approved but, Heat-treating Polycarbonate. This is an option but is not practical unless you can find a spare oven.

Yes, and one which is calibrated to Celsius, apparently.

[481IceDragon]

My question is how do you get out the brass after the poly carb has formed to it?

[BiwinningPanda]

'481IceDragon', on 19 Feb 2013 - 01:36 AM, said:

My question is how do you get out the brass after the poly carb has formed to it?

The material is PETG, not polycarbonate. Also, I have done something similar before and the PETG does not stick when you heat it, so you can just pull it right off.

[Samurai kidd]

'Draconis', on 18 Feb 2013 - 11:14 PM, said:

No, it is not. I was attempting to use a similar method when attempting to create my own sleeves for the rockets. No matter how slow and even I heated the plastic (I was using PETE pop bottles), they would come out all mottled and distorted when they shrank. This seems to be partially due to the water which is trapped in the polymer matrix (PETx polymers are hygroscopic, and thus absorb a small amount of water), because it does not heat at the same rate and then wants to evaporate out, which in turn cools that area slightly. This is a problem for reuse, but not really during the original manufacturing process because the new, hot plastic bottle blanks have not had time to absorb any water yet.

All that said, you are better off using a different material and shoving it inside the PETG.

Both of the sections I used are straight. I don't understand how they wouldn't be, seeing as how it's being molded onto something else that's perfectly straight. There are a few wrinkles along the tubing, but that's due entirely to human error and laziness. The pictures here are from mainly my first attempt, the next few trials went much more smoothly.

Based on what you're saying, PETG can't be successfully tightened and we should all just give up.

'Crusher9051', on 18 Feb 2013 - 11:03 PM, said:

Is there any noticeable difference like range, and/or accuracy?

I don't know, is there any difference in ranges when you use 17/32" brass instead of 9/16"?

Edited by Samurai_kidd, 18 February 2013 - 09:32 PM.

[ShaNayNay]

'Samurai_kidd', on 19 Feb 2013 - 02:25 AM, said:

Both of the sections I used are straight. I don't understand how they wouldn't be, seeing as how it's being molded onto something else that's perfectly straight. There are a few wrinkles along the tubing, but that's due entirely to human error and laziness. The pictures here are from mainly my first attempt, the next few trials went much more smoothly.

Based on what you're saying, PETG can't be successfully tightened and we should all just give up.



I don't know, is there any difference in ranges when you use 17/32" brass instead of 9/16"?

Could we please see some images of your later attempts instead of the imperfect 1st attempt pictures? I feel like that may solve the argument.

Also, do the occasional wrinkles cancel out any potential range increase, or do you really get more range and/or accuracy out of this method?

[Samurai kidd]

'ShaNayNay', on 19 Feb 2013 - 04:07 AM, said:

Could we please see some images of your later attempts instead of the imperfect 1st attempt pictures? I feel like that may solve the argument.

Also, do the occasional wrinkles cancel out any potential range increase, or do you really get more range and/or accuracy out of this method?

I'll try to get some tomorrow. The wrinkles don't really affect the seal, definitely not more so than rings would. Something I've noticed from the spring method is that it can cause spaces between the rings to expand. The real advantage of this is that it's easier to do and easier to get the materials for. The only spring I've found that can tighten PETG is the stock vulcan spring.

[andtheherois]

With the effort it takes to do this, I would say just buy the 17/32 brass and slip it in the PETG. Assuming you place a mcmaster order to get your PETG, adding 3 lengths of brass is only 10 bucks more. Small price to pay to save you the effort of dealing with fire and iffy methods. Not only that but stretching it also weakens the PETG. Using this in a high powered springer would most likely cause it to shatter.

[Draconis]

'Samurai_kidd', on 19 Feb 2013 - 02:25 AM, said:

Both of the sections I used are straight. I don't understand how they wouldn't be, seeing as how it's being molded onto something else that's perfectly straight. There are a few wrinkles along the tubing, but that's due entirely to human error and laziness. The pictures here are from mainly my first attempt, the next few trials went much more smoothly.

ANY wrinkles would cause a sealing problem, as they run the length of the barrel. Tightening rings run perpendicularly and would not have the same issue.

Quote

Based on what you're saying, PETG can't be successfully tightened and we should all just give up.

Not at all. I'm saying that it is unlikely to be able to be shrunk consistently using even heating sources, and using flame is just retarded.

Quote

I don't know, is there any difference in ranges when you use 17/32" brass instead of 9/16"?

Don't be a dick. It was a simple, pertinent question that was not (and still hasn't been) answered.

[burning-ice]

'Draconis', on 19 Feb 2013 - 01:23 AM, said:

Yes, and one which is calibrated to Celsius, apparently.

If you are in Canada, or outside the US, or simple conversion can be done. I do see this method of brass as a way to do "rifling." Instead of stretching the PETG, twist itsto it has spirals, yes this would be a sealing problem, maybe even a crooked barrel. If someone finds out a way to do this with out ruining the integrity of an air seal, bravo!
EDIT: Twisting the PETG whilst pulling it apart could possibly result in better air seal and a "rifled" barrel!

Edited by burning-ice, 19 February 2013 - 04:22 PM.

[Samurai kidd]

Alright, I've got some new pictures and some new info.
First and foremost, here's one of my later attempts. It's much less wrinkled than the original. It's still a bit warped in places; this would be easier if I had both hands to manipulate the PETG, but I can't find my Zippo.



