Vac700, O-Ring Problem

[stephanos]

I bought my Vac700 in late March 2015 (i.e. just over a year ago) and it has seen moderate use. The large ink capacity makes it ideally-suited for use at conferences or on longer trips, and I enjoy writing with it. The pen has probably been fully inked-up and subsequently cleaned out about half-a-dozen times, perhaps as many as ten times since I got it.

 

There is now a specific problem with the pen, and I have a few questions for you:

1) Have you experienced a similar problem?

2) Is my diagnosis correct (could there be something else causing it, and if so, what?)

3) Any suggestions on how best to proceed?

 

Here's my problem:

When I last tried to fill the pen, it would not fill - it somehow failed to make the necessary vacuum, and couldn't get more than a dribble of ink into the barrel.

I disassembled the pen for the first time, made sure everything was properly clean and lubricated and properly reassembled. Of course, the problem persisted.

So I took it apart again and looked at everything under a loupe. I discovered that there are actually two O-Rings on the end of the barrel (the part that screws in). The larger O-Ring is the more obvious, and the smaller O-Ring is easier to overlook.

The problem seems to be with the smaller O-Ring. It actually seems a little flimsy, and it has become a little 'floppy' or stretched over time. That is, it no longer makes the necessary tight fit with the thread. See picture.

 

 

(Image: end-of-barrel unit, with O-Rings highlighted)

 

 

I was surprised to see this part failing so quickly, particularly if it is crucial for the pen's operation. I don't know why a problem with that O-Ring should cause the vacuum to fail - the larger O-Ring is fine, and should be sufficient by itself. But in the absence of any other obvious cause, I'm assuming that the perished smaller O-Ring is indeed the problem. I am therefore looking to replace it.

 

It's only a small part, and I can probably find it cheaply at my local DIY/hardware store, but that's a hassle (the store is not all that local). Also, I'm wondering whether this is a potential issue for others, and whether I should approach the company I bought my pen from.

 

Any thoughts in response to my questions? Have I missed something? Thanks!

[Flounder]

Let's get the insultingly simple question out of the way first. Are you immersing the whole nib & feed in ink before depressing the plunger, or has the ink level gotten too low in the bottle?

 

If the nib & feed are getting adequately immersed, the first seal I would suspect in this scenario is the sliding seal on the other end of the plunder rod. That's the seal that generates the vacuum as you press the plunger down.

 

That's my first instinct, because

 

• If there was a breach in the seals at the back other issues would flare up too, like messed up metering - an increase in ink flow over the usual as you write, or even dripping blobs out the nib.
• Generally, seals that have to slide about wear out faster than stationary seals. You've already cleaned and regreased it, so i reckon that seal is the traitor.

edited for spelling. I meant to write ink level, not lever!

Edited June 12, 2016 by Flounder

[stephanos]

Hi, Flounder

 

Simple question, but not insulting. (My wife provided tech support in a call centre for a while - you'd be surprised how often the solution to a major technical problem was to, er, plug in the computer and turn it on.) The nib and feed were adequately immersed - and just to be sure, I had also tried using the special Vac20 bottle that TWSBI produced for the Vac700 (very useful little item when travelling).

 

It does make more sense that the large sliding seal at the front would be the culprit. But it looks OK. There is actually an O-Ring stuck to the base of the seal, to sit flush with the metal 'arrester' that is immediately behind the seal, up the barrel towards the turning-knob. But again, that looks OK, too. The seal is a little loose on the rod (I can wiggle it around), but as I hadn't previously taken the pen apart, I can't tell whether that is a problem or not. The sealing-O-Ring at the base of large seal does look like it should create a snug fit when the mechanism is in use.

 

Perhaps I should contact TWSBI directly to ask them to advise, and possibly send me a new seal... (?)

[stephanos]

UPDATE: Problem solved

 

I e-mailed TWSBI and received a reply from Philip, within seven minutes (!) of sending my message. Kudos for awesome response time!

 

Following Philip's suggestion, I double-checked that everything was clean (it was) and that there was no dried ink anywhere (there wasn't). Then I re-applied silicone grease. But this time, I used quite a lot of grease. That did the trick, and everything is working as it should. I'm used to pistons on Pelikans, where if you think you might be using too much grease, then you probably are; so this was a learning moment for me.

 

Note for next time: don't be too stingy with the lubricant in the vac mechanism, and if in doubt, use more.

[Padawan]

I would like to draw your attention to the superior review referenced below and the latest photos there

https://www.fountainpennetwork.com/forum/topic/309142-review-of-a-twsbi-vac-700-with-a-vac-20-travel-inkwell/page-2

 

I don't think you have a problem with a "thin o-ring" but probably with the sealing between the shaft and the feeling collar.

You fixed it with extra silicone grease which is water/ink repelling.

[Erik Dalton]

Great job. Many would have put the pen down and started bad mouthing TWISBI. But you stuck with it and figured it out. Proud to have you as one of us.

[Flounder]

I don't buy this as a long lasting fix, guys. If you have to use 'quite a lot' of grease for the sliding seals to generate any vacuum, it will fail again as soon as the grease stops taking up the slack.

[stephanos]

I agree that it does seem a danger.

But I didn't lather the lubricant on - I simply used quite a bit more than the very austere amount that I had previously used, and it now seems to work.

 

I'll be taking my Vac700 with me on a couple of longish trips over the next few months. That will give me a chance to see how it works in practice. If the vacuum fails again any time soon, then I'll know it really is a problem with the seal. In that case, I would get back to TWSBI for a replacement part, and update here. For the moment, though, I would prefer to give the benefit of any doubt.

[sannidh]

I agree that it does seem a danger.

But I didn't lather the lubricant on - I simply used quite a bit more than the very austere amount that I had previously used, and it now seems to work.

 

I'll be taking my Vac700 with me on a couple of longish trips over the next few months. That will give me a chance to see how it works in practice. If the vacuum fails again any time soon, then I'll know it really is a problem with the seal. In that case, I would get back to TWSBI for a replacement part, and update here. For the moment, though, I would prefer to give the benefit of any doubt.

 

Thank you for highlighting this issue, stephanos. I had a similar experience & used silicone grease with more kindness , Like you, I found it to fix the filling problem. We are bound to lose some silicone grease, while cleaning the VAC. Though this kind of issue is non-existent with my pilot custom 823, but then we don't disassemble the pen