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No Puff Of Air On Upstroke With Tm Snorkel

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#1 oreos

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Posted 01 September 2014 - 13:27

Hey guys, so i bought a TM snorkel of Ebay, and through a very silly mistake on my part, i used a aerosol can of silicone spray (big no no) to lubricate the plunger of which ate away the O - ring at the top of the barrel. after a good time of kicking myself i replaced the O - ring with the proper replacement, but now no air escapes on the up stroke. The end effect is a vacuum being made within the barrel which pulls the plunger back down with it. All seals have been replaced and sac is new, all vents are clear, but i'm stumped as to the cause. Any ideas? I did a search of the network and couldnt find anything specific (maybe im just silly) all i could find is people saying that it should release a puff of air on both the upstroke and down stroke. It releases perfectly fine on the downstroke though. I can upload a video of it happening if my description is sub par (i have trouble explaining things like this)

 

Thanks for your time all.



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#2 ANM

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Posted 01 September 2014 - 15:15

It should create a vacuum on the down-stroke.  If it fills on the downstroke and does not leak at either end or drip ink from the nib, you pen is OK.


Edited by ANM, 01 September 2014 - 15:16.

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#3 Ernst Bitterman

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Posted 01 September 2014 - 18:03

On the upstroke, there is vacuum; the sac protector is in part there to prevent the sac from distending.  At the top of the stroke, the barrel should vent.  The downstroke compresses the interior air, collapsing the sac; when it vents, the sac expands, and that draws in the ink.

 

The problem at hand suggests that the little hole at the forward end of the touchdown tube, which allows the upstroke venting, is blocked.  However, the upstroke vent is a more subtle sound than the filling stroke's-- if it makes a noise on the way down, there's compression, and if there wasn't something releasing at the top, the downstroke would just get the interior pressure back to the status quo.


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#4 pen lady

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Posted 01 September 2014 - 19:41

I hope I'm not hi-jacking this thread, but I had to share a tip for replacing "O" rings.  I found a disposable mechanical pencil that's the right diameter to almost fill the outer barrel but leaves just enough room to push the lubed-up "O" ring into place. bracing it against the pencil nose-cone.  Inserted an "O" ring yesterday in under a minute with minimal cursing!


Edited by pen lady, 01 September 2014 - 19:45.


#5 ANM

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Posted 01 September 2014 - 22:21

I don't believe it "puffs" on the up-stroke.  More like it 'breathes'  The fact that you can pull it up easily enough is evidence that the air is escaping on the up-stroke. 


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#6 oreos

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Posted 02 September 2014 - 16:07

On the upstroke, there is vacuum; the sac protector is in part there to prevent the sac from distending.  At the top of the stroke, the barrel should vent.  The downstroke compresses the interior air, collapsing the sac; when it vents, the sac expands, and that draws in the ink.

 

The problem at hand suggests that the little hole at the forward end of the touchdown tube, which allows the upstroke venting, is blocked.  However, the upstroke vent is a more subtle sound than the filling stroke's-- if it makes a noise on the way down, there's compression, and if there wasn't something releasing at the top, the downstroke would just get the interior pressure back to the status quo.

Ernst thats it, from what i can hear it doesn't not breath at the top stroke. If i use the mechanism multiple times (i know dont place snorkel in the ink on upstroke haha) , the puff of air at the bottom of the downstroke essentially stops. in all it works perfectly fine on the first 'pump' but there after it gives diminishing returns. Thanks all for replying and again i hope i'm making sense XD



#7 Ron Z

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Posted 02 September 2014 - 16:16

You may not hear anything at all on the upstroke of the TD tube.  Silence is not unusual.   You should hear a "chiff" at the end of the downstroke.

 

A basic misunderstanding of how a snorkel works here....

 

The snorkel is a pneumatic filler.  When you push the touchdown down (TD) tube,  the air in the barrel is compressed, as is the sac inside the sac guard.  There is a 1/4" long notch at the top of the TD tube.  When the end of the notch slips past the 0-ring in the barrel, the air pressure is released, the sac expands, and ink flows into the sac.  The upstroke therefore has nothing to do with the filling process.  On the contrary, it produces a vacuum in the barrel, which is why it's especially important not to pull the TD tube back with the nib and/or snorkel tube immersed in ink.  The vacuum created may draw ink in past the point holder gasket around the snorkel tube and into the barrel instead of the sac.  Note that the sac itself can't expand because it's encased in the sac guard.  To fill, put the snorkel tube in the ink, push the TD tube down, wait 10 seconds, withdraw.   If you want to do it again, don't immerse again until the TD tube is all of the way back.  Not that there is much benefit to that, but some folks like to do it a couple of times.

