7 replies to this topic

[Pablo]

I wanted to buy some 3/8" square nylon rods but then I noticed that they are $5.56 per foot which is just way too expensive for me. I wanted to know if acrylic or PVC also worked.
8728K14
8660K31
Edit: Thanks for all the comments, I decided to use delrin but I need to make 5 NF rifles so I'll try PVC for one of them. I'll tell you guys how it works out.

Edited by Pablo, 03 July 2014 - 04:31 PM.

[Drev]

Just buy delrin 8741K34 or 8663K15. A lot of people use it for their plunger rods and it is a very strong plastic. It's cheaper than the nylon you were looking at too.

[Naturalman7]

It's still pricey, but worth it due to machine-ability and reliability.

8741K34

Edited by Naturalman7, 01 July 2014 - 04:16 PM.

[Draconis]

I wanted to buy some 3/8" square nylon rods but then I noticed that they are $5.56 per foot which is just way too expensive for me. I wanted to know if acrylic or PVC also worked.
8728K14
8660K31

Acrylic no, as it has neither the compression impact strength, nor the tensile strength needed for this application. While I personally have not used PVC for plunger rods, Ryan201074362340576 has used it for a bunch of his home-made blaster with great success. I'd still go with Delrin/acetal, though. Nylon is kind of sucky to machine.

[Bchamp22795]

Acrylic no, as it has neither the compression impact strength, nor the tensile strength needed for this application. While I personally have not used PVC for plunger rods, Ryan201074362340576 has used it for a bunch of his home-made blaster with great success. I'd still go with Delrin/acetal, though. Nylon is kind of sucky to machine.

While Ryan has used PVC in the past, I don't recall it being with the same application as a NF Rifle Plunger rod. I have extensive experience using 3/8" square PVC bar with the NF plunger rod specifically.

The problem with the NF plunger rod is that you have to cut a notch in it for the catch. This is okay, as if you cut it correctly (just less than halfway deep has worked in my experience), there aren't any short term issues if the movement of the plunger rod is pulling it straight back, then pulling the trigger.

Here is where the problem is.....most people don't pull the rod straight back. They pull it back and upwards, flexing the plunger rod. Guess which point it flexes at the most? You guessed it, the notch. This will cause it to snap overtime. Why do people do this? Most of the time it is because they aren't strong enough or used to the pull of spring. It could also be that they have short arms, or they are just not conscious of how they are pulling the plunger rod.

The long term affects are mainly due to how soft PVC is. The catch notch will degrade over time, and eventually it will not catch anymore.

I switched to Delrin, but in my experience Delrin is slightly too big for the NF shell as is, so some light dremeling will have to be done on the rear, square hole of the shell that the plunger rod goes through. There are other little issues you'll see with Delrin since it isn't exactly 3/8" square, but I won't get into them now.

Long story short, get Nylon or Aluminum because they are the best options. Avoid PVC for longevity, and Delrin is great, just takes a tad bit more work occasionally.

Edited by Bchamp22795, 02 July 2014 - 01:33 PM.

[Draconis]

Long story short, get Nylon or Aluminum because they are the best options.

I'm ALWAYS going to argue against aluminum use for plunger rods, catches, and triggers. Aluminum will eat eanything else it comes in to contact with, especially plastics, even itself. Lubrication helps, but doesn't eliminate the problem. Polishing helps, but only for a limited time. Beside that, it has a higher density than almost any plastic, and ALL plastics we normally would use, which WILL reduce performance.

[Bchamp22795]

I'm ALWAYS going to argue against aluminum use for plunger rods, catches, and triggers. Aluminum will eat eanything else it comes in to contact with, especially plastics, even itself. Lubrication helps, but doesn't eliminate the problem. Polishing helps, but only for a limited time. Beside that, it has a higher density than almost any plastic, and ALL plastics we normally would use, which WILL reduce performance.

It's true. Don't use aluminum if you don't have the equipment to machine it properly with clean, smooth edges that won't cut into plastic. If you do it well, it shouldn't be a problem, so I take back my previous statement.

Just get Nylon. Don't get aluminum because it doesn't sound like you have any experience with it.

[Draconis]

It's true. Don't use aluminum if you don't have the equipment to machine it properly with clean, smooth edges that won't cut into plastic. If you do it well, it shouldn't be a problem, so I take back my previous statement.

Just get Nylon. Don't get aluminum because it doesn't sound like you have any experience with it.

To be clear, even clean, smooth edges of aluminum will eat plastic due to the surface being comprised of microscopic crystals of corundum.