Vac Mini

[onotopen]

Hi SirGilber357, I've attached photo showing Vac-Mini and Piston-Mini. Apologies for poor picture...my phone is useless in low light, and we don't get much sunshine at this time of year !

One of the measurements is obscured; it's the Vac-Mini Diameter at the Barrel Thread...it reads 12.85mm

[sirgilbert357]

Wow, Onotopen, that's exactly what I needed! Your drawing with measurements is actually more insightful than just a side by side pic! Thank you!

[ravantra]

I always carry a Mini 1.1 with me, filled with KTC. I just received the Mini Vac with a 1.1mm. Awesome! I have a Vac 700 and it tends to be a very dry writer. This Mini is very "juicy" and a smooth writer. Love it.

[TSherbs]

Awesome, Onotopen, but I can't read the diameter measurement for the threads-area of the barrel on the Vac drawing. Can anyone read that number up in the shadow area (I hold pens usually on the threads, so I am interested most in that number.

[onotopen]

TSherbs, it's annotated in the text accompanying photo...it's 12.85mm diameter. Sorry for poor photos.

[TSherbs]

TSherbs, it's annotated in the text accompanying photo...it's 12.85mm diameter. Sorry for poor photos.

oops, thanks, just saw that now

[Fishkabob]

What size nib does the vac mini use? Would a fpr 5.5 nib fit?

[onotopen]

Fishkabob, check-out this site

http://www.penucopia.com/twsbi-its-all-about-the-ecosystem/

 

Looks like #5 for 5x0 series, and this is same for Vax-Mini and Piston-Mini. #6 for the standard (Maxi) Vac. Goulet Pens sells replacement #5 nibs, which are also made by Jowo I believe. I've fitted TWSBI nibs into Noodlers Ahab pens

[Algester]

I'm curious does the VAC mini have a proprietary feed collar or is it a genereic TWSBI nib collar? IE can I uses the nib collar from the 580 to the VAC mini I forgot if it was covered already or not and will the cap still fit?

[EternalMonsoon]

I don't know about using the collar but you can certainly swap out the nib units (the nib and black part surrounding it. The collar is probably smaller and unable to be swapped but I don't know for sure. I know the Classic Mini collar doesn't fit... and yet the nibs certainly do!

 

Here is my Vac Mini with a 1.5mm Classic Mini nib applied...

 

http://i.imgur.com/77Btbmm.jpg

[Fishkabob]

Is the nib unit friction fit?

[Draconis85]

I'm waiting for a "smoke" color and hoping they will fix some of the cross-threading issues I've heard about.

[onotopen]

I've made some more measurements of the Vac Mini and the Piston Mini.. I've use Vernier Callipers, a micrometer would be better but results are reasonably accuate.

 

Vac-Mini

 

Bore: 7mm Diameter - Tentative (I've deduced this from measuring the piston-seal, but considering that this is compressed whilst in-situ there's a degree of wiggle/squishing factor here. Better to offer up millimetric drills to the bore, but I only have Imperial drills).

 

Steel Piston Rod: 3mm Diameter

 

Barrel: It's quite complex when one views it closely; The 12 sided 'flutes' are not totally flat, they are slightly rounded laterally (around the barrel) and slope longitudinally (along the barrel).

 

Measurements at Nib end

 

Between Flats (of the 12 sided rhomboid); 12.64mm dia

Between Points; 12.87mm dia

 

Measurement at Filler end

 

Between Flats; 13.14mm dia

Berween Points; 13.29mm dia

 

Cap thread 12.85mm

 

Stroke of Vacuum Piston; 39.5mm (approx)

 

The minimum wall thickness of the barrel (excl Plenum) is roughly (5.64)/2 mm minimum (considerably more than that of the Piston-Mini); the Plenum chamber (ink bi-pass chamber) is several mm wider than the 7mm bore, and this is at the wider end of the barrel.

 

Piston-Mini

 

Bore; 8.5mm. Little compression from 'O' rings so measurement of piston reasonably accurate.

 

A more complex, faceted barrel, again 12-sided, equidistant only at the two ends and the centre. The Filler end is wider than the nib end, but the centre of the barrel is widest.

 

Measurements at Nib end

 

Between Flats; 11.82mm dia

Between Points; 12.34mm dia

 

Measurement at Filler end

 

Between Flats; 12.06mm dia

Between Points; 12.63mm dia

 

Measurement at Centre of Barrel

 

Between Flats; 12.40mm

Between Points; 12.92mm

 

Cap Thread; 12.25mm

 

Stroke of Piston' 22.3mm (approx)

 

Minimum wall thickness (3.32)/2 mm

Edited January 24, 2016 by onotopen

[sirgilbert357]

Is the nib unit friction fit?

The nib and feed are friction fit into the collar, but the collar itself screws into the pen.

