In keeping with my luck today, or lack thereof, I took apart a Parker 51 aerometric
this evening for an overhaul and discovered that the breather tube had a bend in
it... of course it broke when I tried to straighten it. The tube is about a 1/2 inch shorter
than normal. Will this function this way or should I look for a replacement?

I was at the local flea-market today, searching for fountain pens. While I was there, I bumped into my friendly neighbourhood repairman. Taking the chance to get some free advice, I consulted him about a Parker 51 aero that I was working on. I asked him what I should do with regards to the breather-tube. It went something like this:

"Where can I find something to make a new breather tube?"
"I don't know if there is anywhere around here. But you can just use the old one"
"Huh?"

According to Peter Ford, the breather-tube does not have to be very long. He said a length of old, good-condition and clean breather-tube of a length between 1.5-2 inches long, will suffice.

It will work just fine, you probably will even get much the same fill. However, if it broke because it was corroded (the usual reason), it's likely shedding junk into the collector, which will often make for bad ink flow.

SmallParts.com sells stainless steel hypodermic needle tubing -- you want thin wall 0.046" I think. You will have to use a dremel tool and a cutoff wheel to cut it, and it needs the breather hole drilled (0.020" I think) by a machine shop. You cannot do this by hand, it requires a jig (which you can make, of course).

Good thing is that the pen will work just fine without the hole in the breather.

Peter

David Nishimura lists breather tube material on his site ( http://www.vintagepens.com ).
There is another source: some spray cans, like WD40 or some dust removers have a small tube that can be attached to the button to direct the contents at the point where you want to apply them. If you have an empty can like that, you can use this little tube.
I think if you use plastic instead of metal, you can create the hole much easier (last time I had to do this, I punched a hole on the tube with a hot pin, and then used a drill bit with a screwdriver handle to make the hole bigger). Cutting plastic tube to size is also much simpler than the metal one (no Dremel needed).

Thanks for the tips and advice, gang. Just for giggle I went ahead and
re-assembled the pen with the original breather tube, which is about
1/2 an inch shorter than it should be, and tested it. I gave the compression
bar it's normal 5 squeezes, then ejected all the ink, and then did the same
with another 51, and the amount of ejected ink looks, for all purposes,
about equal.

In the case of a P51 the amount of ejected ink is not a good measure of the amount of ink the pen takes with a fill. By pressing the bar, you can only eject the ink above the hole in the breather tube from the pen. You have to measure the amount of ink the pen takes (eg. by filling the pen from a think container, like a test tube, and marking the level of ink in it before and after).
However, I think that the pen would work correctly with the shorter tube as well. Perhaps it would be more sensitive to air pressure variations during a flight than another P51 which has a hole in its (longer) breather tube (but, I would think that still less sensitive than most other fountain pens).

The shorter the tube, the less ink the pen will take up. Without the side vent hole the Hi-Flight Leak Prevention mechanism will be absent.

--Daniel

Well, as I said before, I'm not going to worry about it. It takes up plenty of ink, and I do NOT
fly, so it will be ok. If a replacement breather tube can be found I'll switch it out then.

Ray,

for your reference it may be worth looking at Shangas's thread on a broken breather tube and repairing it here:-

http://www.fountainpennetwork.com/forum/in...showtopic=61513

I describe the method of drilling a cross hole in a metal breather tube in post 13 of that thread ( http://www.fountainpennetwork.com/forum/in...st&p=593639 ).

Regards

Richard.

Richard (or someone else), I'd like to get opinions.

As I mentioned above, I met Peter Ford of Melbourne Vintage Pens, at my local flea-market on Sunday. We were both searching for...vintage fountain pens (of course!).

Well since I had him there, I asked him about my concerns regarding the breather-tube of my currently half-restored '51'.

He said that a remaining length of breather-tube of a length between 1-2 inches long, which was clean and hollow and in good condition, may be re-used as a new breather-tube in the pen and that drilling a hole in this length of tube was not necessary. When I asked him about tube-lengths, he explained that several of the later '51's had their breather-tubes shortened to just about an inch-and-a-half long.

He suggested I should select the better length of remaining breather-tube, clean it out and then drill away the remaining tube in the feed (which I explained to him, I could not remove) and then slot the new, cleaned, hole-less tube, into the feed. Then, reassemble the pen and write with it.

Will such a tactic work? It sounds too easy to be true.