 

If you have been cycling the TD tube up and down to pump ink into the pen I strongly suggest that you take the pen apart and check to see if it's wet inside.  If it is, dry everything off and don't think of using the pen until it is serviced.


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#8 kirchh

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Posted 02 September 2014 - 17:58

You may not hear anything at all on the upstroke of the TD tube.  Silence is not unusual.   You should hear a "chiff" at the end of the downstroke.

 

A basic misunderstanding of how a snorkel works here....

 

The snorkel is a pneumatic filler.  When you push the touchdown down (TD) tube,  the air in the barrel is compressed, as is the sac inside the sac guard.  There is a 1/4" long notch at the top of the TD tube.  When the end of the notch slips past the 0-ring in the barrel, the air pressure is released, the sac expands, and ink flows into the sac.  The upstroke therefore has nothing to do with the filling process.  On the contrary, it produces a vacuum in the barrel, which is why it's especially important not to pull the TD tube back with the nib and/or snorkel tube immersed in ink.  The vacuum created may draw ink in past the point holder gasket around the snorkel tube and into the barrel instead of the sac.  Note that the sac itself can't expand because it's encased in the sac guard.  To fill, put the snorkel tube in the ink, push the TD tube down, wait 10 seconds, withdraw.   If you want to do it again, don't immerse again until the TD tube is all of the way back.  Not that there is much benefit to that, but some folks like to do it a couple of times.

 

If you have been cycling the TD tube up and down to pump ink into the pen I strongly suggest that you take the pen apart and check to see if it's wet inside.  If it is, dry everything off and don't think of using the pen until it is serviced.

 

This is incorrect. For the downstroke to produce maximum compression, thus deflating the sac, the upstroke must not produce a vacuum in the interior volume when the mechanism is at full extension. Therefore, the vacuum that is created while the filler is withdrawn and the volume in the chamber increases must be released at the top of the upstroke so the pressure is equalized with that of the atmosphere.

 

There is, of course, a short notch or groove at the top (knob end) of the Touchdown tube that breaches the seal between the tube and the O-ring when the plunger is depressed, allowing the pressure inside the pen to be released and permitting the sac to expand and resume its natural shape, drawing in ink in the process. However, there is also a vent hole at the bottom (nib end) of the Touchdown tube (a simple hole in Snorkels, a rather more involved depression in a non-Snorkel Touchdown pen). This vent hole releases the vacuum at the terminal extent of the upstroke of the filler. Here's what the vent hole looks like in a Snorkel:

 

Snorkel_vent_hole.jpg

 

This feature (labeled feature 61) is clearly described in the Touchdown patent:

 

"One of more longitudinally extending grooves 60 are also provided on the forward end of the tubular member 40 so that when the tubular member is in the fully extended position the groove 60 spans the packing gland [O-ring] 54, thus again venting the chamber to the atmosphere. Thus any vacuum created when the tubular member 40 is extended is dispelled through the groove 60  prior to the time that the compression stroke is commenced as above described. In addition, tubular member 40 is provided with one or more vent holes 61 in the groove or grooves, these vent holes also being positioned so that they are positioned to the read of the packing gland 54 when the tubular member is fully extended. If desired, the grooves 60 may be omitted, the function thereof being supplied by the vent holes 61. In such a case any vacuum created in the chamber will, upon full extension of the tubular member, be dispelled through the vent holes 61  and the annular passageway between the tubular member 41 and the sheath 30."

 

Indeed, when the filler is extended on a properly-functioning Touchdown, there is an ingress of air at the top of the stroke; this can be clearly heard, though likely by virtue of the air being draw in, rather than expelled, the sound is not as obvious. If there is no such sound, or, as has been described in this thread, if there "is a vacuum being made within the barrel which pulls the plunger back down with it," it is an indication that the vacuum is not being released, and the filler may not function properly, as the sac may not be sufficiently evacuated on the downstroke.