On a related note, I realized that this method has a much different fit and use than the spring method. I didn't remember at first, but I made another ringed barrel for comparison's sake and realized that it's much looser than the stretched PETG.

As you can see, the stretched tubing has a springer fit:



and the ringed tubing has a loose push fit, somewhere between airgun and springer:



I believe MIG was trying to create something to replace the brass stubs in turreted airguns, and for that purpose, his method works perfectly. However, I was trying to create something that would allow me to use airgun PETG, which is thin and cheap, as a springer material to replace the barrels in blasters like the maverick and to replace seated brass in stock barrels. I feel that the stretch method accomplishes this better.

It is very possible, however, that I messed up MIG's spring method and used the wrong sized spring or something, and that is what's affecting the dart fit. I couldn't really imagine trying to fit a tighter spring on, though.

'andtheherois', on 19 Feb 2013 - 05:44 AM, said:

With the effort it takes to do this, I would say just buy the 17/32 brass and slip it in the PETG. Assuming you place a mcmaster order to get your PETG, adding 3 lengths of brass is only 10 bucks more. Small price to pay to save you the effort of dealing with fire and iffy methods. Not only that but stretching it also weakens the PETG. Using this in a high powered springer would most likely cause it to shatter.

10 bucks is a lot to me. Gotta eat.
Is there really that much energy transferred into the barrel? I guess I'll have to test it out.

*edit
I nested a piece in PVC and then took several shots out of my snapbow. I don't think it's going to break any time soon; how many shots would you expect before it cracks/shatters?

'Draconis', on 19 Feb 2013 - 6:10 PM, said:

ANY wrinkles would cause a sealing problem, as they run the length of the barrel. Tightening rings run perpendicularly and would not have the same issue.


Not at all. I'm saying that it is unlikely to be able to be shrunk consistently using even heating sources, and using flame is just retarded.

The wrinkles are small enough that any war-legal darts have enough foam to seal both sides before escaping air would be an issue. Here's what I mean:


Compared to the spring method:




The wrinkles can also be avoided, or at least minimized, like in the newer barrel. The spiral rings created by the spring method allow a small channel for air to pass through and get ahead of the dart. The leak is still probably negligible, but from blow-testing (yeah, I know, I'm gay) some air escapes around the dart in my ringed PETG and no air escapes in the stretched PETG. This may be a result of the looser dart fit/me messing up,though.

It's consistent enough. I don't own a heatgun, and the hairdryer was too loud to use (During weekdays I mod ~midnight-2 AM). I'll give it a go with the hairdryer this weekend and see if I can improve results. Using fire isn't retarded, but I do agree that a heatgun would be a better path. So far I haven't burned myself, and I think it would take an awful lot of incompetence for someone to do so. You're really more likely to hurt yourself making glue domes.

'burning-ice', on 19 Feb 2013 - 9:21 PM, said:

Twisting the PETG whilst pulling it apart could possibly result in better air seal and a "rifled" barrel!

The spirals would actually provide channels through which the air could escape.
Rifled barrels do absolutely nothing to improve range or accuracy of nerf darts. The trajectories are too different.

'Crusher9051', on 18 Feb 2013 - 11:03 PM, said:

Is there any noticeable difference like range, and/or accuracy?

If you're still wondering, yes. It depends on your darts, but if they have a "springer" fit (tight push fit) in 17/32" brass then they will have a very similar fit in this.

Quote

Upon review, yes they would. On another hand, use a candle for the flame as it requires no hands to operate past the lighting.

I thought about using a candle, but all of mine are sunken too much. Maybe if I can find one without big wax walls.

Edited by Samurai_kidd, 21 February 2013 - 08:34 AM.

[burning-ice]

Quote

The spirals would actually provide channels through which the air could escape.
Rifled barrels do absolutely nothing to improve range or accuracy of nerf darts. The trajectories are too different.

Upon review, yes they would. On another hand, use a candle for the flame as it requires no hands to operate past the lighting.

[Exo]

'burning-ice', on 21 Feb 2013 - 03:11 AM, said:

Upon review, yes they would. On another hand, use a candle for the flame as it requires no hands to operate past the lighting.

Other than Bob and MiG's slight playing with pre-rifled PETG, there has been nothing done with streamlines and rifling. And the Asian faction doesn't count, their darts are way too different, and they haven't posted much about their rifling anyways.

[makeitgo]

The 'Vulcan' spring you used is weak in comparison to the Lowe's springs I sighted:



The PETG is strong enough to stretch the Vulcan spring that it doesn't tighten enough.

Plus, you stated that you couldn't use your hair dryer because it's too loud. Does that mean you used your flame method to create the rings?

I haven't had a problem with them being springer or airgun fit. All I can say is it works for me, my darts and my springer and air blasters.

Edited by makeitgo, 21 February 2013 - 09:51 AM.

[Samurai kidd]

'makeitgo', on 21 Feb 2013 - 12:35 PM, said:

The 'Vulcan' spring you used is weak in comparison to the Lowe's springs I sighted:

The PETG is strong enough to stretch the Vulcan spring that it doesn't tighten enough.

I was worried about that.
I'll look for the lowes springs next time I'm there to do a better comparison.

[azrael]

A hot air gun would probably work much better than a lighter, I might try this with mine.