[Starguard]

I got a vac 20 a inkwell to use with my vac mini, it works very well, but I had an odd thing happen afterward, I got a full fill and I do mean full, I had closed the valve, habit more than anything, I had posted the cap and was making an entry in my journal when I noticed there was ink in the cap! There wasn't any ink in it before I posted it, I took the cap off and ink had seeped out around the piston knob and gotten inside the posted cap. It cleaned right up and hasn't seeped since. Any one have any idea what could have caused it?

[onotopen]

Katherinnes, maybe if valve was closed and the barrel/reservoir was very full, an increase in temperature will increase pressure build-up and ink has managed to get by the filler rod seal/gland. Capillary action will be enough for the ink to migrate into posted cap.

 

Solution - as with eye-dropper pens, leave a bit of air space in the reservoir. (It was also percieved wisdom not to totally fill-up pens if they were taken onto aircraft...maybe an urban myth).

 

The filler-rod seal itself should have the slightest touch of silcon grease. If the valve is open, any increase in pressure will easily escape into the feeder/collector rather than the filler-knob seal/gland

 

All the foregoing is guesswork. With eye-dropper pens, it's often normal to leave up to 25% airspace. I haven't encountered this problem with the Vac-Mini or standard Vac, or indeed with ant of my Onoto pens which are all Vac-plungers (but there again, I always open the valve when I use them)

[Starguard]

Katherinnes, maybe if valve was closed and the barrel/reservoir was very full, an increase in temperature will increase pressure build-up and ink has managed to get by the filler rod seal/gland. Capillary action will be enough for the ink to migrate into posted cap.

 

Solution - as with eye-dropper pens, leave a bit of air space in the reservoir. (It was also percieved wisdom not to totally fill-up pens if they were taken onto aircraft...maybe an urban myth).

 

The filler-rod seal itself should have the slightest touch of silcon grease. If the valve is open, any increase in pressure will easily escape into the feeder/collector rather than the filler-knob seal/gland

 

All the foregoing is guesswork. With eye-dropper pens, it's often normal to leave up to 25% airspace. I haven't encountered this problem with the Vac-Mini or standard Vac, or indeed with ant of my Onoto pens which are all Vac-plungers (but there again, I always open the valve when I use them)

 

All this makes sense, my first thought that perhaps it was too full, I did put some silicone grease on the seal when I cleaned the pen, this particular filling was my second time and it hasn't happened since, from now on I'm going to be sure there is some air in there!

[onotopen]

The TWSBI ink bottle could conceivably exacerbate the over-filling problem. The volume of the Vac-Mini and the Ink bottle is fixed and not open to atmosphere ?...so in this situation as the Plunger is forced down, thereby creating a vacuum in the Vac-Mini barrel/ink reservoir, the pressure in the ink bottle will increase.

 

The net effect (once the piston passes the plenum /ink by-pass chamber is to suck more ink into the barrel by virtue of the increased pressure differential compared to a normal ink bottle open to atmosphere.

 

I vaguely recall that the TWSBI ink bottles may be inverted and this could further increase the pressure as well as force the ink by gravity and pressure on the Filler-rod seal/gland. So it's possible that some ink was already forced past (unnoticed) the seal/gland without any added temperature input.

 

A modicum of cappiliary action...and Robert's your Father's brother !

[Starguard]

The TWSBI ink bottle could conceivably exacerbate the over-filling problem. The volume of the Vac-Mini and the Ink bottle is fixed and not open to atmosphere ?...so in this situation as the Plunger is forced down, thereby creating a vacuum in the Vac-Mini barrel/ink reservoir, the pressure in the ink bottle will increase.

 

The net effect (once the piston passes the plenum /ink by-pass chamber is to suck more ink into the barrel by virtue of the increased pressure differential compared to a normal ink bottle open to atmosphere.

 

I vaguely recall that the TWSBI ink bottles may be inverted and this could further increase the pressure as well as force the ink by gravity and pressure on the Filler-rod seal/gland. So it's possible that some ink was already forced past (unnoticed) the seal/gland without any added temperature input.

 

A modicum of cappiliary action...and Robert's your Father's brother !

 

This was what I was thinking too, you explained better than I could! It hasn't happened since, and yes you do invert the inkwell, so next time I'll put less ink in. Thank you for the excellent explanation!

[onotopen]

For anyone not conversant with how vacuum plungers work, the attached link gives a very good explanation. It's for an Onoto pen, but the principle remains the same.

 

http://www.pencentral.com/files/pages_8_and_9.pdf

 

which I believe is taken from this book

 

http://www.pencentral.com/files/marshallcover_1may_1_.pdf

 

I'm not entirely convinced that a shut-off valve is generally needed; remember that this design was developed well over a 100yrs ago when transport , other than rail, was - more likely as not - on horseback or on horse-drawn coaches with all the bumps and vibrations. People were more active, more physical, then too; so a shut-off valve was possibly more essential.

Edited January 31, 2016 by onotopen