The cheap-o-naut in me is pondering an alternative means of making the side vent, which I put here for comment rather than as a suggestion-- using a jeweller's saw to cut into the side of the tube at the correct point, going only deep enough to produce the needed hole. A vent slot, in effect. Not ideal, but for those in need of the part and without the means to drill it properly, would it work?

Yes, it will work.
Just remember when you go on an aeroplane to remove some of the ink. The difficult to drill 'aero' hole is the one that releases the pressure differential between the sac and the outside world. When the hole isn't there the 'Fountain' pen can do just that - fountain ink out to equalise the pressure, because the air in the sac cannot escape and expand, instead it expands where it is (in the sac), and the ink is pushed out instead. The pen won't fountain, though, if the ink level in the sac doesn't cover the end of the breather tube (as the air can escape freely), so a half empty pen shouldn't be a problem regardless of whether it has an 'aero' hole or not.

Regards

Richard.

Yep, it would work.
The only thing against the idea is that it's very difficult to get a small cut with beautifully rounded edges. If the edges are not rounded you get a stress concentration at the edges of the nick, and a fatigue crack is more likely to start than if you drill a hole. So, if you do it this way, the tube life is likely to be shorter than if you drill a hole. I - without evidence or calculation - would expect a fatigue life of around 1/4 the drilled hole, so you may have to replace the tube every 10 years or so. Vacumatic P51 owners are happy to replace the diaphragm that frequently, so it's probably acceptable. It's up to you.

When I drilled my 'aero' hole, I considered just filing away one side of the tube myself. However, as I had all the tools I needed to do it properly, I drilled it instead.

Regards

Richard.

It might produce an orifice with approximately the right function, but I would be concerned about structural weakness. A little-recognized fact is that the breather tube is often contacted and deflected during the squeezing of the pressure bar, which explains the leaning-to-one-side shape often seen in these tubes (and it is the reason I am not satisfied with the Teflon tube substitution -- the material flattens appreciably and permanently when pinched). I would worry that this repeated flexing would cause work-hardening at the stress risers produced by the shape of the slot, eventually causing the tube to crack off at the slot.

--Daniel

I wonder if he thought you were discussing a Vacumatic-filling "51", because Parker, in an attempt to address the problem of ink being forced back up the breather tube due to a drop in external air pressure, patented a design which did nothing more than shorten the breather tube to the point where the pen couldn't quite fill half-full, so that when the pen was point up (as when capped and clipped in a shirt pocket) the open end of the breather tube wouldn't be submerged in ink, but rather would be in the (rather large) air pocket in the reservoir, allowing equalization to take place without ink from the reservoir being ejected.

Obviously, shortening the breather tube (in a Vac or Foto-Fill "51") will decrease the ink uptake correspondingly.

I wrote a rather extensive article examining the development of the various pressure-venting approaches employed and proposed by Parker vis-a-vis the "51"; if there is interest, I will try to find time to produce a PDF version that I can email.

--Daniel

Thanks, Richard!! That was a great help. What size (or diameter) drill-bit should be used to remove the old breather-tube?

And no, Kirchh. I had actually *showed* Peter the pen in question some weeks before, so he knew I was asking about an aerometric one. When I first showed it to him I had asked how to remove the hood and the innards of the pen, so he knew what I was talking about.

That would be great! If you do produce a PDF file, please send me a copy.

Sounds like fiddly minutiae-- so I'd definitely want to see it!

I've done a quick PDF conversion of my Parker "51" venting article. I hope it is informative.

Click to view attachment
--Daniel

If you really need to gt it out, I think the tube is 0.046", so the nearest number size below is #57 at 0.043" (#56 is 0.0465"). A 1.15mm is nearer at 0.0453". Any of those would do if you aren't using a lathe, as the precision in anything else isn't good enough.

Regards

Richard.

One of the repair people on the forum suggested using a metric tap that just fits inside the tubing to use as a "handle" to remove it. I think I like that idea best. 1.1mm? 1.0mm? one or the other, you can "screw" it in, giving you a nice handle to pull the remnants out. You won't bore out the hole that way, like I did. Fortunately for me, I was putting 0.050" tubing in anyway, so the slightly larger hole is fine, I don't anticipate that stainless steel going bad in my lifetime!

Peter

"I've got my fingers crossed,
Not that I'm superstitious,
I just think it's too good to be true..."

Today dad and I are going to try and drill out the old breather tube. Wish us luck!