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Effects of plunger seal (Teflon tape)

 
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Effects of plunger seal (Teflon tape)
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SSGT
Nerf Addict


Joined: 12 Jan 2013
Posts: 1273
Fav. Blaster: 'Rave-N' CS-18, Elite Alpha Trooper (EAT) CS-12
Location: Durham



Post Effects of plunger seal (Teflon tape)  Reply with quote
Data for EAT with a 5+kg OMW spring and AR removed. Tested with and without Teflon tape as "seal improvement".

It's something I've wondered for a while now (something similar was discussed a while ago regarding how larger plunger tubes don't necessarily yield better performance with a stock breech). With such a small length of "sealed" barrel (especially since only the first half inch or so is a tight fit) does plunger seal improvement really make a difference? As prep for a game tomorrow I chrono'd a couple of shots from my EAT in it's current form (with about 2 layers of Teflon tape under the o-ring which was only just enough to allow the plunger head to seal along most of the length of the plunger tube) and kept getting around 80fps. More than stock but, if anything, slightly less than the EAT tested by OldNoob/FDS. Which was odd considering mine has also had it's AR removed.

Anyway, I reduced it to 1 layer of Teflon tape (with only a couple of shots it was already firing about 5fps faster) followed by no Teflon tape but this time I recorded the data.

I didn't have a brand spanking new set of darts, or enough of just one code, so I just filtered through them and picked out the newest/best condition Elites (mainly J code) most of which had only been fired once or twice before. Even so, the data is pretty consistent and appears to suggest an approximate loss of around 10fps by adding one layer of Teflon tape under the o-ring.

Although the data is a bit too limited to conclude definitively, it does appear that Elite springers (with their tapered plunger tubes) don't need a "perfect" seal to work to their full potential. In fact, if anything, it prevents it. As far as I can tell this is because a poor seal (and low friction) for the first 3/4 of the plunger stroke allows the plunger to reach a greater velocity which allows for a greater peak pressure in the final 1/4 of the plunger stroke. With a good seal the dart leaves the barrel before the plunger rod has travelled very far at all and whilst it is still travelling relatively slowly. I'm pretty sure this is only applicable to stock breech systems as, in those cases, the effective barrel is so short that peak pressure is more important than outright plunger volume.

In short, don't bother with seal improvements around the plunger head area in blasters with stock breeches and especially in Elite blasters.

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Last edited by SSGT on Tue Oct 07, 2014 12:24 pm; edited 1 time in total
Sat Oct 04, 2014 10:57 pm View user's profile Send private message
OldNoob
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Joined: 07 May 2013
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Post Reply with quote
Thanks for that- as a small sample it supports my argument that seal padding hurts performance, as do o rings that are too tight. A full test on this should be on our agenda as numerous YouTube mod guides by well established modders still include this as a thing.
Very useful data as a starting point for debunking another myth.

EDIT- I hit Reddit with this....

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Big_Poppa_Nerf wrote:

Boff whats the damage? I have spent over 3 times my Nerf budget this month already. Part of me is trying to be a responsible parent/husband/house owner. The other half is just says 'Ahhhh, Screw it!'.
Sun Oct 05, 2014 11:12 am View user's profile Send private message Send e-mail
old_man_nerf
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Joined: 25 Jan 2013
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Post Reply with quote
And I thought I was supposed to do the opening of tinned worms..... Good luck over there!
Sun Oct 05, 2014 7:33 pm View user's profile Send private message Visit poster's website
MarcusH
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Post Reply with quote
old_man_nerf wrote:
And I thought I was supposed to do the opening of tinned worms..... Good luck over there!


The worms arent just out of the can over there.... they have left the can and are all over the floor Very Happy

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Sun Oct 05, 2014 8:08 pm View user's profile Send private message Send e-mail
DukeWintermaul
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Joined: 05 Feb 2014
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Post Checkout this brilliant subject line Reply with quote
An interesting find that needs much more exploration and variation.
Sun Oct 05, 2014 8:20 pm View user's profile Send private message Visit poster's website
OldNoob
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Joined: 07 May 2013
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Fav. Blaster: Xtreme 180 Rapidstrike
Location: In the Boonies



Post Reply with quote
I thought so. We could do with a "myth busters" type thread where we test everything like spring stretching, penny mods eat and see if they actually work. That has always been the purpose of this sub forum, so anyone (not just me!) can test stuff and post their results.

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Big_Poppa_Nerf wrote:

Boff whats the damage? I have spent over 3 times my Nerf budget this month already. Part of me is trying to be a responsible parent/husband/house owner. The other half is just says 'Ahhhh, Screw it!'.
Sun Oct 05, 2014 8:34 pm View user's profile Send private message Send e-mail
Antonius
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Post Reply with quote
OldNoob wrote:
I thought so. We could do with a "myth busters" type thread where we test everything like spring stretching, penny mods eat and see if they actually work. That has always been the purpose of this sub forum, so anyone (not just me!) can test stuff and post their results.

Shhh! We want to get easy answers to hard questions.
Questions like: "I only have £5. How do I get the best blaster EVAR?!?!1one!"

Razz

Kidding! More data, more testing, better blasters!

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Sun Oct 05, 2014 9:29 pm View user's profile Send private message
SSGT
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Joined: 12 Jan 2013
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Fav. Blaster: 'Rave-N' CS-18, Elite Alpha Trooper (EAT) CS-12
Location: Durham



Post Reply with quote
DukeWintermaul wrote:
An interesting find that needs much more exploration and variation.

I completely agree. This was a small scale test with only one blaster. Other blasters and even other EATs may respond differently to plunger seal improvement. This particular EAT may already have a near optimal setup (hence why it only took one layer of Teflon tape to cause a noticeable performance drop) whereas other EATs may have a particularly poor seal in which case a layer or two of Teflon tape (or an ever so slightly larger o-ring) could actually increase performance. The only thing I'd take from this data is that a "near perfect" or "99%" seal won't necessarily increase the blaster's performance, at least not with a stock barrel/breech system. It definitely shouldn't be taken as the be-all and end-all against seal improvement mods.

EDIT:
I noticed on reddit that a lot of people have mentioned that Elite blasters shouldn't have their seal improved because of the floating o-ring/ported design of the plunger head. In certain blasters, where there is a constant seal between the barrel and the exit of the plunger tube (Jolt, FireStrike etc.) the o-ring must be free to move to allow air to enter as the plunger moves back otherwise, if the blaster is fired too rapidly for air to leak past the dart or any seals, the plunger won't be able to reach the desired pressure (less air in the plunger to compress). During priming in a blaster like the EAT, where the back of the bolt moves into the plunger itself and there is a second o-ring to seal it, this isn't as big an issue as the bolt-plunger interface doesn't seal until the blaster is fully primed with the priming slide/pump fully forward. With or without a ported plunger head/floating o-ring air can enter the plunger between shots. The plunger tube, at least in an EAT, also has a small slit acting as a port at the back of it (just before the plunger retention ring) which also allows air to enter the plunger tube while the blaster is primed.

tl;dr - As far as I can tell (since the blaster has two other means of allowing air into the plunger tube between shots) it's excessive friction not the lack of a floating o-ring/ported plunger head that caused the 10fps drop in the EAT tested with Teflon tape. I did not add or remove lubricant between tests either (if anything the test with no Teflon tape had less lubricant since the Teflon tape setup was tested first).



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Trust me, I'm an engineer! Very Happy

Antonius wrote:
Compoooter bits make shiny Nerf blaster go whoosh!
Mon Oct 06, 2014 1:19 pm View user's profile Send private message
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