 

I suggest examining the vent hole in the pen under discussion. My suspicion is that you will find that it is blocked, perhaps by some debris from an old sac, or by a bit of shellac, or corrosion, or random crud.

 

--Daniel


Edited by kirchh, 02 September 2014 - 18:01.

"The greatest mental derangement is to believe things because we want them to be true, not because we observe that they are in effect." --Jacques-Bénigne Bossuet

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#9 kirchh

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Posted 02 September 2014 - 18:03

I don't believe it "puffs" on the up-stroke.  More like it 'breathes'  The fact that you can pull it up easily enough is evidence that the air is escaping on the up-stroke. 

 

Note that this is not accurate. The plunger should, in fact, offer increasing resistance on the upstroke of a properly-sealed Touchdown as it creates a vacuum in the barrel. That vacuum is released at the top of the upstroke.

 

--Daniel


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#10 kirchh

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Posted 02 September 2014 - 18:05

On the upstroke, there is vacuum; the sac protector is in part there to prevent the sac from distending.  At the top of the stroke, the barrel should vent.  The downstroke compresses the interior air, collapsing the sac; when it vents, the sac expands, and that draws in the ink.

 

The problem at hand suggests that the little hole at the forward end of the touchdown tube, which allows the upstroke venting, is blocked.  However, the upstroke vent is a more subtle sound than the filling stroke's-- if it makes a noise on the way down, there's compression, and if there wasn't something releasing at the top, the downstroke would just get the interior pressure back to the status quo.

 

Credit goes to Ernst for first identifying this likely cause of the problem.

 

--Daniel


"The greatest mental derangement is to believe things because we want them to be true, not because we observe that they are in effect." --Jacques-Bénigne Bossuet

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#11 Ernst Bitterman

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Posted 02 September 2014 - 20:50

...and thanks to Daniel for a picture of the item I'm concerned about; all of my TD pens are closed and I'm not anxious to take one apart unless it wants me to.


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#12 oreos

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Posted 03 September 2014 - 18:29

So i pulled the barrel assembly apart, and the hole at the base of the filler tube (not sure if right term, the one pictured above haha) is clear as day. Now i'm stumped. Anyone have any other suggestions? Thanks again for all the helpful replies.



#13 kirchh

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Posted 03 September 2014 - 19:47

So i pulled the barrel assembly apart, and the hole at the base of the filler tube (not sure if right term, the one pictured above haha) is clear as day. Now i'm stumped. Anyone have any other suggestions? Thanks again for all the helpful replies.

 

This may seem like a silly question, but are you certain that you installed the new O-ring in the proper location? If it's too high, the vent hole in the tube will not clear it and the vacuum will not be broken.

 

--Daniel


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#14 oreos

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Posted 04 September 2014 - 03:55

Thanks Daniel, Im certain it is in the right place, under the hole at the top end of the barrel in it's neat little groove. If i have happened to place it in the wrong spot feel free to point out my stuff up ahah. Im not really sure how to use the attachment mechanisms on this board sorry, so i just provided a link instead. Thanks again

http://imgur.com/uj0oCo5



#15 KBeezie

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Posted 04 September 2014 - 04:40

Also to re-iterate with the snorkels. Moving the plunger slowly does nothing, they're pneumatic fillers, not vac fillers. By quickly changing the air pressure surrounding the sac (Either by extending or pressing down quickly) it forces a change inside of the sac either by expanding or contracting. 

 

It also takes time to do this sometimes up beyond 10 seconds if the seals are not good (to not at all if the seals are really bad). 

 

It helps to grease the o-ring if you're doing a restoration (ie: silicon grease) to help make it a bit more air tight.

 

In regards to actually filling it:

 



#16 kirchh

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Posted 04 September 2014 - 05:57

Thanks Daniel, Im certain it is in the right place, under the hole at the top end of the barrel in it's neat little groove. If i have happened to place it in the wrong spot feel free to point out my stuff up ahah. Im not really sure how to use the attachment mechanisms on this board sorry, so i just provided a link instead. Thanks again

http://imgur.com/uj0oCo5

 

Looks right, though I can't be absolutely certain.

 

Try to examine the area with a good light and a loupe; when the plunger is fully extended, can you see the vent hole above the O-ring? The vent hole must clear the O-ring in order to release the vacuum in the barrel. Obviously, the vent hole must be clear, and also it must not be obstructed when the plunger is fully extended; might there be something stopping the full extension of the plunger?

 

With the tube installed in the barrel (complete with filler knob with gasket sealing up the tube) you should be able to blow through the mouth of the barrel and have the air come out from the vent hole when the plunger is fully extended.

 

--Daniel


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#17 kirchh

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Posted 04 September 2014 - 06:03

Also to re-iterate with the snorkels. Moving the plunger slowly does nothing, they're pneumatic fillers, not vac fillers. By quickly changing the air pressure surrounding the sac (Either by extending or pressing down quickly) it forces a change inside of the sac either by expanding or contracting. 

 

It also takes time to do this sometimes up beyond 10 seconds if the seals are not good (to not at all if the seals are really bad). 

 

It helps to grease the o-ring if you're doing a restoration (ie: silicon grease) to help make it a bit more air tight.

 

In regards to actually filling it:

 

 

The speed with which the pressure changes inside the barrel is not relevant, as long as it does change enough to deflate the sac; whether the sac is deflated rapidly or slowly, as long as it's deflated, it will fill fully when the pressure is released. Now, the amount of pressure that can be built over a given duration of plunger depression is dependent on the quality of the seals involved; if all the seals are perfect, you can take as long as you want depressing the plunger and you will still achieve complete evacuation of the sac; there is no momentum of pressurization involved. If the seals are less than perfect they will bleed pressure during the downstroke, so depressing the plunger rapidly will minimize the amount of time a pressure differential is presented to those leaky seals and will preserve more of the pressure needed to deflate the sac.

 

--Daniel


Edited by kirchh, 04 September 2014 - 14:42.

"The greatest mental derangement is to believe things because we want them to be true, not because we observe that they are in effect." --Jacques-Bénigne Bossuet

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#18 oreos

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Posted 05 September 2014 - 09:32

 

Looks right, though I can't be absolutely certain.

 

Try to examine the area with a good light and a loupe; when the plunger is fully extended, can you see the vent hole above the O-ring? The vent hole must clear the O-ring in order to release the vacuum in the barrel. Obviously, the vent hole must be clear, and also it must not be obstructed when the plunger is fully extended; might there be something stopping the full extension of the plunger?

 

With the tube installed in the barrel (complete with filler knob with gasket sealing up the tube) you should be able to blow through the mouth of the barrel and have the air come out from the vent hole when the plunger is fully extended.

 

--Daniel

Hey Dan, i tried the blowing air through the barrel method you said, and it was solid, no air was moving anywhere when the plunger was fully extended. It appears thats my problem. Would it be the O ring itself or simply the positioning of it in the barrel in your (or anyones) opinion? when i get home ill snap a pick of the plunger extended, but i don't feel as if something is blocking it and stopping it from fully extending because it did work pre stuff up on my behalf

Thanks



#19 Ernst Bitterman

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Posted 05 September 2014 - 15:19

Sounds like something occluding the vent at the tail of the barrel, if the one in the TD tube is clear.  It could be an over-enthusiastic daub of grease (I know I've done that), but if it's standing up to the power of lungs then it's probably something more solid.  If the o-ring isn't in its groove, that could cause the problem, but if it's not in the groove it's usually quite in the way of putting the pen back together.  I'd take the pen apart (again, and a sigh is appropriate at this point) and run a pin into that tail vent to see if it's clear.


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#20 Ron Z

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Posted 05 September 2014 - 15:58

Apparently I hadn't read your post completely.  There are days....

 

I wonder if something that was lodged in the barrel was knocked loose when you sprayed the lubricant on things or maybe the original 0-ring wasn't eaten away but was dislodged and pulled down, and is still in the barrel?  A bit of rusted spring, the original 0-ring or something could be inside at the end and be just thick enough that the TD tube doesn't pull back completely.  Take the TD tube out of the barrel again and look inside with a penlight and a loupe if you need to.  It could right at the end, just below the sharp step below the 0-ring that the end of the TD tube hits to stop the tube from being pulled out the end.  Not saying that IS the case, but I'd check to be sure.


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